ML17229A094
| ML17229A094 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 08/30/1996 |
| From: | Rachel Johnson, Otis M SCIENCE APPLICATIONS INTERNATIONAL CORP. (FORMERLY |
| To: | |
| Shared Package | |
| ML17229A091 | List: |
| References | |
| SAIC-05-5049-05, SAIC-05-5049-05-6734, SAIC-5-5049-5, SAIC-5-5049-5-6734, NUDOCS 9610280084 | |
| Download: ML17229A094 (34) | |
Text
St. Lucie Unit 1 Docket No. 50-335 273 Enclosure 3 SAIC 05-5049-05-6734-500 STEAM GENERATOR DEGRADATION SPECIFIC MANAGEMENT (SGDSM)
LEAKAGE LIMIT CALCULATION FOR ST LUCIE UNIT a'lef'n Employee-Owned Company SAIC 05-5049-05-6734-500 Aptech Agreement Sept.,
1 996 Revision A PREPARED BY:
oem:
KBAHNEDSY:
APPROYED BY:
qe~oa8008+ 9i Xoae PDR 'DOCK 05000335 P
PDR 10260 Campus Point Orive, San Diego, California 92121 (6191 546 6000 Othe'AiO Oirceei Arououeioue. Bosion. Coloieoo Sonnyg. Oevion, Hunt~le. Lie viz uie Anoeiea Afcleen. Oe>> Ridge. Oiienoa psio Alia Seenie. eno ruoeon
Leaka e Limit Ca culation for St Lucie Unit 1 Table of Contents Page INTR0 D UCTI0 N o ~ ~ ~ ~
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~ eel oo 1 ETHODOLOGY.....................................................................................1 M
Radiation Release Model Leakage Limit Model.
Quality Assurance,.
~ ~ ooooo3 EAKAGE LlMIT...................................................................~......~...........
3 L
Screening Assessment.
Basic Assumptions
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~ o ~o4 Detailed Calculation..
~ ~ ~ ~ ~ oooooo ~ ~oooo4 Plant Specific Data.
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o ~ o ~ ooooo5 E S ULTS o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ o o ~ e o o o 6 R
Screening Assessment.
~ oo ~ oooooooooo6 Detailed Calculation.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o 0 ~
~ ~ o ~ ~ ~ ~ 0 ~ ~ oooo ~o7 0 N C LUS i0 N S o ~ ~ oooo oooo oo
~ ~ ~ oo ~ oo ~ ~ oo ~ eo ~ ~ oo ~ ~ ~ ~ ~ oo ~ oo ~ oo ~ ~ oo ~ ee ~ ~ ~ ~ ~ ~ ~ ~ ~ oooeo ~ ~ ~ ~ ~ oe ~ oooooooeeeoo 9 C
EfERENCES.........................................................................................1 0
R Appendix A Meteorological And Site Data from St. Lucle....................11 Appendix B Cumulative Probability Distributions for X/Q & Leak Rate..23 Appendix C Screening Methodology...........................
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Leaka e LimitCalculation for St Lucie Unit 1 List of Tables and Figures Page Table 1
Screening results for dose limited leakage at 95% confidence level...,...,.7 Table 2. Leakage to Meet Dose Limits at the EAB for a Pre-Accident Spike............9 Table 3, Leakage to Meet Dose Limits at Control Room for a Pre-Accident Spike..9 Table 4. Leakage to Meet Dose Limits at the EAB for an Accident-Initiated Spike..9 Table 5. Leakage to Meet Dose Limits at the CR for an Accident-Initiated Spike....10 Table C 1. Screening results for dose limited leakage at 95% confidence level.....29 25 27 Figure 8-1 Cumulative Frequency of c/Q at the EAB Figure 8-2 Confidence vs leakage limit at the EAB for ais and pas 95%
meteorological conditions
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~t ~ ~ttrt ~ ~ ettotooo ~oottott24 Figure 8-3 Confidence vs leakage limit at the EAB for ais and pas 99%
meteorological conditions Figure 8-4 Confidence vs leakage limit at the EAB for ais and pas 99%
meteorological conditions
................25 Figure 8-5 Cumulative Frequency of c/Q at the control room intake,.
~
~..........26 Figure 8-6 Confidence vs leakage limitfor control room for ais and pas 95%
meteorological conditions Figure 8-7 Confidence vs leakage limit for control room for ais and pas 99%
meteorological conditions........................................
~. ~..~...~.......~............................27 Figure 8-8 Confidence vs leakage limit for control room for ais and pas worst observed meteorological condition Page iii
Leaka e LimitCalculation for St Lucie Unit 1 INTRODUCTION The purpose of this calculation is to determine the dose limiting steam generator tube leakage for a postulated main steam line break accident considering St. Lucie's site specific conditions.
The purpose of the leakage limitcalculation is to provide a site specific leakage value that would not exceed 10CFR100(>l and General Design Criteria 19 accident dose limits with a high degree of confidence.
The confidence level recommended in the industry proposed methodology for this calculation is a 95% confidence level on radiation dose for atmospheric dispersion conditions for the 95 percentile of observed conditions.
This 95/95 value can be used to quantify margins that exist between the estimated leakage for a main steam line break due to the steam generator condition and the dose limiting leakage.
This calculation uses the probabilistic option@I for quantifying the leakage limitfor both control room (CR) operators and individuals at exclusion area boundary (EAB).
The calculations use site specific data collected at St Lucie for meteorological and plant systems.
METHODOLOGY The basis of the methods, assumptions and tools for these calculations are outlined in current documents provided by EPRIPI and NRC(41 in support of steam generator integrity rule makingPl.
The calculation is divided into two parts: a screening assessment and a detailed calculation.
The methodology for calculating the primary coolant accident leakage limit is used solely to determine the conditions that would result in I>3> releases large enough to exceed radiation dose limits at a specified confidence level. They do not constrain leakage based on the accident assumptions or the internal characteristics of an operating plant.
Therefore, these analyses can yield leakage limitvalues larger than allowed by the accident assumptions or the physical capabilities of the plant. The leakage value results should not be taken to mean "real" plant capabilities, or that margins are available up to these leakage values.
Rather such results mean only that radiation dose limits are not exceeded for I>3> releases corresponding to these leakage values, as long as the plant is capable of operating within the stated engineering assumptions.
If the plant operates outside these assumptions, the limits on leakage must be based, on considerations other than compliance with dose limits for the postulated main steam line break (MSLB) accident with associated steam generator tube leakage (SGTL).
Project 6783 Page 1 ot'9 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 Radiation Release Model The phenomena of interest that leads to potential radiation exposure is the increase.
in iodine release rate from the fuel to the primary coolant which stems from power and pressure transients.
The magnitude of this temporary increase in the iodine release rate (called a spike ) represents a source term for the postulated MSLB/SGTL accident pressure and power transient.
Two types of iodine spiking events are identified in the standard review plan methodologyl6l.
The first is a transient-induced spike that is assumed to occur prior to a MSLB/SGTL event or a pre-accident spike (PAS). In this case the postulated accident is assumed to occur at a time when the iodine concentration in the primary coolant is maximum.
The second event involves a spike induced by the MSLB/SGTL event itself. For this event the primary coolant iodine concentration is predicted on the basis of a prescribed release rate from the fuel or an accident initiated spike (AIS). Both of these source terms are considered in the screening assessment and the detailed calculation as recommended in the SG integrity rulemaking documentation.
The data on iodine spiking has been greatly expanded over the decade since the review plan was written. A study of the iodine spiking data by Postmat7l was carried out to quantify the peak iodine concentration (p,Ci/g) for nearly two hundred events and release rates (Ci/hr) from nearly one hundred events at a variety of PWRs.
By noting that the distributions of spike events are representative of the population spikes that could exist prior to and result from MSLB/SGTL events, Postma's iodine concentration data were converted into distributions for release from the PWR secondary system to the environment as a function of the primary to secondary leak rate (Ci/gpm). A generic MSLB/SGTL PWR thermal hydraulics model was used to evaluate a reference 100 gpm leak from the primary to secondary system.
The combination of spike data and the leak rate was used to produce I>3> release distributions as a function of leak rate for the postulated accident as described in Ref.
- 3. This model provides generic "best estimate with uncertainty distributions" for I>>> release from the secondary side of a PWR as a function of the PAS and AIS source terms and the primary to secondary leakage.
Leakage Limit Model For this leakage limit assessment the generic accident release distributions were combined with the other dose model elements such as site specific St. Lucie dispersion factors determined by the local meteorology measures using Monte Carlo Simulation.
The resulting distributions are used to assess the leakage limitthat would assure with a high confidence that postulated accident dose at the exclusion area boundary and the control room do not exceed the dose limits in the regulations.
Site specific meteorology and features such as EAB distance, and control room features have the largest impact on the limiting leak rate.
Project 6783 Page 2 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 Use of the generic source terms requires several engineering assumptions.
These are that the primary coolant activity is maintained within the technical specification limits, and that the primary makeup systems are capable of maintaining primary coolant inventory at the selected leak rate limit. No iodine plate-out is assumed in the steam generator, thus the generic release term has some elements of conservatism which can be re-examined if necessary.
Quality Assurance Allcalculations for this analysis have been conducted according to the requirements of SAIC quality assurance procedures.
These include: documentation of all engineering assumptions, independent review of engineering assumptions, reference citations for all parameter values, independent review of the contents of all computerized spreadsheets, confirmatory calculations (either by hand or using a separate computer code) for all spreadsheet calculations, and independent review of all final reports.
Archived copies of all computerized spreadsheets and associated quality assurance files are maintained by the SAIC project manager.
LEAKAGE LIMIT Screening Assessment The screening assessment is based on the results of generic analyses of uncertainty in radiation dose models as a function of stability class, distance to the EAB and type of control rooml3l. Monte Carlo simulations were used to develop generic tables to describe the leakage value that, with 95% confidence, would not exceed the dose limits in 10CFR100 and GDC 19 for the postulated MSLB/SGTL. The leakage limitis a function of the site characteristics and the I 131 accident source term. This leakage limitis independent of the calculation for the projected accident leakage which uses non destructive examination measures of the SG tubes such as volts projected to the end of cycle to estimate an the accident induced leakage value.
Models for the dose calculations were taken from USNRC Regulatory Guide 1.78~81 for the EAB and control room. Atmospheric dispersion models were taken from USNRC Regulatory Guide 1.145Ãl. Generic data for covering the range of wind speeds and dispersion parameters were taken from stability class definitions.
Modeling uncertainties for relevant plant features are based on industry averages rather than site specific calculations 'and, therefore, represent greater variance than would be observed at a specific site.
For initial screening the dose limiting leakage values were taken from tabulated results in Ref. 3. Values were chosen that correspond to the site boundary distance for St. Lucie and the atmospheric stability class representing dispersion conditions less favorable than 95% of those observed at St. Lucie during calendar year 1995~>ol.
Of the two source terms considered, the PAS is always more restrictive than the AIS Project 6783 Page 3 of 29 8/29/96
Leaka e Limit Cali;ulation for St Lucie Unit 1 at the higher confidence levels above 90%. The AIS is more restrictive at confidence levels below 70%.
Basic Assumptions The following assumptions do not appear explicitly in the methodology used for this analysis but are key to interpreting the results:
1)
St. Lucie willoperate with the primary activity within the limits stated in the FSAR. The I>3> release data base includes measures of I>3> released during plant transients from plants that maintained primary coolant activity within the FSAR lirruts on primary coolant activity.
2)
The MSLB-SGTL transient causes no new cladding or fuel damage.
3).
The primary coolant injection rate is assumed equal to the leakage throughout the transient.
4)
The makeup inventory is large enough to maintain primary coolant inventory during the controlled shutdown which is on the order of two hours.
5)
There is no reduction in the source term due to plateout in the secondary system.
6)
The 95% confidence level is dominated by the pre-accident I>3> spike.
In general, leakage rates greater than about 400 gpm are outside the regime postulated for the MSLB-SGTR accidents considered here.
Several assumptions key to the MSLB-SGTR accident scenario do not apply above this leakage rate.
For example, the assumption that the injection rate is equal to the leak rate is based on the automatic response of the controls and safety systems to the MSLB-SGTR accident without operator intervention.
Above about 400 gpm operator actions will be needed to control safety injection. In addition, the 03> release model could change according to the accident scenario being examined, For example, in lower probability accidents treated in probabilistic risk assessment studies additional systems such as the injection system could be assumed unavailable, and without compensating operator actions to restore injection, releases at 400 gpm could result in higher doses due to cladding or core damage.
These issues are discussed in industry reports prepared by SGDSM committees l ~.
The cladding and core damage scenarios are outside the bounds of this assessment.
Therefore, the values in the allowed leakage graphs above 400 gpm are considered not representative of the postulated MSLB-SGTR accident transient.
Detailed Calculation The detailed calculation uses plant specific data to develop a 95/95 dose limitingleak rate for the St. Lucie site. The objective of the detailed calculation is to ensure that no unique site characteristics cause a more limiting condition than identified by the Project 6783 Page 4 of 29 8/29/96
Leaka e LimitCalculation for St Lucie Unit 1 generic screening process.
These site specific calculations use measured St Lucie meteorological data, site-specific distances to the site boundary and the control room, and plant-specific control room characteristics.
Using these site-specific data, values of X/Q were calculated for the control room and the EAB for each of about 15,000 individual meteorological observations taken at St.
Lucie during calendar year 1995. Atmospheric dispersion calculations used the equations specified in NRC Regulatory Guide 1.145.
These values were ranked to permit selection of the 95%, 99% and worst observed meteorological conditions, Cumulative probability distribution of X/Q for the EAB and control room appears in Appendix B.
Dose modeling uncertainties were determined for the selected 95%, 99% and worst observed dispersion conditions using the Monte Carlo simulation methods described in Ref. 3. The purpose of this step in the calculation is to ensure that sufficient conservatism is included in the leak rate values to account for uncertainties in dose modeling while avoiding the over-conservatism associated with a "worst-case" analysis.
The Monte Carlo simulation incorporates uncertainties in the postulated I>3> release, individual dose model parameters, and control room.
In this detailed analysis the 95th percentile of 1000 Monte Carlo simulations, based on the 95th percentile least favorable atmospheric dispersion conditions, was used to determine the 95/95 leak rate. In addition, 1000 simulations were conducted for both the 99% least favorable and the worst dispersion condition observed in the St Lucie data setto).
These calculations were used to evaluate whether site specific outlier meteorological conditions could result in a situation were radiation dose would be the limiting consideration in setting operating margins for leak rate.
Cumulative frequency distributions for all Monte Carlo analyses are presented in Appendix B.
Piant Specific Data Most of the data required for this analysis were obtained from the Final Safety Analysis Report (FSAR) for the St. Lucie plantl<<l. Additional data, including more recent meteorological data were obtained directly from staff at Florida Power and Lights>ol. These data are presented in Appendix A. They include:
1)
Distance to site boundary in sixteen directions corresponding to the wind rose sectors. For St. Lucie the plant boundary is circular with a radius of 1561 m.
2)
Joint-frequency tables of wind speed and direction for stability classes A through G based on hourly data collected at St. Lucie during calendar year 1995.
3)
Data describing key features of the control room vent system, air exchange rates and isolation features.
Project 6783 Page 5 of 29 8/29/96
Leaka e LimitCalculation for St Lucie Unit 1 RESULTS Screening Assessment The screening assessment provides only a simple assessment to indicate the potential for large margins in the leak rate limit. Because industry-wide, generic assumptions are used in the screening assessment and site-specific assumptions are used in the detailed calculation, it is unlikely that the same conditions will generate the same limiting conditions at a given confidence level.
Screening results show that the potential for a large margin of safety on the leakage limit exists at St Lucie based on site specific dose limitingfeatures.
It also indicates there is a potential for the control room dose limitto be reached before the EAB limit is reached.
As shown in Table 1 the leakage values determined from the screening assessment for 95% confidence of not exceeding the dose limits for a pre-accident spike are 545 gpm for the control room and 3,310 gpm for the EAB distance. Ifan accident induced spike is assumed the control room limit is 1700 gpm and the EAB limitis 12,900 gpm.
Table 1 Screening results for dose limited leakage at 95% confidence level (using Tables from Ref. 3)
EAB, Class F
EAB, Class E
Control Room, Type B Leakage Limit Pre-accident Spike (gpm) 3310 12,100 545 Leakage Limit Accident-Initiated Spike (gpm) 12,900 44,000 1,700 For each case shown in Table 1 the values are much greater than the recommended limitof 200 gpm currently proposed by NEI during the steam generator integrity rule making process.
This indicates that the leakage limit is not likely to be bounded by dose for either the EAB or the CR for this accident.
That is, there is a potential for large margins on dose, and the leakage limit depends on plant features other than dose.
Thus, a detailed calculation using site specific data from St. Lucie is justified in order to:
1) verify the limiting dose criteria for SG tube integrity in terms of leakage by taking into account the site specific meteorology data at St Lucie, 2) refine estimates of available margin by estimating the leakage that could result in a dose limiting situation, and 3) verify the engineering model assumptions that apply for both screening and detailed models.
Project 6783 Page 6 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 The key engineering assumptions used for the screening level iodine dose models are:
1)
During normal operation the iodine concentration in the primary coolant is limited by technical specifications.
2)
The primary coolant injection rate is equal to the leakage during the postulated MSLB-SGTR accident.
3)
A single generic dose analysis equation was used to model the EAB leakage limitin the screening analysis (L e., the detailed analysis selects from 3 equations in RG 1.145).
4)
Site-specific parameter values vary less than the generic screening (e. g., the plant cross section area, A, has no uncertainty for a specific plant) 5)
Site specific wind speed has a variance driven by the data bin size rather than the whole range allowed by the definitions of stability class.
6)
The tabulated values represent an allowed leakage for the MSLB-SGTR accident assuming no accident caused cladding or fuel damage.
7)
Sufficient defense-in-depth features are in place to keep a MSLB accident from also causing core damage.
Detailed Calculation Tables 2 through 5 summarize the results of the detailed site-specific calculation.
Table 2 presents the dose-limiting leak rates at the EAB for the pre-accident spike scenario.
This is the most limitingscenario for establishing margins on leakage at St Lucie. The table includes the 95/95 condition as well as more restrictive combinations of higher confidence levels for both dispersion conditions and dose model uncertainties, Compliance with the dose limit at the EAB does not restrict leak rates to less than 200 gpm for the 95/95 condition. A 200 gpm limitmay be appropriate, ifhigher confidence of compliance with dose limits at the EAB is required.
For example, at the 95th percentile on meteorological conditions and a 99% confidence level for compliance with dose limits (e. g., the 95/99 condition) requires an accident leakage of 211 gpm or less.
The table also presents the 99/95 and the 99/99 conditions.
The worst observed meteorological conditions require leakage to be limited to 403 gpm for a 95% confidence of dose compliance and 110 gpm at a 99% confidence level. The right-hand column of Table 2 indicates the confidence level on dose compliance that would be achieved by limiting the leakage to 200 gpm for each meteorological condition evaluated.
Table 3 presents the dose-limiting leak rates at the control room for a pre-accident spike scenario. No condition limits leakage to 200 gpm or less.
Restricting leakage to 200 gpm achieves confidence levels for compliance with dose limits of greater than 99% for even the worst observed meteorological conditions.
Project 6783 Page 7 of 29 8/29/96
Leaka e LimitCalculation for St Lucie Unit 1 Tables 4 and 5'present the dose-limiting leak rates at the EAB and the control room for the accident-initiated spike scenario.
In every case, limitations on leakage are less restrictive for this accident scenario than for the pre-accident spike.
Table 2. Leakage to Meet Dose Limits at the EAB for a Pre-Accident Spike Meteorological Conditions Leakage Limit at Stated Confidence Level for Dose Model (gpm)
Confidence Level for Dose Model Stability Wind speed centile (m/s) 95%
99%
O 200 gpm 95%
99%
worst E
0.22 - 1.56 F
0.22 - 1.56 G
0.22 - 1.56 1,670 211 214 110 99.2 99.1 97.8 Table 3. Leakage to Meet Dose Limits at the Control Room for a Pre-Accident Spike Meteorological Conditions Stability Wind speed centlle (m/s)
Leakage Limit at Stated Confidence Level for Dose Model (gpm) 95%
99%
Co nfl d ence Level for Dose Model I 200 gpm 95%
99%
worst D
F G
0.22 - 1.56 0.22 - 1.56 0.22 - 1.56 1,650 1,750 1,600 420 401 384 99.4 99.9 99.6 Table 4. Leakage to Meet Dose Limits at the EAB for an Accident-Initiated Spike s Meteorological Conditions Leakage Limit at Stated Confidence Level for Dose Model (gpm)
Confidence Level for Dose Madel Stablllty Wind speed centlle (m/s) 95%
99%
200 gpm 95%
99'/o worst E
F G
0.22 - 1.56 0.22 - 1.56 0.22 - 1.56 5380 3,040 1,650 2,780 1,310 696 N/A N/A N/A Project 6783 Page 8 of 29 8/29/96
Leaka e Limit Cah.'f//ation for St Lucie Unit 1 Table 5. Leakage to Meet Dose Limits at the CR for an Accident-Initiated Spike Meteorological Conditions Leakage Limit at Stated'onfidence Level for Dose Model (gpm)
Confidence Level for Dose Model Per-Stability Wind speed centlle (m/s) 95%
99%
200 gpm 95%
99%
worst D
F G
0.22 - 1.56 0.22 - 1.56 0.22 - 1.56 6,110 5,910 5500 2,910 2,990 2,440 N/A N/A N/A CONCLUSIONS The results show that the leakage level needed to produce dose limiting conditions up to the 95/95 confidence level at St. Lucie is much greater than the industry recommended upper bound of 200 gpm.
~
The screening results indicated the potential for large margins on the leakage which was confirmed with a detailed site assessment.
~
At the 95/95 confidence level the detailed assessment indicated the most limiting case was the pre-accident spike with the control room and EAB about equal at 1600 gpm,
~
For a MSLB/SGTL of 200 gpm the confidence level is approximately 99/99 that the regulatory dose limitat the St Lucie site would not be exceeded, Since dose is unlikely to be the limiting constraint on leakage, the plant physical features can be used in determining the leakage limitfor the postulated MSLB.
Examples of the plant physical constraints that can be considered as limits are the combined charging pump capacity for the St. Lucie plant FSAR, or the sum of the charging pump and high pressure safety injection make up capacity.
Project 6783 Page 9 of 29 8/29/96
Leaka e LimitCalculation for St Lucie Unit 1 REFERENCES 1.
2.
3.
4, 5.
6.
7.
8.
9.
10.
11.
Reactor Site Criteria in Title 10 Code of Federal Regulations, 10 CFR Part 100, US NRC, Washington D. C., June 24, 1975.
NEI, 1996. "Industry Guide for Implementing Steam Generator Tube Integrity Rule" Draft 0, Nuclear Energy Institute, Washington D. C. January 1996.
EPRI TR-103878, "Methodology for Considering Uncertainties in I>3> Release and Dose Limits for a Postulated Accident." M. Otis, D Bradley and G.
Hannaman, Electric Power Research Institute, Palo Alto, California Rev 2 March 1996.
View Graph notes from NRC - Comments on dose uncertainty methods EPRI report EPRI TR-103878 R1(1994) April1996..
Federal Register, NRC Rule RIN3150-AFO4, October, 1994.
NRC, NUREG-0800. "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants," LWR Edition, U.S. Nuclear Regulatory Commission, Washington, D.C., July 1981.
Postma, A. K., 1995. "Empirical Study of Iodine Spike Data in PWR Power Plants," EPRI TR-103680, Rev. 1 Electric Power Research Institute, Palo Alto, CA, November 1995.
NRC, 1974. Regulatory Guide 1.78, "Assumptions for Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release",
U.S. Nuclear Regulatory Commission, Washington, D.C.,
June 1974.
NRC, 1983. Regulatory Guide 1.145, "Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants", U.S.
Nuclear Regulatory Commission, Washington, D.C., August 1976.
Pete Bailey, Personnel Communication "St. Lucie Meteorology and CR Data."
August, 1996.
Florida Power and Light, " St. Lucie Unit 1 FSAR" Docket No. 50-335 version 88-01 Section 9.4, (Micro Film version 1988).
Project 6783 Page 10 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 Appendix A METEOROLOGICAL AND SITE DATA FROM ST. LUCIE Project 6783 Page ll of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 TO: BillHannaman 8 Hoh/ard Pippen, SAIC From: Peter 8. Bailey, FPL
Subject:
Response to your data needs St. I.ucmo Unft 0 CroaWsa5onal Area: 2867 m'ased on RCS )64 ft Dfa, 207A ft Hf above ground.
Sourca:
Specification for an Emergency Dose Cafcuhtian System far the St. Lucie Pfant", (HMMDoc. 0804T?-8) H.M.M.Assoc, October 18, $982 Cantrof Acorn Emergency Rlbmtlon System Infeakago: Assumed 109 elm Source:
St. Lucie Un@ 0 UFSAR g 9.4.1, pg 9.~ (ammendment12, 12/93), Calculated to be 34.2 cfm 1/S "Vfsh,P, assumed 100 cfm, w/0.$2 one-pass fHter effeclency, foremergency dose cafcufatfona (Q6.4.1 stuH).
Anemometer Startfng Speed: 1.0-1.6 mph Sourc9:
St Lucia Unit1 UFSAR, g 2.3.3.3, pg 2.3-33, undated page.
Met Data for gjQ Calcs: Attached Annual JFD forCY '95 The foffeeing nine pages [nctude the 1996 annual summary JFDI by Stability CI838, by VlindSpeed Groups, by Sector, they are fn the Reg Gufde 1.2) suggested format.
ifyou need more ofthh type info, just call 407 8944179; l can Fax copi68 oftho UFSAR pages ffthey're needed.
Project 6783 Page 12 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 To:
RL Rechette Hmm: A. J. Gonld Date: February g 1996 Department: SNAB
~r~L
~A+
Subject:
St. Lacy Joint Fmqnextcy DfstrfhuQon Report, Agrtual Re ortin f x T Hnclosed axe the joint Gtquency dLstabuttons of 10-meter wind cHrection axtd whtd speed by atxnospheric stability category for the St. Lacie sita.
Thh xspaxt covers the Fourth Qnarter 1995 and the Annual Reporting for 199$. These tables axe ia the foxxaat suggested by NRC Regahtotyegde
>>> TaM
<A.
~
percent jontt data xecovay vras ntet foratmospheac stability, wind speed, axut vtiad direction, as xecomtnended by the Second Ptoposed Revision 1 to NRC Regulataxy Guide 1M. Por th6 Fourth Quarter, 100 percent joint data recovery wxLtrealized. For the annual l995 joint faquency distribution report, the joint data recovery percentage was 9%32.
Kyon have any questions, please contact me at 4071N4-4199.
CC'. Q. BaBey R. E. Cox
- 6. Rhmid R. Ohon BS-RC-96410 PBe Project 6783 Page l3 of 29 8/29/96
Leaka e Limit C ~.'culation for St Lucie Unit 1 PLOazna SOMSa 4
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1S.123 project 67S3 Page I4 nf 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 PrrdRZOA Pdltd'R d
ZrIOHT COMPANY CZe ZIR' PXJWT PERZOQ Ot.RECORDS Jan 1
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3.253 Project 6783 Page t5 of 29 8/29/96
Leaka e LimitCalculation for St Lucie Unit 1 rx oazoa 3 oMxa a
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3~2la Project 6783 Page 16 of 29 8/29/96
Leaka e LimitCalculation for St Lucie Unit 1 Fr,r:azrI C Oars 4
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2S.LSL Project 6783 Page 17 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 rrORZDa 9O~SR a
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~ PSRCSNI7ea raa Isaa 1.374 Project 6783 Page 20 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 Fuoazoa Fowza r
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92.317 Project 6783 Page 2l of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 iodine 131 Concentration in the Control Room St. Lucie unit 1 control room with RG 1.78/1.95 assumptions GWH 8/20/96 SAIC project 6734 Data for isolated case Ref 11(FSAR148)
Ref 10 Control room volume 56,292 cu ft Control filtered inlet 100 cfm 100 cfm Filtered Recirculation 1900 cfm (2000-100)
HEPA Filters Eff
.997 Unfitered inleakage 56 cfm 34.2cfm calculated Best estimate model Uncertainty ranges considered in estimating the IPF in Monte Carlo Simulations for leakage limit This shows the results of modeling the transport and concentration of iodine I-131 for the St Lucia 1 control room.
I-131 released from a MSLB/SGTL moves from the release point to the intake of the ventilitation system A concentration (release
'/Q) then to the control room through either a filtered or unfiltered path (CRI). B is the concentration of l-131 that stays in the control room volume.
It is the difference between the rate of I131 into and out of the control room -(i.e., the Iodine Protection Factor (IPF)). The input data from control room design features are used to calculate the Iodine Protection Factor, and quantify the time dependent concentration in the control roomassuming that a postulated main stream line break has occurred.
This produces the basis for the constant source term assumed for the air in the control room.
Data forthe St. Lucie Control room parameters are taken from Ref 10 and 11 for isolated condition. Normal unfiltered flowinto the control room is 750 cfm which is isolated 35 seconds after close signal. The model for isolation below treats both unfiltered inleakage and filtered. Therefore, the published filter efficiences from FSAR were applied in calculations. The unfiltered leakage is treated as distribution to approximately represent the 35 second closing time.
Input data for the control room design features mean values:
LU:=.06 ltr LF:=.11 hr LR:=2 lu'r@:=
.95 Ffe '.=.95 A,:=.00358 lu'nfiltered inleakage ( vol per hr)-.06 test to showc.08 Filtered intake flow-.2 to.05 Recirculation flow-2.3 to 1.9 Recirculation filter efficiency -.90 to.997 Intake filter efficiency-.90 to.997 Decay constant for 1131 T1/2= 8.05 day Calculations for control room design:
Transport rate into the Control room sec.
Transport rate out of the Control room sec CRI:"-LU+ ( I Ffs) LF CRI = 1.819'10
'time 4
t CRO:=LF+ LU+ Frs LR+ A, CRO = 5.76'10
'time iodine Protection Factor mean value CRO IPF:=
CRI IPF = 31.658 Initial event conditions:
Initial amount of l131 accident.
0:=1. 'oncentration factor at the intake, Ao assumed to be constant from from release point Compute removal and increase constants:
Functions for l131 Transport into Control room:
kl:= CRI kO:= CRO A(t):= AX e ii(t>:=
(e e
"kO t kl.t Q
klkO t '.=0 lu,.25 hr.. 24 hr t2:= 0 Itr, 1.0'hr.. 12 hr Project 6783 Page 22 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 Appendix 8 CUMULATIVE PROBABILITY DISTRIBUTIONS FQR X/Q AND LEAK RATE This appendix provides graphical illustrations of the detailed site specific assessments.
Figure B-1 presents the cumulative distribution for X/Q at the EAB for St. Lucie based on the measured atmospheric conditions described in Appendix A. This figure represents all the combinations of wind speed, direction, atmospheric stability class at the EAB. The flat portions of the curve are due to the constant distances to the EAB. Figures B-2 through B-4 present families of curves for the leakage limitas a function of confidence level. They were obtained by combining the distributions from the St. Lucie specific atmospheric dose models for the 95% 99% and worst case meteorology conditions at the EAB with the generic release models for I>3> PAS and AIS conditions based on the thyroid limitof 300 rem.
Selected points on these cumulative distributions provide the data for Tables 2 and 3.
Figures B-5 presents the equivalent of Figure B-1 for the Control Room.
Figures B-6 to B-8 are the equivalent of B-2 to B-4. These control room leakage limit distribution provide the data for Table 4 and 5.
Project 6783 Page 23 of 29 8/29l96
Leaka e LimitC"/'u/ation for St Lucie Unit 1 Cumulative Frequency for x/Q at EAS for St. Lucie (meteorological data for 111/95 - 12/31/95) 1.00E-03 1.00E-04 1.00E-OS 1.00E-06 O'.00E-07 1.00E-08 0
0.2 0.4 0.6 Cumulative Frequency Figure B-1 Cumulative Frequency of X/Q at the EAB 0.8 1.00E+09 Ea. 1.00E+08 1.00E+07 m 1.00E+06
~o 1.00E+05 o 1.00E+04 I 1.00E+03 0
~ 1.00E+02 1.00E+01 I-131 Release Resulting in <300 rem at EAB, Stability E (95% meteorological condition)
- - - Pre-accident Spike Accident-initiated Spike 0
10 20 30 40 50 60 70 80 90 100 Cumulative Percentage (Confidence Level)
Figure B-2 Confidence vs leakage limitat the EAB for AIS and PAS.O 95%
meteorological conditions Project 6783 Page 24 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 1.00E+08 Eo-1.00E+07 I 1.00E+06
~ 1.00E+05 1,00 E+04 m 1.00E+03 0
~ 1.00E+02 1.00 E+01 I-131 Release Resulting in (300 rem at EAB, Stability F (99% meteorological condition)
Pre-accident Spike Accident-initiated Spike
'tl
~
0 10 20 30 40 50 60 70 80 90 100 Cumulative Percentage (Confidence Level)
Figure B-3 Confidence vs leakage limitat the EAB for AIS and PAS 8 99%
meteorological conditions 1
~ OOE+08 E
~~ 1.00E+07 I 1.00E+06
~ 1.00E+05 1.00 E+04 m 1.00E+03 O= 1.00E+02 l-131 Release Resulting in <300 rem at EAB, Stability 8 (worst observed meteorological condition)
Pre-accident Spike Accident-initiated Spike
%w ~
1.00E+01 0
10 20 30 40 50 60 70 80 90 100 Cumulative Percentage (Confidence Level)
Figure B-4 Confidence vs leakage limitat the EAB for AIS and PAS I 99%
meteorological conditions Project 6783 Page 2S of 29 8/29/96
Leaka e LimitCalculation for St Lucie Unit 1 1
~00E-02 Cumulative Frequency for X/Q for Control Room at St. Lucie (meteorological data for 1/1/95 12/31/95) 1.00E-03 E
1.00E-04 1.00E-05 1
~ OOE-06 0.2 0.4 0.6 0.8 Cumulatl ve Frequency Figure B-5 Cumulative Frequency of X/Q at the control room intake I-131 Release Resulting in <30 rem at Control Room, Stability D (95% meteorological conditions)
Pre-Accident Spike Accident-initiated Spike 1.00E+08 Ea. 1.00E+07 1.00E+06 1,00E+05 1.00E+04 1.00E+03 O
1.00E+02 1.00E+01 0
10 20 30 40 50 60 70 80 90 100 Cumulative Percentage (Confidence Level)
Figure B-6 Confidence vs leakage limitfor control room for AIS and PAS 8 95%
meteorological conditions Project 6783 Page 26 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 I-131 Release Resulting in <30 rem at Control Room, Stability F (99% meteorological conditions)
Pre-accident Spike Accident-initiated Spike 1.00E+09 o 1.00E+08 1.00E+07 m 1.00E+06
~o 1.00E+05 o 1.00E+04 I 1.00E+03 0
1.00E+02 1.00E+01
~ ~
0 10 20 30 40 50 60 70 80 90 100 Cumulative Percentages (Confidence Level)
Figure B-7 Confidence vs leakage limitfor control room for AIS and PAS 8 99%
'meteorological conditions 1-131 Release Resulting in <30 rem at Control Room, Stability G (worst observed meteorological condition)
Pre-accident Spike Accident-initiated Spike 1.00E+08 fa. 1.00E+07 o 1.00E+06
~ 1.00E+05 1.00E+04 ctr 1.00E+03 0
~ 1.00E+02 1.00E+01 e ~
0 10 20 30 40 50 60 70 80 90 100 Cumulative Percentage (Confidence Level)
Figure B-8 Confidence vs leakage limitfor control room for AIS and PAS 8 worst observed meteorological condition Project 6783 Page 27 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 7 Appendix C SCREENING METHODOLOGY This appendix describes the screening process for using the generic leakage limit tables whose purpose is to indicate the potential for additional margin and justify a site-specific analysis. It makes use of the tabulated results published in EPRI TR-103878, "Methodology for Considering Uncertainties in I-131 Release and Dose Limits for a Postulated Accident." The screening assessment steps are:
1 Obtain Plant Specific Physical Data a.
St. Lucie minimum distance to the Exclusion Area Boundary is 1561 meters b.
Bounding Atmospheric Dispersion Type for EAB and CR (Class E is the 95%
bounding atmospheric condition) c.
Category of the control room protection is Type B.
2.
Obtain Generic Allowed leakage data for EAB and Control Room and verify that local engineering assumptions apply.
a.
Use tabular results for the EAB (Tables 5-1 and 5-2 in Reference 3) b.
Use tabular results for the control room (Table 5-3 in Reference 3) 3.
Verify source term assumptions for the two accident model types a.
Select the generic pre-accident source term, which is typically the most limiting at 95% confidence.
The 95% confidence bound pre-accident source term comes from the data fitting process and the allowed leakage is 33 times greater than the Standard Review Plan.
b.
Select a site-specific model of the source term if conditions are not bounded by the generic source term.
4.
Determine the generic allowed leakage limit a.
Look up the allowed leakage for the minimum distance and control room type, and select allowed leak rates from screening tables which represent the case for a leakage that willnot exceed the dose limits with 95% confidence as shown in Table C-1.
Assume bounding stability class (F for EAB and A for control room), or use the FSAR allowed leakage.
Project 6783 Page 28 of 29 8/29/96
Leaka e Limit Calculation for St Lucie Unit 1 Table C 1. Screening results for dose limited leakage at 95% confidence level (using Tables from Ref. 3)
EAB, Class F
EAB, Class E
Control Room, Type B Pre-accident Spike (gpm) 3310 12,100 545 Accident-Initiated Spike (gpm) 12,900 44,000 1,700 b.
For the conditions shown in Table C-1 a site specific detailed evaluation to produce a 95/95% confidence leakage limitestimate using the measured site stability class frequency, wind speed, direction and distance is likely to demonstrate significant margins.
5.
Compare the leakage limitwith the estimated steam generator leakage based on NDE measures in support of condition monitoring and operational assessments.
Using Leakage Limit Results A suitable margin between the generic leakage limitfor the EAB and the control room, and the projected EOC steam generator leakage can be calculated for various degrees of confidence (e. g., the ratio of the projected EOC leakage at 95/95 to the 95/95 allowed leak rate). Ifthis is a small number (i.e., less than 0.1a), then the generic screening process clearly indicates that the site characteristics provide the capability of meeting the regulatory dose limits.
A more detailed evaluation can be used to demonstrate effectiveness of other plant specific features in providing additional protection for keeping predicted accident doses within regulatory limits.
The value of 0.1 is suggested as an acceptable margin when screening values are used, because the analysis is based on measures of I131 thyroid dose.
The variation between the whole body and thyroid dose in a sample of FSARs indicates that the doses from all isotopes would be bounded ifthe margin was 0.1. A detailed assessment which includes evaluation of the whole body dose would remove this assumption.
Project 6783 Page 29 of 29 8/29/96