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Enclosure 1, Evaluation of Proposed Changes Attachment 1 Proposed SQN Units 1 and 2 UFSAR Text Changes (Markups), Page 2.4-42 Through Enclosure 2
	ML12226A563
Person / Time
Site:	Sequoyah
Issue date:	08/10/2012
From:	; Tennessee Valley Authority
To:	; Office of Nuclear Reactor Regulation
References
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SQN-2.4.8 Cooling Water Canals and Reservoirs (HISTORICAL INFORMATION) 2.4.8.1 Canals The intake channel, as shown in Figure 2.1.2-1, referenced in paragraph 2.4.1.1, is designed for a flow of 2,250 cfs. At minimum pool (elevation 675.0 ft), as shown in Figure 2.4.8-1, this flow is maintained at a velocity of 2.7 fps.

The protection of the intake channel slopes from wind-wave activity is afforded by the placement of riprap, shown in Figure 2.4.8-1, in accordance with TVA Design Standards, from elevation 665.0 ft to elevation 690.0 ft. The riprap is designed for a wind velocity of 45 mph.

2.4.8.2 Reservoirs (HISTORICAL INFORMATION)

Chickamauga Reservoir provides the cooling water for SQN. This reservoir and the extensive TVA system of upstream reservoirs, which regulate inflows, are described in Table 2.4.1-42. The location in an area of ample runoff and the extensive reservoir system assures sufficient cooling waterflow for the plant.

2.4.9 Channel Diversions (H,'ISTORDICAL.,

.N FORMATION)

Channel diversion is not a potential problem for the plant. There are now no channel diversions upstream of SQN that would cause diverting or rerouting of the source of plant cooling water, and none are anticipated in the future. The floodplain is such that large floods do not produce major channel meanders or cutoffs. Carbon 14 dating of material at the high terrace levels shows that the Tennessee River has essentially maintained its present alignment for over 35,000 years. The topography is such that only an unimaginable catastrophic event could result in flow diversion above the plant.

2.4.10 Flooding Protection Requirements Assurance that safety-related facilities are capable of surviving all possible flood conditions is provided by the discussions given in Paragraph 21.2.2Section 2.4.14, SeetieO-3.4, SeetiGR-3.8.1, 3.8.2, and Appendix2.4 3.8.4.

The plant is designed to be shutdown and remain in a safe shutdown condition for any rainfall flood exceeding plant grade, up to the "design basis flood" discussed in Su*bsection 2.4.37 and for lower, seismic-caused floods discussed in Subsection 2.4.4. Any rainfall flood exceeding plant grade will be predicted at least 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months in advance by TVA's Reservoir Operations.

-Warning of seismic failure of key upstream dams will be available at the plant at4 eastapproximately 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months before a resulting flood surge would reach plant grade. Hence, there is adequate time to prepare the plant for any flood.

See Appendix-2AASection 2.4.14 for a detailed presentation of the flood protection plan.

2.4.11 Low Water Considerations Because of its location on Chickamauga Reservoir, maintaining minimum water levels at SQN is not a problem. The high rainfall and runoff of the watershed and the regulation afforded by upstream dams assure minimum flows for plant cooling.

2.4.11.1 Low Flow in Rivers and Streams The targeted minimum water level at SQN is elevation 675.0 ft, which cOrresponds to the lower bound of the..

iFnte operating zone fr Chickamrauga Re.....ir and would occur in the winter flood season as a result of Chickamauga Reservoir operation. On rare occasions, the water level may be slightly lower

(.1 or.2 tenths of a foot) for a brief period of time (hours) due to hydropower peaking operations at 2.4-42

SQN-Chickamauga and Watts Bar Dams during the winter season. A minimum elevation of 675.0 ft must be maintained in order to provide the prescribed commercial navigation depth in Chickamauga Reservoir.

The "Preferred Alternative" Reservoir Operating Policy was designed to provide increased recreation opportunities while avoiding or reducing adverse impacts on other operating objectives and resource areas. Under the Preferred Alternative, TVA will no longer target specific summer pool elevations at 10 tributary storage reservoirs. Instead, TVA tends to manage the flow of water through the system to meet operating objectives. TVA will use weekly average system flow requirements to limit the drawdown of 10 tributary reservoirs (Blue Ridge, Chatuge, Cherokee, Douglas, Fontana, Nottely, Hiawassee, Norris, South Holston, and Watauga) June 1 through Labor Day to increase recreation opportunities. For four main stem reservoirs (Chickamauga, Guntersville, Wheeler, and Pickwick),

summer operating zones will be maintained through Labor Day. For Watts Bar Reservoir, the summer operating zone will be maintained through November 1.

Weekly average system minimum flow requirements from June 1 through Labor Day, measured at Chickamauga Dam, are determined by the total volume of water in storage at the 10 tributary reservoirs compared to the seasonal total tributary system minimum operating guide (SMOG). If the volume of water in storage is above the SMOG, the weekly average system minimum flow requirement will be increased each week from 14,000 cfs (cubic feet per second) the first week of June to 25,000 cfs the last week of July.

Beginning August 1 and continuing through Labor Day, the weekly average flow requirement will be 29,000 cfs. If the volume of water in storage is below the SMOG curve, 13,000 cfs weekly average minimum flows will be released from Chickamauga Dam between June 1 and July 31, and 25,000 cfs weekly average minimum flows will be released from August 1 through Labor Day.

Within these weekly averages, TVA has the flexibility to schedule daily and hourly flows to best meet all operating objectives, including water supply for TVA's thermal power generating plants. Flows may be higher than these stated minimums if additional releases are required at tributary or main river reservoirs to maintain allocated flood storage space or during critical power situations to maintain the integrity and reliability of the TVA power supply system.

In the assumed event of complete dam failure of the north embankment of Chickamauga Dam resulting in a breach width of 400 feet, with the Chickamauga pool at elevation 681.0 ft, the water surface at SQN will begin to drop within one hour and will fall to elevation 641.0 ft about 6051 hours0.07 days 1.681 hours 0.01 weeks 0.0023 months after failure. TVA will begin providing steady releases of at least 14,000 cfs at Watts Bar within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months of Chickamauga Dam failure to assure that the water level recession at SQN does not drop below elevation 641.0 ft. The estimated minimum river flow requirement for the ERCW system is only 45 cfs.

Reference:

Programmatic Environmental Impact Statement, TVA Reservoir Operations Study, Record of Decision, May 2004.

2.4.11.2 Low Water Resulting From Surges, Seiches, or Tsunamis Because of its inland location on a relatively small, narrow lake, low water levels resulting from surges, seiches, or tsunamis are not a potential problem.

2.4.11.3 Historical Low Water From the beginning of stream gauge records at Chattanooga in 1874 until the closure of Chickamauga Dam in January 1940, the lowest daily flow in the Tennessee River at SQN was 3,200 cfs on September 7 and 13, 1925. The next lowest daily flow of 4,600 cfs occurred in 1881 and also in 1883.

Since January 1942, low flows at the site have been regulated by TVA reservoirs, particularly by Watts Bar and Chickamauga Dams. Under normal operating conditions, there may be periods of several hours daily when there are no releases from either or both dams, but average daily flows at the site 2.4-43

SQN-have been less than 5,000 cfs only 0.65 p-rnabout 2.2% of the time and have been less than 10,000 cfs,45-peF~eet about 10.4% of the time.

On March 30 and 31, 1968, during special operations for the control of water milfoil, there were no releases from either Watts Bar or Chickamauga Dams during the two-day period. The prey4eus minimumn daily flow was 700 cfs On Novcmnber 1, 1953. TVA no longer conducts special operations for the control of water midfoil on Chickamnuga Reser-oirOver the last 25 years (1986 - 2010) the number of zero flow days at Watts Bar and Chickamaugqa Dams have been 0 and 2, respectively.

Since January 1940, water levels at the plant have been controlled by Chickamauga R*sscvoir. Since then, Dam. For the period (1940 - 2010), the minimum level at the dam was elevation 673.3 ft on January 21, 1942. TVA no longer routinely conducts pre-flood drawdowns below elevation 675.0 ft at Chickamauga Reservoir and the minimum elevation in the past 20 years (1987 - 2006) was elevation 674.97 ft at Chickamauga head water.

2.4.11.4 Future Control Future added controls which could alter low flow conditions at the plant are not anticipated because no sites that would have a significant influence remain to be developed. However, any control that might be considered would be evaluated before implementation.

2.4.11.5 Plant Requirements 2.4.11.5.1 Two-Unit Operation The safety related water supply systems requiring river water are: the essential raw cooling water (ERCW) (Subsection 9.2.2), and that portion of the high-pressure fire-protection system (HPFP)

(Subsection 24A.42.4.14.4.1) supplying emergency feedwater to the steam generators. The fire/flood mode pumps are submersible pumps located in the CCW intake pumping station. The CCW intake pumping station sump is at elevation 648.0 ft. The entrances to the suction pipes for the fire/flood mode pumps are at elevation 651.0 ft-feet-I 4knhes which is 32 feet and 24 feet, respectively, below the maximum normal water elevation of 683.0 ft and the normal minimum elevation of 675.0 ft for the reservoir. Abnormal reservoir level is elevation 670 feet with a technical specification limit of elevation 674 ft. For flow requirements of the HPFP during engineering safety feature operation (Reference 22). The ERCW pump sump in this independent station is at elevation 625.0 ft, which is 58.0' ft below maximum normal water elevation, 50.0! ft below minimum normal water elevation, and 16'ft below the 641 'ft minimum possible elevation of the river.

Since the ERCW pumping station has direct communication with the river for all water levels and is above probable maximum flood, the ERCW system for two-unit plant operation always operates in an open cooling cycle.

2.4.11.6 Heat Sink Dependability Requirements The ultimate heat sink, its design bases and its operation, under all normal and credible accident conditions is described in detail in Subsection 9.2.5. As discussed in Subsection 9.2.5, the sink was modified by a new essential raw cooling water (ERCW) pumping station before unit 2 began operation.

The design basis and operation of the ERCW system, both with the original ERCW intake station and with the new ERCW intake station, is presented in Subsection 9.2.2. As described in these sections, the new ERCW station is designed to guarantee a continued adequate supply of essential cooling water for all plant design basis conditions. This position is further assured since additional river water may be provided from TVA's upstream multiple-purpose reservoirs, as previously discussed during Low Flow in Rivers and Streams.

2.4.11.6.1 Loss of Downstream Dam The loss of downstream dam will not result in any adverse effects on the availability of water to the ERCW system or these portions of the original HPFP supplying emergency feedwater to the steam 2.4-44

SQN-generator. Loss of downstream dam reduces ERCW flow about 7% to the component cooling and containment spray heat exchangers. ERCW flow does not decrease below that assumed in the analysis (analyzed as 670' to 639') until more than two hours after the peak containment temperature and pressure occurs. (See Section 6.2.1.3.4.)

2.4.11.6.2 Adequacy of Minimum Flow The cooling requirements for plant safety-related features are provided by the ERCW system. The required ERCW flow rates under the most demanding modes of operation (including loss of downstream dam) as given in Subsection 9.2.2 are contained in TVA calculations and flow diagrams.

Two other safety-related functions may require water from the ultimate heat sink; these are fire protection water (refer to Subparagraph 2.4.11.6.3) and emergency steam generator feedwater (refer to Subsection 10.4.7). These two functions have smaller flow requirements than the ERCW systems.

Consequently, the relative abundance of the river flow, even under the worst conditions, assures the availability of an adequate water supply for all safety-related plant cooling water requirements.

River operations methodology for maintaining UHS temperatures are discussed in "Monitoring and Moderating Sequoyah Ultimate Heat Sink," Reference 21.

2.4.11.6.3 Fire-Protection Water Refer to the Fire Protection Report discussed in Section 9.5.1.

2.4.12 Environmental Acceptance of Effluents The ability of surface waters near SQN, located on the right bank near Tennessee River Mile (TRM) 484.5, to dilute and disperse radioactive liquid effluents accidentally released from the plant is discussed herein. Routine radioactive liquid releases are discussed in Section 11.2.

The Tennessee River is the sole surface water pathway between SQN and surface water users along the river. Liquid effluent from SQN flows into the river from a diffuser pond through a system of diffuser pipes located at TRM 483.65. An accidental, radioactive liquid effluent release from SQN would enter the Tennessee River after it reached the diffuser pond and entered the diffuser pipes.

The contents of the diffuser pond enter the diffuser pipes and mix with the river flow upon discharge.

The diffusers are designed to provide rapid mixing of the discharged effluent with the river flow. The flow through the diffusers is driven by the elevation head difference between the diffuser pond and the river [1] (McCold 1979). Descriptions of the diffusers and SQN operating modes are given in Paragraph 10.4.5.2. Flow is discharged into the diffuser pond via the blowdown line, ERCW System (Subsection 9.2.2) and CCW System (Subsection 10.4.5). A layout of SQN is given in Figures 2.1.2-1 and 2.1.2-2. Two pipes comprise the diffuser system and are set alongside each other on the river bottom. They extend from the right bank of the river into the main channel. The main channel begins near the right bank of the river and is approximately 900 feet wide at SQN [1] (McCold, 1979). Each diffuser pipe has a 350-foot section through which flow is discharged into the river. The downstream diffuser leg discharges across a section 0 to 350 feet from the right bank of the main channel. The upstream diffuser leg starts at the end of the downstream diffuser leg and discharges across a section 350 to 700 feet from the right bank of the main channel. The two diffusers therefore provide mixing across nearly the entire main channel width.

The river flow near SQN is governed by hydro power operations of Watts Bar Dam upstream (TRM 529.9) and Chickamauga Dam downstream (TRM 471.0). The backwater of Chickamauga Dam extends to Watts Bar Dam. Peaking hydro power operations of the dams cause short periods of zero (i.e., stagnant) and reverse (i.e., upstream) flow near the plant. Effluent released from the diffusers during these zero and reverse flow periods will not concentrate near the plant or affect any water intake upstream. The maximum flow-reversal during 1978-1981 were not long enough to cause discharge from the diffusers to extend upstream to the SQN intake [2] (EI-Ashry, 1983), which is the nearest intake and located at the right bank near TRM 484.7. Moreover, the warm buoyant discharge from the diffusers will tend toward the water surface as it mixes the river flow and away from the 2.4-45

SQN-cooler, denser water found near the intake opening below the skimmer wall. The intake opening extends the first 10 feet above the riverbed elevation of about 631 feet mean sea level (MSL). The minimum flow depth at the intake is approximately 45 feet [3] (Ungate and Howerton, 1979). There are no other surface water users between the diffusers and this intake.

Subsection 2.4.13 discusses groundwater movement at SQN. Effluent released through the diffusers will have no impact on SQN groundwater sources along the banks of the river. Paragraph 2.2.3.8 discusses the effect on plant safety features from flammable or toxic materials released in the river near SQN.

The predominant transport and effect of a diffuser release is along the main channel and in the downstream direction. The nearest downstream surface water intake is located along the left bank at TRM 473.0 (Table 2.4.1-41).

A mathematical analysis is used to estimate the downstream transport and dilution of a contaminant released in the Tennessee River during an accidental spill at SQN. Only the main channel flow area without the adjacent overbank regions is considered in the analysis. The mathematical analysis of a potential spill scenario can involve: (1) a slug release, which can be modeled as an instantaneous release; (2) a continuous release, which can be modeled as a steady-state release; (3) a bank release, which can be modeled as a vertical line source; and (4) a diffuser release, which can be modeled either as a vertical line or plane source, depending on the width of the diffuser with respect to the channel width.

The following assumptions are used in the mathematical analyses to compute the minimum dilution expected downstream from SQN and, in particular, at the nearest water intake.

1. Mixing calculations are based on unstratified steady flow in the reservoir. River flow, Q, is assumed to be 27,474 cubic feet per second (cfs), which is equalled or exceeded in the reservoir approximately 50 percent of the time (Paragraph 2.4.1.2). Because various combinations of the upstream and downstream hydro power dam operations can create upstream flows past SQN, a minimum flow is not well defined. Larger (smaller) flows will decrease (increase) the travel time to the nearest intake but cause less than an order of magnitude change in the calculated dilution.

2.

Because the SQN diffusers and the nearest downstream water intake are on opposite banks of the river, and the diffusers extend across most of the main channel width, an analysis using a diffuser release (rather than a bank release) is selected to yield a lesser (i.e., more conservative) dilution at the intake. Thus, the accidental spill is modeled as a vertical plane source across the width of the main channel.

3. The contaminant concentration profile from a slug release is assumed to be Gaussian (i.e.,

normal) in the longitudinal direction.

4. The contaminant is conservative, i.e., it does not degrade through radioactive decay, chemical or biological processes, nor is it removed from the reservoir by adsorption to sediments or by volatilization.

5. The transport of the contaminant is described using the motion of the river flow, i.e., the contaminant is neutrally buoyant and does not rise or sink due to gravity.

The main channel and dynamic, flow-dependent processes of the reservoir reach between SQN and the first downstream water intake are modeled as a channel of constant rectangular cross section with the following constant geometric, hydraulic and dispersion characteristics.

Longitudinal distance, x = 10.6 miles Average water surface elevation = 678.5 feet MSL (Figure 2.4.1-34 (1))

Average width, W = 1175 feet 2.4-46

SQN-Average depth, H = 50 feet Average velocity, U (= Q/(W H)) = 0.468 feet per second (fps)

Average travel time (for approximate peak contaminant), t (= x/U) = 1.4 days Manning coefficient n (surface roughness) = 0.03 Longitudinal dispersion parameter, alpha = 200 where: alpha = Ex / (H u)

Ex = constant longitudinal dispersion coefficient (square feet per second) u

shear velocity (fps)

-gRS g

= acceleration due to gravity = 32.174 ft/s 2 R

= hydraulic radius (ft)

S

= slope of the energy line (ft/ft)

The average width and depth were estimated from measurements of 9 cross sections in the reach [4]

(TVA) [5] (TVA). For wide channels (i.e., large width-to-depth ratio), the hydraulic radius can be approximated as the average depth. The value of alpha = 200 is on the conservative (i.e., low) side

[6] (Fischer, et al., 1979). The value of the Manning coefficient n is representative for natural rivers [7]

(Chow, 1959).

The equation used to describe the maximum downstream activity (or concentration), C, at a point of interest due to an instantaneous plane source release of volume V is [8] (Guide 1.113):

C V

CG WH -4

-EX t (2.4.12-1) where:

C, = initial activity (or concentration) in the plant of the released contaminant

= 3.14156 Any consistent set of units can be used on each side of Equation 2.4.12-1 (e.g., C and Co in mCi/mI; V in cf; W and H in ft; E, in ft2/s; t in s).

The term, C/Co, is the relative (i.e., dimensionless) activity (or concentration) and its reciprocal is the dimensionsless dilution factor. Equation 2.4.12-1 simplifies to C/Co = 8.3E-10

V (V expressed in cubic feet (cf)) when the parameters are substituted and the Manning equation [7] (Chow, 1959) is used in the definition of the shear velocity, u. In the substitution, u = 0.028 ft/s and Ex = 282.1 ft2/s.

The equation used to describe the maximum downstream concentration at a point of interest due to a continuous plane source release rate, Qs, where Q, << Q, is [8] (Guide 1.113):

2.4-47

SQN-(2.4.12-2)

C Q_

Co Q

Any consistent set of units can be used on each side of Equation 2.4.12-2 (e.g., C and Co in mCi/ml; Q. and Q in cfs).

Equation 2.4.12-2 simplifies to C/Co = 3.64E-05

Qs (Qs expressed in cfs) for Q = 27,474 cfs.

Examples of quantities and concentrations of potential contaminant releases and the use of Equations 2.4.12-1 and 2.4.12-2 follow. Because C, is defined as the in-plant activity (or concentration) and not that of the diffuser release, an estimate of the dilution of liquid waste occurring in the diffuser pond and diffuser pipes is not needed. This is because the flow available for dilution in the plant (e.g., CCW and ERCW) is taken from and returned to the river. Only effluent extraneous to the river flow requires consideration in the analyses to calculate the dilution. More information on the possible means which liquid waste from the plant enters the diffuser pond is contained in Subsection 10.4.5.

The largest outdoor tanks whose contents flow into the diffuser pond are the two condensate storage tanks (Paragraph 11.2.3.1), which each have an overflow capacity of 398,000 gallons. Liquid waste that reaches the diffuser pond enters the Tennessee River through the diffuser system. The diffuser pond is approximately 2000 feet long and 500 feet wide with a depth that, although it depends on the Chickamauga Reservoir elevation, averages about 10 feet [9] (McIntosh, et al., 1982). The design flow residence time of the pond is approximately one hour (i.e., diffuser design flow is 2,480 cfs at maximum plant capacity [3] [Ungate and Howerton, 1979]).

For example, assume an instantaneous plane source release into the Tennessee River of the contents of one condensate storage drain tank. Assume the full 398,000 gallon (53,210 cf) volume contains Iodine-131 (1-131) at an activity of 1.5E-06 mCi/gm (Table 10.4.1-1). From Equation 2.4.12-1, the activity, C, at the first downstream water intake would be 6.6E-1 1 mCi/gm, which is within the acceptable limit [10] (CFR) for soluble 1-131.

For a continuous plane source release, assume the contents of the 398,000 gallon (53,210 cf) floor drain tank leak out steadily over a 24-hour period. The effective release rate is 0.6 cfs at an activity of 1.5E-06 mCi/gm. The expected activity at the first downstream water intake would be 3.4E-1 1 mCi/gm using Equation 2.4.12-2 and is within the acceptable limit [10] (CFR) for soluble 1-131.

REFERENCES (for Section 2.4.12 only)

[1]

McCold, L. N. (March 1979), "Model Study and Analysis of Sequoyah Nuclear Plant Submerged Multiport Diffuser," TVA, Division of Water Resources, Water System Development Branch, Norris, TN, Report No. WR28-1-45-103.

[2]

EI-Ashry, Mohammed T., Director of Environmental Quality, TVA, February 1983 letter to Paul Davis, Manager, Permit Section, Tennessee Division of Water Quality Control, SEQUOYAH NUCLEAR PLANT---NPDES PERMIT NO. T0026450.

[3]

Ungate, C. D., and Howerton, K. A. (April 1978; revised March 1979), "Effect of Sequoyah Nuclear Plant Discharges on Chickamauga Lake Water Temperatures," TVA, Division of Water Management, Water Systems Development Branch, Norris, TN, Report No. WR28-1-45-101.

[4]

TVA, Chickamauga Reservoir Sediment Investigations, Cross Sections, 1940-1961, Division of Water Control Planning, Hydraulic Data Branch.

[5]

TVA, Measured Cross Sections of Chickamauga Reservoir, 1972, Flood Protection Branch.

[6]

Fischer, H. B., List, E. J., Koh, R.C.Y., Imberger, J., Brooks, N. H. (1979), Mixing in Inland and 2.4-48

SQN-Costal Waters, Academic Press, New York.

[7]

Chow, V. T. (1959) Open-Channel Hydraulics, McGraw-Hill, New York.

[8]

United States Nuclear Regulatory Commission, Office of Standards Development, Regulatory Guide 1.113 (April 1977), "Estimating Aquatic Dispersion of Effluents from Accidental and Routine Reactor Releases for the Purpose of Implementing Appendix I," Revision 1.

[9]

McIntosh, D. A., Johnson, B. E. and Speaks, E. B. (October 1982), "A Field Verification of Sequoyah Nuclear Plant Diffuser Performance Model: One-Unit Operation," TVA, Office of Natural Resources, Division of Air and Water Resources, Water Systems Development Branch, Norris, TN, Report No. WR28-1-45-110.

[10] 10 CFR Part 20, Appendix B, Table II, Column 2.

[11] TVA SQN Calculation SQN-SQS2-0242, SQN Site Iodine-131 Release Concentration in Tennessee River.

2.4.13 Groundwater (HISTORICAL INFORMATTON) 2.4.13.1 Description and Onsite Use The peninsula on which SQN is located is underlain by the Conasauga Shale, a poor water-bearing formation. About 2,000 feet northwest of the plant site, the trace of the Kingston Fault separates this outcrop area of the Conasauga Shale from a wide belt of Knox Dolomite. The Knox is the major water bearing formation of eastern Tennessee.

Groundwater in the Conasauga Shale occurs in small openings along fractures and bedding planes; these rapidly decrease in size with depth, and few openings exist below a depth of 300 feet.

Groundwater in the Knox Dolomite occurs in solutionally enlarged openings formed along fractures and bedding planes and also in locally thick cherty clay overburden.

There is no groundwater use at SQN.

2.4.13.2 Sources The source of groundwater at SQN is recharged by local, onsite precipitation. Discharge occurs by movement mainly along strike of bedrock, to the northeast and southwest, into Chickamauga Lake.

Rises in the level of Chickamauga Lake result in corresponding rises in the water table and recharge along the periphery of the lake, extending inland for short distances. Lateral extent of this effect varies with local slope of the water table, but probably nowhere exceeds 500 feet. Lowering levels of Chickamauga Lake results in corresponding declines in the water table along the lake periphery, and short-term increase in groundwater discharge.

When SQN was initially evaluated in the early 1970s, it was in a rural area, and only a few houses within a two-mile radius of the plant site were supplied by individual wells in the Knox Dolomite (see Table 2.4.13-1, Figure 2.4.13-1). Because the average domestic use probably does not exceed 500 gallons per day per house, groundwater withdrawal within a two-mile radius of the plant site was less than 50,000 gallons per day. Such a small volume withdrawal over the area would have essentially no effect on areal groundwater levels and gradients. Although development of the area has increased, public supplies are available and overall groundwater use is not expected to increase.

Public and industrial groundwater supplies within a 20 mile radius of the site in 1985 are listed in Table 2.4.13-2. The area groundwater gradient is towards Chickamauga Lake, under water table conditions, and at a gradient of less than 120 feet per mile. The water table system is shallow, the surface of which conforms in general to the topography of the land surface. Depth to water ranges from less than 10 feet in topographically low areas to more than 75 feet in higher areas underlain by Knox Dolomite. Figure 2.4.13-2 is a generalized water-table map of SQN, based on water level data from 2.4-49

SQN-five onsite observation wells, and in private wells adjacent to the site in April 1973, and also based on surface resistivity measurements of depth to water table made in 1972.

Because permeability across strike in the Conasauga Shale is extremely low, and nearly all water movement is in a southwest-northeast direction, along strike, the Conasauga-Knox Dolomite Contact is a hydraulic barrier, across which only a very small volume of water could migrate in the event large groundwater withdrawals were made from the adjacent Knox.

Although some water can cross this boundary, the permeability normal to strike of the Conasauga is too low to allow development of an areally extensive cone of depression.

Groundwater recharge occurs to the Conasauga Shale at the plant site. Recharge water moves no more than 3,000 feet before being discharged to Chickamauga Lake.

2.4.13.3 Accident Effects Design features in SQN further protect groundwater from contamination.

Category I structures in the SQN facility are designed to assure that all system components perform their designed function, including maintenance of integrity during earthquake.

Buildings in which radioactive liquids could be released due to the equipment failure, overflow, or spillage are designed to retain such liquids even if subject to an earthquake equivalent to the safe shutdown earthquake. Outdoor tanks that contain radioactive liquids are designed so that if they overflow, the overflow liquid is redirected to the building where the liquid is collected in the radwaste system. Two outdoor tanks that contain low concentrations of radioactivity at times overflow to yard drains which discharge into the diffuser pond. Overflow liquid is discharged near the discharge diffuser.

The capacity for dispersion and dilution of contaminants by the groundwater system of the Conasauga Shale is low. Dispersion would occur slowly because water movement is limited to small openings along fractures and bedding planes in the shale. Clay minerals of the Conasauga Shale do, however, have a relatively high exchange capacity, and some of the radioactive ions would be absorbed by these minerals. Any ions moving through the groundwater system eventually would be discharged to Chickamauga Lake.

The Conasauga Shale is heterogeneous and anisotropic vertically and horizontally. Water-bearing characteristics change abruptly within short distances. Standard aquifer analyses cannot be applied, and meaningful values for permeability, time of travel, or dilution factors cannot be obtained.

Bedrock porosity is estimated to be less than 3 percent based on examination of results of exploratory core drilling. It is known from experience elsewhere in this region that water movement in the Conasauga Shale occurs almost entirely parallel to strike. Subsurface movement of a liquid radwaste release at the plant site would be about 1,000 feet to the northeast or about 2,000 feet to the southwest before discharge to Chickamauga Lake.

Time of travel can only be estimated as being a few weeks for first arrival, a few months for peak concentration arrival, and perhaps two or more years for total discharge. The computed mean time of travel of groundwater from SQN to Chickamauga Lake is 303 days.

No radwaste discharge would reach a groundwater user. At the nearest point, the reservation boundary lies 2,200 feet northwest of the plant site, across strike. Groundwater movement will not occur from the plant site in this direction across this distance.

During initial licensing, the radionuclide concentrations were determined for both groundwater and surface water movement to the nearest potable water intake (Savannah Valley Utility District, which is no longer in service) and found to be of no concern (see Safety Evaluation Report, March 1979, 2.4-50

SQN-Section 2.4.4 Groundwater).

2.4.13.4 Monitoring or Safeguard Requirements SQN is on a peninsula of low-permeability rock; the groundwater system of the site is essentially hydraulically isolated and potential hazard to groundwater users of the area is minimal. The environmental radiological monitoring program is addressed in Section 11.6.

Monitor wells 1, 2, 3, and 4 were sampled and analyzed for radioactivity during the period from 1976 through 1978. Well 5 was not monitored because of insufficient flow. An additional well (Well 6) was drilled in late 1978 downgradient from the plant and a pump sampler installed.

Wells 1, 2, 4, and 5 are each 150 feet deep, Well 6 is 250 feet deep, and Wells L6 and L7 are 75-80 feet deep. All of the wells are cased in the residuum and open bore in the Conasauga Shale.

2.4.13.5 Conclusions SQN was designed to provide protection of groundwater resources by preventing the escape of the leaks of radionuclides. Site soils and underlying geology provide further protection in that they retard the movement of water and attenuate any contaminants that would be released. All groundwater movement is toward Chickamauga Lake. The Knox Dolomite is essentially hydraulically separated from the Conasauga Shale; therefore, offsite pumping, including future development, should have little effect upon the groundwater table in the Conasauga Shale at the plant.

Even though the potential for accidental contamination of the groundwater system is extremely low, the radiological monitoring program will provide ample lead times to mitigate any offsite contamination.

As a consequence of the geohydrologic conditions that remain unchanged from evaluations conducted in the 1970s, the information in Chapter 2.4.13 Groundwater is historical and should not be subject to updating revisions.

2.4.14 TchRni*al Reguircments aRnd Em-ergenY OperationFlooding Protection Requirements E*m.RGcncy flood protecti.

plans, designed to minimize impact of floodS above plant grade on safety ilated facilities, a le deslribld in Appendix 2A.IA.

Proeenlidurei for predicting rainfall floods, arrangements to Warn Of upStream d-am failure floods, and lead times available and typcs of action to bhe taken to mect related safety requirements for both SOUrcos of flooding aro described therein. The Technical RcqUircments Manual specify the action to be takcn to mini~mize the consequences et fleeds.The plant grade elevation at SQN can be exceeded by large rainfall and seismically-induced dam failure floods. Assurance that SQN can be safely shut down and maintained in these extreme flood conditions (Section 2.4.2.2 and this Section 2.4.14) is provided by the discussions given in Sections 3.4, 3.8.1, and 3.8.4.

2.4A.-2.4.14.1 Introduction This appeR subsection describes the methods by which the Sequeyah Nuc'ear PRantSQN will be made capable of tolerating floods above plant grade without jeopardizing public safety. Since flooding of this magnitude, as explained in seetien-24,Sections 2.4.2 and 2.4.4, is most unlikely, extreme steps are considered acceptable including actions that create or allow extensive economic damage to the plant. The actions described herein will be implemented for floods ranging from slightly below plant grade, to allow for wave runupT to the Design Basis Flood (DBF).

2.4A.42.4.14.1.1 Design Basis Flood The DBF is the calculated upper limit flood that includes the probable maximum flood (PMF) plus the wave runup caused by a 45-mile-per-hour overwater wind; this is discussed in subsection 2.4.3.6. The table below gives representative levels of the DBF at different plant locations.

2.4-51

SQN-Design Bases Flood (DBF) Levels Probable maximum flood (still reservoir) 74-9.722.0 ft DBF runup on Diesel Generator Building 723.2 ft DBF runup on vertical external, unprotected walls 7-2=3.726.2 ft DBF surge level within flooded structures 720.4722.5 ft The lower flood elevations listed above are actual DBF elevations and are not normally used for the purpose of design but are typically used in plant procedures including procedures which direct plant actions in response to postulated DBF. For purposes of designing the flood protection for systems, structures, and components, the following higher elevations should be used thus ensuring additional margin has been included in the development of design analysis.

Design Analysis Flood Levels Maximum still reservoir 723.5 ft Runup on vertical external, unprotected walls 729.5 ft Surge level within flooded structures 724.0 ft See FSAR-References 2AA-40--11[271 and 2AA

[0 2r281.

In addition to level considerations, plant flood preparations will cope with the "fastest rising" flood which is the calculated flood that can exceed plant grade with the shortest prediction notice. Reservoir levels for large floods in the Tennessee Valley can be predicted well in advance.

A minimum of 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months , divided into two stages, is provided for safe plant shutdown by use of this prediction capability. Stage I, a minimum of 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months long, will commence upon a prediction that flood-producing conditions might develop. Stage II, a minimum of 17 hours1.967593e-4 days 0.00472 hours 2.810847e-5 weeks 6.4685e-6 months long, will commence on a confirmed estimate that conditions will provide a flood above plant grade. This two-stage scheme is designed to prevent excessive economic loss in case a potential flood does not fully develop. Refer to Section 2.4.14.4.

24A-4_.22.4.14.1.2 Combinations of Events Because floods above plant grade, earthquakes, tornadoes, or design basis accidents, including a loss-of-coolant accident (LOCA), are individually very unlikely, a combination of a flood plus any of these events or the occurrence of one of these during the flood recovery time or of the flood during the recovery time after one of these events is considered incredible.

Surges from seismic, failur of upstream. dams, however, can oxe

.d plant grade, but to I.wer.. DBF levels, when imposed coincident With Wind and cortain floods. A MRn~imwn 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months of warning is as.ur.d so that ample t*me 6 available to pr..paro the plant foflooding. However, as an exception, certain reduced levels of floods are considered together with seismic events. Refer to Section 2.4.14.10 and 2..4.

2AA--*32.4.14.1.3 Post Flood Period Because of the improbability of a flood above plant grade, no detailed procedures will be established for return of the plant to normal operation unless and until a flood actually occurs. If flood mode operation (subsec'tin.2.

Section 2.4.14.2) should ever become necessary, it will be possible to maintain this mode of operation for a sufficient period of time (100 days) so that appropriate recovery steps can be formulated and taken. The actual flood waters are expected to recede below plant grade within 1 to 6 days.

2.4-52

SQN-2AA 42.4.14.1.4 Localized Floods Localized plant site flooding due to the probable maximum storm (subsection 2..3Section 2.4.2.3) will not enter vital structures or endanger the plant. Plant shutdown will be forced by water ponding on the switchyard and around buildings, but this shutdown will not differ from a loss of offsite power situation as described in Chapter 15. The other steps described in this appeRdsubsection are not applicable to this case. Refer to Section 2.4.2.3.

2.4A.22.4.14.2 Plant Operation During Floods Above Grade "Flood mode" operation is defined as the set of conditions described below by means of which the plant will be safely maintained during the time when flood waters exceed plant grade (elevation 705.0 ft) and during the subsequent period until recovery (subsection 2.I Section 2.4.14.7) is accomplished.

2.4A242.4.14.2.1 Flooding of Structures Qoly-4heThe Reactor Building, the Diesel Generator Building (DGB), and the Essential Raw Cooling Water Intake Station will be maintained dry during the flood mode. Walls and penetrations are designed to withstand all static and dynamic forces imposed by the DBF.

The lowest floor of the DGB is at elevation 722.0 ft with its doors on the uphill side facing away from the main body of flood water. This celvation is lower th1n thc prcv'ius DBF e!cvation of 722.6. The 1998 reanalysis determined the still wate. With the PMF elevation te 71-.6 f 722.0 ft, wi4h-wind wave runup at the DGB teis elevation 721-1.8723.2 ft. Therefore, flood levels de-et-exceed floor elevation of 722.0 ft. The entrances into safety-related areas and all mechanical and electrical penetrations into safety-related areas are sealed either prior to or during flood mode to prevent major leakage into the building for water up to the PMF, including wave runup. Du-o to thc 998 reanalysis this only applies to below grade features. Redundant sump pumps are provided within the building to remove minor leakage.

The Essential Raw Cooling Water (ERCW) intake station is designed to remain fully functional for floods up to the PMF, including wind-wave runup. The deck elevation (elevation 720.0 ft) is below the PMF plus wind wave runup, but it is protected from flooding by the outside walls. The traveling screen wells extend above the deck elevation up to the design basis surge level. The wall penetration for water drainage from the deck in nonflood conditions is below the DBF elevation, but it is designed for sealing in event of a flood. All other exterior penetrations of the station below the PMF are permanently sealed. Redundant sump pumps are provided on the deck and in the interior rooms to remove rainfall on the deck and water seepage.

All other structures, including the service, turbine, auxiliary, and control buildings, will be allowed to flood as the water exceeds their grade level entrances. All equipment, including power cables, that is located in these structures and required for operation in the flood mode is either above the DBF or designed for submerged operation.

2.4A.2.22.4.14.2.2 Fuel Cooling Spent Fuel Pit Fuel in the spent fuel pit will be cooled by the normal Spent Fuel Pit Cooling (SFPC) System. The pumps are located on a platform at elevation 721.0 ft which is abey'ebelow the surge level of 72.1elevation 722.5 ft. However, the pumps are located in an enclosure that provides flooding protection up to elevation 724.5 ft. During the flood mode of operation, heat will be removed from the heat exchangers by ERCW instead of component cooling water.

As a backup to spent fuel cooling, water from the Fire Protection (FP) System can be dumped into the spent fuel pool, and steam removed by the area ventilation system.

2.4-53

SQN-Reactors Residual core heat will be removed from the fuel in the reactors by natural circulation in the Reactor Coolant (RC) system. Heat removal from the steam generators will be accomplished by adding river water from the FP System (subsection 9.5.1) and relieving steam to the atmosphere through the power relief valves. Primary system pressure will be maintained at less than 500 lb/in 2g by operation of the pressurizer relief valves and heaters. This low pressure will lessen leakage from the system.

Secondary side pressure will be maintained at or below 90 psig by operation of the steam line relief valves.

An analysis has been performed to ensure that the limiting atmospheric relief capacity would be sufficient to remove steam generated by decay heat. At times beyond approximately 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months following shutdown of the plant two relief valves have sufficient capacity to remove the steam generated by decay heat. Since a minimum of 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months flood warning is available it is concluded that the plant could be safely shutdown and decay heat removed by operation of only two relief valves.

Reference FSAR 2.A.1&A4[271.

The main steam power operated relief valves will be adjusted to maintain the steam pressure at or below 90 psig. If this control system malfunctions, then the controls in the main control room can be utilized to operate the valves in an open-closed manner. Also, a manual loading station and the relief valve handwheel provide additional backup control for each relief valve. The secondary side steam pressure can be maintained for an indefinite time by the means outlined above.

The cooling water flow paths conform to the single failure criteria as defined in FSAR Section 3.1.1. In particular, all active components of the secondary side feedwater supply and ERCW supply are redundant and can therefore tolerate a single failure in the short or long term. A passive failure, consistent with the 50 gpm loss rate specified in FSAR Section 3.1.1, can be tolerated for an indefinite period without interrupting the required performance in either supply.

If one or both reactors are open to the containment atmosphere as during the refueling operations, then the decay heat of any fuel in the open unit(s) and spent fuel pit will be removed in the following manner. The refueling cavity will be filled with borated water (approximately 2000 ppm boron concentration) from the refueling water storage tank. The SFPC System pump will take suction from the spent fuel pit and will discharge to the SFPC System heat exchangers. The SFPC System heat exchanger output flow will be directed by a piping connection to the Residual Heat Removal (RHR)

System heat exchanger bypass line. The tie-in locations in the SFPC System and the RHR System are shown in Figures 9.1.3-1 and 5.5.7-1, respectively. This connection will be made using prefabricated, in-position piping which is normally disconnected. During flood mode preparations, the piping will be connected using prefabricated spool pieces.

Prior to flooding, valve number 78-513 (refer to Figure 9.1.3-1) and valves FCV 74-33, and 74-35 (refer to Figure 5.5.7-1) will be closed; valves HCV 74-36, 74-37, FCV 74-16, 74-28, 63-93, and 63-94 (refer to Figure 5.5.7-1 and 6.3.1-1)will be opened or verified open. This arrangement will permit flow through the RHR heat exchangers and the four normal cold leg injection paths to the reactor vessel.

The water will then flow downward through the annulus, upward through the core (thus cooling the fuel), then exit the vessel directly into the refueling cavity. This results in a water level differential between the spent fuel pit and the refueling cavity with sufficient water head to assure the required return flow through the 20-inch diameter fuel transfer tube thereby completing the path to the spent fuel pit.

Except for a portion of the RHR System piping, the only RHR System components utilized below flood elevation are the RHR System heat exchangers. Inundation of these passive components will not degrade their performance for flood mode operation. After alignment, all valves in this cooling circuit located below the maximum flood elevation will be disconnected from their power source to assure that they remain in a safe position.

The modified cooling circuit for open reactor cooling will be assured of two operable SFPC System 2.4-54

SQN-pumps (a third pump is available as a backup) as well as two SFPC System heat exchangers. Also, the large RHR System heat exchangers are supplied with essential raw cooling water during the open reactor mode of fuel cooling; these heat exchangers provide an additional heat sink not available for normal spent fuel cooling.

Fuel coolant temperature calculations, assuming conservative heat loads and the most limiting, single active failure in the SFPC System, indicate that the coolant temperatures are acceptable.

The temperatures can be maintained at a value appreciably less than the fuel pit temperature calculated for the nonflood spent fuel cooling case when assuming the loss of one equipment train.

As further assurance, the open reactor cooling circuit was aligned and tested, during pre-operational testing, to confirm flow adequacy. Normal operation of the RHR System and SFPC System heat exchangers will confirm the heat removal capabilities of the heat exchangers.

High spent fuel pit temperature will cause an annunciation in the MCR, thus indicating equipment malfunction. Additionally, that portion of the cooling system above flood water will be frequently inspected to confirm continued proper operation.

For either mode of reactor cooling, leakage from the Reactor Coolant System will be collected, to the extent possible, in the reactor coolant drain tank; nonrecoverable leakage will be made up from supplies of clean water stored in the four cold leg accumulators, the pressurizer relief tank, the cask decontamination tank, and the demineralized water tank. If these sources prove insufficient, the FP System can be connected to the Auxiliary Charging System (subsection 9.3.5) as a backup. Whatever the source, makeup water will be filtered, demineralized, tested, and borated, as necessary, to the normal refueling concentration, and pumped by the Auxiliary Charging System into the reactor (see Figures 2-A-.22.4.14-1 and 2AA 32.4.14-2).

9(wef ElFcIticepeor Will be supplied by the OnSite diesel gonorators 6taFting at the beginRing of Stage I! Or

'hcn offsite power is lost, whicheve, r o.ur.s fi*'t (subsectin 2.4A.5.3).

2.4.14.2.3 Cooling of Plant Loads Plant cooling requirements, with the exception of the FP System which must supply feedwater to the steam generators, will be met by the ERCW System (refer to subsectienSection 9.2.2).

2.4.14.2.4 Power Electric power will be supplied by the onsite diesel generators starting at the beginning of Stage II or when offsite power is lost, whichever occurs first (Section 2.4.14.5.3).

2.4.14.2.5 Plant Water Supply The plant water supply is thoroughly discussed in suseeGtieiSection 9.2.2. The following is a summary description of the water supply provided for use during flooded plant conditions. The ERCW station is designed to remain fully functional for all floods up to and including the DBF. The CCW intake forebay will provide a water supply for the fire/flood mode pumps. If the flood approaches DBF proportions, there is a remote possibility that Chickamauga Dam will fail. Such an event would leave the Sequoyah Plant CCW intake forebay isolated from the river as flood water recedes below EL 665.

Should this event occur, the CCW forebay has the capacity of retained water to supply two steam generators in each unit and provide spent fuel pit with evaporation makeup flow until CCW forebay inventory makeup is established. The ERCW station is designed to be operable for all plant conditions and includes provisions for makeup to the forebay. Reference FSAR 2-4A.1-1[27].

24A.32.4.14.3 Warning PlaRScheme 2.4-55

SQN-See Section 2.4.14.8 (Warning Plan).

Pla*t grade elevation. 705 can be eXceeded by both rainfall floods and seismic caused dam. failu, r

floods. A warning plan is nceded to assure plant safety fromn these floods 2.4A.3.1 Rainfall Floods PFte*tioRn of the Sequ'yah Plant from the lW pFrobability rainfall floods that might eXeed plant gfrade depends on a flood warning issued by TVA's RiVer OpeFations as desc-ribedh in Secnfion 224A8. W 1ith TVA's extensive climate monitoringand flood predictig*

systems and flood control facilitie., flo+d. in the Se.u.yah area can be reliably predicted well in advance. The Sequoyah Nuclear Plant flotd a,-ing plan will pro.vide a minimum preparation time of 27 ho urS including a 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months ma*rin for operation in the flood mode. Four additional, preceding hours will provide time to gather data and pro4dUce the waring. The wa.ring plan w-llhbe divided intO MG stages the first a mini;mum o.. f 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months long and the second of 17 hours1.967593e-4 days 0.00472 hours 2.810847e-5 weeks 6.4685e-6 months so that unnecessary economic penalty can be avoided while adequate time is ensured. for preparing for operation in the lood, m.-,,4.

The first stage, Stage 1, of shutdown will begin when there is suffic~ient rainfall onA the ground in the upstream watershed t yi4eld a projected plant site wate+r level of 6,97 in. the w.inter months (October 1 through April 1) aRnd 703 in the 6umme*

(April 16 through September 30). This assuF6e that the ad-ditionAal. time rouirFed is aV-ail-able whe.

htow...ntitd The wa;ter level of 703 (two feet beo plant grade) will allow imargin so that waves due to high Winds ca*nnot disrupt the 9fod mnde preparation;. Stage 1 will allow preparation steps causing some damage to be sustained but will w:ithhold major ecnRomc*

damage until the Stage II warning assures a f,,fh-ominRg flood above grade.

The plant preparation status will be held at Stage I until either Stage II begins or TVA's Rive Operations determines that floo waters.will not eXceed eleevation 703 at the plant. The Stage II

.:anig will be issued only when eno)ugh rain has fallen to predict that elevationR 703 is likely to be eXoeeded-2.4A.3.2 Seismoic Dam Fai!ure Floods Protection of the S

,quyah plaRt from flood waves generated by seisFmh* Glly caused dam-failures

.hih exceed plant grade depends on WA's River Operation eoganization to identify when a critical combination of dam failures -and-flooedis exi~st. The-re are nine upstreamn dams, whose failure, in combination coincident With ce~taiR storm conditions, would cause a flood to exceed plant grade These dams are Norris, Cherokee, Douglas, PFot Loudoun, Fon)tana, Hiwassee, Apalachia, Blue Ridge, and Tellico.

2-4A42.4.14.4 Preparation for Flood Mode An abnormal operating instruction is available to support operation of the plant.

At the time the initial flood warning is issued, the plant may be operating in any normal mode. This means that either or both units may be at power or either unit may be in any stage of refueling.

24A-4-.-2.4.14.4.1 Reactors Initially Operating at Power If both reactors are operating at power, Stage I and then, if necessary, Stage II procedures will be initiated. Stage I procedures will consist of a controlled reactor shutdown and other easily rounkablerevocable steps such as moving supplies necessary to the flood protection plan above the DBF level and making temporary connections and load adjustments on the onsite power supply.

Stage II procedures will be the less easily Fevokablerevocable and more damaging steps necessary to have the plant in the flood mode when the flood exceeds plant grade. The fire/flood mode pumps may supply auxiliary feedwater for reactor cooling (Refere-i.[)291. Other essential plant cooling loads will be transferred from the component cooling water to the ERCW System (subsection 9.2.2). The Radioactive Waste (Chapter 11) System will be secured by filling tanks below DBF level with enough water to prevent flotation; one exception is the waste gas decay tanks, which are sealed and anchored 2.4-56

SQN-against flotation. The CVCS hold up tank will also be filled and sealed to prevent flotation. Some power and communication lines running beneath the DBF and not designed for submerged operation will require disconnection. Batteries beneath the DBF will be disconnected.

2 4A422.4.14.4.2 Reactor Initially Refuelinq If time permits, fuel will beis removed from the unit(s) undergoing refueling and placed in the spent fuel pit; otherwise fuel cooling will be accomplished as described in subsection 2.4A.2.2Section 2.4.14.2.2.

If the refueling canal is not already flooded, the mode of cooling described in sub~eGtion

24AA2 2Section 2.4.14.2.2 requires that the canal be flooded with borated water from the refueling water storage tank. If the flood warning occurs after the reactor vessel head has been removed or at a time when it could be removed before the flood exceeds plant grade, the flood mode reactor cooling water will flow directly from the vessel into the refueling cavity. If the warning time available does not permit this, then the upper head injection piping will be disconnected above the vessel head to allow the discharge of water through the four upper head injection standpipes. Additionally, it is required that the prefabricated piping be installed to connect the RHR and SFPC Systems, and that ERCW be directed to the secondary side of the RHR System and SFPC System heat exchangers.

2.4A-.132.4.14.4.3 Plant Preparation Time All steps needed to prepare the plant for flood mode operation can be accomplished within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months of receipt of the initial warning that a flood above plant grade is possible. An additional 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months are available for contingency margin before wave runup from the rising flood might enter the buildings.

Site grading and building design prcvcnt any flooding bcforce the end of thc 27 hour: preflood pcriod-.

2.4A.52.4.14.5 Equipment Both normal plant components and specialized flood-oriented supplements will be utilized in coping with floods. All such equipment required in the flood mode is either located above the DBF or is within a nonflooded structure or is designed for submerged operation. Systems and components needed only in the preflood period are protected only during that period.

2.4A.542.4.14.5.1 Equipment Qualification To ensure capable performance in this highly unlikely but rigorous, limiting design case, only high quality components will be utilized. Active components are redundant or their functions diversely supplied. Since no rapidly changing events are associated with the flood, repairability offers reinforcement for both active and passive components during the long period of flood mode operation.

Equipment potentially requiring maintenance will be accessible throughout its use, including components in the Diesel Generator Building.

2.4A.5.22.4.14.5.2 Temporary Modification and Setup Normal plant components used in flood mode operation and in preparation for flood mode operation may require modification from their normal plant operating configuration. Such modification, since it is for a limiting design condition and since extensive economic damage is acceptable, will be permitted to damage existing facilities for their normal plant functions. However, most alterations will be only temporary and nondestructive in nature. For example, the switchover of plant cooling loads from the component cooling water to the ERCW System will be done through valves and a prefabricated spool piece, causing little system disturbance or damage.

Equipment especially provided for the flood design case includes both permanently installed components and more portable apparatus that will be emplaced and connected into other systems during the preflood period.

Detailed procedures to be used under flood mode operation have been developed and are incorporated in the plant's Abnormal Operating Instructions.

2.4-57

SQN-2AA5.32.4.14.5.3 Electric Power Because there is a possibility that high winds may destroy powerlines and disconnect the plant from offsite power at any time during the preflood transition period, only onsite power will be used once Stage II of the preparation period begins. While most equipment requiring alternating current electric power is a part of the permanent emergency onsite power system, other components will be temporarily connected, when the time comes, by prefabricated jumper cables.

All loads that are normally supplied by onsite power but are not required for the flood will be switched out of the system during the preflood period. Those loads used during the preflood period but not during flood mode operation will be disconnected when they are no longer needed. During the preparation period, all power cables running beneath the DBF level, except those especially designed for submerged operation, will be disconnected from the onsite power system. Similarly, direct current electric power will be disconnected from unused loads and potentially flooded lines. Charging will be maintained for each battery by the onsite alternating current power system as long as it is required.

Batteries that are beneath the DBF will be disconnected during the preflood period when they are no longer needed.

2.4A..42.4.14.5.4 Instrument Control, Communication and Ventilation Systems All instrument, control, and communication lines that will be required for operation in the flood mode are either above the DBF or within a nonflooded structure or are designed for submerged operation.

Unneeded cables that run below the DBF will be disconnected to prevent short circuits.

Redundant means of communications are provided between the central control area (the main and auxiliary control rooms) and all other vital areas that might require operator attention, such as the Diesel Generator Building.

Instrumentation is provided to monitor all vital plant parameters such as the reactor coolant temperature and pressure and steam generator pressure and level. Control of the pressurizer heaters and relief valves and steam generator feedwater flow and atmospheric relief valves will ensure continued natural circulation core cooling during the flood mode. All other important plant functions will be either monitored and controlled from the main control area or, in some cases where time margins permit, from other points in the plant that are in close communication with the main control area. Ventilation, when necessary, and limited heating or air-conditioning will be maintained for all points throughout the plant where operators might be required to go or where required by equipment heat loads.

2-.4A.62.4.14.6 Suplies All equipment and most supplies required for the flood are on hand in the plant at all times. Some supplies will require replenishment before the end of the period in which the plant is in the flood mode.

In such cases supplies on hand will be sufficient to last through the short time (sub*eetie 2

3Section 2.4.14.1.3) that flood waters will be above plant grade and until replenishment can be supplied. For instance, there is sufficient diesel generator fuel available at the plant to last for 3 or 4 weeks; this will allow sufficient margin for the flood to recede and for transportation routes to be reestablished.

2 4A-72.4.14.7 Plant Recovery The plant is designed to continue safely in the flood mode for 100 days even though the water is not expected to remain above plant grade for more than 1 to 6 days. After recession of the flood, damage will be assessed and detailed recovery plans developed. Arrangements will then be made for reestablishment of offsite power and removal of spent fuel.

The 100-day period provides more than adequate time for the development of procedures for any maintenance, inspection, or installation of replacements for the recovery of the plant or for a continuation of flood mode operations in excess of 100 days. A decision based on economics will be 2.4-58

SQN-made on whether or not to regain the plant for power production. In either case, detailed plans will be formulated after the flood, when damage can be accurately assessed.

2.4A.92.4.14.8 Basis For Flood ProtecGtio*

Plan In Rainfall FlooWarninq Plan Plant grade elevation 705.0 ft can be exceeded by both rainfall floods and seismic-caused dam failure floods. A warning plan is needed to assure plant safety from these floods.

The warning plan is divided into two stages: Stage I, a minimum of 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months long and Stage II, a minimum of 17 hours1.967593e-4 days 0.00472 hours 2.810847e-5 weeks 6.4685e-6 months so that unnecessary economic consequences can be avoided, while adequate time is allowed for preparing for operation in the flood mode. Stage I allows preparation steps causing minimal economic consequences to be sustained but will postpone manor economic damage until the Stage II warning forecasts a likely forthcoming flood above elevation 703.0 ft.

2.4.14.8.1 Rainfall Floods Protection of the Sequoyah Plant from the low probability rainfall floods that might exceed plant grade depends on a flood warning issued by TVA's River Operations (RO). With TVA's extensive climate monitoring and flood forecasting systems and flood control facilities, floods in the Sequoyah area can be reliably predicted well in advance. The SQN flood warning plan will provide a minimum preparation time of 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months including a 3 hour3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months margin to prepare for operation in the flood mode. Four additional, preceding hours will provide time to gather data and produce the warning.

The first stage, Stage I, of shutdown will begin when there is sufficient rainfall on the ground in the upstream watershed to yield a forecasted plant site water level of 694.5 ft in the winter months and 699.0 ft in the summer. This assures that the additional time required is available when shutdown is initiated. The water level of 703.0 ft (two feet below plant grade) will allow margin so that waves due to high winds cannot disrupt the flood mode preparation. Stage I will allow preparation steps causing some damage to be sustained but will withhold maior economic damage until the Stage I1 warning assures a forthcoming flood above grade.

The plant preparation status will be held at Stage I until either Stage I1 begins or TVA's RO determines that flood waters will not exceed elevation 703.0 ft at the plant. The Stage II warning will be issued only when enough rain has fallen to predict that elevation 703.0 ft (winter or summer) is likely to be exceeded.

2.4.14.8.2 Seismically-Induced Dam Failure Floods Four postulated combinations of seismically induced dam failures and coincident storm conditions were shown to result in floods which could exceed elevation 703.0 ft at the plant. SQN's notification of these floods utilizes TVA's RO forecast system to identify when a critical combination exists. Stage I shutdown is initiated upon notification that a critical dam failure combination has occurred or loss of communication prevents determining a critical case has not occurred. Stage I shutdown continues until it has been determined positively that critical combinations do not exist. If communications do not document this certainty, shutdown procedures continue into Stage II activity. Stage I1 shutdown continues to completion or until lack of critical combinations is verified.

.... mar.2.4.14.9 Basis For Flood Protection Plan In Rainfall Floods 2.4.14.9.1 Overview Large Tennessee River floods can exceed plant grade elevation 705.0 ft at S..uoyah Nucl,'r PaRatSQN. Plant safety in such an event requires shutdown procedures which may take 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months to implement. TVA flood forecast procedures will provide at least 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months of warning before river levels reach elevation 703.0 ft. Use of elevation 703.0 ft, 2 feet below plant grade, provides enough freeboard to prevent waves from 45-mile-per-hour, overwater winds from endangering plant safety during the final hours of shutdown activity. For conservatism the fetches calculated for the PMF (Figures 2.4.3-14-24 and 2.4.3-4-625) were used to calculate maximum wind wave additive to the 2.4-59

SQN-reservoir surface at elevation 703.0 ft feet--msl. The maximum wind additive to the reservoir surface would be 2-.S4.2 feet and would not endanger plant safety during the final hours of shutdown. This is due to the long shallow approach and the waves breaking at the perimeter road (elevation 705.0 ft4eet msl). After the waves break there is not sufficient depth or distance between the perimeter road and the safety-related facilities for new waves to be generated. Forecast will be based upon rainfall already reported to be on the ground.

Different target river level criteria are needed for winter use and for summer use to allow for seasonally varied reservoir levels and rainfall potential.

To be certain of 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months for preflood preparation, warnings of floods with the prospect of reaching elevation 703.0 ft must be issued early; consequently, some of the warnings may later prove to have been unnecessary. For this reason preflood preparations are divided into two stages. Stage I steps, requiring 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months , would be easily revokablerevocable and cause minimum damage. The estimated probability is less than 0.0026small that a Stage I warning will be issued during the 40-year-life of the plant.

Additional rain and stream-flow information obtained during Stage I activity will determine if the more damaging steps of Stage II need to be taken with the assurance that at least 17 hours1.967593e-4 days 0.00472 hours 2.810847e-5 weeks 6.4685e-6 months will be available before elevation 703.0 ft is reached. The estimated probability of a Stage II warning during the life of the plant is less tha.Q0010 thnat shutdown will need to continue inRt Stage 11 during plant lifevery small.

Flood forecasting and warnings, to assure adequate warning time for safe plant shutdown during floods, will be conducted by Ric. Operatiens f River System

,OpeationsTVA's RO.

2.4.14.9.2 TVA Forecast System (H ISTORCAL INFORMATION)

TVA has in constant use an extensive, effective system to forecast flow and elevation as needed in the Tennessee River Basin. This permits efficient operation of the reservoir system and provides warning of when water levels will exceed critical elevations at selected, sensitive locations which includes SQN.

Elements of the present (20042012) forecast system above Sequoyah Nuc!ear PlantSQN include the following:

1.

One hundred sixty (160)More than 100 rain gages measure rainfall, with an average density of 465about 200 square miles per rain gage. Of these gages 112 are Ownd by TVA, 35 are owned by the National Weather Scr.'icc (ISMS), 7 aro ownod by the United Stater, Geological Seprdice (USGS), 2 are owned by the United States Corps of Engineers (USACE), and 4 are owned by Aircea. Most of these gages are tipping buckets collector type and the transmission

-of the-dAta isb either by satellite or telephone. At some of the gages located at hydrOplants, the data is manually read.All are Geostationary Operational Environmental Satellites (GOES)

Data Collection Platform (DCP) satellite telemetered gages.

Information Rnormally is roeived daily from the gages. at 6 a.mh. and at least eVerY 6 hqurs during flood periods. Close interval rainfall reports can be obtained fromA a majority Of the g

r IAll of the rainfall -gages transmit hourly rainfall data.

Streamflow data are received for 3523 gages from 16 TVA gages amd 19 USGS gages.

Those gages trasmit their dat eihrb atellite Or telephone or both-., Discharge data are 2.

rFGive*o *nrm 2_ nynronnl.nte iSTno.

Oh

plnan, 25 a1o6 tranRmfI nuauwonater elelvation alta, andi 13 transmnit tailWateF elevation data. Therefore, steamnflio da;ta ;;areavalable from6 during flood

.P..at.....in the system. All are GOES Data Collection Platform satellite telemetered gages. The satellite gages transmit 15-minute stage data every hour during normal operations.

2.4-60

SQN-

3.

Real-time headwater elevation, tailwater elevation, and discharge data are received from 21 TVA hydro proiects (Watts Bar, Melton Hill, Fort Loudoun, Tellico, Norris, Douglas, Cherokee, Fort Patrick Henry, Boone, Watauga, Wilbur, South Holston, Chickamauga, Ocoee No. 1, Ocoee No. 2, Ocoee No. 3, Blue Ridge, Apalachia, Hiwassee, Chatuge and Nottely) and hourly data are received from non-TVA hydro plants (Chilhowee, Cheoah, Calderwood and Santeetlah).

34.

Weather forecasts including quantitative precipitation forecasts are received few imesat least twice daily and at other times when changes are expected.

45.

Computer programs which translate rainfall into streamflow based on current runoff conditions and which permit a forecast of flows and elevations based upon both observed and predicted rainfall. Two sepatateA network of UNIX servers and personal computers are utilized and are designed to provide backup for each other. One computer is used primarily for data collection, with the other used for executing forecasting programs for reservoir operations. The time interval between receiving input data and producing a forecast is less than 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months . Forecasts normally cover at least a 8three-day period.

As effective as the forecast system already is, it is constantly being improved as new technology provides better methods to interrogate the watershed during floods and as the watershed mathematical model and computer system are improved. Also, in the future, improved quantitative precipitation forecasts may provide a more reliable early alert of impending major storm conditions and thus provide greater flood warning time.

The TVA feFca*St ccnt-o is manned 24 h.ous a day. No"rmal oprFation prdUcS,*

w ho forccasts daily, one by 12 noon based on data collected at 6 a.mR. Ccntral time, and the second by 4 A. m. based o data collected at mnidnight Centfral Time. When serious flood situations demand, forecaStS are produced eVery 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months .

2.4.14.9.3 Basic Analysis Toevelop aThe forecast procedure to assure safe shutdown of scqu.yah Nuclear PlantSQN for flooding-4-7 is based upon an analysis of nine hypothetical PMP storms, incudi;g tho*i antecedet*

storms, were analyzed. They up to PMP magnitude. The storms enveloped potentially critical areal and seasonal variations and time distributions of rainfall. To be certain that fastest rising flood conditions were included, the effects of varied time distribution of rainfall were tested by alternatively placing the maximum daily PMP efin the fiFsPthe middle7 and the last day of the 3three-day main storm. In eah* day the m;aXi mum 6-hour depth was placed during the secend inte,'al except when the maximum daily rain was placed on the last day. Then the maximum 6 hour6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months amount was placed in the last 6 hew*s.Earlier analysis of 17 hypothetical storms demonstrated that the shortest warning times resulted from storms in which the heavy rainfall occurred on the last day and that warning times were significantly longer when heavy rainfall occurred on the first day. Therefore, heavy rainfall on the first day was not reevaluated. The warning system is based on those storm situations which resulted in the shortest time interval between watershed rainfall and elevation 703.0 ft at SQN, thus assuring that this elevation could be predicted at least 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months in advance.

The procedures used to compute flood flows and elevations are described in subsections 2.4.3.1, 2.4.3.2, and 2.4.3.3 Section 2.4.3. Some flood events, were analyzed using earlier versions of the Wateshed, moAdel described in sub..ectioen 22.4.3.3.

Those events which eotablished impertant elements of the warning system or tho-s-e whe-re the present model might produce significant d-iffe~renes, in w.arning times have been reevaluated. EvYent6 reevaluated have been noted either iR t~ablesF-or figures where appropriate.

The warniRg system is based en these sterm situations which resulted inthe shortest time,n-er...

betw.e. waterhed rainfall and-elevatin 703, thus assuring that this

,levati*,

could be predicted at lest27 hours in advance.

2.4.14.9.4 Hydrologic Basis for Warning System 2.4-61

SQN-A minimum of 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months has been allowed for preparation of the plant for operation in the flood mode, three hours more than the 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months needed. An additional 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months for communication and forecasting computations are provided to allow TVA's RO to translate rain on the ground to river elevations at the plant. Hence, the warning plan must provide 31 hours3.587963e-4 days 0.00861 hours 5.125661e-5 weeks 1.17955e-5 months from arrival of rain on the ground until GlitiGaI elevation 703.0 ft could be reached. The 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months allowed for shutdown at the plant are utilized for a minimum of 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months of Stage I preparation and an additional 17 hours1.967593e-4 days 0.00472 hours 2.810847e-5 weeks 6.4685e-6 months for Stage II preparation that is not concurrent with the Stage I activity. This 27 hour3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months allocation includes a 3-hour margin.

Although river elevation 703.0 ft, 2 feet below plant grade to allow for wind waves, is critical during final stages of plant shutdown for flooding, lower forecast target levels are used in most situations to assure that the 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months preflood transition interval will always be available. The target river levels differ with season.

During the October 1 through April 15 "winter" season, Stage I shutdown procedures will be started as soon as target river elevation 6W7694.5 ft has been forecast. ShutdownStage I1 shutdown will be initiated and carried to completion if and when target river elevation 703.0 ft at SQN has been forecast.

Corresponding target river elevations for the April 16 through September 30 "summer" season at SQN is 703 are elevation 699.0 ft and elevation 703.0 ft. The one target river elevation in the summer season peFrmit waiting to initiate shutdown procc3dUres until enough rain is On the ground to forecas reaching critical elcvatiOn 703-- shutdoWn would then be initiated and carried to comnpletion.

Inasmuch as the hydrologic procedures and target river elevations have been designed to provide adequate shutdown time in the fastest rising flood, longer times will be available in other floods. In such cases there w4I#may be a waiting period after the Stage 1, 10-hour shutdown activity during which activities shall be in abeyance until it iG predicted f.ro recorded rainfall that Stage I

Shutdown should be implemented Or it is deter:mF*ed f.ro.m wther

.onditios that plant operation can be resumed weather conditions determine if plant operation can be resumed, or if Stage II shutdown should be implemented.

Resumption of plant operation following Stage I shutdown activities will be allowable only after flood levels and weather conditions, as determined by TVA's RO, have returned to a condition in which 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months of warning will again be available.

River Scheduling of River Operations prepares at least aR 9 day.wate level forecast seven days per

.Aoeek fo-r Te~nnesseep River locations. DurWing prospective flooding conditions forecasts can be prepared 4 times a day so that warnings for Soqueyah will assure that 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months always will be available to shut down the plant and prepare it for flooding.

2.4.14.9.5 Hydrologic Basis for Target Stages Figure 2.A. 4, in fo.ur parts, shows hoW target forc*ast floo,,d elevations at the Sequoyah plant ha.e been determined to assure adequate warning times. The flo-ods shown are the fastest rising floods a the site which are producod by the 21,100 square mile PMVP with downstream contoring deScribed i a 3 day s*trm having 40 percent of the main storm rainfall This has caused so.I moisture to be high and reser.'oirs to be 'well above seasonal cyvels w;hen the main storm benins.Fiaure 2.4.14-3 (Sheet 11 and Figure 2.4.14-3 (Sheet 2) for winter and summer respectively, show target forecast flood warning time and elevation at SQN which assure adequate warning times. The fastest rising probable maximum flood for the winter at the site is shown in Figure 2.4.14-3 (Sheet 1A). Figure 2.4.14-3 (Sheets 1 B and 1 C) show the adopted rainfall distribution for the 21,400 square mile storm and the 7,980 square mile storm, respectively. An intermediate flood with average basin rainfall of 10 inches (rainfall heavy at the end) is shown in Figure 2.4.14-3 (Sheet ID). Figure 2.4.14-3 (Sheet 2A) shows the 7,980 square mile fastest rising probable maximum flood for the summer with heavy rainfall at the end. The 7,980 square mile adopted rainfall distribution is shown in Figure 2.4.14-3 (Sheet 2B). An intermediate flood with average basin rainfall of 10 inches heavy at the end is shown in Figure 2.4.14-3 (Sheet 2C). All of these storms have been preceded three days earlier by a three-day storm having 40% of PMP storm rainfall.

2.4-62

SQN-Figuro 2.4A. 4 (A, B, a*d G) shows the Wint.. PMP

.Whic cou.1ld produce the fatest risng 6

,flood which coss plant gr.ade* and-variations. causod by changed timoi distribution. -The fastest rising flood occurs during a PMP when the 6six-hour increments increase throughout the storm with the maximum 6-heurssix-hour increment increase occurring in the last period. Figure-2.4A-4 2.4.14-3 (BSheet 1A) shows the essential elements of this storm which provides the basis for the warning s4hemeplan. In this flood 9,27.35 inches of rain would have fallen 31 hours3.587963e-4 days 0.00861 hours 5.125661e-5 weeks 1.17955e-5 months (27 + 4) prior to the flood crossing elevation 703.0 ft and would produce elevation 697694.5 ft at the plant. Hence, any time rain on the ground results in a predicted plant stage of 6W7694.5 ft a Stage I shutdown warning will be issued.

Examination of Figure 2.4A. 4 (A and-C)_2.4.14-3 (Sheets 1 B and 1 C) shows that following this procedure in these nencr44ical-floods would result in a lapsedtime-.f longer times to reach elevation 703.0 ft after Stage I warning was issued. These times would be 4233.6 and 4443.6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months between

.:hPn A.2 inches had fallon and the flooed woul-id cross critical oleyation 703(icue4horfr

)*,,,

,,4**,.

4 *,

,*4...

l..

z, includes 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months for forecasting and communication) for Figure 2.4.14-3 (Sheet 1 B) and (Sheet 1C), respectively. This compares to the 31 hours3.587963e-4 days 0.00861 hours 5.125661e-5 weeks 1.17955e-5 months for the fastest rising flood as shown in Figure 2.4.14-3 (Sheet 1A). Stage I warning would be issued for the storm shown in Figure 2.4.14-3 (Sheet 1 D) and 63 hours7.291667e-4 days 0.0175 hours 1.041667e-4 weeks 2.39715e-5 months would pass before elevation 703.0 ft would be reached.

ARA Stage II warning would be issued if an additional 2--2-2.44 inches of rain must-fal4fel_

promptly for a total of 4-4149.79 inches of rain to cause the flood to cross critical elcv-tion 703. In the fastest rising flood, Figure-2.4A,.-44B)2.4.14-3 (Sheet 1A), this rain would have fallen in the next 56.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months . Thus, 6.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months after issuance of a Stage I warning, enough rain would have fallen to reguire a Stage II warning. A Stage II warning would be issued within the next 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months and the flood wood exceed elevation 703.0 ft in 24.1 hours1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months . Thus, the Stage 11 warning would be issued 5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months after issuanc of a Stage I warning and 22 hourcs befo-re the flooed wou-ld-cro4s~s c-ritica,-l flooed elevatio-n 7032 In the slower rising floods, Figure 2.4A.. 4 (A -a-GC 2.4.14-3 (Sheets 1 B and 10), the time between issuance of a Stage I warning and when the 4-1-49.79 inches of rain required to put the flood to elevation 703.0 ft would have occurred is 63.6 and 1-03.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months , respectively. This would result in issuance of a Stage II warning not loss than 4 ho-urs later or 32 and 3030 or 40.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months , respectively, before the flood would reach elevation 703.0 ft.

The summer flood shown by Figure-24A.-4-(D) 2.4.14-3 (Sheet 2A), with the maximum 1-one-day rain on the last day provides controlling conditions when reservoirs are at summer levels. At a time 31 hours3.587963e-4 days 0.00861 hours 5.125661e-5 weeks 1.17955e-5 months (27 + 4) before the flood reaches elevation 703.0 ft, 448.18 inches of rain would have fallen.

This 448.18 inches of rain, under these runoff conditions, would produce Giti*alelevation 7-93699.1 ft, so this lpeoel brcomes both the Stage I and-Stage4l-target. An additional 1.3 inches of rain must fall promptly for a total of 9.48 inches of rain to cause the flood to exceed elevation 703.0 ft.

The above criteria all relate to forecasts which use rain on the ground. In actual practice quantitative rain forecasts, which are already a part of daily operations, would be used to provide advance alerts that need for shutdown may be imminent. Only rain on the ground, however, is included in the procedure for firm warning use.

Because the above analyses have used fastest possible rising floods at the plant, all other floods will allow longer warning times than required for all physical plant shutdown activity.

In summary, the predicted target levoLsforecast elevations which will assure adequate shutdown times are:

Forecast Flood Elevations at Sequoyah For For Season Stage I Shutdown Stage II Shutdown Winter-(O*t*ber, 1 April 15 697694.5 ft 703.0 ft Summer (Apr!i 16 September 30) 7*0*699.0 ft 703.0 ft 2.4.14.9.6 Communications Reliability (HISTORICAL INFORMATION) 2.4-63

SQN-Communication between projects in the TVA power system is via (a) TVA owned microwave network, (b) Fiber-Optic System, and (c) by commercial telephone. In emergencies, additional communication links are provided by Transmission Power Supply radio network. The four networks provide a high level of dependability against emergencies. Additionally, RO have available satellite telephone communications with the TVA hvdro proiects upstream of Chattanooga (listed in Section 2.4.14.9.2).

The hydrologic neptwPork fo-r the iWAte;rsqhe~d_ above Seguoyah that would be available in flood emegeniesif commecial telcphone communications is lost include 138 rainfall gages (21 at power inst-allations -and 1114 satellite and Aile transfer gages) and 47 streamfiow gages (26 at hydroplants, sate ~ ~

~

~ ~ ~ ~ ~~~s.

I~

III gaea

~~tFgg)

R~FShdl 0is inU LO the I V1A power systemI by all fetwfive communication networks. The data from the satellite gages are received via a data collection platform-satellite computer system located in the River ScRh, eduling'sRO office. These are so ditstnbuted over the watershed that reaSonabic fleed trecasting can be done #Gro this data whole the balance of data is bcing secured from the remaining hydrologic nctwork stationS.-

The preferred, complete coereage of the watershed, employ 160 rainfall and-61 streamfiow locatin abovo the Sequoyah plant. Involved in the commR~unicationsR link to these locations are routine radio-,

radio) satellite, and commR~ercial telephone systemR nctwerks. In an emergcncY, available radio communications would be called upon to assist.

The va;rious networks proved to be capablc in the large fioods of 1957, 1963, 197-3, 1981, 1994, ad 1998 of provYiding the rain and-streamrfoiow d-ataa necded-for reliable forecasts.

2AA-92.4.14.10 Basis for Flood Protection Plan in Seismic-Caused Dam Failures Floods resulting fromR combined seismicG and flood events can exceed plant grade, thureiin emnergencGy measures. The 1 998 reanalysis showed that only two combinatfions, of seismice da failures coincident with a flood would result in floods above plant grade: (1) failure Of Fontana, Hiwassee, Apalachia, and Blue Ridge Dams in the on.e ha-lf

=

...cn.urrent with a 1/2 PMF, (2) SSE failuhre o-f NorFris, Cherokee, and Douglas concurrent with a 25 year flood. A s shon in ; Table 2.1414 all other potentially critical c0and-idates wsould-create flooad levels below plant grade elevation 705-Plant grade would be exceeded by four of the five candidate seismic failure combinations evaluated, thus requiring emergencv measures. Table 2.4.4-1. shows the maximum elevations at SQN for the candidate combinations. The combination producinq the shortest time interval between seismic event and plant qrade crossinq is a OBE located so as to fail Fontana, Tellico, Hiwassee, Apalachia, and Blue Ridge Dams during the one-half PMF. The time between the seismic event and the resulting flood wave crossing plant grade elevation 705.0 ft is 40 hours4.62963e-4 days 0.0111 hours 6.613757e-5 weeks 1.522e-5 months . The time to elevation 703.0 ft, which allows a marain for wind wave considerations. is 32 hours3.703704e-4 days 0.00889 hours 5.291005e-5 weeks 1.2176e-5 months . The event Droducina the next shortest time interval to elevation 703.0 ft involves the OBE failure of Tellico and Norris durino the one-half PMF resultinq in a time interval of 34 hours3.935185e-4 days 0.00944 hours 5.621693e-5 weeks 1.2937e-5 months . These times are adeguate to permit safe plant shutdown in readiness for flooding.

Dam failure during non-flood periods -would net nFeSeRt a nFONeM at Me 1312M 1 no Feanal -

snewea Q-A

'A i

i

'i i

A S-----------.

k; f;

Qcc f

I f K!

r1k 6

.4 7M CZ f fin

,.I f., 1 A fnl t

fI,.

K I~n 1

f All,hfin-k;..

4nIt;

+1 A

14

!14 n*n produce elevations mF.

uh lower,.

was not evaluated, but would be bounded by the four critical failure combinations.

The time from seismcocurrene to arrival of failre surge at the plant is adequate to permit safe plant shutdown in readiness forF flooding. Tabhle 2 4A-:2lit the timeq betwmeen the postulated seismic, event and when. the fooed-wlave wolexcoeed plant grad~e elevatfion 70-5 -anAd eeain73 1_s6 of elevation 703 provides a margin for possible wind wave effec-ts.

v The warning plan for safe plant shutdown is based on the fact that a combination of critically centered large earthquake and 4Rai produced flood conditions must coincide before the flood wave from seismically caused dam failures will eess~approach plant grade. In flood situations, an extreme earthquake must be precisely located to fail threetwo or more major dams before a flood threat to the 2.4-64

SQN-site would exist.

The comFbinationR produc~ing the 8ho9486t time inteR'al between seism~ic event and plant grade crossinSmg is a one half SS-" located s as to fail Fontana, Hiwassee, Apalachia, and Blue Ridge DamS during the one half RMF. The time bebween the sciSMic event and the resulting flood wave crossing"plant grade elevation 705 is 40 hours4.62963e-4 days 0.0111 hours 6.613757e-5 weeks 1.522e-5 months . The time to elevation 703, which allows a mnargin forind wave cGrsiderations, i6 35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months . The event pfrduin*g the next shotest time intep'al to elevation 703 s the SSE failure of Norris, ChcrOk..,

and Douglas during the 25 year flood resulting in a time intePval of 63 hours7.291667e-4 days 0.0175 hours 1.041667e-4 weeks 2.39715e-5 months .

The warning system utilizes TVA's flood forecast system to identify when flood conditions will be such that seismic failure of critical dams could cause a flood wave to exceed elevation 703.0 ft at the plant site. In addition to the critical combinations, failure of a single major upstream dam will lead to an early warning. A Stage I warning is declared once failure of (1) Norris, Cherokee, Douglas, and Tellico Dams or (2) Norris and Tellico Dams, or (3) Fontana, Tellico, Hiwassee, Appalachia, and Blue Ridge Dams, or (4) Cherokee, Douglas and Tellico Dams has been confirmed.

Two levels of warning will be provided: (1) an earlywarning will be issued to SQN whenever a dam failure has occuFred OF is inmminent for any s.ngle critia-l dam; or it appeasF fonm ra*in and flod forecasts that a critical situation may develop and (2) a flood wa.rnig or ale+t to begin preparation for plant shutdown when a critical situation exists that will result in the flood level to exceeding plant grade. A Stage 1 flood warning is declared Once failure Of critical dam~s has been ~onfirmed andl flood cOnditions; are such that the flood surge will eXceed plant grade.*

It shall he issued at least 27 hours3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months before the flood-level exceeds elevation 703 at the site. A Stage 11 fleed-warning will be issued at least 17 hours1.967593e-4 days 0.00472 hours 2.810847e-5 weeks 6.4685e-6 months before the flood lo'vel exceeds elevation 703 at the site. Communication will1 be established and mnaintained during these two levels of warning to assure the 27 hour3.125e-4 days 0.0075 hours 4.464286e-5 weeks 1.02735e-5 months flood preparation period. Any prolonged interruptionR Of commFunication Or failure to confirmn that a critical case has not occurred will result in theitiato of flood preparation at the plant site. The flood preparation shall continue unti cOmpletion, unless communication is Fe established and the site is notified that a critical case has not GuF-ed-.4lf loss of or damage to an upstream dam is suspected based on monitoring by TVA's RO, efforts will be made by TVA to determine whether dam failure has occurred. If the critical case has occurred or it cannot be determined that it has not occurred, Stage I shutdown will be initiated. Once initiated, the flood preparation procedures will be carried to completion unless it is determined that the critical case has not occurred.

Communications between the-platSQN, dams, power system control center, and River Operations at Knoxville, Te,.esseeTVA RO, are iaccomplished by TVA-owned microwave networks, fiber-optics network, radio networks, and commercial and satellite telephone service.

9A 1A 1I Q

-rini (crn-fiti-~ Ali I

n~x~n-H The flood orotection nlan is based uDon the minimum time available for the worst case. This worst case provides adequate preparation time including contingency margin for normal and anticipated plant conditions including anticipated maintenance operations. It is conceivable, however, that a plant condition might develop for which maintenance operations would make a longer warning time desirable. In such a situation the Plant Manager determines the desirable warning time. He contacts TVA's RO to determine if the desired warning time is available. If weather and reservoir conditions are such that the desired time can be provided, special warning procedures will be developed, if necessary, to ensure the time is available. This special case continues until the Plant Manager notifies TVA's RO that maintenance has been completed. If threateninq storm conditions are forecast which might shorten the available time for special maintenance, the Plant Managqer is notified by RO and steps taken to assure that the plant is placed in a safe shutdown mode.

2.4A.10 References

1. -SQN DG V 1.1, Design of Reinforced ConcreFte StructreAis; Design Criteria

2.

UN DG. V 12.1, Flood rotectio-,n rovisions Doign Criteria 2.4-65

SQN-

3.

SQN DG V 43.0, High Pr.....e Fire Protection Water Supply System 2.4.15 References

1.

U.S. Weather Bureau, "Probable Maximum and TVA Precipitation Over The Tennessee River Basin Above Chattanooga," Hydrometeorological Report No. 41, 1965.

2.

U.S. Weather Bureau, "Probable Maximum and TVA Precipitation for Tennessee River Basins Up To 3,000 Square Miles in Area and Duration to 72 Hours," Hydrometeorological Report No.

45, 1969.

3.

Garrison, J. M., Granju, J. P., and Price, J. T., "Unsteady Flow Simulation in Rivers and Reservoirs," Journal of the Hydraulics Division, ASCE, Vol. 95, No. HY5, Proceedings Paper 6771, September 1969, pp. 15559-1576.

4.

PSAR, Phipps Bend Nuclear Plant, Docket Nos. 50-553, 50-554.

5.

Tennessee Valley Authority, "Flood Insurance Study, Hamilton County, Tennessee, (Unincorporated Areas)," Division of Water Resources, February 1979.

6.

U.S. Army Engineering, Corps of Engineers, Omaha, Nebraska, "Severe Windstorms of Record,"

Technical Bulletin No. 2, Civil Works Investigations Project CW-178 Freeboard Criteria for Dams and Levees, January 1960.

7.

U.S. Army Corps of Engineers, "Computation of Freeboard Allowances for Waves in Reservoirs,"

Engineering Engineer Technical Letter No. 1110-2-8, August 1966.

8.

U.S. Army Coastal Engineering Research Center, "Shore Protection, Planning, and Design," 3rd Edition, 1966.

9.

Reference removed per Amendment 6.

10.

Hinds, Julian, Creager, William P., and Justin, Joel D., "Engineering For Dams," Vol. II, Concrete Dams, John Wiley and Sons, Inc., 1944.

11.

Bustamante, Jurge I., Flores, Arando, "Water Pressure in Dams Subject to Earthquakes," Journal of the Engineering Mechanics Division, ASCE Proceedings, October 1966.

12.

Chopra, Anil K., "Hydrodynamic Pressures on Dams During Earthquakes," Journal of the Engineering Mechanics Division, ASCE Proceedings, December 1967.

13.

Zienkiewicz, 0. C., "Hydrodynamic Pressures Due to Earthquakes," Water Power, Vol. 16, September 1964, pp. 382-388.

14.

Tennessee Valley Authority, "Sedimentation in TVA Reservoirs," TVA Report No. 0-6693, Division of Water Control Planning, February 1968.

15.

Reference removed per Amendment 6.

16.

Cristofano, E. A., "Method of Computing Erosion Rate for Failure of Earthfill Dams," Engineering and Research Center, Bureau of Reclamation, Denver 1966.

17.

"The Breaching of the Oros Earth Dam in the State of Ceara, North-East Brazil," Water and Water Engineering, August 1960.

18.

NRC letter to TVA dated December 8, 1989, "Chickamauga Reservoir Sediment Deposition and Erosion - Sequoyah Nuclear Plant, Units 1 and 2."

2.4-66

SQN-

19.

Programmatic Environmental Impact Statement, TVA Reservoir Operations Study, Record of Decision, May 2004.

20.

Updated Predictions of Chickamauga Reservoir Recession Resulting from Postulated Failure of the South Embankment at Chickamauga Dam; TVA River System Operations and Environment, Revised June 2004 (B85 070509 001).

21.

Monitoring and Moderating Sequoyah Ultimate Heat Sink, June 2004, River System Operations and Environment, River Operations, River Scheduling (B85 070509 001).

22. SQN Calculation MDQ0026970001A, "High Pressure Fire Protection Supply to the Steam Generators for Flood Mode Operation."

23.

Newton, Donald W., and Vineyard, J. W., "Computer-Determined Unit Hydrographs From Floods," Journal of the Hydraulics Division, ASCE, Volume 93, No. HY5, September 1967.

24.

U.S. Army Corps of Engineers, Hydrologic Engineering Center, River Analysis System, HEC-RAS computer software, version 3.1.3.

25.

Federal Emergency Management Agency (FEMA), "Federal Guidelines for Dam Safety:

Earthquake Analysis and Design of Dams," FEMA 65, May 2005.

26.

Price, J. T. and Garrison, J. M., Flood Waves From Hydrologic and Seismic Dam Failures," paper presented at the 1973 ASCE National Water Resources Engineering Meeting, Washington, D. C.

27.

SQN-DC-V-I.1, Design of Reinforced Concrete Structures Design Criteria.

28.

SQN-DC-V-12.1, Flood Protection Provisions Design Criteria.

29.

SQN-DC-V-43.0. Hiah Pressure Fire Protection Water SuDDlV System.

2.4-67

ENCLOSURE1 EVALUATION OF PROPOSED CHANGES ATTACHMENT 2 Proposed SQN Units I and 2 UFSAR Tables

SQN-Table 2.4.1-1 Public and Industrial Surface Water Supplies Withdrawn from the 98.6 Mile Reach of the Tennessee River between Dayton Tennessee and Meade Corp. Stevenson Ala.

Approximate Distance From Site (River Miles)

Plant Name City of Dayton Cleveland Utilities Board Bowaters Southern Paper Hiwassee Utilities Olin Corporation Soddy-Daisy Falling Water U.D.

Sequoyah Nuclear Plant East Side Utility

Chickamauga Dam DuPont Company Tennessee-American Water Rock-Tennessee Mill Dixie Sand and Gravel Chattanooga Missouri Portland Cement Signal Mountain Cement Racoon Mount. Pump Stor.

Signal Mountain Cement Nickajack Dam South Pittsburg Penn Dixie Cement Bridgeport Widows Creek Stream Plant Mead Corporation Use (MGD) 1.780 5.030 80.000 3.000 5.000 0.927 1615.680 5.000 7.200 40.930 0.510 0.035 0.100 2.800 0.561 0.200 0.900 0.00001 0.600 397.440 4.400 Location TRM 503.8 R TRM 499.4 L Hiwassee RM 22.9 TRM 499.4 L Hiwassee RM 22.7 TRM 499.4 L Hiwassee RM 22.5 TRM 499.4 L Hiwassee RM 22.3 TRM 487.2 R Soddy Cr. 4.6 Plus 2 Wells TRM 484.7 R TRM 473.0 L TRM 471.0 TRM 469.9 R TRM 465.3 L TRM 463.5 R TRM 463.2 R TRM 456.1 R TRM 454.2 R TRM 444.7 L TRM 433.3 R TRM 424.7 TRM 418.0 R TRM 417.1 R TRM 413.6 R TRM 407.7 R TRM 405.2 R Type Supply 19.1 (Upstream) 37.6 (Upstream) 37.4 (Upstream) 37.2 (Upstream) 37.0 (Upstream) 7.1 (Upstream) 0.0 11.7 (Downstream) 13.7 (Downstream) 14.8 (Downstream) 19.4 (Downstream) 21.2 (Downstream) 21.5 (Downstream) 28.6 (Downstream) 30.5 (Downstream) 40.0 (Downstream) 51.4 (Downstream) 60.0 (Downstream) 66.7 (Downstream) 67.6 (Downstream) 71.1 (Downstream) 77.0 (Downstream) 79.5 (Downstream)

Municipal Municipal Industrial

& Potable Municipal Industrial

& Potable Municipal Industrial Municipal Industrial Industrial Municipal Industrial Industrial Industrial Industrial Industrial Industrial Industrial Municipal Industrial Municipal Industrial Industrial

Water usage is not metered Flow Rate fluctuates as needed and is directed by power control center in Chattanooga.

2.4-68

SQN-Table 2.4.1-2 Facts About TVA Dams and Reservoirs (Page 1 of 2) 0a10L216ns, a

6100290

LAAJo, a1 1 habrA/ao (FeA Ab ~oeMenSea Leoo)

R60 orAVoume(Ao e Fo )

an AboAe FirstUniti LOOI7 UA.

Wflt-Ne Ab0ve S

-0,

Widt, 6,Roi OrNl2l Jan 1 Jn 1 Conttolled Dam,1 Seolc SOIAN Depend4ble Number of M.t do Height L SLengh 107n170 Surface R2 PIAlo Flood AIJan1 A. June I1-RtAge Nu-,e MainRivt (qua Cot~b)

Contrutio Da (A-1 or)

(A-tul or Cpciy

-Gnrting (i-r

.1-1a -fa Type.fM1 iu LAf Re kr=

ile If Area.)

ef Gid Toe-uie lo G..,!e A, Top o Fl-od GuIde.

ceelD PrAojets

-rive 810.

M09

.s)

(M-ons)

B-aI AAA)u0 Shedule) hed9 d MgA)

(M A

UAits (MoNes) I-) (

F.1)

OF-)

(Mles)

NhlA --

1

(-

(A-)

E AI EAAesIEleati1on OeaA

aOe, leIonA F0 t)

Pto, t PAoc=

KentuAckyc) 700nes 74AKY 40,200 126.OAI 1193A 8191344 91411414 110

.1946 lA4 7

22A4

2.

.422 AGA 110,6A047NF 1

1-0.

0 20-IN 21,-

ANA A

A

-5A 2,121,OO 6,129,A0O 2.6739AO@

4,4860AA AN Av-A piTkwick Tenoooo AN 32,62A 12A IAOAI194 211-1901 6Oll1-338 12/3111952 229 6

206,7 113 7,715 CGE 1-0,1-00x63(1 52.7 4W06 42,74 9AO0 408.

41800 414A1 O1.,OO 1.A02,000 1.1190.0A 492.700 TN R.-eo A

LaOdoig 110x6I O63 W0o0l-1)

Ten0s0e AL E0.7-A 133.5 411411918 411411924.1211-4A12)1192 N-A 21 2474 117 4,A.l C A 1Ax60xo7('

155 166I2 17646 9,1A 50I7 7 A7-6

.07.7

..A,7W0

-4A,200 637.2N0 NA,SAO TN 0Iet A

WtAl-I.--

AL 2H..0 6940 1112101933 10-1936 10 11021530 17181143 361 11 274-12 S.3A2 CAG A

x4A 12 7-1 10212 6711A 1,600 5505 550.28 O5N.A 742,000 1,06O,000 10500 320.500 T7 R-,

110.600.5211 00untei"O Tennes4 AL 24,450 74.2

-A11935 111611939 811/1040

.3A.1196 124 4

14A 0 -

AA9 A cAE NA,60,S4 757 6961 66.046 12406 5-0 A 595.44 A95.0 886,60 1,048,700 1.A18,000 162.100 R-

Rie, I

110.600.451, kiN.j4 T e T7 21.67A 50.1 411116-12-141107 2-201344 4/3-1966 lOS 4

4247 86 2,167 A-E 110x04 l4JA 463 106.1 10.,200 4,00 6325-635.00 632.5-NIA 251,600 NTA 1-,A 79 RioeI 1106041 635 634 5 ACh~lek ug

Tenne, 7TN 20.740 744 111911630 1115/1140 3/4)1840 31711-52

11.

4 4A1

12.

54 000 1...

.SE 6

03 5 SBA 760-7 36,OA 9500 6750 685.44 662.5 32,.000 737.300

-22.500 027.00 TN 50 1 W

Itts,64a 74T6n0ess 7TN 77.,10 66T 71171939 11111-2 071/1942 4124-4 12 15I')

2,460 000 601041.70 9-33r) 2217

-7,500 10,34 7350 7456 741.0 74.,000 1,175,000 1.0107001 379,000 TN Riet I

Fe21L4do4n Ten46s4e 7N 0.574 45.3 7

-81700 6011023 1111023 1127-9 162 4

600.3 129(-) 4,190 CGE N-80 60-(

32 14046 4,420 4070 615-4 61610 02A00I 303,000 303.000 110,0 TN R-,ve I

Raul~l n

TN 1

207.6 11111971 171111177 1 1100111176 1811.420A.7

]..26 f 153 ] _-

11111 N61 1 1

11 011 I

N-A II 1t5o I-T-.,tar P.-,

-rje-t 71-Ford E6k TN 7

529 43.8 3081967 12111170 1711972 -11972 36 1

13-175 1".0 E3R 7A 02 30067 10.50, 365 6730 605.00 860,0 3M6.446 602,000 530000 219.600 Elk 06,1 1

H-.-0.0 0iw04000 N.

1,018 294 011171-1 21411023

-221103 111171143 862 2

660 146 1.706 0G N.A 91N AI.

1100 807 1270 0-126000 12212.0. 6 67,600 700 N0A 001-00 4

HiwasB Hiwass.

NC 96 46 2

7411-1936 081100

-21)1040 5l24l19M0 141 21"1 705 307 1.378 00 N.A 202 1646

.670 1,000 1466,0 102650 1521.0 226,400 402,000 399.000 205,600 H6,4S4 4

Chatug5 Hiw..4 NC 1189

.5 7E1711-41 211-1122 1

-611962 100)1462 10 1

1210 130 2.800 E

600 lAO 1260 6.700 107 191810 132800 102.0 177,900 2421,00 205,500 62,600 Has0 4

coo,, l)'B1) 6046 75 593 11.6 4,001010 1211611 1-281912 0011414 0

5 7

11 9 735 0

0 G

N.A 7 5 470 1,620 170 6200 07.16 623.0 02,00 63,000 70.900 13000 O.

3 ooe2(h)

O046 TN 512 26-

-146/912 10001913 10-01913 100040913 23 2

242 30 4.0 O

N.)

600 N)0 610 600 700 111520 600 60A 8I) 610 610 00 3

-cee3 O-oe TN 092 49ý 711711.41

-1./92 4-31.93 4-01.43 29 1

2.2 110 612.1 C G TO 7

24.

600 26D 14428.0=- 1435.00 1442.-

1,1A 4.2.0 WNA O.

3 4350

.43I El-e To GA 232 204 1190limu92) 12196300 7-01931 7-01931 13 1

530 175 1000 0E N.

110 661 3,220 162 16-o.0 1691.00 1687.0 127,400 105,000 162,646 66,SOO looo/

I R73,,(h6' O-e N1o3ly Noelly GA 214 1772 711711941 11241022 1/lI01950 1110119.0 1 1

210 197 2,346 R6E 60 22 102.1 3,.70 170 1762.0 178000 17770 112700 174,300 162,000 61,600 H...s0 4

Me.1-Hil)

Chneh TN 3,023 21.5

-61196B94 115111964 7-0 21.1 109 1700 2 0 75-46,60 44 1034 5090 1,'23 7920-796.00 7920 kA 126,000

)A NA C30nch 2

1 1

795.0 7950

-00s Q-inh TN 2.-12 461 10l1)B33

-30)796 7-081976 9-001936 110 2

796 263 1660 00GE

5) 12.0.&1) 002 2

N 4ON 2,930 1-0 1703400 71,020,0 1,439M.0 2,552,00O 2043,460 1,1137946 016 2

Tello ittle T14 TN 2027 11770 3)N1967 711A9l1971 (1)

B)

(4)

(0) 0.3 133))

3,236 006 (0) 3342 3570 17660 2.133 807.0 81500 8130 304,0 424,000 392,000 120.460 L1100N 2

FotOno LittleTN TN 1,71 64-1 11111622 1117117 4

102023 2)4)1460 3

610 460 2,365 0G N1A 209 297.

10,290 1,03 1653.0 171 00 17030 929O04 1,443,400 1,370,000 514,000 Ltte TN 2

001u9l0 F

707nch1463 TN 461 890 022/-.2

-19)1643 1 3 6)017354 I1I 4

021 0155 1,705 00

)0 431 61251 20,070 3.170 9300 100246 9020 373046 1.461,000 7.223.300 7.062046 Frenco 1

Ch05704 A14.1,-

TN 3,428 293

-111940 12 941 4B161-42 7007962 148 0

52.3 178(') 6,760 CGER N-0 040 902.

29,560 2,426 10-50 107534 10710 797,600

7l427, 900 7,400,40 749,46 H0I0)0) 4 F46 P.I1o-S4u1h -or 7N 1,903 109 5/141)1977 17027)1902 12-51953 2001694 41 2

62 95 737 C0G

3) 104 390 600 333 72760- 126030 7 1236 N.0 0604 N2ANW0 lo-4 21,03 0

126370 Boo Soh Fo TN 17740 15.7 8-201950 12/1611952 903-1953 89 3

810 178 1.532 ECG 6)0 32,7) 120.6 4300 716 1762.0 138564 13820 117,600 193,400 180,500 15,800 H207 3

60th HolIto SOh Fo1k TN 703 217

-04l197(P) 110950 2101357 2-111951 44 1

497 285 1.6w6 E5 N1A 237

-17.9 7,060 710 17760 174246 17290 51,.300 76 65480 36,000 252,800 H0A.-

4

-040,96 00001g9 TN 468 22.1 7022S14( l12/111006 w001700

-00)1749 66 2

-7 002 9NO E7R N.

10.3 10.0 60,440 313 1.520 1975 N 19590 52I.200 6770 0

61646 102,300 WN040g11 W4lbN11r) W-.ug.

TN 471 7.6 11 00-1909 00N0,-/1912 0-9012 7/19)1950 7

0 020 761033 3755 0 G N)A

,8

40.

70 014641 1650300 7671-N)A 714 N)A N)A0 w90o3g A

G0a, Cosoy -or TN 1,670 21.4 101)1615 1081916 00)1116 0/0)125 36 2

910 00 846 00 61 220 10.0 1,800 1.4N0 7850 60330 6000 19.7.0 3004 4.,1004 3,00.

COny Fo.

1 N.i)00110 N-l4-0u1k, T7 1.173 01 00-1913 (q)

()

0610 482 0G 20-0 1

0 124610 Noh-tlueky 1

2.4-69

SQN-Table 2.4.1-2 Facts About TVA Dams and Reservoirs (Page 2 of 2) a) All i. -ae T

-n

,asm

,except for G-Fas w

-bb u ieeamaada aey b) Csit e1 pa t iudd d

te c-b*on botan.f hel plant -a.dall dd b -Id1an d

1-ts e

MheM plan Tn ssyeaaayaaai a-nicdedad a) winter dat daysydabs *ayacta aaaof Octberdd mad iner nes depey~adile caaaay isale aidnleeidposraa plant *npraoedue onie aseegsewinter day. tesmis se elCsamty ased by m eaei~t am')lf I) E: E-ay; R -

htl; G: G itya C: Conlea. Om OM, (C-dss lb, h-,.a 1-ea.1 pesieii

-)deroimaat

)

e) At Juie Isao guidec a6 a.

F) V -

fute.w-n eeeJanac3 I dsicaiianead td p If gates.

g) C-

-td ta laiticy yIsy r by 1-lid eisa 1, -hi op-teed July 14.1966

,) A uii: WilAan by t-e f.. -

U S u-a y C-.. Egy 1933; Xy:O 1, Ames 2, due didge.

ard re.t rails D.y pamnas tm GTtFen1ess, biacaic POb.

Tompaniy iP 1939; Wilbreaedd No*ciahky

(.b-ed) by yiemyas frm E-si Tayy.asse Pace, ayd Liget Campanyminaa4.

Seb uaot to ameiisibaon Tu sAisaled alddbai anc ai Wilsa Did Wilur, aeReens1,ead flame at Itas deaa pmacd in se11a.e an Naemcer 1.d3

,)

A-i -ck plac-in -

--a~o,in 59 It *isn1963.1 Whi l.,

- 195a G-

-11.,~e

.. d1 4 iwc Land.,.

j) Caeaneatn If baman

-c ait Ndkajaaa I-mitea

t. u

-ae -aieren t -ai.

k) G--eeaig unitsat R-.a.o Mount-ai arrea Francistype up-turbinee-it. each th 428y400 kW g

-eerao ygana 612,000 hp puy p i

tormratig a)

-at 2 et Hwi Ie

-ble F

ci y-e p ptb iee ait with 95,1 kW-g-seaera i n-.g -d 121,530 hp p p oair Iatein t 2Wa ft Ie ad m)O-a 1 creates Pearksci Re-.sae, Natichcky

(

)

tes,)t aa ayecr attaRese ir andssaRd-,. sd

-.u Rdge a a T.a. Reair n) Ca-syaa-af Ble RidgeaioM-e0- -a,,yiy 1926, -esudaiM1med 19-o) T111-*

p,,Iect haI no Ib~k or -

-flO Str 11. -qogh navigable 1a t, Fort Loub0 t R-111i pIer1 I.-*

Iaalo ira saeag nuleegy output.t F-r Loudou pi Iarol aanstaaa at daam msionad

.ay a ua.ga st-artd Facbae 161.942; t-m; am ly d-any-eD a aanee t,

al 1ae-a1 da-yg -1dII.

a) Aeaeatngaaiia atsciaaaky werea av.d from sys-emgse.-.-g--Anerg ayieusi h

1972 Te-dh

,,am -

a

-s eaneaaedmdletod*naeritse sreaair fia a asfacwiidfbs pae r)

WIlu 72,4 -Ie p 0, Ten -

Rier IFot

-L.-d~

D.

23.1 -1 up Oln-R-v lb ael-H,1 Dam a) i 6cl.u 5 -l. up -

F.-en Ba d -d1.and 4 dmda ump.ieH.- Rive.

I) ieud 17.4 -des up th

-oh F-H.lso Feer a d 15 3 -

P -s a

Watua R-iae.

a) leatades -

m Ites -

C-

-,n c I andaei 56 -aItI1 u

o e.

a) TheUS. Armyc aorp b! E-i-ie -e-.ng thsie aoIf -

IsacJsaaiet nJky a-d Catb aa uga.

c) Thysta1actiu deeg at dam jam isath -i d -iaca 1m-at.

p-

-t A me saaatsd icndaom tame my-aims am. T96 at dam ee ts e*sesest bacb ct

m ter Iamce mean cbane nyt (b, t aeaet wali) ayd deak 1ct-1, im tad af -adapt c1l) Ice ace ta daecs

5) As ay interm m.-Ie A1 ieant aaera. them

-oat dams ace e'usad by HESCO Cona-aine flOdintyuayS.

Fad Lad - 3 fft ct am aabnt at e ataab e 767 a

e* a y.1-tda t

770 F-r L~d

, - 3.75 f~t:

Im~

e t.1 e

-l 3 was r-se I -~ I, alla=

837 (3,75 %we

.bov opo n-et.

Iatltelao83 T.-li - 4 1-t

-ba1-n It.l1--~o 830 rise. Ito.

-e v

Bý,

Chb~k*.-3f t~t ma ~ la l~l 09rie oee hn1 2.4-70

SQN-Table 2.4.1-3 TVA Dams - River Mile Distances to SQN (Page 1 of 2)

Distance from River Structure/River Mouth River Mile(a)

SQN (mi.)

Tennessee River Chickamauga Dam 471 13.7 SQN 484.7 Hiwassee River 499.5 14.8 Watts Bar Dam 530 45.3 Clinch River 568 83.3 Little Tennessee River 601 116.3 Fort Loudoun Dam 602 117.3 Holston River 652 167.3 French Broad River 652 167.3 Hiwassee River 0

14.8 Ocoee River 34.5 49.3 Apalachia Dam 66 80.8 Hiwassee Dam 76 90.8 Nottely River 92 106.8 Chatuge Dam 121 135.8 Ocoee River 0

49.3 Ocoee #1 Dam 12 61.3 Ocoee #2 Dam 24 73.3 Ocoee #3 Dam 29 78.3 Toccoa River 38(b) 87.3 Toccoa River 0

87.3 Blue Ridge Dam 15(b) 102.3 Nottely River 0

106.8 Nottely Dam 21 127.8 Clinch River 0

83.3 Melton Hill Dam 23 106.3 Norris Dam 80 163.3 Little Tennessee River 0

116.3 Tellico Dam 0.5 116.8 2.4-71

SQN-Table 2.4.1-3 TVA Dams - River Mile Distances to SQN (Page 2 of 2)

Distance from River Structure/River Mouth River Mile(a)

SQN (mi.)

Chilhowee Dam 33.5 149.8 Calderwood Dam 43.5 159.8 Cheoah Dam 51.5 167.8 Fontana Dam 61 177.3 Holston River 0

167.3 Cherokee Dam 52 219.3 French Broad River 0

167.3 Douglas Dam 32 199.3 a) Approximated to the one-half river mile based on U.S. Geological Survey Quadrangles river mile designations.

b) Estimated river mile. River miles not provided for Toccoa River on U.S. Geological Survey Quadrangles.

2.4-72

SQN-Table 2.4.1-4 Facts about TVA Dams Above Chickamauga Project Spillway Type Outlet Works Spillway Crest Elevation Top of Gate Capacity, cfs at Gate Elevation Top Apalachia Blue Ridge Boone Chatuge Cherokee Chickamauga Douglas Fontana Fort Loudoun Fort Patrick Henry Hiwassee Melton Hill Norris Nottely South Holston Tellico Watauga Watts Bar a) At elevation 1752.

b) At elevation 1985.

Ogee, radial gates Ogee, tainter gates Ogee, radial gates Concrete chute, curved weir, vertical-lift gates Ogee, radial gates Concrete gravity, vertical-lift fixed roller gates Ogee, radial gates Ogee, radial gates Ogee, radial gates Ogee, radial gates Ogee, radial gates Ogee, radial gates Ogee, drum gates Concrete chute, curved weir vertical-lift gates Uncontrolled morning-glory with concrete-lined shaft and discharge tunnel Ogee, radial gates Uncontrolled morning-glory with concrete-lined shaft and discharge tunnel Ogee, radial gates 1257 1675 1350 1923 1043 645 970 1675 783 1228 1503.5 754 1020 1775 1742 773 1975 713 1280 1691 1385 1928 1075 685.44 1002 1710 815 1263 1526.5 796 1034 1780 N/A 815 N/A 745 135,900 39,000 141,700 11,700 255,900 436,300 312,700 107,300 392,200 141,700 88,300 115,600 55,000 11,500 41, 2 0 0 (a) 117,900 41, 2 0 0 (b) 560,300 2.4-73

SQN-

.-Jkl,.

'2 A 4_

C

-0,#*

At.*,. 6KIL

-MIlA n-r%,.-n, DA 0

-*^;

V T-kI '

4

~

k.~.4L0%,-raL

%~'JUL %J" a

0I~ a"a~i woolu~ VLDII R Drainage Area (so. mi.)

Distance from Mouth (mi.u Maximum

Height, (ft-Area of Lake Length(ft.)

(ac.i Length of Lake Lmi.L Proiects Major Dams Calderwood Cheoah Chilhowee Nantahala Santeetlah Thorpe (Glenville)

River Total1

Storage, (ac.-ft.)

41,160 35,030.

49,250 138,730 158,250 Construction Started Little Tennessee Little Tennessee Little Tennessee Nantahala Cheoah West Fork Tuckasegee 1,856 1,608 1,976 108 176 36.7 43.7 51.4 33.6 22.8 9.3 9.7 232 225 91 250 212 150 Minor Dams Bear Creek East Fork Tuckasegee Cedar Cliff East Fork Tuckasegee Mission (Andrews)

Queens Creek Wolf Creek East Fork Tuckasegee Hiwassee Queens Creek Wolf Creek East Fork Tuckasegee West Fork Tuckasegee 75.3 80.7 292 3.58 15.2 24.9 54.7 455 4.8 215 916 750 1,373 1,042 1,054 900 740 600 390 382 810 385 254 536 595 1,690 1,605 2,863 1,462 476 4.5 70,810 4.6 34,711 2.4 106.1 1.5 1.7 10.9 3.1 38.0 165 50 78 180 140 61 200 121 2.4 6,315 8

10 8.9 4.6 7.5 61 37 176 39 9

340 1.46 0.5 2.2 283 817 10,056 1928 1916 1955 1930 1926 1940 1952 1950 1924 1947 1952 1952 1949 1927 1.4 1,797 0.5 183 5.5 25,390 Walters (Carolina P&L)

Pigeon 870 (1) Volume at top of gates.

2.4-74

SQN-Table 2.4.1-6 Flood Detention Capacity - TVA Projects Above Sequoyah Nuclear Plant Flood Storage January 1 (ac-ft)

Project Tributary Boone Chatuge Cherokee Douglas Fontana Hiwassee Norris Nottely South Holston Tellico Watauga Blue Ridge Main River Fort Loudoun Watts Bar 75,800 62,600 749,400 1,082,000 514,000 205,600 1,113,000 61,600 252,800 120,000 152,800 68,500 111,000 379,000 4,948,100 Flood Storage March 15 (ac-ftI 60,000 62,600 749,400 1,020,000 514,000 205,600 1,113,000 61,600 220,000 120,000 152,800 49,500 111,000 379,000 4,818,500 Flood Storage Summer (ac-ft1 12,900 13,900 118,100 237,500 73,000 35,000 512,000 12,300 106,000 32,000 108,500 13,100 30,000 165,000 1,469,300 Total 2.4-75

SQN-Table 2.4.2-1 Water Year(a) 1867 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 Peak Streamflow of the Tennessee River at Chattanooga, TN (USGS Station 03568000) 1867-2007 (Page 1 of 5)

Date Discharge (cfs) 3/11/1867 459,000 5/01/1874 195,000 3/01/1875 410,000 12/31/1875 227,000 4/11/1877 190,000 2/25/1878 125,000 1/15/1879 252,000 3/18/1880 254,000 12/03/1880 174,000 1/19/1882 275,000 1/23/1883 261,000 3/10/1884 285,000 1/18/1885 174,000 4/03/1886 391,000 2/28/1887 181,000 3/31/1888 178,000 2/18/1889 198,000 3/02/1890 283,000 3/11/1891 259,000 1/17/1892 252,000 2/20/1893 221,000 2/06/1894 167,000 1/12/1895 212,000 4/05/1896 269,000 3/14/1897 257,000 9/05/1898 167,000 3/22/1899 273,000 2/15/1900 159,000 5/25/1901 221,000 1/02/1902 271,000 4/11/1903 210,000 2.4-76

SQN-Table 2.4.2-1 Water Year(a) 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 Peak Streamflow of the Tennessee River at Chattanooga, TN (USGS Station 03568000) 1867 - 2007 (Page 2 of 5)

Date Discharge (cfs) 3/25/1904 144,000 2/11/1905 146,000 1/26/1906 140,000 11/22/1906 222,000 2/17/1908 163,000 6/06/1909 163,000 2/19/1910 86,600 4/08/1911 198,000 3/31/1912 190,000 3/30/1913 222,000 4/03/1914 105,000 12/28/1914 185,000 12/20/1915 197,000 3/07/1917 341,000 2/02/1918 270,000 1/05/1919 189,000 4/05/1920 275,000 2/13/1921 213,000 1/23/1922 229,000 2/07/1923 188,000 1/05/1924 143,000 12/11/1924 138,000 4/16/1926 92,900 12/29/1926 249,000 7/02/1928 184,000 3/26/1929 248,000 11/19/1929 180,000 4/08/1931 125,000 2/01/1932 192,000 1/01/1933 241,000 3/06/1934 215,000 2.4-77

SQN-Table 2.4.2-1 Peak Streamflow of the Tennessee River at Chattanooga, TN (USGS Station 03568000) 1867 - 2007 (Page 3 of 5)

Water Year(a)

Date Discharge (cfs) 1935 3/15/1935 175,000 1936 3/29/1936 234,000 1937 1/04/1937 204,000 1938 4/10/1938 136,000 1939 2/17/1939 193,000 1940 9/02/1940 89,400 1941 7/18/1941 58,200 1942 3/22/1942 72,300 1943 12/30/1942 235,000 1944 3/30/1944 201,000 1945 2/18/1945 115,000 1946 1/09/1946 225,000 1947 1/20/1947 186,000 1948 2/14/1948 225,000 1949 1/06/1949 179,000 1950 2/02/1950 192,000 1951 3/30/1951 140,000 1952 (b)

(b) 1953 2/22/1953 107,000 1954 1/22/1954 185,000 1955 3/23/1955 118,000 1956 2/04/1956 187,000 1957 2/02/1957 208,000 1958 11/19/1957 189,000 1959 1/23/1959 110,000 1960 12/20/1959 108,000 1961 3/09/1961 178,000 1962 12/18/1961 190,000 1963 3/13/1963 219,000 1964 3/16/1964 122,000 1965 3/26/1965 180,000 2.4-78

SQN-Table 2.4.2-1 Water Year(a) 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 Peak Streamflow of the Tennessee River at Chattanooga, TN (USGS Station 03568000) 1867 - 2007 (Page 4 of 5)

Date Discharge (cfs) 2/16/1966 104,000 7/08/1967 120,000 12/23/1967 148,000 2/03/1969 121,000 12/31/1969 186,000 2/07/1971 90,700 1/11/1972 116,000 3/18/1973 267,000 1/11/1974 181,000 3/14/1975 148,000 1/28/1976 67,200 4/05/1977 191,000 1/28/1978 115,000 3/05/1979 145,000 3/21/1980 168,000 2/12/1981 50,800 1/04/1982 133,000 5/21/1983 116,000 5/9/1984 239,000 2/02/1985 81,000 2/18/1986 66,200 2/27/1987 109,000 1/21/1988 74,100 6/21/1989 173,000 2/19/1990 169,000 12/23/1990 185,000 12/04/1991 146,000 3/24/1993 113,000 3/28/1994 202,000 2/18/1995 99,900 1/28/1996 145,000 2.4-79

SQN-Table 2.4.2-1 Water Year(a) 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Peak Streamflow of the Tennessee River at Chattanooga, TN (USGS Station 03568000) 1867 - 2007 (Page 5 of 5)

Date Discharge (cfs) 3/04/1997 138,000 4/19/1998 207,000 1/24/1999 4/05/2000 2/18/2001 1/24/2002 5/8/2003 9/18/2004 12/13/2004 1/23/2006 1/09/2007 91,400 137,000 86,100 184,100 241,000 160,000 153,000 63,800 66,300 (a) Water Year runs from October 1 of prior year to September 30 of year identified.

(b) Not reported.

[36]

2.4-80

SQN-Table 2.4.3-1 Seasonal Variations of Rainfall (PMP)

Antecedent (in.)

3-Day PMP (in.)

Month March April May June July August September Ratio to Main Storm (Percent) 40 40 40 40 30 30 30 7,980 Sq.-

Mi. Basin 8.14 8.08 7.96 7.81 5.72 5.72 6.09 21,400 Sq.-Mi.

Basin 6.71 6.44 6.10 5.63 3.87 3.87 4.47 Dry Interval Before PMP (Days) 3 3

3 3

21/2 2/

21/2 7,980 Sq.-Mi.

Basin 20.36 20.20 19.92 19.53 19.07 19.07 20.30 21,400 Sq.-Mi.

Basin 16.78 16.11 15.27 14.09 12.92 13.09 14.92 Source: HMR Report 41 2.4-81

SQN-Table 2.4.3-2 Probable Maximum Storm Precioitation and Precipitation Excess Index No.

1 2

3 4

5 6

7 8

9 10 11 12 13 14 & 15 Unit Areaa Name Asheville Newport, French Broad Newport, Pigeon Embreeville Nolichucky Local Douglas Local Little Pigeon River French Broad Local South Holston Watauga Boone Local Fort Patrick Henry Gate City Total Cherokee Local Holston River Local Little River Fort Loudoun Local Needmore Nantahala (Page 1 of 2)

Antecedent Storm

Rain, Excessb (inches) linches) 6.18 2.91 6.18 3.67 6.18 2.91 6.18 3.67 6.18 3.67 6.18 4.43 6.18 3.81 6.18 3.81 6.18 4.60 6.18 3.67 6.18 3.81 6.18 4.60 6.18 4.60 6.18 4.60 Main Storm

Rain, Excessc (inches)

(inches) 18.12 15.44 18.42 16.43 19.26 16.58 15.30 13.31 15.42 13.43 17.16 15.94 21.12 19.13 19.38 17.39 12.12 10.90 12.96 10.97 13.86 11.87 14.34 13.12 12.30 11.08 15.42 14.20 16 17 18 19 20 21 Bryson City 22 Fontana Local 23 Little Tennessee Local -

Fontana to Chilhowee Dam 24 Little Tennessee Local -

Chilhowee to Tellico Dam 25 Watts Bar Local above Clinch River 26 Norris Dam 27 Melton Hill Local 33 Local above mile 16 34 Poplar Creek 35 Emory River 36 Local Area at Mouth 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 4.60 3.81 3.81 2.73 2.73 2.91 2.91 2.91 2.91 3.81 4.60 4.27 4.43 4.43 4.43 4.43 16.74 20.82 17.28 20.22 20.94 20.04 19.56 22.50 19.26 15.84 13.56 15.42 15.42 14.88 12.78 14.94 15.52 18.83 15.29 17.54 18.26 17.36 16.88 19.82 16.58 13.85 12.34 14.01 14.01 13.47 11.37 13.53 2.4-82

SQN-Table 2.4.3-2 Probable Maximum Storm Precioitation and Precioitation Excess (Continued)

(Page 2 of 2)

Index Unit Areaa No.

Name 37 Watts Bar Local below Clinch River 38 Chatuge 39 Nottely 40 Hiwassee Local 41 Apalachia 42 Blue Ridge 43 Ocoee No. 1, Blue Ridge to Ocoee No. 1 44A Hiwassee River Local at Charleston 44B Hiwassee River Local mouth to Charleston 45 Chickamauga Local Average above Chickamauga Dam Antecedent Storm

Rain, Excessb (Inches)

(inches) 6.18 4.43 Main Storm

Rain, Excessc (Inches)

(inches) 14.28 12.87 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18 2.91 2.91 2.73 3.81 2.91 2.91 3.81 4.27 4.27 3.85 21.12 18.66 18.18 18.18 22.14 18.42 15.48 14.52 13.56 16.25 18.44 15.98 15.50 16.19 19.46 15.74 13.49 13.11 12.15 14.39

a. Unit area corresponds to Figure 2.4.3-5 numbered areas.

b. Adopted antecedent precipitation index prior to antecedent storm varies by unit area, ranging from 0.78-1.29 inches.

c. Computed antecedent precipitation index prior to main storm, 3.65 inches.

2.4-83

SQN-Table 2.4.3-3 Historical Flood Events Unit Area 1

Basin French Broad at Asheville 2

French Broad Newport Local 3

Pigeon at Newport 7

Little Pigeon at Sevierville 9

South Holston Dam 10 Watauga Dam 17 Little River at Mouth 18 Fort Loudoun Local 23 Chilhowee Local 24 Tellico Local 26 Norris Dam 27 Melton Hill Local 42 Blue Ridge Dam 44A Hiwassee at Charleston (RM 18.9)

Flood 4/05/1957 5/03/2003 3/13/1963 3/17/1973 3/28/1994 3/28/1994 5/06/2003 3/1712002 5/06/2003 3/12/1963 3/16/1973 3/18/2002 3/12/1963 3/17/1973 1/14/1995 3/17/1973 3/17/1973 3/16/1973 5/06/2003 3/17/1973 5/06/2003 3/17/2002 3/16/1973 3/29/1951 3/27/1965 3/16/1973 Rain (in.)

5.53 5.66 5.31 4.68 5.60 6.19 7.18 4.61 6.19 3.12 3.33 4.41 3.64 3.61 6.97 6.26 6.81 6.97 6.19 7.34 7.84 5.00 6.66 5.70 6.04 7.36 Runoff (in.)

2.30 1.44 2.47 2.20 2.33 2.92 2.68 3.46 3.85 1.55 1.29 1.55 2.16 1.84 3.75 3.82 3.14 3.24 3.13 3.56 3.72 2.90 4.85 1.61 3.52 5.84 2.4-84

SQN-Table 2.4.3-4 Unit Hvdroaraoh Data (Page 1 of 2)

Unit Area GIS Drainage Area Duration (sq. mi.)

(hrs.)

Qp Cp Tp W50 W75 TB Number Name 1

2 3

4 5

6 7

8 9

10 11 12 13 14&15 Asheville Newport,French Broad Newport, Pigeon Embreeville Nolichucky Local Douglas Local Little Pigeon River French Broad Local South Holston Watauga Boone Local Fort Patrick Henry Gate City Total Cherokee Local 944.4 913.1 667.1 804.8 378.7 835 352.1 206.5 703.2 468.2 667.7 62.8 668.9 854.6 289.6 378.6 323.4 436.5 90.9 653.8 389.8 404.7 650.2 295.3 2912.8 431.9 14,000 0.21 12 43,114 0.66 12 30,910 0.65 12 33,275 0.65 12 11,740 0.44 12 47,207 0.27 6

17,000 0.75 12 8,600 0.20 6

15,958 0.53 18 37,002 0.74 8

22,812 0.16 6

2,550 0.19 6

11,363 0.56 24 25,387 0.42 12 8,400 0.27 9

11,726 0.68 16 20,000 0.29 6

9,130 0.49 18 3,130 0.38 8

26,000 0.43 10 17,931 0.14 4

16,613 0.58 12 39 15 10 4

8 4

10 7

14 6

8 5

10 6

13 6

25 17 6

3 13 7

12 7

34 26 20 10 18 12 15 7

10 5

22 12 16 11 13 7

14 7

10 4

168 48 90 80 90 60 66 60 96 32 90 66 108 54 96 96 36 126 54 60 28 84 16 Holston River Local 17 Little River 18 Fort Loudoun Local 19 Needmore 20 Nantahala 21 Bryson City 22 Fontana Local 23 Little Tennessee Local-Fontana to Chilhowee Dam 24 Little Tennessee Local-Chilhowee to Tellico Dam 25 Watts Bar Local above Clinch River 6

4 6

6 2

6 4

6 6

22,600 0.49 12 6

11,063 0.18 6

15 8

54 10 4

90 18 6

102 19 10 90 26 27 Norris Dam Melton Hill Local 6

6 43,773 0.07 6

12,530 0.14 6

2.4-85

SQN-Table 2.4.3-4 Unit Hvdroaraph Data (Continued)

(Page 2 of 2)

Unit Area GIS Drainage Area Duration (sq. mi.)

(hrs.)

Number Name Qp Cp Tp W5 0 W7 5 TB 33 Local above mile 16 37.2 2

4,490 0.94 6

3 2

48 34 Poplar Creek 135.2 2

2,800 0.61 20 26 13 90 35 Emory River 868.8 4

36,090 0.39 8

11 6

84 36 Local area at Mouth 29.3 2

3,703 0.99 6

3 2

48 37 Watts Bar Local below 408.4 6

16,125 0.19 6

10 4

90 Clinch River 38 Chatuge 189.1 1

19,062 0.24 2

3 2

37 39 Nottely 214.3 1

44,477 0.16 1

1 1

12 40 Hiwassee Local 565.1 6

23,349 0.58 12 11 6

96 41 Applachia 49.8 1

5,563 0.26 2

4 1

23 42 Blue Ridge 231.6 2

11,902 0.40 6

10 7

60 43 Ocoee No. 1 Local 362.6 6

17,517 0.23 6

12 8

36 44A Hiwassee at Charletson 686.6 6

9,600 0.59 30 39 23 108 44B Hiwassee at Mouth 396.0 6

16,870 1.00 18 11 6

78 45 Chickamauga Local 792.1 6

32,000 0.38 9

14 7

36 Definition of Symbols Qp = Peak discharge in cfs Cp =Snyder coefficient Tp = Time in hours from beginning of precipitation excess to peak of unit hydrograph W50 = Width in hours at 50% of peak discharge W75 = Width in hours at 75% of peak discharge TB = Base length in hours of unit hydrograph 2.4-86

SQN-Table 2.4.4-1 Floods from Postulated Seismic Failures of Upstream Dams Plant Grade is Elevation 705.0 ft OBE Failures With Sequoyah Nuclear Plant One-Half Probable Maximum Flood Elevation (ft)

1.

Tellico - Norris 706.7

2.

Partial Fontana - Tellicoa 702.2

3.

Partial Fontana. - Tellico - Hiwassee - Apalachia - Blue Ridgea 706.3

4.

Cherokee - Douglas - Tellico 708.6 SSE Failures With 25-Year Flood

5.

Norris - Cherokee - Douglas - Tellicob 706.0

a.

Includes failure of four ALCOA dams and one Duke Energy dam - Nantahala (Duke Energy, formerly ALCOA), upstream; Santeetlah, on a downstream tributary; and Cheoah, Calderwood, and Chilhowee, downstream. Fort Loudoun gates are inoperable in open position.

b. Gate opening at Fort Loudoun prevented by bridge failure.

2.4-87

SQN-Table 2.4.13-1 (Sheet 1)

Well and Spring Inventory Within 2-Mile Radius of Sequoyah Nuclear Plant Site (1972 Survey Only)

Map Ident.

No.

Location Latitude Estimated Well Elevation, Feet

Depth, Water Longitude Feet Ground Surface Well Dia.,

Feet Remarks 1

3513-34" 2

35°13'23" 3

35 13'30" 4

35 13'58" 5

35 14'15" 6

35 14'34" 7

35 14'35" 8

35 14'36" 9

35 15'06" 10 35 14'46" 11 35 14'55" 12 35 14'53" 13 35 14'52" 14 35 14'50" 15 35 14'45" 16 35 14'44" 17 35*14'45" 18 35 14'21" 19 35 14'26" 20 35 14'34" 21 3 514'311 22 35 14'29" 23 35 14'23" 24 35 14'22" 25 35 14'24" 26 35 14'28" 27 35 14'26" 28 35 14'32" 29 35 14-34" 30 35 14'38" 31 35 14'41" 32 35 14'45" 33 35 14-43" 34 35 14'41" 35 35 14'39" 36 35 14'39" 37 35 14'40" 38 35 14'41" 39 35 14'35" 40 35 14'36" 41 35 14'37" 42 35 14'33" 85*06'09" 85*06,12" 85*06'47" 85 05'45" 85*06'25" 85*06-46" 85*06'52" 85*06'57" 85*06'32" 85*0616" 85*0615" 85 06'13" 85 06'13" 85*0612" 85 06,14" 85*06'18" 85*06,22" 85*05,30" 85*05'27" 85 05'29" 85*05'29" 85*05-29" 85*0532" 85*05'40" 85 05'46" 85 05'45" 85 05'41" 85 05'44" 85 05'44" 85 05'41" 85 05'41" 85 05'46" 85 05'47" 85 05'48" 85 05'50" 85 05'53" 85 05'58" 85 05'56" 85 05'54" 85 05'57" 85 06'01" 85 05'02" 725 75 720 116 745 42 700 680 85 720 65 720 73 735 27 780 110 720 725 77 800 800 800 50 720 275 795 740 695 200 695 150 695 695 110 690 85 700 695 52 710 130 740 90 740 141 740 735 58 700 720 715 720 695 48 695 60 700 695 50 695 700 700 715 223 720

.5 685 696 670 687 761 680 525

.5

.5 3.0

.5 15 2.5

.5 5.0

.5

.75

.5 Serves 2 families; submersible Submersible pump Submersible pump 1/4-hp pump Submersible pump 3/4-hp pump 1/3-hp pump Bucket Submersible Summer home Summer home 1-hp submersible pump 1-hp pump 1-hp pump 1/2-hp pump I-hp pump I-hp jet pump Serves 2 familes; I-hp pump 3/4-hp pump Summer home 1/3-hp pump Summer home 1-hp pump Submersible pump 1 -hp pump 3/4-hp pump Summer home Summer home 680 620 710 650 670 650 653 655 530

.5

.5 NOTE: The information in this table is historic and not subject to updating revisions.

2.4-88

SQN-Table 2.4.13-1 (Sheet 2)

Well and Sprinq Inventory Within 2-Mile Radius of Sequoyah Nuclear Plant Site (1972 Survey Only)

Estimated Map Well Elevation, Feet Well Ident.

Location

Depth, Water Dia.,

No.

Latitude Longitude Feet Ground Surface Feet Remarks 43 35'14'46" 85'05'54" 65 695 655

.5 3/4-hp pump 44 35°14'47" 85°05'54" 95 705 655

.5 45 35'14'48" 85'05'53" 700 Summer home 46 35'14'50" 85'05'53" 257 695 665

.5 I-hp submersible pump 47 35'14'52" 85'05'48" 710 Summer home 48 35'15'04" 85*05'56" 725 Summer home 49 35'15'06" 85'06'02" 720 Summer home 50 35*15'06" 8*506'05" 90 705 625

.5 Submersible pump 51 35'14'58" 85'06'06" 695 Summer home 52 35'15'01" 85'06'02" 65 720 680

.5 3/4-hp pump 53 35*14'47" 85'05'57" 46 700 670

.5 2 familes; 1-hp pump 54 35*14'42" 85'06'01" 48 695 675

.5 1/2-hp pump 55 35'14'41" 85'06'02' 695 Summer home 56 35*14-40" 85*06'03" 695 Summer home 57 35'14'37" 85'06'08" 155 690 670

.5 1-hp pump 58 35 14'34" 85 06'09" 695 59 35 14'23" 85 05'53" 760

.5 Submersible pump 60 35 14'49" 85 05'58" 705 61 35'13'01" 85'04'41" 720 Summer home 62 35 13'18" 85 04'24" 845

.5 1-hp pump 63 35'13'19" 85'04'23" 206 845 645

.5 1/2-hp pump 64 35'13'33" 85'04'19" 50 720 680

.5 1-hp pump 65 35'13'49" 85'04'14" 100 720 640

.5 Servies clubhouse, 15 houses 66 35'13'57" 85'03'55" 175 741

.6 l-hp pump 67 35'13'53" 85'03'49" 100 738 690

.5 I-hp submersible pump 68 35'13'50" 85'03'52" 133 720 675

.5 1/2-hp pump 69 35 13'48" 85 03'43" 85 736

.5 l-hp pump 70 35 *1343" 85°03'38" 80 780

.5 1-hp pump 71 35'13'37" 85'03'36" 130 800 715

.5 1-hp pump 72 35'13'38" 85*03'43" 800 Well not used 73 35'13'16" 85'03'30" 227 880 680

.5 Submersible pump 74 35'13'09" 850341" 397 900 820

.5 2-hp pump 75 35'12'47" 85'03'58" 190 860 800

.5 Serves 2 families; submersible 76 35'13'03" 85'04'17" 720 Summer home 77 35'13'05" 85'04'10" 90 740 670

.5 1/2-hp pump 78 35*12'50" 85*04'13" 85 760

.5 1-hp pump 79 35*12'45" 85 03'59" 190 880

.5 Serves 2 families; 1-hp pump 80 35 12'26" 85°04'07" 290 860

.5 Serves 5 families; submersible NOTE: The information in this table is historic and not subject to updating revisions.

2.4-89

SQN-Table 2.4.13-1 (Sheet 3)

Well and Sprinq Inventory Within 2-Mile Radius of Sequoyah Nuclear Plant Site (1972 Survey Only)

Map Ident.

No.

Estimated Well Elevation. Feet

Depth, Water Longitude Feet Ground Surface Location Latitude Well Dia.,

Feet Remarks 81 82 83 84 85 35 12'20" 35 12'15" 35 12'24" 35 12,22" 35°12'21" 85 04'33" 265 940 85 04'34" 250 965 735 665 690 85-04'35" 85°05'05" 85°05'08" 305 965 135 740 120 740 86 35°12'17" 85 05'06" 190 800 87 88 89 90 91 92 93 94 95 96 35 12'23 35 12'16" 35°12'07" 35011,54" 35 12'19" 35 12,22" 35' 12'22" 35 12,22" 35 12'20" 35 12,04" 85'05'09" 85'05'12" 85'05'09" 85 04'56" 85'05'20" 85'05'33" 85 05'35" 85'05'36" 85 05'44" 85'05'56" 85 05'59 740 55 740 251 775 170 980 125 740 725 700 705 700 160 700 65 700 720 700 705

.5

.5 2.5

.5

.5 Submersible pump 1-hp submersible pump Submersible pump 1-hp pump Serves 2 families; 3/4-hp jet pump 3/4-hp submersible pump 1-hp pump Bucket Serves 2 families; 3/4-hp pump 1/2-hp pump Submersible pump Summer home 1-hp pump Summer home Summer home Serves 5 families; 1-hp pump House and cottage; I-hp pump 97 35°12'04" NOTE: The information in this table is historic and not subject to updating revisions.

2.4-90

SQN-Table 2.4.13-2 (Sheet 1)

Ground Water Supplies Within 20-Mile Radius of the Plant Site (1972 Survey Only)

Average Daily Use mcid Approximate Distance From Sitea tMiles Location Owner Source 1.

2.

3.

4.

5.

Chattanooga Chattanooga Chattanooga Chattanooga Chattanooga

6.

Chattanooga

7.

Chattanooga

8.

Chattanooga

9.

Chattanooga

10.

Chattanooga Kay's Ice Cream Company Selox, Inc.

Stainless Metal Products American Cyanamid Dixie Yarns, Inc.

Scholze Tannery Southern Cellulose Products, Inc.

Alco Chemical Corporation Chattem Drug and Chemical Cumberland Corporation Bacon Trailer Park Bethel Church of Christ Blue Water Trail and Campground Cohulla Baptist Church Crystal Springs Recreation Area Eastview School Fort Bluff Youth Camp Frazier Elementary School Grasshopper Church of God 0.0400 0.0250 0.0100 0.0727 0.5350 0.1560 4.0000 0.1000 0.2300 0.8500 0.2380 0.2380 0.0150 Well Well Well Well Wells (2) and Tennessee-American Water Company Wells (2) and Tennessee-American Water Company Well (1) and Tennessee-American Water Company Well (1) and Tennessee-American Water Company Wells (3) and Tennessee-American Water Company Well (1) and Tennessee-American Water Company Well Well Well 20.4 21.0 16.4 21.0 13.3 24.0 24.2 24.0 17.4 20.0 19.0 9.5 19.0 9.5 19.0 19.0 11.3 11.

12.

13.

14.

15.

16.

17.

18.

19.

Chattanooga Dunlap Dayton Cleveland Dayton Georgetown Dayton Dayton Birchwood Well Spring Well Well Well Well NOTE: The information in this table is historic and not subject to updating revisions.

2.4-91

SQN-Table 2.4.13-2 (Sheet 2)

Ground Water Supplies Within 20-Mile Radius of the Plant Site (1972 Survey Only)

Approximate Average Distance Daily Use From Sitea Location Owner mqd Source (Miles)

20.

Dayton Hastings Mobile Home Park Spring 19.0

21.

Ooltewah High Point Baptist Church Well 10.0

22.

Dayton Lake Richland Apartments Well 19.0

23.

Dayton Laurelbrook Sanitarium School

.017 Wells (7) 19.0

24.

Cleveland Labanon Baptist Church Well 13.5

25.

Cleveland Mt. Carmel Baptist Church Well 13.5

26.

Sale Creek Mt. Vernon Baptist Church Well 11.0

27.

Dayton Mt. Vista Mobile Home Park Wells (2) 19.0

28.

Dayton New Bethel Methodist Church Well 19.0

29.

Cleveland New Friendship Baptist Church Well 13.5

30.

Dayton Ogden Baptist Church Well 19.0

31.

Dunlap Old Union Water System Spring 20.0

32.

Dunlap P.A.W., Inc. #2 Well 20.0

33.

Cleveland Red Clay State Historic Area Well 13.5

34.

Chattanooga Riverside Catfish House Well 25.0

35.

Cleveland Robert Allen Well 13.5

36.

Dayton Salem Baptist Church Well 19.0

37.

Dunlap Sequatchie-Bledsoe VO-Well 20.0 Training

38.

Dayton Seventh Day Adventist Church Well 19.0

39.

Chattanooga Shamrock Motel Well 20.1

40.

Dayton Sinclair Packing House Well 19.0

41.

Dunlap Stonecave Institute Water 0.0064 Spring 20.0 System

42.

Dunlap Old Union Water System Spring 20.0

43.

Sale Creek Sale Creek Marina Well 11.0 Multiboating NOTE: The information in this table is historic and not subject to updating revisions.

2.4-92

SQN-Table 2.4.13-2 (Sheet 3)

Ground Water Supplies Within 20-Mile Radius of the Plant Site (1972 Survey Only)

Average Daily Use mod Approximate Distance From Sitea (Miles)

Location Owner Source 44.

45.

46.

47.

48.

49.

50.

51.

52.

53.

54.

Sale Creek Sale Creek Graysville Graysville Dayton Birchwood Cleveland Cleveland Cleveland Cleveland Cleveland

55.

Cleveland

56.

Cleveland

57.

Cleveland

58.

Hamilton County

59.

Hamilton County

60.

Hamilton County

61.

Soddy

62.

Hamilton County

63.

Hamilton County

64.

Hamilton County Sale Creek P.U.A. - TVA Sale Creek Utility District Graysville Water Supply Graysville Nursing Home Dayton Golf & CC % Mokas Birchwood School Cassons Grocery Water System Black Fox School Blue Springs Baptist Church Blue Springs School Bradley Limestone, Div. of Dalton Rock Product Co.

Hardwick Stone Company Cleveland-Tenn. Enamel Magic Chef, Inc.

Savannah Valley U.D.

Eastside Utility District Hixson Utility District Union Fork Bakewell, U.D.

Walden's Ridge, U.D.

Container Corporation of America Dave L. Brown Company 0.204 0.220 0.0170 0.2400 0.1130 0.2240 0.4200 0.720 3.0130 0.0920 4.0000 0.3330 0.192 0.0010 0.471 1.9200 0.0200 Well Wells (2)

Wells (2)

Well Well Well Well Well Well Well Well Well Well Spring Wells (2)

Wells (3) and Tennessee American Water Company Cave Springs (3) and Tennessee American Water Company Wells (3) and Sale Creek Utility District Wells (2)

Well Well 11.0 10.8 15.0 15.0 19.0 11.3 19.7 13.5 13.5 13.5 13.5 13.5 13.5 13.5 5.0 7.9 12.9 9.8 17.4 22.0 NOTE: The information in this table is historic and not subject to updating revisions.

2.4-93

SQN-Table 2.4.13-2 (Sheet 4)

Ground Water Supplies Within 20-Mile Radius of the Plant Site (1972 Survey Only)

Approximate Average Distance Daily Use From Sitea Location Owner mqd Source (Miles)

65.

Hamilton De Sota, Inc.

0.0750 Well County

66.

Hamilton Hamilton Concrete Products 0.0050 Spring 24 County

67.

Cleveland Thompson Spring Baptist Well 13.5 Church

68.

Dayton Vaughn Trailer Park Well 19.0

69.

Dayton Walden's Ridge Baptist Well 19.0 Church

70.

Dayton Walden's Ridge Elementary Well 19.0 School

71.

Cleveland White Oak Baptist Church Well 13.5

72.

Bradley Bockman Childrens Home Well 10.2 County

73.

Catoosa Catoosa County U.D.

Well 19.0 County a River mile distance from differences (TRM 483.6) for supplies taken from the Tennessee River channel; radial distance to other supplies.

NOTE: The information in this table is historic and not subject to updating revisions.

2.4-94

SQN-Table 2.4.14-1 Time between Floods from Postulated Seismic Failures of Upstream Dams and Sequoyah Nuclear Plant Elevation 703.0 ft OBE Failures With One-Half Probable Maximum Flood

1.

Tellico - Norris

2.

Partial Fontana - Tellicoa

3.

Partial Fontana. - Tellico - Hiwassee - Apalachia - Blue Ridgea

4.

Cherokee - Douglas - Tellico SSE Failures With 25-Year Flood

5.

Norris - Cherokee - Douglas - Tellicob Flood Wave Travel Time (hr)c 34 N/A 32 46 53

a.

Includes failure of four ALCOA dams and one Duke Energy dam - Nantahala (Duke Energy, formerly ALCOA), upstream; Santeetlah, on a downstream tributary; and Cheoah, Calderwood, and Chilhowee, downstream. Fort Loudoun gates are inoperable in open position.

b. Gate opening at Fort Loudoun prevented by bridge failure.

c.

Time from seismic dam failure to arrival of failure wave at SQN elevation 703.0 ft (two ft below plant grade).

(1) Elevation 705.0 ft not reached (2) Elevation 703.0 ft not reached 2.4-95

ENCLOSUREI EVALUATION OF PROPOSED CHANGES ATTACHMENT 3 Proposed SQN Units I and 2 UFSAR Figures (Public)

SQN-V L

Seq

uocyahi, NPucanr.t--

Plant r -I

$L AI F. I -

I Topographic Map Plant Vicinity 1,000 2,

0 000 Figure 2.4.1-1 Topographic Map, Plant Vicinity 2.4-96

SQN-NwM Fork Holston 0DD10101 06010206 UpperfClinch 06010206 SoutEl Fork Hohton 06010102 0610103 Nolchucky 06010106 LOWS" T-.newsee 0040006 Moiston OW01104 Emory 06010208 Kenrucky L.ke S040006 Lower clinch 06010207 Mile BwLako 06002D1 L-w Little Tenn O5I 0204 H6wasse.

06020002 Low. French Broad Upper French Broad 0010107 05010106 Pigeon 06010106 TlUcka..g..

ssee 05010203 UpperLittle Tennessee 06010202 Lower Duck 0640003 UpperDuck 0402 Buffdo 06040004 Lower Tennelses-Beech 06040001 Upper Bk 06030)03 0ce..

56020003 Lower Elk 06030004 Pickwick Loe 06030005 WMetler Lake 0030002 B.a W023006 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT USGS Hydrogogic Units within the Tennessee River Watershed Figure 2.4. 1-2 0

25 50 Mies

Sequoyah Nuclear Plant Hydrologic Cataloiging Unit Number and Name SM~iddle Tennessee-Chickamrauga Watershed Boundary Figure 2.4.1-2 USGS Hydrologic Units within the Tennessee River Watershed 2.4-97

SQN-Security-Related Information -Withheld Under IOCFR2.390 Figure 2.4.1-3 TVA Water Control System 2.4-98

SQN-686 685

684 C 683 z 682

-J 0)

E 681 0 680 I--

" 679 w

U-z 678 0

< 677 w

-J W 676 675 674 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seasonal Operating Curve, Chickamauga Figure 2.4.1-4 (Sheet 1 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Chickamauga (Sheet 1 of 16) 2.4-99

SQN-(0 0

I-746 745 744 743 742 741 740 739 738 737 736 735 734 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Seasonal Operating Curve, Watts Bar Figure 2.4.1-4 (Sheet 2 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Watts Bar (Sheet 2 of 16) 2.4-100

SQN-817 816 6; 815 C%1 O814 C,-

z

i 813 812 0m 811 w

w U-

, 810 z

0 809 uJ

, w 808 807 806

-TELLICO EMERGENCY SPILLWAY CREST: EL. 817.0

-- TOP OF GATES: EL. 815.0 (FORT LOUDOUN AND TELLICO)

=NORMAL OPERATING ZONE TOP OF NORMAL OPERATING ZONE MEINELIEVATI01IN BOTTOM OF NORMAL OPERATING ZONE

-FT.

LOUDOUN SPILLWAY CREST: EL. 783.0

-TELLICO SPILLWAY CREST: EL. 773.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seasonal Operating Curve, Fort Loudoun - Tellico Figure 2.4.1-4 (Sheet 3 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Fort Loudoun - Tellico (Sheet 3 of 16) 2.4-101

SON-1390 1385

-- TOP OF GATES: EL. 1385.0 a

01380 z

-j w

'U z

01370

_j

'U 1365 1360 C

C 0

C C

0 F

o LOOD GUIDE MEDIAN

o CO Co

---SPILLWAY CREST: EL. 1350.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seasonal Operating Curve, Boone Figure 2.4.1-4 (Sheet 4 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Boone (Sheet 4 of 16) 2.4-102

SQN-1080 1070 o 1060

-J

= 1050

'U 0

4 Lu 1040

'u t.

z0 4 1030 w

-j

'U 1020 1010 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYA FIr ANAL Seasonal Op Figure 2 Figure 2.4.1-4 Seasonal Operating Curve, Cherokee (Sheet 5 of 16) kH NUCLEAR PLANT NAL SAFETY LYSIS REPORT erating Curve, Cherokee

.4.1-4 (Sheet 5 of 16) 2.4-103

SQN-1010 1000 04 990 z

980 w

0> 970 I-ww 960 z

950 940 930 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seasonal Operating Curve, Douglas Figure 2.4.1-4 (Sheet 6 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Douglas (Sheet 6 of 16) 2.4-104

SQN-1720 1710

" 1700 1690 W 1680 1670 w

zo 1660 w-1650 1640 1630 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOY)

Fl ANA Seasonal C Figure Figure 2.4.1-4 Seasonal Operating Curve, Fontana (Sheet 7 of 16)

\\H NUCLEAR PLANT NAL SAFETY LYSIS REPORT

)perating Curve, Fontana 2.4.1-4 (Sheet 7 of 16) 2.4-105

SQN-0 LU w

0 w

I-uJ 1264 1263 1262 1261 1260 1259 1258 1257 1256 13 -0 I

-SPILLWAY CREST: EL. 1228.0;.

-- SPILLWAY CREST: EL. 1228.0 JAN FEB MAR APR MAY JUN JUL SEP AUG OCT NOV DEC SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seasonal Operating Curve, Fort Patrick Henry Figure 2.4.1-4 (Sheet 8 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Fort Patrick Henry (Sheet 8 of 16) 2.4-106

SQN-797

4) 796 C~4 0)

> 795 0z

.J u, 794 w

0 S793 LLI w

W 792 I-z0 791 w

" 790 789 7----

--TOP OF GATES: EL. 796.0 7--

--- SPILLWAY CREST: EL. 754.0 I

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seasonal Operating Curve, Melton Hill Figure 2.4.1-4 (Sheet 9 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Melton Hill (Sheet 9 of 16) 2.4-107

SQN-1040 1030

---TOP OF GATES: EL. 1034.0 a;

O 1020 z

-J O 1010 w

_j U-w zo 1000

'U

-J 990 980

-- SPILLWAY CREST:

EL. 1020.0 F

i a

FLOOD GUIDE MEDIAN JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seasonal Operating Curve, Norris Figure 2.4.1-4 (Sheet 10 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Norris (Sheet 10 of 16) 2.4-108

SQN-

'.j 0

0 z

0 w

uj U.'

1745 1740 1735 1730 1725 1720 1715 1710 1705 1700 1695

---CREST OF MORNING GLORY SPILLWAY: EL. 1742.0 eooeooo0

.0e S

S 0

0 0

0 MEDIAN FLOOD GUIDE 0

0 0

0e 0

0e 00 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH I FINAl ANALY5 Seasonal Operatin Figure 2.4.1-Figure 2.4.1-4 Seasonal Operating Curve, South Holston (Sheet 11 of 16)

N1LUCLEAR PLANT

- SAFETY SIS REPORT g Curve, South Holston

-4 (Sheet 11 of 16) 2.4-109

SQN-1980 1975 a)S1970 C

z 1965 w

o 1960 4

, 1955 z0 L 1950

-j 1945 1940

---CREST OF MORNING GLORY SPILLWAY: EL. 1975.0 m

0 0*

0 MEDIAN eo0 FLOOD GUIDE JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAI Fir' ANAL Seasonal Op Figure 2.ý Figure 2.4.1-4 Seasonal Operating Curve, Watauga (Sheet 12 of 16)

H NUCLEAR PLANT IAL SAFETY

.YSIS REPORT erating Curve, Watauga 4.1-4 (Sheet 12 of 16) 2.4-110

SQN-1695

-TOP OF GATES: EL 1691.0 1690 0

CD 1685 UJ 1680 0

FLOOD GUIDE w

u

-- SPILLWAY CREST: EL 1675.0 U,..

1675 z

olo 00 MEDIAN a,

16700 Li, 1665 1660 1655 1650 1645 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH FINA ANALY*

Seasonal Opern Figure 2.4.1 Figure 2.4.1-4 Seasonal Operating Curve, Blue Ridge (Sheet 13 of 16)

NUCLEAR PLANT L SAFETY SIS REPORT ating Curve, Blue Ridge

-4 (Sheet 13 of 16) 2.4-111

SQN-1930 C) z 0

I-ww z0 w

-Jw 1925 1920 1915 1910 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seasonal Operating Curve, Chatuge Figure 2.4.1-4 (Sheet 14 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Chatuge (Sheet 14 of 16) 2.4-112

SQN-0 CD z

0 LU 1530 1525 1520 1515 1510 1505 1500 1495 1490 1485 1480 1475 1470 1465 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seasonal Operating Curve, Hiwassee Figure 2.4.1-4 (Sheet 15 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Hiwassee (Sheet 15 of 16) 2.4-113

SQN-w 0

C,,

U, u.

wLt z

0 I-LU 1785 1780 1775 1770 1765 1760 1755 1750 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seasonal Operating Curve, Nottely Figure 2.4.1-4 (Sheet 16 of 16)

Figure 2.4.1-4 Seasonal Operating Curve, Nottely (Sheet 16 of 16) 2.4-114

SQN-N

_j 0,

w

'U 14U 720 700

-- TOP OF GATES: EL. 685.44 680-660-

-- SPILLWAY CREST: EL. 645.0 640 620 600 0

500 1000 1500 2000 VOLUME IN THOUSANDS OF ACRE-FEET 2500 3000 3500 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Chickamauga Figure 2.4.1-5 (Sheet 1 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Chickamauga (Sheet 1 of 17) 2.4-115

SON-790 770 a 750

-.4 a

z 730

-s

,In w

0 710 14.

w z 690 0

w

-- TOP OF GATES: EL. 745.0

-SPILLWAY CREST: EL. 713.0

(

w 6501 win 0

500 1000 1500 2000 2500 3000 3500 VOLUME IN THOUSANDS OF ACRE-FEET SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Watts Bar Figure 2.4.1-5 (Sheet 2 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Watts Bar (Sheet 2 of 17) 2.4-116

SQN-860 a,

z

_j w

0 w

z w

820 820-

-- TOP OF GATES: EL. 815.0 800

-7/SPILLWAY CREST: EL. 783.0 780 760 740 0

200 400 600 800 VOLUME IN THOUSANDS OF ACRE-FEET 1000 1200 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Fort Loudoun Figure 2.4.1-5 (Sheet 3 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Fort Loudoun (Sheet 3 of 17) 2.4-117

SQN-860 o 2 8 2 01 2

-- TOP OF GATES: EL. 815.0 U,

a 800 Uj70 0

P 780 U.

.SILVY CREST: EL. 773.0 2

740 720

0 200 400 600 800 1000 1200 VOLUME IN THOUSANDS OF ACRE-FEET SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Tellico Figure 2.4.1-5 (Sheet 4 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Tellico (Sheet 4 of 17) 2.4-118

SON-('.

0 z

04 Un w

0m 14 w

0 4

wJ 4

1420 1400 1380 1360 1340 1320 1300 1280 1260 1240 TOP OF GATES: EL. 1385.0-

.ý-SPILLWAY CREST: EL. 1350.0 0

50 100 150 200 VOLUME IN THOUSANDS OF ACRE-FEET 250 300 350 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Boone Figure 2.4.1-5 (Sheet 5 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Boone (Sheet 5 of 17) 2.4-119

SQN-1110 1090 TOP OF GATES: EL. 1075.0---

1070 Z

1050 C)

-- SPILLWAY CREST: EL. 1043.0 z

1030 cn 0

1010 I-w 990 z0I..-

970 w

-J LU 950 930 910 0

500 1000 1500 2000 2500 VOLUME IN THOUSANDS OF ACRE-FEET SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Cherokee Figure 2.4.1-5 (Sheet 6 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Cherokee (Sheet 6 of 17) 2.4-120

SQN-O 980 z.ILWYCET EL. 970.0 U,

2 960 0

w Wj 940 0

920 900 880 860 0

500 1000 1500 2000 2500 VOLUME IN THOUSANDS OF ACRE-FEET SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Douglas Figure 2.4.1-5 (Sheet 7 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Douglas (Sheet 7 of 17) 2.4-121

SQN-z 0

z0 w

1 7 4 0 -

T O P IO F G A T E S : E L.1 7 1 0.0 -

1690 1640 1590-______

1540-1490 1390 1340 1290 0

200 490 600 800 1000 1200 VOLUME IN THOUSANDS OF ACRE-FEET 1400 1600 1800 2000 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Fontana Figure 2.4.1-5 (Sheet 8 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Fontana (Sheet 8 of 17) 2.4-122

SQN-C.,4 0

z 0

I 3UU 1280.

12

-TOP OF GATES: EL. 1263.0 1260 1240 1220 SPILLWAY CR IEST: EL.1228.0 1220 1200 1Th04 4

i 0

10 20 30 40 VOLUME IN THOUSANDS OF ACRE-FEET 50 60 70 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Fort Patrick Henry Figure 2.4.1-5 (Sheet 9 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Fort Patrick Henry (Sheet 9 of 17) 2.4-123

SQN-840 820 N

>600 800

--TOP OF GATES: EL. 796.0 780 z

760

>--SPILLWAY CREST: EL. 754.0 740 720 0

50 100 150 200 250 300 350 400 VOLUME IN THOUSANDS OF ACRE-FEET SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Melton Hill Figure 2.4.1-5 (Sheet 10 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Melton Hill (Sheet 10 of 17) 2.4-124

SQN-1100 1050 a

> 1000 0

2 900 w

w 950 4

0 F900

'U TOP OF GATES: EL. 1034.0---

~--S*PILLWAY CREST: EL. 1020.0 850 800 0

500 1000 1500 2000 2500 VOLUME IN THOUSANDS OF ACRE-FEET 3000 3500 4000 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Norris Figure 2.4.1-5 (Sheet 11 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Norris (Sheet 11 of 17) 2.4-125

SQN-1800 1750 -

1700 z

-J S 1650 w

0 w 1600 z

0 w 1550

-Jw 1500-1450-

__II

_ I I

-- SPILLWAY CREST: EL. 1742.0 10 0

100 200 300 400 500 600 700 VOLUME IN THOUSANDS OF ACRE-FEET 800 900 1000 1100 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, South Holston Figure 2.4.1-5 (Sheet 12 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, South Holston (Sheet 12 of 17) 2.4-126

SQN-0 0

'U 2050 2000 1950 1900 1850 1800 1750 1700 1650 0

100 200 300 400 500 600 VOLUME IN THOUSANDS OF ACRE-FEET 700 800 900 1000 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Watauga Figure 2.4.1-5 (Sheet 13 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Watauga (Sheet 13 of 17) 2.4-127

SQN-04 z

LU 0

I-LU LL z

0 LU

-j LU 1740 1720 1700 1680 1660 1640 1620 1600 1580 1560

--- TOP OF GATES: EL. 1691.0 1

--- SPILLWýAY CREST: EL. 1675'.0

-40 0

50 100 150 200 VOLUME IN THOUSANDS OF ACRE-FEET 250 300 350 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Blue Ridge Figure 2.4.1-5 (Sheet 14 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Blue Ridge (Sheet 14 of 17) 2.4-128

SQN-F 04 m,

z

y co~

LU.

0 LU.

LU.

z0 LU.

-j U.

1960 1940 1920 1900 1880 1860 1840 1820 1800 SPILLWAY CRES I:

L. 1923.0---

I

-- TOP OF GATES: EL. 1928.0 SP W

YC ET

.12.--_ _ _ __ _ _____ ______ _ _ _ _

.50 0

50 100 150 200 250 VOLUME IN THOUSANDS OF ACRE-FEET 300 350 400 4

SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Chatuge Figure 2.4.1-5 (Sheet 15 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Chatuge (Sheet 15 of 17) 2.4-129

SQN-1550 1500 0

0z

.- I LU LJ I-u~l w

U.w 1450 1400 1350 1300 TOP OF GATES: EL. 1526.5

---.qPll I \\AIAVY irI:? ;T" P1 IfnA C_._

1250 0

100 200 300 400 500 600 700 VOLUME IN THOUSANDS OF ACRE-FEET SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir Elevation - Storage Relationship, Hiwassee Figure 2.4.1-5 (Sheet 16 of 17)

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Hiwassee (Sheet 16 of 17) 2.4-130

SQN-0 CD w

0 LU

_j U-1850 1800 1750 1700 1650 1600 TOP OF GATES: EL. 1780.0---

---SPILLWAY CREST: EL. 1775.0 0

50 100 150 200 250 300 350 VOLUME IN THOUSANDS OF ACRE-FEET SEQUOYAH NUC FINAL SA ANALYSIS F Reservoir Elevati Relationship, Figure 2.4.1-5 (:

Figure 2.4.1-5 Reservoir Elevation - Storage Relationship, Nottely (Sheet 17 of 17)

LEAR PLANT kFETY REPORT on - Storage Nottely Sheet 17 of 17) 2.4-131

SQN-60 so 52 45

~44 40 36 29 omIo B p

g Im s400lo ANawdw w

1900 1905 1010 11!5 1*

9 ISM 1930 1935 1040 1'U45 1'90 1M I

19 0O 0170 1 1000 6 1M 0 1966 2000 2010

_Obmu

Obswwd wft 960O14 WA cAuaW abswwo A

i-AMWW Wsuwd COW.ETB

Fat, 2010 TENNESSEE RIVER MW 464.2 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Tennessee River Mile 464.2 -

Distribution of Floods at Chattanooga, Tennessee Figure 2.4.2-1 Figure 2.4.2-1 Tennessee River Mile 464.2 - Distribution of Floods at Chattanooga, Tennessee 2.4-132

SQN-SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Probable Maximum Precipitation Isohyets for 21,400 Sq. Mi. Event, Downstream Placement Figure 2.4.3-1 Figure 2.4.3-1 Probable Maximum Precipitation Isohyets for 21,400 Sq. Mi. Event, Downstream Placement 2.4-133

SQN-SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Probable Maximum Precipitation Isohyets for 7980 Sq. Mi. Event, Centered at Bulls Gap, TN Figure 2.4.3-2 Figure 2.4.3-2 Probable Maximum Precipitation Isohyets for 7980 Sq. Mi. Event, Centered at Bulls Gap, TN 2.4-134

SQN-100-6-J 40 I-o 40 12---

_ 24

-36 48 60 7

20 0

12 24

.36 48 60 7:

TIME - HOURS SEC Figure 2.4.3-3 Rainfall Time Distribution - Typical Mass Curve 2

1UOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Rainfall Time Distribution -

Typical Mass Curve Figure 2.4.3-3 2.4-135

SQN-Figure 2.4.3-4 Not Used 2.4-136

SQN-KY NC SC GA "j Mawft"NO a

Do S

o0I 6 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Drainage Areas above Chickamauga Dam Figure 2.4.3-5 AL Figure 2.4.3-5 Drainage Areas above Chickamauga Dam 2.4-137

SQN-U)

TL 0

50,000 45,000 40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 0

"-I I------

-p f I d

0 12 24 36 48 6o 72 TIME - HOURS

-AREA 1 - FRENCH BROAD RIVER AT ASHEVILLE. 944.4 SQ. Mi.; 6-HOUR DURATION AREA 2 - FRENCH BROAD RIVER, NEWPORT TO ASHEVILLE;-913.1 SQ. MI.; 6-HOUR DURATION AREA 3 -PIGEON RIVER AT NEWPORT: 667.1 SQ. Mi.; 6-,HOUR DURATION, AREA 4-NOLICHUCKY RIVER AT EMBREEVILLE; 804.8 SQ. MIL; 4-HOUR DURATION AREA5 - NOLICHUCKY LOCAL; 378;7 SQ. MI.: 6&HOUR DURATION SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unit Hydrographs, Areas 1-5 Figure 2.4.3-6 (Sheet 1 of 11)

Figure 2.4.3-6 Unit Hydrographs, Areas 1-5 (Sheet 1 of 11) 2.4-138

SQN-0)

LL CD 60,000 46,000 40,000 35,000 30,000 25,000 20,000 165;000 10,000.

6,.0000ooo

-I - -

S I

4/

0 0

12 24 36 48 6

TIME-HOURS AREA 6-DOUGLAS DAM LOCAL; 835.0 SO. Ml!; '6-HOUR DURATION AREA,7-.LITTLE PIGEON RIVER AT SEVIERVILLE; 352.1 SO. MI.; 4-HOUR DURATION AR-AEA 8 - FRENCH BROAD LOCAL;.206.5 SQ. MI;.;6-HOUR DURATION

-AREA9 - SOUTH HOLSTON DAM; 703.2 SQ. Mi.; 6-HOUR DURATION SEQI U

Fic Figure 2.4.3-6 Unit Hydrographs, Areas 6-9 (Sheet 2 of 11)

UOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT nit Hydrographs, Areas 6-9 lure 2.4.3-6 (Sheet 2 of 11) 2.4-139

SQN-4s,ooo.

3 o, 0 0 b..................

40,000 - -

35,000

. I iI~pl 62,0O0,0---------/

0 12 24 36 46 TIME..HOURS 1*00EA W - WATAUGA DA-468-2,S(i. MI.;,4HO RDURATION AREA 11 - BOONE LOCAL; 667:7 SQ. Mii: 6-HOURDU)RATION AREA 12 -FORT PATRICK,I HENRY DMVI'62.8. SQ..M 'I.: 6-HOUR DURATION 50-- --

AREA 13-- NORTH FO K HOLSTON RIVER'NEAR GATE-IrY :9:.

-UR DU TION SEQUC AI Unit F Figur Figure 2.4.3-6 Unit Hydrographs, Areas 10-13 (Sheet 3 of 11)

)YAH NUCLEAR PLANT FINAL SAFETY NALYSIS REPORT

-ydrographs, Areas 10-13 e 2.4.3-6 (Sheet 3 of 11) 2.4-140

SQN-30,0004-20,000-4 0

2 48 s

TIME

-OUR

(;)

4)

I

,5 I

1 0-..R0 1 4',$ -.

12 24 3

j86

-TIME OUR

--AREA+S 14 & CHEROKESE ILOCAL; 854.6 SQ. MI,;6-HIiOUR DURATION EA 16-HOLSTON RIVER LO.AL, CHEROKEE DAM TO KNOXILLE GAUGE;319.6 SQ..ML; 6HOUR DURATION

.AREA 17-LITTLE RIVER; 376.SQ. Mi.; 4ýHOUR DURATION AREA 18-FORT LQUDOUN LOCAL; 323A SQO.

MI. 6-HOUR DURATION SEQU Unit Figu Figure 2.4.3-6 Unit Hydrographs, Areas 14-18 (Sheet 4 of 11)

OYAH NUCLEAR PLANT FINAL SAFETY

,NALYSIS REPORT Hydrographs, Areas 14-18 re 2.4.3-6 (Sheet 4 of 11) 2.4-141

SQN-C')

U-C,.,

w U) a 0

12 24 36 48 TiME-HOURS 60 AREA 19-LITTLE TENNESSEE RIVER AT NEEDMORE; 436:5 SQ MI.; 6.-HOUR DURATION

- AREA 20 - NANTAH.ALA DAM; 90.9 SQ. MI.: 2-HOUR DURAT!ON

...... AREA 21 - tUCKASEGEE RIVER AT BRYSON CITY, 653.8 SQ. ML; 6-HOUR DURATION AREA 22 - FONTANA LOCAL; 389.8 SQ. MI.; 4-HOUR DURATION SEQU Unit FigL Figure 2.4.3-6 Unit Hydrographs, Areas 19-22 (Sheet 5 of 11)

OYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Hydrographs, Areas 19-22 ire 2.4.3-6 (Sheet 5 of 11) 2.4-142

SQN-50,000 I

0 0

I 450000

,O'J I"

",I*

II I

I 1.I S30,000,

.1 23,0"00- ---

1? 0,000 2,00 1

/1IS 5I,+/

'S,,*

x.._I..

15,000

./jTIMIE-HOURS

RA2 AT A

OA AOECIC IE,

9.

SQ.

MI.

-MDRT

,,E/

2 "O L M

M 5

I*+/-*.l

.*+i

..............~~~~~~ni Hy rgrps Ara 23-27=+*+

+

Fu0 12 24 36 48 60 72 84 96 TIMEt HOURS

-AREA 23:- UITThE TENNESSEE RIVER LOC;AL, FONTANA TO CHILNOWEE DAM: 404.7-SQ. MI.: 6-HOUR DURATION.

ARE*FA 24,- "LITPTLE~ TENN E:SSEE: RIVER LOCAL, CHILHOWE*ETO TEL2LICO DAM: 650.2 SQ.

MI.

6-HFOUR D*URATION AREA* 25 - WATTIS BAR LOCAL ABOVE CLINCH RIVE=R; 295.3 SQ. MI.; 6-HOUR+DURATloN S-*

AREA+26 - CLINCHRIVER AT NORRIS DAM; 2,912.8SQ.:* MI.; 6-HOUR DURATION

-AEA 27[- MELTON HILL LOCAL: 431.9 SQ. MI.; 6, HOUR DURATION SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unit Hydrographs, Areas 23-27 Figure 2.4.3-6 (Sheet 6 of 11 )

Figure 2.4.3-6 Unit Hydrographs, Areas 23-27 (Sheet 6 of 11) 2.4-143

SQN-10,000 0EL (3

w 0

4z (3

05 5,000 ]

0 I

0 12 24 36 48 60 TIME-HOURS AREA33 - CLINCH RIVER LOCAL ABOVE MILE 16: 37.2SQ. MI.; 2-HOUR DURATION AREA 34-POPLAR CREEKAT MOUTH; 135.2 SQ.MI.; 2-HOUR DURATION AREA 36 - CLINCH RIVERLOCAL, MOUTH TO MILE 16; 293 SQ. MI.; 2-HOUR DURATION SEQUO' AN Unit Hyd Figure Figure 2.4.3-6 Unit Hydrographs, Areas 33, 34, 36 (Sheet 7 of 11)

YAH NUCLEAR PLANT FINAL SAFETY IALYSIS REPORT rographs, Areas 33, 34, 36 2.4.3-6 (Sheet 7 of 11) 2.4-144

SQN-U-

Uj 40,UUU 40,000-35,000.

30,000 25.000-20.000 15,000.

10,000 5,000 60

-~~~~~ ~ ~

~ ~

- -~

T 0

12 24 36 48 60 TIME - HOURS

-AREA 35 - EMORY RIVER At MOUTH; 868.8 SQO MI.; 4-HOUR DURATION

- - - AREA37 - WATTS BAR LOCAL BELOW CLINCH AIVER,,408.4 SQ. MI.; 6-HOUR DURATION SEQU A

Unit Figu Figure 2.4.3-6 Unit Hydrographs, Areas 35, 37 (Sheet 8 of 11)

OYAH NUCLEAR PLANT FINAL SAFETY kNALYSIS REPORT Hydrographs, Areas 35, 37 ire 2.4.3-6 (Sheet 8 of 11) 2.4-145

SQN-60,000-46,000-40,000 --- -

35,000 -c-0 0

12 24 36 TIME - HOURS

AREA 38 -,CHATUGE DAM; 189.1 SQ..Mi; 1-HOUR DURATION AREA 39-NOTTELY DAM. 214.3 SQ. MI; 1-HOUR.DURATION

---AREA 41 - APALACHIALOiCAL: 49.8 SQ. Mi.; 1-HOUR DURATION AREA 42-BLUE RIDGE DAM; 231.6 SQ. MI.; 2LHOUR DURATION SEQUOYI Fl ANA Unit Hydrogr Figure 2 Figure 2.4.3-6 Unit Hydrographs, Areas 38, 39, 41, 42 (Sheet 9 of 11)

,H NUCLEAR PLANT NAL SAFETY LYSIS REPORT aphs, Areas 38, 39, 41,42

.4.3-6 (Sheet 9 of 11) 2.4-146

SQN-30,000, 2 5,0 00..........----

aJ' S

I 20,00 0.--

12,0000------

20.000

'0 12 24 36 48 60 n

.. 4 96 TIME - HOURS AREA 40 - HIWASSEE RIVER LOCAL* 565.1i S.Q. M.; &*HOUR DURATION

-- -- -- AREA 43- -OCOEEý'ýO_ I LOCAL; 3616 SO. MI.; "*OUR DURATION

....--- -AREA 44A - HIWASSEE RIVER FROM CHARLEETOIWTIO APALACHIA,AND OCOEE NO, 1:686,6 SQ, MI 6-HOUR DURATlON A-

.,RE.A 44B - HIWAssEE RIVER FROM MOUTH To CHARLES'TON; 396.0 SO, Mi.; ($HOR DUtRATION

+

SEQUOYAH FIN/

ANALY Unit Hydrograph, Figure 2.4.3 Figure 2.4.3-6 Unit Hydrographs, Areas 40, 43, 44A, 44B (Sheet 10 of 11)

NUCLEAR PLANT

,L SAFETY

'SIS REPORT s, Areas 40; 43, 44A, 44B 1-6 (Sheet 10 of 11) 2.4-147

SQN-U.

U) a

'40,000 35,000 30,000 25,000 20,000-10,000-5,000 A

1-1, -----------------

0 12 24.

TIME - HOURS

-'AREA 45 - CHICKAIMIAUGA LOCAL; 792.1 SQ. MIL; 8-HOUR DURATION SEQ Fi)

Figure 2.4.3-6 Unit Hydrographs, Area 45 (Sheet 11 of 11) 36

}UOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unit Hydrographs, Area 45 jure 2.4.3-6 (Sheet 11 of 11) 2.4-148

SQN-740 z

NJ 0

al 720-

---TOP OF NORTH EMB: EL. 706.0

-TOP OF SOUTH EMB: EL. 707.0 700 -

690 -

680-j

---TOP OF GATES: EL. 685.44 670

-SPILLWAY CREST. 645.0 640-HEADWATER RATING, CURRENT CONFIGURATION I2j 630 I

62 0

200 400 600 800 DISCHARGE - 1000 CFS 1000 1200 1400 1600 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Chickamauga Dam Figure 2.4.3-7(Sheet 1 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Chickamauga Dam (Sheet I of 17) 2.4-149

SQN-N 0

C_

z w

U.

0 alt.

F w

770 -

TOP OF EMBANKMENT EL 770 0 760 -

750-

---TOP OF GATES. EL 745 0 740 -

730 -

720

-- SPILLWAY CREST. EL 7130 0 710-HEADWATER RATING 700

- TAILWATER RATING 690 I

680O 0

100 200 300 400 500 600 700 DISCHARGE - 1000 CFS 800 900 1000 1100 1200 1300 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Watts Bar Dam Figure 2.4.3-7 (Sheet 2 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Watts Bar Dam (Sheet 2 of 17) 2.4-150

SQN-840

= I I TOP OF EMBANKMENT EL 837 0 830 C) 820-

-- TOP OF GATES EL 815 0 z 810.

800 -

0 790 F-1_

t

--- SPILL* AY CREST-EL 783 0 780 70*

r-w HEADWATER RATING 760 TAILWATER RATING 750 740 0

50 100 150 200 250 300 350 400 450 500 550 600 DISCHARGE - 1000 CFS SEQU(

/

D Fig Figure 2.4.3-7 Discharge Rating Curve, Fort Loudoun Dam (Sheet 3 of 17)

)YAH NUCLEAR PLANT FINAL SAFETY

,NALYSIS REPORT ischarge Rating Curve, Fort Loudoun Dam ure 2.4.3-7 (Sheet 3 of 17) 2.4-151

SQN-a) a C,

z 0J 84O-

---TOP OF EMBANKMENT EL. 8330 830 820 J

--EMERGENCY SPILLWAY CREST EL 810TOPO GATES E 8150 800--

T 790-780 -

0 o

---SP LLWAY CREST EL 7730 760-

-HEADWATER RATING'

- TAILWATER RATING"

Includes emergency spillway discharge Tailwater shown at Tellico Dam 740-730 0

100 200 300 400 500 600 700 DISCHARGE - 1000 CFS 800 900 1000 1100 1200 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Tellico Dam Figure 2.4.3-7 (Sheet 4 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Tellico Dam (Sheet 4 of 17) 2.4-152

SQN-1410 1400

-TOP OF EMBANKMENT EL 1408 5

---TOP OF CONCRETE DAM EL xllý 0

z 0

Co

-A w

1392 0 1390

---TOP OF GAT :S EL 1385 0 1380 -

1370-1360-1350 SPILLWAY CREST. EL 13500 Note Tailwater rating not shown, no effec on outflow t34n I

I III 0

50 100 150 200 DISCHARGE - 1000 CFS 250 300 350 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Boone Dam Figure 2.4.3-7 (Sheet 5 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Boone Dam (Sheet 5 of 17) 2.4-153

SQN-1100 1080 1060 N

1040 C,

z 1020 W

aw

, 1000 w

IL z

0 r

980

-JuJ 960 940 920

---TOP OFI EARTH SADD ILE DAMS EL 11092 75

-- TOP OF GATES EL 1075 0

---SPILLWAY CREST EL 1043 0 H___

EADWATER RATING

- - TAILWATER RATING 0

50 100 150 200 250 DISCHARGE - 1000 CFS 300 350 400 450 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Cherokee Dam Figure 2.4.3-7 (Sheet 6 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Cherokee Dam (Sheet 6 of 17) 2.4-154

SQN-IN 0

z 0

lu 1040 O

---TOP CONCRETE DAM EL 1022 5

---TOP OF SADDLE DAMS EL 1023 5 1020

--TOP OF GATES EL 1002 0 1000 980 960

---SPILLWAY CREST EL 970 0 960 940 920

900, HEADWATER RATING

- - TAILWATER RATING 680 860 0

100 200 300 400 DISCHARGE - 1000 CFS 500 600 700 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Douglas Dam Figure 2.4.3-7(Sheet 7 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Douglas Dam (Sheet 7 of 17) 2.4-155

SQN-a 0

(0 W

1760 1740

-- TOP OF MAIN DAM EL 1727 0 1720-17200

-- TOP OF GATES. EL 17100 1700 1660-I

---SPILLWAY CREST EL 1675 0 1680 1640 1620o Note Tailwater rating not shown no effect on outflow 18600 1

0 100 200 300 DISCHARGE - 1000 CFS 400 500 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Fontana Dam Figure 2.4.3-7 (Sheet 8 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Fontana Dam (Sheet 8 of 17) 2.4-156

SQN-0 t-J w4 I--

U..

z0

-.J Lu 1300-1290-1280-1270 -

-TOP OF DAM: EL. 1270.0

-- TOP OF GATES: EL. 1263.0 1260 1250 1240 1230

-- SPILLWAY CREST: EL. 122860 Note: Tailwater rating not shown, no effect on outflow.

1220 I

I 0

50 100 150 200 DISCHARGE - 1000 CFS 250 300 350 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Fort Patrick Henry Dam Figure 2.4.3-7 (Sheet 9 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Fort Patrick Henry Dam (Sheet 9 of 17) 2.4-157

SQN-820 810 m 800 z2 M 790 Lu 014.

t-m 780 0

770

,-J LU 760 750

-- TOP OF NORTH NONOVERFLOW DAM: EL. 805.48

-TOP OF SOUTH NONOVERFLOW DAM: EL. 802.0

--TOP OF GATES: EL. 796.0

-SPILLWAY CREST: EL. 754,0 Note: Tailwater rating not shown, no effect on outflow.

_I__

_II 0

50 100 150 200 DISCHARGE - 1000 CFS 250 300 350

'SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Melton Hill Dam Figure 2.4.3-7 (Sheet 10 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Melton Hill Dam (Sheet 10 of 17) 2.4-158

SQN-1070 1060 1050 0 0 w

1030 t-w 1020 z 1020 iu 1010 1000 990

---TOPOF DAM EL 10610

-- TOP OF GATES EL 1034 0

/--SPILLWAY CREST EL 1020 0 Note - Tajiwater rating not shown, no effect on spillway outflow 0

50 100 150 200 DISCHARGE - 1000 CFS 250 300 350 400 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Norris Dam Figure 2.4.3-7 (Sheet 11 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Norris Dam (Sheet 11 of 17) 2.4-159

SQN-17701 1765...--

TOP OF DAM: EL. 1765.0 a)

> 1760 C,

z

-jIn LU wo 1755-0 1750-j 175

.. M RB*

~*

~pL*w*

1 11*:0 Note: Tailwater rating not shown, no effect on outflow.

1740 050 100 150 200 250 DISCHARGE - 1000 CFS SEQUOYJ Fl ANA*

Disch; LSo Figure 2 Figure 2.4.3-7 Discharge Rating Curve, South Holston Dam (Sheet 12 of 17)

AH NUCLEAR PLANT INAL SAFETY LYSIS REPORT arge Rating Curve, uth Holston Dam

.4.3-7 (Sheet 12 of 17) 2.4-160

SQN-m 0

C, 0

-TOP OF DAM EL 20120 2010 2005 2000-1995 1990 START OF 'THROAT CONTROL" EL 19890 TO 1990 0 1980-1975

---MORNING GLORY SPILLWAY CREST EL 19750 Note Tailwater rating not shown no effect on outflow 1970 1 0

10 20 30 40 50 60 70 80 90 100 DISCHARGE - 1000 CFS SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Watauga Dam Figure 2.4.3-7 (Sheet 13 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Watauga Dam (Sheet 13 of 17) 2.4-161

SQN-1 7 1 5 rT

_T.....

1710 a

1705

-TOP OF DAM: EL 1705 0

Lii LU 1695 0

=_j I-4 4

1 6 8 5 16850 1675

-SPLL WAY CRESTL O75A Note; Tailwater rating not shown, no effect on outflow 1670 I

0 20 40 60 80 1 00 120 140 160 180 200 DISCHARGE - 1000 CFS SEQUOYAHI FINAL ANALYS Discharge Rating Figure 2.4.3-7 Figure 2.4.3-7 Discharge Rating Curve, Blue Ridge Dam (Sheet 14 of 17) 4JUCLEAR PLANT SAFETY IS REPORT Curve, Blue Ridge Dam (Sheet 14 of 17) 2.4-162

SQN-1950 1945 z

-LJ 0

u.1 z

0

-1Lu 1940 1935 1930 TOP OF DAM: EL 1940

-TOP OF GATES: EL 1928 I

1925

-SPILLWAY CF EST: EL 1923 Note: Tailwater rating not shown, no effect on outflow I

I 1920 4-0.00 20.00 40.00 60.00 80.00 DISCHARGE - 1000 CFS 100.00 120.00 140.00 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Chatuge Dam Figure 2.4.3-7 (Sheet 15 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Chatuge Dam (Sheet 15 of 17) 2.4-163

SQN-1550 1545.

-TOP OF DAM: EL 1537.5 1540 C0 1535 1530 0

-jTOP OF GATES: EL 1526 U

1525 z0 1520 1515 1510 1505

-SPILLWAY CREST: EL 1503.5 1500 0

50 100 150 200 DISCHARGE - 1000 CFS SEQUOYAI-FIN/

ANALY Discharge Ratin Figure 2.4.3 Figure 2.4.3-7 Discharge Rating Curve, Hiwassee Dam (Sheet 16 of 17)

NUCLEAR PLANT

,L SAFETY

'SIS REPORT g Curve, Hiwassee Dam 3-7 (Sheet 16 of 17) 2.4-164

SQN-0 CD z

-J U) uJ 0

U) 4 I-U)

UJ 2

0 4

U)

-j U) 1810 1805 1800 1795 1790 1785 1780 1775 1770

-TOP OF DAM: EL 1807.5

-TOP OF GATES: EL 1780

-SPILLWAY CREST: EL 17 75 0

20 40 60 80 100 120 140 160 180 20 DISCHARGE - 1000 CFS 00 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Nottely Dam Figure 2.4.3-7 (Sheet 17 of 17)

Figure 2.4.3-7 Discharge Rating Curve, Nottely Dam (Sheet 17 of 17) 2.4-165

SQN-fo DouglaS Diff R

F6RM3230' lfolilcoDamr vfWm 0.30 4

Chilhowee Duni SEQUOYAH NUCLEAR PLANT

LTRM 33.60.

FINAL SAFETY ANALYSIS REPORT Fort Loudoun - Tellico SOCH Unsteady Flow Model Schematic Figure 2.4.3-8 Figure 2.4.3-8 Fort Loudoun - Tellico SOCH Unsteady Flow Model Schematic 2.4-166

SQN-I a'.

OR IWItft4 C..pMaThk I7W7n IWn W73 W11 3

3MW7 3P&W73 X?3f DATE SEQUOYAH NUCLEAR FINAL SAFETY ANALYSIS REPOF Unsteady Flow Model Fort l Reservoir March 1973 F Figure 2.4.3-9 (Sheet 1 Figure 2.4.3-9 Unsteady Flow Model Fort Loudoun Reservoir March 1973 Flood (Sheet I of 2)

PLANT I*T Loudoun Flood of 2) 2.4-167

SQN-940 m2 020 Alm ODm im

-41"MN Rhl 0 Do TaM~sl m1 73 31M197 MOM97 3117m7 3*19 DATE 1173M WIAM 3M21*3 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Fort Loudoun Reservoir March 1973 Flood Figure 2.4.3-9 (Sheet 2 of 2)

Figure 2.4.3-9 Unsteady Flow Model Fort Loudoun Reservoir March 1973 Flood (Sheet 2 of 2) 2.4-168

SQN-I" 8S14 813 lmeal

=

w~lmmms aft LitW1U 02 6111L

=

WM3 M3 &=

=3 SO=103 WM MM M3 W1 8

WNW $M1G3 103 811733 W8 DATE SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Fort Loudoun - Tellico Reservoir May 2003 Flood Figure 2.4.3-10 (Sheet 1 of 3)

Figure 2.4.3-10 Unsteady Flow Model Fort Loudoun - Tellico Reservoir May 2003 Flood (Sheet I of 3) 2.4-169

SQN-maa S,

0 Ina M

0m 3 DATf b4WTWg1 p-=3 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Fort Loudoun - Tellico Reservoir May 2003 Flood Figure 2.4.3-10 (Sheet 2 of 3)

Figure 2.4.3-10 Unsteady Flow Model Fort Loudoun - Tellico Reservoir May 2003 Flood (Sheet 2 of 3) 2.4-170

SQN-an1 m

Ws.

M tt R II 811 DATE umao HWdTWDB OW43~

SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Fort Loudoun - Tellico Reservoir May 2003 Flood Figure 2.4.3-10 (Sheet 3 of 3)

Figure 2.4.3-10 Unsteady Flow Model Fort Loudoun - Tellico Reservoir May 2003 Flood (Sheet 3 of 3) 2.4-171

SQN-Melton Hill Dam tRM 601.1 F.ort'Loud6udh Dam-Mile, q602.-3 River LTIRM,107.

TRM 520.9 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Watts Bar SOCH Unsteady Flow Model Schematic Figure 2.4.3-11 Figure 2.4.3-11 Watts Bar SOCH Unsteady Flow Model Schematic 2.4-172

SQN-m~

766 DATE 760 Udo*

Unsead Flo Mode aat a

FWmevwyig FlW MarchS1973F

~~DUE FINA SAFETY FINALYSSAFEPOTY Unsteady Flow Model Watts Bar Reservoir March 1973 Flood Figure 2.4.3-12 Figure 2.4.3-12 Unsteady Flow Model Watts Bar Reservoir March 1973 Flood 2.4-173

SQN-ITMMI mmM LUTW LTO

/(*-----

ob--~

lamm 533614103 5/15163 510103 S763 51 6103 5616#3 6t1103 5111163* 5126 511303 51/4103 51161035116103 51171/03 511603 DAT_

SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Watts Bar Reservoir May 2003 Flood Figure 2.4.3-13 Figure 2.4.3-13 Unsteady Flow Model Watts Bar Reservoir May 2003 Flood 2.4-174

SQN-Watt Di*r:Da in TRV4499-t Chadeston Gauge hýH-RM I.9ý-

ChioK'a'mi-U'gi! DWm'

'RM 471A

`yRM480!5, SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Chickamauga SOCH Unsteady Flow Model Schematic Figure 2.4.3-14 Figure 2.4.3-14 Chickamauga SOCH Unsteady Flow Model Schematic 2.4-175

SQN-M 6"

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=in17 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Chickamauga Reservoir March 1973 Flood Figure 2.4.3-15 Figure 2.4.3-15 Unsteady Flow Model Chickamauga Reservoir March 1973 Flood 2.4-176

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WS2UC1, SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Chickamauga Reservoir May 2003 Flood Figure 2.4.3-16 Figure 2.4.3-16 Unsteady Flow Model Chickamauga Reservoir May 2003 Flood 2.4-177

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EWESMSM MM MILE SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Chickamauga Steady State Profile Comparisons Figure 2.4.3-17 Figure 2.4.3-17 Chickamauga Steady State Profile Comparisons 2.4-178

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1in no 460 6NO OYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT railwater Rating Curve, Wafts Bar Dam Figure 2.4.3-18 2.4-179

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SQN-Security-Related Information -Withheld Under IOCFR2.390 Figure 2.4.3-20 West Saddle Dike Location Plan and Section 2.4-181

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Sequoyah Nuclear Plant Final Safety Analysis Report PMF Elevation Hydrograph at Sequoyah Nuclear Plant 3/16 Figure 2.4.3-21 675 3/15 3/17 3/18 3/19 Date 3/20 3/21 3/22 3/23 3/24 Figure 2.4.3-21 PMF Elevation Hydrograph at Sequoyah Nuclear Plant 2.4-182

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Ls 447 15,03"A0 19 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Results of Analysis For Operating Basis Earthquake-Watts Bar Dam Figure 2.4.4-1 Figure 2.4.4-1 Powerhouse & Spillway Results of Ananlysis For Operating Basis Earthquake - Watts Bar Dam 2.4-188

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v 1-d 1/172 4oo 9iil.V SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Results of Analysis For Operating Basis Earthquake-Fort Loudoun Dam Figure 2.4.4-2 Figure 2.4.4-2 Powerhouse & Spillway Results of Analysis For Operating Basis Earthquake - Fort Loudoun Dam 2.4-189

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SAM W W.Vd 3 improvements have icreased the etecdive height of the embankment to a nonmium El 836 (See Foil Loudoun Protect Drawing 10W222-1)

Fiekd surveys ndi:ate a minrtlqrr height Ei 836.9 was achieved T YPICAL e-(MAAe-*r sec rlayo~

SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Embankment Results For Operating Basis Earthquake, Fort Loudoun Dam Figure 2.4.4-3 Figure 2.4.4-3 Embankment Results Of Analysis For Operating Basis Earthquake - Fort Loudoun Dam 2.4-190

SQN-Security-Related Information - Withheld Under IOCFR2.390 Figure 2.4.4-4 Analysis For OBE & 1/2 PMF Assumed Condition of Dam After Failure of Norris Dam 2.4-191

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SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Spillway & Nonoverflow Results Of Analysis For OBE, Cherokee Dam Figure 2.4.4-5 Figure 2.4.4-5 Spillway & Nonoverflow Results of Analysis For Operating Basis Earthquake - Cherokee Dam 2.4-192

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SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Embankment Results Of Analysis For OBE, Cherokee Dam Figure 2.4.4-6 Figure 2.4.4-6 Embankment Results of Analysis For Operating Basis Earthquake - Cherokee Dam 2.4-193

SQN-Security-Related Information -Withheld Under 10CFR2.390 Figure 2.4.4-7 Assumed Condition Of Dam After Failure OBE & 112 Probable Max Flood - Cherokee Dam 2.4-194

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PooA,4.A SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Spillway & Nonoverflow Results Of Analysis For OBE, Douglas Dam Figure 2.4.4-8 Figure 2.4.4-8 Spillway & Nonoverflow Results of Analysis For Operating Basis Earthquake - Douglas Dam 2.4-195

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SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Saddle Dam No. 1 Results Of Analysis For OBE, Douglas Dam Figure 2.4.4-9 Figure 2.4.4-9 Saddle Dam No. 1 Results of Analysis For Operating Basis Earthquake - Douglas Dam 2.4-196

SQN-Security-Related Information -Withheld Under 1 OCFR2.390 Figure 2.4.4-10 Douglas Dam Assumed Condition of Dam After Failure OBE & 1/2 Probable Maximum Flood - Douglas Project 2.4-197

SQN-Security-Related Information - Withheld Under 10CFR2.390 Figure 2.4.4-11 Fontana Dam Assumed Condition of Dam After Failure OBE & 1/2 PMF 2.4-198

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-A 0.9 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Spillway Results Of Analysis For SSE Earthquake. Fort Loudoun Dam Figure 2.4.4-13 Figure 2.4.4-13 Spillway Results of Analysis For SSE Earthquake Fort Loudoun Dam 2.4-200

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SQN-Security-Related Information - Withheld Under 10CFR2.390 Figure 2.4.4-15 Fort Loudoun Dam Assumed Condition of Dam After Failure SSE Combined with a 25 Year Flood - Fort Loudoun 2.4-202

SQN-Security-Related Information - Withheld Under 10CFR2.390 Figure 2.4.4-16 Norris Dam SSE & 25 Year Flood Judged Condition of Dam After Failure - Norris Dam 2.4-203

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UOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT SSE With Epicenter In North Knoxville Vicinity Figure 2.4.4-17 2.4-204

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-L 3/15 3/16 3/17 3/18 3/19 3/20 3/21 3/22 3/23 3/24 3/25 3/26 3/27 DATE 3/28 3/29 SEQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Seismic Combinatinon With Failure Of Cherokee, Douglas & Tellico In OBE withl/2 PMF Figure 2.4.4-18 Figure 2.4.4-18 OBE Failure Of Cherokee, Douglas & Tellico With 1/2 PMF 2.4-205

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Figure 2.4.4-19 SSE With Epicenter In West Knoxville Vicinity 3EQUOYAH NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT SSE With Epicenter In West Knoxville Vicinity Figure 2.4.4-19 2.4-206

SQN-Security-Related Information - Withheld Under IOCFR2.390 Figure 2.4.4-20 Tellico Dam Assumed Condition of Dam After Failure SSE Combined With a 25 Year Flood Tellico Project 2.4-207

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Figure 2.4.14-3 (Sheet 2 of 2) - Sequoyah Nuclear Plant Rainfall Flood Warning Time Basis for Safe Shutdown For Plant-Flooding - Summer Events 2.4-214

ENCLOSURE 2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING On March 29, 2012, a Category I public meeting was held between the U.S. Nuclear Regulatory Commission (NRC) and representatives of the Tennessee Valley Authority (TVA) at NRC Headquarters, One White Flint North, 11555 Rockville Pike, Rockville, Maryland.

The purpose of the meeting was to discuss TVA's planned submittal of a license amendment request to revise the licensing and design basis for hydrologic engineering as described in the Watts Bar Nuclear Plant (WBN), Unit 1 Updated Final Safety Analysis Report (UFSAR).

Following this pre-application meeting, the NRC Staff published a meeting summary, "Summary of March 29, 2012, Pre-Application Meeting with Tennessee Valley Authority on Changing the Licensing Basis for Hydrologic Engineering (TAC No. ME8200)," dated April 11, 2012 (ADAMS Accession No. ML12097A306).

In this letter, the NRC Staff recommended that TVA consider addressing the following issues in the submittal. Any issue only related to WBN Unit 1 or for which the response is the same as that for WBN Unit 1 as described in the TVA submittal to the NRC Document Control Desk, "Application to Revise Watts Bar Nuclear Plant Unit 1 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, TAC No. ME8200 (WBN-UFSAR-12-01)," is noted below.

1. The chronology and basis for the changes made to the hydrologic engineering design basis from 1995 to 1998 to 2009.

This response is the same as WBN Unit 1 except for references to the applicable site, and applies to the hydrologic analysis for Sequoyah Nuclear Plant (SQN) Units 1 and 2.

The probable maximum flood (PMF) for SQN Units 1 and 2 at the time of Operating License issuance was elevation 722.6 ft, and included assumptions based on the existing understanding of dam structural stability and capability during seismic and extreme flood events in the 1970's. In the 1980's and 1990's, TVA implemented a Dam Safety Program (DSP) that resulted in dam safety modifications that increased dam structural stability and capability Between 1995 and 1998, TVA completed a hydrologic reanalysis to credit the results of the dam safety modifications that had been completed. This reanalysis resulted in lowering the SQN Units 1 and 2 calculated PMF to elevation 719.6 ft, but no physical changes to SQN Units 1 and 2 site flooding protection features were implemented as a result of the decreased design basis flood (DBF) elevations.

In 2009, TVA completed a hydrologic reanalysis to address closure of issues involving the hydrologic analysis for the application for a combined operating license '(COLA) for the proposed Bellefonte Nuclear Plant (BLN) Units 3 and 4, in accordance with 10 CFR 52. This reanalysis resulted in raising the SQN Units 1 and 2 calculated PMF to elevation 722.0 ft. Although this was not higher than the original PMF but is higher than the earlier revised PMF, no physical changes to SQN Units 1 and 2 site flooding protection features were required based on the changes to PMF alone.

However, because of the updates to the Design Basis Flood (DBF) levels based on the most recent wind-wave runup calculations, the Spent Fuel Pit Pump Motors and equipment required for flood mode operation located in the Diesel Generator Building are affected. Temporary compensatory measures are in place and documentation changes and permanent plant modifications are planned to provide adequate flooding protection for this equipment. This is described in Section 1.0 of Enclosure 1, Summary Description.

Page 1 of 14

ENCLOSURE2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING

2. An update of the status of TVA's resolution of long-term hydrology issues, per the staff's request in the NRC letter dated January 25, 2012.

This response is the same as WBN Unit 1 except for references to the applicable site, and applies to the hydrologic analysis for SQN Units 1 and 2.

On May 31, 2012, a Category 1 public meeting was held between the NRC staff and representatives of the IVA at NRC Headquarters, Two White Flint North, 11545 Rockville Pike, Rockville, Maryland.

The purpose of the meeting was to discuss (1) the current licensing basis for flooding at WBN Unit 1 and SQN Units 1 and 2, (2) the status of TVA's current licensing basis reanalysis, (3) flooding protection and flood mode operation at WBN and SQN, (4) modular flood barriers at TVA dams, and (5) TVA's flooding reevaluation plan regarding the NRC's Fukushima 50.54(f) letter dated March 12, 2012.

Following this senior management meeting, the NRC Staff published a meeting summary, "Summary of May 31, 2012, Senior Management Meeting with Tennessee Valley Authority on the Licensing Basis for Flooding/Hydrology," dated June 6, 2012 (ADAMS Accession No. ML12157A457).

The TVA slide presentation is provided in ADAMS Accession No. ML12156A076. In the meeting summary, the NRC Staff acknowledged the following related to the status of TVA's resolution of long-term hydrology issues:

a. TVA discussed the challenges faced with the complexities of the revised hydrology modeling used for the licensing basis re-analysis, and TVA acknowledged the lack of timeliness in resolving the flooding issue.

b. TVA discussed the management commitment for regaining safety margin for flooding and updating the current licensing basis through a high quality analysis, ensuring plant operability, and improved timeliness.

c. TVA made a number of commitments at the end of the presentation.

These commitments have now been formalized in the TVA submittal to the NRC Document Control Desk, "Commitments Related to Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," dated June 13, 2012 (ADAMS Accession No. ML12171A053).

Therefore, the NRC Staff including senior management has been provided an updated status based on the TVA presentation, responses provided by TVA during the presentation, and the commitments provided by TVA regarding future actions to complete the hydrologic analysis and applicable documentation changes and permanent plant and dam embankment modifications. With the exception of implementing the commitments provided to the NRC, there are no other actions required for this issue for SQN Units 1 and 2.

3. The relationship and use of the 25-year flood level versus the May 2003 flood level in TVA's new analysis.

This response is the same as for WBN Unit'1 and applies to the hydrologic analysis for SQN Units 1 and 2.

As described in the second paragraph of Section 3.2 of Enclosure 1, Uncertainties, per NUREG/CR-7046 the only manner to address the uncertainty in the hydrologic analysis is Page 2 of 14

ENCLOSURE2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING through calibration of the model to historic flood events or sensitivity analyses.

TVA calibrated the model to historic flood events using the two highest recent flood events where data exists. The floods used for calibration are March 1973 and May 2003 storms. The May 2003 flood event was a much larger flood than the 25-year flood. The May 2003 flood reached a maximum elevation of 657.2 feet on May 8, 2003 on the Tennessee River at the Walnut Street gage at Tennessee River Mile (TRM) 464.2.

This compares with the March 1973 flood, the maximum flood of record since regulation by the TVA system, which reached a maximum elevation of 658.06 feet on March 18, 1973.

Based on the flood frequency elevations at the Walnut Street gage the May 2003 flood was about a 100-year event as shown in the tabulation below.

The flood frequency elevations at the Walnut Street gage TRM 464.2 are as follows:

Flood Elevation (ft.)1 1 -year 644.0 2-year 649.2 5-year 650.6 10-year 653.4 50-year 655.9 100-year 657.0 500-year 663.6 1 National Geodetic Vertical Datum (NGVD) 1929 Based on review of observed elevations at key locations in the vicinity of SQN, the May 2003 flood event was about a 100-year event over the reach of interest with May 2003 maximum elevations exceeding flood of record elevations at some locations. A comparison of the maximum elevations reached during the May 2003 flood at key locations is shown in the tabulation below.

Location Maximum Elevation (ft.) NGVD 1929 Flood of Record May 2003 Chickamauga Dam Headwater 686.99 5/9/84 687.13 5/7/2003 Watts Bar Dam Tailwater 696.95 3/17/1973 694.17 5/7/2003 Using the calibrated model based upon the two highest recent flood events where data exists (i.e., March 1973 and May 2003), the 25-year flood event specified in RG 1.59 was used for application with the postulated Safe Shutdown Earthquake (SSE) failure of upstream dams as described in Section 2.1 of Enclosure 1, Proposed Changes, under the subheading Section 2.4.4, Potential Dam Failures, Seismically Induced. The 25-year flood magnitude was developed using flood volume frequency relationships.

The inflow hydrographs were developed using the March 1973 flood, the flood of record, and a large regional flood, scaled by the ratio of the 25-year volume to the 1973 volume. This provides an estimate of the 25-year flood based on historical watershed experience.

4. The justification for the proposed combinations of dam failure scenarios used in TVA's new analysis.

This response is the same as WBN Unit 1 except for references to the applicable site, and applies to the hydrologic analysis for SQN Units 1 and 2.

Page 3 of 14

ENCLOSURE 2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING The methodology used to develop the controlling seismic/flood condition at SQN is the same as previously followed for the site evaluations described in the SQN Units 1 and 2 UFSAR as follows:

1. A ground motion attenuation function was generated to describe the peak horizontal acceleration of rock at the free surface versus distance from the epicenter.

2. Using the attenuation relationship, the seismic base accelerations for various dams having large stored inventory (reservoir storage) and low spatial separation were determined.

3. The seismic stability of the dams for the seismic event centered at the dam (maximum base acceleration) and seismic events which cause dam failures at adjacent dams (less than maximum base acceleration) were then determined.

4. Based on the predicted seismic stability of the dams (individually and in combination) and reservoir storage, the potential seismic failure/flooding combinations were screened to identify the controlling case for SQN.

5. Hydrological routing for the potential controlling cases was then performed.

The ground motion attenuation functions to permit evaluation of simultaneous failure of two or more dams were based on the attenuation characteristics of an Operating Basis Earthquake (OBE) and a SSE occurring in the geographic area encompassing the Tennessee Valley above Guntersville dam.

Utilizing historical earthquake data from locations near the Tennessee Valley, an attenuation curve was developed.

Using this OBE/SSE relationship, a representation of the earthquake was developed in the form of concentric circles radiating from a center 0.09g (OBE) or 0.1 8g (SSE) acceleration with each circle representing decreasing levels of base acceleration as the distance from the epicenter increased.

The concentric circles centered at an acceleration of 0.09g/0.18g were then strategically moved around the dams above Guntersville Dam to determine potential multi-site critical base acceleration levels.

The dams above Guntersville were examined for seismic stability based on base acceleration level. During the period from 1970 to 1988, the initial seismic stability analyses were performed on the concrete dam sections and the earth embankments of critical dams.

In this evaluation, some of the concrete dams such as Apalachia, Fort Patrick Henry, Melton Hill and Ocoee No. 3 were not analyzed due to their relatively small storage volume and were postulated to fail. In other cases, more detailed seismic evaluations were performed, such as at Norris Dam. The more detailed evaluation of Norris dam concluded that the dam would not fail in OBE (coincident with one-half PMF) or SSE (coincident with 25-year flood).

However, for purposes of the seismic failure combinations Norris dam was conservatively postulated to fail with only the resulting debris field impeding flow.

Using the dam base accelerations and seismic stability evaluations (or failure assumptions) as screening criteria, various flood-seismic failure combinations were identified. Cases to be evaluated further were selected based on the potential reservoir flood volume released in seismic failures, the relative timing of those releases, and in some cases results of previous flood routing analysis.

Page 4 of 14

ENCLOSURE 2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING The impact of multiple failures of the large reservoir dams identified in the screening evaluations bound the effects of a single dam failure. Thus, single dam failures were not further evaluated.

Using the earthquake attenuation function, the seismic stability determinations, reservoir volume, flood wave timing, and informal routing methods, the following cases were defined as having the potential to control at SQN for OBE coincident with one-half PMF:

1. Simultaneous failure of Norris and Tellico Dams: Melton Hill Dam located below Norris Dam is not failed with the OBE in this scenario to maximize the downstream impact of the seismic failure wave from Norris Dam that overtops and fails Melton Hill Dam which is judged to be more critical.

2. Simultaneous partial failure of Fontana Dam and complete failure of Hiwassee, Apalachia, Blue Ridge, and Tellico Dams due' to an OBE at a location between Hiwassee and Fontana:

Fort Loudoun and Watts Bar Dams are seismically stable at OBE base accelerations for this epicenter.

3. Simultaneous partial failure of Fontana Dam and complete failure of Tellico Dam: Fort Loudoun and Watts Bar Dams are seismically stable at base OBE accelerations.

At least three other failure combinations evaluated in the original SQN Units 1 and 2 UFSAR studies and judged not to be controlling were not re-evaluated as a part of the new analysis since they were not controlling in the original analysis.

The following failure combinations for the SSE coincident with the 25-year flood were defined as having the potential to control at SQN using the evaluation criteria:

1. Simultaneous failure of Norris, Cherokee, Douglas and Tellico Dams with SSE epicenter located in the North Knoxville vicinity: For this combination, Fort Loudoun, Watts Bar and Fontana Dams do not fail since the attenuated base acceleration at these dams is less than the base acceleration for which the dams are seismically stable. Melton Hill Dam is not failed seismically to maximize the downstream impact by allowing Melton Hill Dam to overtop and fail due to the Norris Dam failure wave.

2. Simultaneous failure of Norris, Douglas, Fort Loudoun and Tellico Dams:

For this combination, Cherokee, Fontana and Watts Bar Dams do not fail since the attenuated base acceleration at these dams is less than the base acceleration for which the dams are seismically stable.

Melton Hill Dam is not failed seismically to maximize the downstream impact by allowing Melton Hill to overtop and fail due to the Norris Dam failure wave.

At least seven other failure combinations evaluated in the original SQN Units 1 and 2 UFSAR studies and judged not to be controlling were not re-evaluated as a part of the new analysis.

Flood simulations for the five failure combinations described above were performed to define the maximum bounding elevation at SQN. This is further described in Section 2.1 of Page 5 of 14

ENCLOSURE2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING, Proposed Changes, under the subheading Section 2.4.4, Potential Dam Failures, Seismically Induced.

5. The purpose of the finite element analysis on the Fontana Dam.

This response is the same as WBN Unit 1, and applies to the hydrologic analysis for SQN Units 1 and 2.

As part of TVA's DSP and consistent with the Federal Guidelines for Dam Safety, TVA performed a review of Fontana Dam in the mid-1980s to determine if the dam was capable of withstanding a maximum credible earthquake (MCE) (

Reference:

Fontana Project Dam Safety Analysis Report, April 1986).

The evaluation determined that Fontana Dam was capable of safely passing the PMF but the dam's ability to withstand earthquake loading was not assured. As a result of this finite element analysis, reinforcement of the upper portion of the non-overflow dam was recommended and subsequently implemented to ensure the dam would remain stable for the MCE.

Since this original finite element analysis did not consider the alkali aggregate reaction (AAR) expansion issues at Fontana Dam, additional analyses were performed to evaluate the seismic/hydrostatic stability of the dam and the impacts of stresses associated with AAR expansion in the dam structure.

Patterned cracking was first observed in the dam in 1949. Also, it was noted that the dam was beginning to tilt in the upstream direction at that time. In 1972, cracking was observed in the walls of the drainage gallery in the curved concrete blocks of the dam. A six-inch wide slot with a depth of about 95 feet was cut between November 1975 and July 1976 at the joint of Blocks 32/33 to relieve some of the stress. The slot had completely closed at the top of dam by October 1983. The top third (35 feet) of this slot required re-cutting to a width of five inches between October 1983 and January 1984. Slot closure measurements indicated that the slot closed gradually over time and would require re-cutting in the next several years. The third slot cutting to a width of six inches was performed between February - May 1999 and January - May 2000.

Clearance problems were first detected in the spillway gates of the main spillway in 1967.

Pier tilting due to concrete growth was causing binding of the gates when they were being opened. The gates were trimmed four times between 1967 and 1989. In the late 1990's, it was concluded that slot cuts on each end of the spillway would help reduce the tilting of the end piers of the spillway.

Two slots with the same width of about 0.6 inches, and with depths of 82 and 57 feet at joint Blocks 34/35 and 41/42 respectively, were cut in January 1999. In November 1999, re-cutting of the spillway slots was undertaken. However, slots 34/35 and 41/42 had closed during the summer season at the top of the slot by 2001.

In summary, three slots have been cut in Fontana Dam (Blocks 32/33, Blocks 34/35, and Blocks 41/42) to address problems associated with AAR. The first slot was cut at Blocks 32/33 in 1975.

The slot was required to eliminate the longitudinal force from the long straight portion of the dam. The longitudinal force was tending to push the curved blocks upstream, thus creating the observed cracks. The two spillway slots located at each end of the spillway (Blocks 34/35 and Blocks 41/42) were installed to help control tilting of the piers into the spillway.

Page 6 of 14

ENCLOSURE2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING A finite element analysis was used to evaluate the existing slots in either the open or closed condition, the effects of cutting deeper slots, the effects of cutting additional slots, and to provide recommendations for long-term slot cutting strategy for best management of the Fontana Dam AAR problem.

An August 2006 seismic/hydrostatic stability analysis performed by Acres International which considered the combined impacts of stresses associated with AAR expansion of the dam structure concluded that although the minimum sliding factor of safety is less than 1.0 for the critical section (FS = 0.814) when subjected to a sustained acceleration of 0.26g, the post-earthquake stability of the dam is acceptable.

6. Discuss whether approvals for the dam and river operations modifications are required from other agencies (e.g., U.S. Army Corps of Engineers).

This response is the same as WBN Unit 1, and applies to the hydrologic analysis for SQN Units 1 and 2.

TVA was created as a Federal agency by the Tennessee Valley Authority Act of 1933 with specific responsibilities for the unified development of the Tennessee River system.

Approval is not required from other agencies for TVA's modifications to its dam and river system operations. However, modifications must be consistent with procedures set forth by the National Environmental Policy Act (NEPA), which is the same requirement for other federal agencies.

As a procedural act, NEPA calls for Federal agencies to make informed decisions, consider alternatives, to have decision-making processes that consider the environmental impacts of their proposed actions, and provide full disclosure of the process as applied. The level of environmental review required for a given action depends on the expected impact on the environment and/or when the proposed action is likely to be controversial.

The most recent environmental reviews that effected modification of the WVA river system were completed as Environmental Impact Statements (EIS) as follows:

1. Tennessee River and Reservoir System Operation and Planning Review, TVA, December 1990. Record of Decision issued February 1991.

2. Reservoir Operations Study, TVA, February 2004. Record of Decision issued May 2004.

The U.S. Army Corps of Engineers (USACE) and U.S. Fish and Wildlife Service were cooperating agencies on this EIS.

As a part of the NEPA process, other Federal agencies and the public are invited to participate in the process. Consistent with the NEPA process, the final decision on any action to be taken as a result of the environmental review rests with the initiating Federal agency.

In the case of reviews that have a potential impact resulting in modification of Tennessee River system operation, WVA makes the final decision on what actions are adopted for implementation.

The Act further gave TVA the power to construct dams and reservoirs on the Tennessee River and its tributaries to provide for navigation and control floods on the Tennessee and Mississippi River basins. To date, TVA has either acquired or constructed 49 dams located in seven different states as a part of the unified development of the region. The power given Page 7 of 14

ENCLOSURE2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING to TVA for construction of dams and reservoirs in the Tennessee River basin is much like the authority given to the USACE on other river systems.

TVA has had a DSP since the first dams were acquired and/or built. Dam safety ensures that the impoundments and dams are designed, constructed, operated and maintained as safely and reliable as is practical. The DSP was formalized in 1982 to ensure consistency with the Federal Guidelines for Dam Safety which was issued in 1979. The guidelines apply to management practices for dam safety of Federal agencies responsible for the planning, design, construction, operation, or regulation of dams. Today, the Dam Safety Governance (DSG) procedures define TVA's dam safety responsibilities to ensure compliance with the Federal guidelines.

Since the DSP was formalized in 1982, TVA has systematically evaluated its dams for hydrologic and seismic adequacy which has resulted in several dams being physically modified.

These modifications and operational changes as described above have been completed consistent with NEPA procedures.

The one location on the WVA system where an operational change would require the concurrence of the USACE is at Kentucky Dam. Kentucky Dam, located about 23.0 miles above the confluence of the Tennessee River with the Ohio River, is connected by a navigation canal located just above each dam to Barkley Reservoir, owned by the USACE.

Thus, the Kentucky and Barkley Dams have to be operated in tandem. Further, the USACE has the authority to direct the operation of Kentucky reservoir during critical flood operations on the lower Ohio and Mississippi Rivers. The physical location and the large flood storage available allows Kentucky reservoir to provide significant flood reduction benefits on the lower Ohio and Mississippi Rivers.

There have been no operational changes proposed at Kentucky Dam that would require TVA to obtain concurrence from the USACE.

7. Discuss the overall uncertainties in TVA's revised analysis calculations.

This response is the same as WBN Unit 1, and applies to the hydrologic analysis for SQN Units 1 and 2.

The primary standards followed for development of the PMF are American National Standards Institute/American Nuclear Society (ANSI/ANS) 2.8 and RG 1.59.

These guidance documents state that the PMF be derived from the combination of circumstances that collectively represent a risk probability that is acceptable for nuclear plant accidents.

Each element in the development of the PMF is based on best available data including PMP estimates from the National Weather Service, rain-runoff relationships developed from historical storms, time distribution of PMP consistent with storms in the region, seasonal and areal considerations of rainfall, current reservoir operations, and verification of runoff and stream course models against large historic floods.

Per regulatory guidance, the design-basis flood for nuclear power plants is an estimation. The calculations which support the PMF analysis document assumptions and approaches which are consistent with regulatory guidance. The PMF analysis is a best estimate and is consistent with current guidelines.

However, it is realized that various elements of the analysis can result in different elevations, some higher and some lower, and those elements are discussed in Page 8 of 14

ENCLOSURE2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING further detail in Section 3.2 of Enclosure 1, Uncertainties, in order to explain why the PMF analysis is a reasonable best estimate.

8. Justification for the use of any compensatory measures as a result of TVA's revised analysis.

This response is the same as WBN Unit 1 except for references to the applicable site, and applies to the hydrologic analysis for SQN Units 1 and 2.

The updated DBF analysis for SQN, indicated that some upstream dam earth embankments could be overtopped during the PMF. Four dams were identified as having embankments that could be overtopped during the PMF: Cherokee; Fort Loudoun; Tellico; and Watts Bar.

Once these earth embankment overtopping events were identified, actions were taken to prevent overtopping to ensure continued SQN operability. An evaluation of temporary flood barriers that could be installed in a short period of time and had a proven performance record for dependability led to the use of HESCO Concertainer units filled with stone. A total of approximately 18,000 feet of temporary flood barriers are installed at Cherokee, Fort Loudoun, Tellico and Watts Bar Dams.

This installation was completed by the end of December 2009.

The temporary flood barriers are located on the top of the earth embankments and/or on saddle dams as appropriate at each of the four dams.

The temporary flood barrier configuration consists of HESCO Concertainer units from three feet in height to HESCO Concertainer units stacked based on manufacture recommendation up to seven feet.

The maintenance of the temporary flood barriers and closure of openings during emergency events is a River Operations (RO) - Asset Owner (AO) responsibility, as defined by Dam Safety procedure RO-SPP-27.0. The purpose of the Dam Safety procedure is to protect upstream and downstream lives and property by ensuring that impoundments and dams are designed, constructed, operated and maintained as safely and reliable as is practical. This procedure describes the methods by which the RO Senior Vice-President (AO) will accomplish compliance with Federal Guidelines for Dam Safety and DSG.

As a part of the RO DSP, the temporary flood barriers are inspected on a regular basis.

They are inspected during plant monthly and quarterly inspections and during the 15 month comprehensive site inspections. Any noted damage to the HESCO Concertainer units from these inspections that would compromise the structural integrity or functionality of the temporary flood barriers is repaired promptly. Since completion of installation in December 2009, only minor repairs such as small holes up to three inches in diameter have had to be repaired. Also, as committed to in the TVA submittal to the NRC Document Control Desk, "Commitments Related to Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," dated June 13, 2012 (ADAMS Accession No. ML12171A053), TVA's Nuclear Power Group will issue and initially perform procedures for semi-annual inspections of the temporary HESCO flood barriers installed at Cherokee, Fort Loudoun, Tellico, and Watts Bar reservoirs by August 31, 2012. These inspections will:

a. Ensure the temporary HESCO flood barriers remain in place and are not structurally degraded as specified by the manufacturer's written specifications and recommendations; Page 9 of 14

ENCLOSURE2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING

b. Verify the inventory and staging of the material required to fill the gaps that exist; and

c. Ensure that adequate physical security (e.g., fences and locks) is provided for the staged material against theft.

These inspections will continue until a permanent modification is implemented to prevent overtopping the Cherokee, Fort Loudoun, Tellico, and Watts Bar dams due to the PMF.

For each of the dams, Cherokee; Fort Loudoun; Tellico; and Watts Bar Dams, where the temporary flood barriers have been installed, a supplement to the project Emergency Action Plan (EAP) has been issued which describes the emergency notification responsibilities and procedures. The River Forecast Center has responsibility for identification of events which could exceed critical elevations at each dam consistent with their Emergency Notification procedure and notification to the AO of the flooding condition. The AO declares a Dam Safety emergency which following the Dam Safety procedure (RO-SPP-27.0) implements the Project PMF Barrier Closure Plan. Each of the four dams has openings in the temporary flood barriers which have to be closed. The EAP supplement details the methods to be used by TVA's construction partner GUBMK Constructors for closure of the openings. The closure of the opening can be accomplished by setup of the HESCO Concertainer units linked to the existing HESCO Concertainer units already in place or by overlap of the temporary flood barriers at a given location as appropriate. At each dam where material for closure of the temporary flood barriers is required, the materials (HESCO Concertainer units and stone) are stockpiled in a designated fenced enclosure as described in the supplement to the EAP.

Experience data on the use of the selected temporary flood barriers during historic floods and the vendor documentation on barrier testing were evaluated prior to selection and use.

The USACE has also tested the HESCO Concertainer units by performing hydrostatic testing, wave-induced hydrodynamic testing, overtopping testing, and structural debris impact testing with a floating log. The debris impact testing was based-on two different log sizes: 12 inch and 17 inch diameter logs (12 feet long) with an impact speed of five mph.

The results of the laboratory testing showed that the HESCO Concertainer units were not damaged by the loading conditions used in the testing program.

Stability analysis of the temporary flood barriers was performed for seismic and hydrostatic (PMF) loadings. The analysis showed that the temporary flood barriers are stable under the seismic and PMF loading conditions.

This is described in the proposed revision to SQN Units 1 and 2 UFSAR Subsection 2.4.3.4, which states that while the flood barriers are temporary structures, there is a structural analysis for the headwater loading behind the temporary flood barriers that verifies that failure would not occur. Additionally, a seismic evaluation completed on the flood barriers (without headwater behind the barriers) verifies that failure of the temporary flood barriers would not occur.

A potential exists for runaway barges to float downstream and impact the temporary flood barriers at two of the four dams where the barriers are in place.

Barges along these reservoirs are typically tied off at barge terminals or mooring cells during high flow events, such as a PMF event. The mooring facilities, however, are not designed for PMF elevations and velocities, so the barges could break loose. There is no barge traffic on Cherokee Reservoir, so no potential for impact exists. The Fort Loudoun Reservoir has limited to moderate barge traffic. Using typical barge dimensions, the barge would have to weigh less Page 10 of 14

ENCLOSURE2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING than 70-80% of full load capacity in order to strike the barriers.

However, the earthen embankments of the dam where the temporary flood barriers are placed are located at a distance from the main channel. The stream flow during a high flow event is directed toward the concrete overflow portion of the dam, and the barges would be carried by the current away from the temporary flood barriers. At the Tellico Reservoir, there is very infrequent barge traffic. Conservatively assuming there will be a barge on the reservoir, and using typical barge dimensions, the barge would have to weigh less than 40-50% of full load capacity in order to strike the barriers. However, the earthen embankments of the dam where the temporary flood barriers are placed are located at a distance from the main channel. The stream flow during a high flow event is directed toward the concrete overflow portion of the dam, and the barges would be carried by the current away from the temporary flood barriers. There is limited to moderate barge traffic at the Watts Bar Reservoir. An evaluation using typical barge dimensions for the Tennessee River, and conservatively assuming barges are empty (less draft allows for the barge to run closer to the top of the dam), demonstrates that barges are not likely to impact the temporary flood barriers. A spatial analysis shows that the closest edge of the temporary flood barrier would have to be at least 9.0 ft away from the upstream edge of the earthen embankment in order to prevent impact. The temporary flood barriers are located at least this distance from the edge of the earthen embankment, ensuring that there is no potential for barge impact.

As discussed in the NRC letter to TVA, "Tennessee Valley Authority (TVA) Long-Term Hydrology Issues for Operating Nuclear Plants - Browns Ferry Nuclear Plant, Units 1, 2, and 3 (TAC Nos. ME5026, ME5027, and ME5028); Sequoyah Nuclear Plant, Units 1 and 2 (TAC Nos. ME5029 and ME5030); and Watts Bar Nuclear Plant, Unit 1 (TAC No. ME5031),"

dated January 25, 2012, Accession No. ML11241A166, the NRC Staff found that the sand baskets [temporary flood barriers] are not capable of resisting debris impact. The NRC Staff further states that "documents, [provided by TVA] neither discuss the ability of sand baskets to withstand debris impact, or mention whether the baskets are designed for impact of debris loads. The NRC staff is unable to conclude that these sand baskets were designed to withstand impacts from large debris during a flood. If a design flood were to occur, there is a high likelihood that significant debris would accompany the flood waters which could impact the baskets. There is the potential for this debris to damage the baskets or push the individual baskets.apart causing a breach. There would be no time to repair the baskets because the flood would already be in progress. Therefore, sand baskets that are not designed and constructed to withstand impacts from large debris are not acceptable as a long-term solution."

To resolve this issue, as committed to in the TVA submittal to the NRC Document Control Desk, "Commitments Related to Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," dated June 13, 2012 (ADAMS Accession No. ML12171A053), TVA will implement permanent modifications to prevent overtopping of the embankments of the Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams due to the PMF. The final solution will be established in an evaluation conducted in compliance with the National Environmental Policy Act (NEPA) Environmental Impact Statement (EIS). Based on the current NEPA EIS schedule, these permanent modifications are scheduled to be installed by October 31, 2015.

Based on TVA RO procedures for the maintenance of the temporary flood barriers and closure of openings during emergency events; TVA RO and TVA's Nuclear Power Group periodic inspections of the temporary flood barriers and additional materials required for Page 11 of 14

ENCLOSURE 2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING closure of openings; experience data on the use of the HESCO temporary flood barriers during historic floods; stability analysis of the temporary flood barriers for seismic and hydrostatic (PMF) loadings; USACE tests of the HESCO Concertainer units including hydrostatic testing, wave-induced hydrodynamic testing, overtopping testing, and structural debris impact testing with a floating log; and TVA's qualitative assessment of the potential for runaway barges to float downstream and impact the temporary flood barriers; it is concluded that use of the temporary flood barriers for the period of time required to implement the permanent modifications to prevent overtopping of the embankments of the Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams is adequate.

The use of the temporary flood barriers is described in Section 2.1 of Enclosure 1, Proposed Changes, under subheading Subsection 2.4.3, Probable Maximum Flood (PMF) on Streams and Rivers. The credit or lack of credit for the temporary flood barriers in the hydrologic analysis is described in Section 2.1 of Enclosure 1, Proposed Changes, under subheadings Subsection 2.4.3, Runoff and Stream Course Model, and Subsection 2.4.4, Dam Failure Permutations, respectively.

In the proposed SQN Units 1 and 2 UFSAR Subsection 2.4.3, the increase in the height of the embankments are included in the discharge rating curves for Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams that are used in the hydrologic analysis for rainfall-induced PMF events. Increasing the height of embankments at these four dams prevents embankment overflow and failure of the embankment.

The vendor supplied temporary flood barriers were shown to be stable for the most severe PMF headwater/tailwater conditions using vendor recommended base friction values.

In the proposed SQN Units 1 and 2 UFSAR Subsection 2.4.4, the temporary flood barriers are assumed to fail in the hydrologic analysis for seismically-induced dam failures for the cases where reservoir levels would increase to the top of the embankments, and are thus not credited for increasing the height of the embankments.

9. Discuss the temporary modification to the thermal barrier booster pump flood barrier protection in the UFSAR.

This issue was specific to WBN Unit 1. However, the temporary compensatory measures applicable to SQN Units 1 and 2 are discussed in Section 3.3 of Enclosure 1, Margins.

As committed to in the TVA submittal to the NRC Document Control Desk, "Commitments Related to Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," dated June 13, 2012 (ADAMS Accession No. ML12171A053), TVA will implement a documentation change to require the Spent Fuel Pit Cooling Pump Enclosure caps as a permanent plant feature for flooding protection, and will install permanent plant modifications to 'provide adequate flooding protection with respect to the DBF level for the Diesel Generator Building, by March 31, 2013.

10. Discuss any impact on TVA's individual plant examination of external events or final environmental impact statement due to the revised flood analysis.

This issue was specific to WBN Unit 1 and to the initial licensing of WBN Unit 2, and is not applicable to SQN Units 1 and 2.

11. Discuss whether any flood barriers at the plant are impacted by the revised PMF level.

Page 12 of 14

ENCLOSURE 2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING Only two distinct changes to the physical flooding protection features of SQN Units 1 and 2 are required.

As discussed further in Section 3.3 of Enclosure 1, the SQN Units 1 and 2 Spent Fuel Pit Cooling Pump Enclosure caps in the Auxiliary Building are now required to maintain adequate flooding protection of the Spent Fuel Pit Cooling Pump Motors during flood mode.

The DBF surge level within flooded structures is elevation 722.5 ft. The Spent Fuel Pit Cooling Pump Motors platform is located at elevation 721.0 ft, but is located in an enclosure that provides flooding protection up to elevation 724.5 ft.

However, the Spent Fuel Pit Cooling Pump Enclosure caps were not originally intended to be permanently installed. To restore margin for the Spent Fuel Pit Cooling Pump Motors, installation of the caps at any time prior to or during the event of a Stage I flood warning has been established as a compensatory measure. A documentation change is planned to require the SQN Units 1 and 2 Spent Fuel Pit Cooling Pump Enclosure caps as a permanent plant feature for flooding protection.

As discussed further in Section 3.3 of Enclosure 1, the lowest floor of the common SQN Units 1 and 2 Diesel Generator Building is at elevation 722.0 ft with its doors on the uphill side facing away from the main body of flood water.

This elevation is lower than the updated DBF level of elevation 723.2 ft. Therefore, flood levels exceed the floor level at elevation 722.0 ft. The entrances into safety-related areas and mechanical and electrical penetrations into safety-related areas are sealed to prevent major leakage into the building for water up to the grade elevation of 722.0 ft. Additionally, redundant sump pumps are provided within the building to remove minor leakage. As a result of this increase, staged sandbags to be constructed into a berm at the entrances to the Diesel Generator Building at any time prior to or during the event of a Stage I flood warning has been established as a compensatory measure. These sandbags will be constructed into a berm at least three ft in height (elevation 725.0 ft) to prevent water intrusion inside the building. Permanent plant modifications are planned to provide adequate flooding protection features for the common SQN Units 1 and 2 Diesel Generator Building.

As committed to in the TVA submittal to the NRC Document Control Desk, "Commitments Related to Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," dated June 13, 2012 (ADAMS Accession No. ML12171A053), TVA will implement a documentation change to require the Spent Fuel Pit Cooling Pump Enclosure caps as a permanent plant feature for flooding protection, and will install permanent plant modifications to provide adequate flooding protection with respect to the DBF level for the Diesel Generator Building, -by March 31, 2013.

12. Discuss the use and control of sand baskets (e.g., at the WBN recreational area).

This response is the same as WBN Unit 1, and applies to the hydrologic analysis for SQN Units 1 and 2.

Refer to the response to Issue 8 for more detailed description of use of the HESCO Concertainer units as a temporary flood barrier.

The temporary flood barriers installed in the vicinity of the recreational area at Watts Bar Dam are in place to prevent overtopping of the earth embankment during a PMF. There are three locations where closure of the access openings in the temporary flood barrier would Page 13 of 14

ENCLOSURE2 EVALUATION OF ISSUES FROM PRE-APPLICATION MEETING be required to complete the floodwall in advance of a PMF event. A supplement to the Emergency Action Plan for Watts Bar Dam has been issued to address procedures to be followed during such an event.

The HESCO Concertainer units (20-3'x3'x15' baskets) and stone (approximately 210 tons) needed to complete closure of the floodwall are stored in a designated fenced area near the campground and in proximity to the access points where they would be used. The HESCO Concertainer units are stored on pallets in a folded position.

The TVA River Forecast Center has responsibility for identification of events which could exceed critical elevations at the dam consistent with their Emergency Notification procedure and notification to the RO Senior Vice-President (AO) of the flooding condition. The AO declares a dam safety emergency which following the procedures implements the Watts Bar Dam PMF Barrier Installation Plan.

The supplement details the methods, material and equipment to be used by TVA's construction partner GUBMK for closure of the openings through the floodwall.

The closure of the opening can be accomplished by setup of the HESCO Concertainer units linked to the existing HESCO Concertainer units already in place or by overlap of the temporary flood barriers at a given location as appropriate.

Similar requirements for the use and control of the HESCO temporary flood barriers exist for Cherokee, Fort Loudoun, and Tellico Dams.

The use of the temporary flood barriers, and credit or lack of credit for the temporary flood barriers in the hydrologic analysis, is discussed further in the response to Issue 8.

As committed to in the TVA submittal to the NRC Document Control Desk, "Commitments Related to Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," dated June 13, 2012 (ADAMS Accession No. ML12171A053), TVA will implement permanent modifications to prevent overtopping of the embankments of the Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams due to the PMF. The final solution will be established in an evaluation conducted in compliance with the NEPA EIS. Based on the current NEPA EIS schedule, these permanent modifications are scheduled to be installed by October 31, 2015.

13. Discuss the impact on any safety-related equipment other than the thermal barrier booster pumps.

This issue was specific to WBN Unit 1, and is not applicable to SQN Units 1 and 2.

14. Discuss the impact of TVA's five proposed combinations of dam failure scenarios within its revised flood analysis.

This response is the same as WBN Unit 1, and applies to the hydrologic analysis for SQN Units 1 and 2.

As discussed in the response to Issue 4, the methodology used to develop the controlling seismic/flood condition at SQN is the same as previously followed for the site evaluations described in the SQN Units 1 and 2 UFSAR.

This is further described in Section 2.1 of, Proposed Changes, under the subheading Section 2.4.4, Potential Dam Failures, Seismically Induced.

Page 14 of 14

v t e Letter Sequence Request
TAC:ME8200, (Open)
Initiation Request, Request, Request, Request, Request, Request, Request, Request Acceptance... Supplement, Supplement Administration Meeting, Meeting Questions Answers Results Approval... Other: ML12276A375
MONTHYEAR2012-04-11 [Table View]

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