ML20003C501
| ML20003C501 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 02/25/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20003C493 | List: |
| References | |
| NUDOCS 8103060292 | |
| Download: ML20003C501 (10) | |
Text
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NUCLE AR REGULATORY COMMISSION
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 24 TO PROVISIONAL OPERATING LICENSE N0. DPR-45 DAIRYLAND POWER COOPERATIVE i
LACROSSE BOILING WATER RE ACTOR (LACBWR)
DOCKET NO. 50-409
1.0 INTRODUCTION
A'O DISCUSSION Sy our Order dated February 25, 1980, Dairyland Power Cooperative (DPC)
(the licensee) was ordered to show cause why it should not:
design and install a sitt dewatering system at the LaLrosse Boiling Water Reactor (LACBWR) to preclude the occurrence of liquef action in the event of an earthquale with peal gruJnd surf ace acceleration:.
cf 0.129 or less.
make the dewatering system operational by February 25, 1981 or place the Lacrosse Boiling Water Reactor (LACBWR) in a safe cold shutdowr condition.
In connection with its submittals in response to the Order to Show Cause and the NRC staf f's related reviews of liquef action potential DPC proposed by letter dated August 25, 1980, to install a dedicated safe shutdown system to preclude reliance on the existing river water intake structure and buried piping in the unlikely event of a 0.129 earthquake that causes soil liquefactio-and resultant loss of these facilities.
I-By letter dated August 29, 1980, we issued our Safety Evaluation considering DPC's responses to the February 25, 1980 Order and our April 25, 1980 request for additional information.
Our Safety Evaluation concluded that the soils under the existing turbine building and the reactor containment are adequately safe against liquefaction effects for an earthquake up to a magnitude 5.5 with peak ground acceleration of 0.129 Although we concluded that liquef action remained a concern for the crib house and underground piping, we found that a site desatering system was not necessary to resolve this concern.
We also concluded that the concept for a dedicated safe shutdown system to preclude reliance on the crib house and underground piping was feasible and that i
engineering details and installation could be completed by February 25,19S1.
The dedicated shutdown system woald provide additional assurance that the reactr could be safely shutdown by providing sufficient river cooling water in the unlikely event that the normal supply capability is lost due to seismically indJCed soil liquef action at the pumps intake structure and buried piping.
For the above reasons we concluded that a dewatering system for the LACBWF.
site is not necessary.
We have since completed our evaluation of the dedi-cated safe shutdown system that DPC designed and installed in time to become 810 M n 6 n2 9 2 1
. operational by February 25, 1981.
By letter dated October 14,1980, DPC presented the status of the design and purchase specification related to the Dedicated Safe Shutdown System and later by letter dated November 26,INIL presented a comprehensive engineering report entitled, " Design of an Emergency Service Water Supply System for LACBWR." This was followed by a DPC submittal dated Febraury 2,1981 which included a detailed desip description of the Emergency Service Water Supply System.
Finally, a DPC letter dated February 18, 1981 presented the proposed changes to the Operating Technical Specifications related to the recently added Emergeng Service Water Supply System.
Our evaluation of the new emergency water system is based on these submittals.
By letters dated March 13, 1980, and February 19, 1981 DPC responded to y EE:
"All LWR Licensees" letter dated February 23, 1980 relating to " Event V" ira af coolant accident described in Reactor Safety Study, WASH-1400.
Event V am!iE t(
loss of pressure isolation generally involving check valves or motor operated valves in series as the barrier between the primary coolant sysba and systems intended for low pressure only.
We have completed our evaluaaur.
of Primary Coolant System Pressure Isolation Valves (EVENT V) at LACBWR using the DPC submittal and the attached Technical Evaluation Report, dated October 24, 1980, prepared by our consultant, Franklin Research Cenar.
2.0 EVALUATION 2.1 Emergency Service Water Supply System 2.1.1 Consequences of Crib House Failure Loss of the crib house and its associated pipitg would result in isolatim of the plant from its ultimate heat sink for both normal and accident cont-tions, and also in loss of the water supply for the fire protection syster discussed below.
A.
Loss of Circulating Water Pumps - circulating water to main condenser is lost, main condenser cannot be used as heat sink.*
B.
Loss of Low Pressure Service Water (LPSW) Pumps * - cooling flow to couponent cooling water (CCW) heat exchangers is lost, therefore deog heat cooling system, which uses CCW as an intermediate cooling loop, cannot be used to remove decay heat.
- Primary supply of water to the high pressure service water (HPSW) sysms is lost, so the HPSW is depressurized (see below).
Also would occur on lu.s of offsite power.
3-C.
Loss of Alternate Core Spray Pumps - low pressure core spray flow used for mitigation of loss-of-coolant accidents (LOCA) is lost.
- Supply of water to HPSW system is lost, so HPSW is depressurized (see beloi;.
D.
Depressurization of HPSW (either from loss of pumps or buried piping) -
fire protection water supply is lost.
- Backup water supply for the shutdown condenser and for the overhead storage tank (0HST) is lost.
Without the pumps in the crib house, the remaining systems for plant heat remos?
are the shutdown condenser (with demineralized water makeup) and the high presurt core spray system taking suction on the OHST.
water supplies Both of these systems have finita 2.1.2 Design of the Emergency Service Water Supply System The system is designed to be capable of supplying sufficient water to ensure adequate core cooling and decay heat removal capabilities for all reactor shut-down situations up to and including the design basis LOCA.
The system is designed to be independent of offsite power supplies.
is a backup system, the ESWSS is placed into operation manually.
Since it References 1 and 2 provide the design description for the Emergency Service Wate Supply System (ESWSS).
The desir;n is shown in Figure 1 attached to this evalua:in.
The system consists of three port'able pumps (plus a spare), a three-way ball vaivt distributor, and a relay hose to one of two inlets at the HPSW header.
tion may be made either outside the turbine building or inside.
The come -
Each pump sucts is fitted with a debris screen, but in addition, floating dock, self-leveling strainers are provided for each pump.
This equipment is stored in the turbine building near the overhead freight door.
The pump skids are to the river by four men. provided with litters so that they can be carried Technical Specification 3.2.2.f re be available on site at all times for fire fighting purposes, quires five men so a sufficient number of plant staff would be available to deploy this equipment.
Accessible isolation valves (both inside and outside the turbine building) are provided on all connecting lines between the underground service mains and the HPSW header so that postulated failures in the buried lines or crib house can be isolated from the ESWSS.
System setup and operation is further discussed later in this evaluation.
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. 2.1.3 Conceptual Design Requirements for Pump Capacity and Implementeion Time The licensee considered various situations for which the ESWSS should function to determine required pump capacity and implementation time resp.rictions.
Since the system is manually assembled end operated, sufficient time must exist for the operators to align the system and to initiate ESSd5 flow.
The licensee has considered loss of the crib house and buried piping as a result of liquef action concurrent with another low probability event, a LOCA. This assumption results in more stringent requirements on minimum flow and tine to make the ESWSS operational than would be required just for safe shutdown following an earthquake.
The ESWSS is also capable of providing water for fire fighting purposes since the flow is delivered to the HPSW header.
This aspect of the ESWSS review will be addressed in connection with Appendix R confornE1ce reviews.
The scenarios considered in determining design requirements are the following:
Case 1: Shutdown with loss of the crib house or buried piping as a result of free field liquefaction following a Safe Shutdown Eartnquake (SSE).
For this scenario, the shutdown condenser can initially be used to remove decay heat, using the demineralized water (DMW, system to makeup to the shell side.
This method can remove decry heat for at least 2-1/2 days (based on DM4 tank capacity), after Wiich the decay heat cooling system would have to be used to complete the cooldown to cold shutdown. The ESWSS is needed to supply water for the CCW coolers, which are needed to remo/e heat from the deny heat cooling system.
The flow required to remove decay heat would be approximately 200 gpm.
The cross-tie to the tube side of the CCW coolers is made through an existing line tap from the HPSW.
Case 2: As Case 1, with a below-core break LOCA.
Upon detecting the low reactor water level or the high containment building pressure resulting from the LOCA, the HPCS system, drawing suction on the OHST, is automatically initiated to prodde energency core cooling.
With both pungs operating and the miniann OHST volume allowed by technical specification (no makeup flow), no additional water is required for 2-1/2 hours.
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. For below-core breaks, the containment building must be flooded up to the level of core midplane before the shutdown condenser can This function is normally performed be used to remove decay heat.
This low-pressure, high by the Alternate Core Spray system.
capacity system, which delivers flow af ter reactor pressure has decreased to 150 psig, would not be operational upon loss of the Therefore, ESWSS flow equivalent to the flow of one crib house.
ACS pump is needed to provide sufficient flow so that long-term core cooling is assured.
Once shutdown condenser operation is established, a small amount of ESWSS flow is needed to maintain core inventory.
Same as Class 1, with an above-core break LOCA (i.e., in steam Case 3:
line, shutdown condenser inlet / outlet lines or in the ACS or HPCS connection).
For most above-core breaks, the HPCS system is used to provide short-term As core cooling flow, using the OHST to reestablish vessel water level.
the OHST is emptied, (2-1/2 hours with 2 HPCS numps running) the ESWSS is started to provide the equivalent of the Hew flow (100 gpm) to the tank.
For a break in the HPCS This flow must be initiated within 2-1/2 hours.
system, however, the above method cannot be used since the HPCS piping Until reactor pressure drops below the shutoff head of the is not intact.
ESWSS pumps, there is no injection flow.
The licensee has calculated that the reactor system depressurizes to 150 psig in 28 minutes following a complete break in the HPCS connection.
During this time, decay heat is removed by the upward flow of steam through the core.
If the HPCS is not available for core injection following a small break LOCA or steam line break (or smaller HPCS line breaks), the manual depres-surization system (MDS) can be used to reduce pressure so that the low However, the operator pressure cooling system could provide core injection.
would not initiate the blow-down unless a low pressure cooling water system was available, that is, until the ESWSS is made operational.
The staff has previously reviewed the flow requirements for LOCA mitigation and has determined that the HPCS, with the MDS and ACS as backup, can provide adequate core cooling for the spectrum of above-core and below-core The ACS alone is needed f or the long term.
breaks in the short tern.
With these systems the Lacrosse reactor was determined to be in full compliance with the Interim Acceptance Criteria for Emergency Core Cooling Systems for Light Water Power Reactors (Referencc 3).
}
. Thus, the limiting factors on the system design are 28 minutes for system setup, based on an HPCS break, and a flow rate equivalent to one ACS pump (i.e. 900 gpm at 150 psig), based on below-core-break LOCA requirements.
As discussed above, the emergency service water supply system can provide needed water for shutdown following an earthquake as well as for LOCA requirements.
2.1.4 System Operation The ESWSS is manually assembled for use following postulated failures of the crib house or buried piping.
The actions necessary to align this system include the following:
(Refer to Figure 1)
Transport three of the portable pumps to a suitable river location.
Set up the suction and discharge hoses for each pump.
Lay out the relay hose and connect the discharge to the selected inlet station.
Close the HPSW in-plant piping header isolation valves (75-24-091 and 75-24-092) and open valve 75-24-093.
Open the selected ESWSS inlet station valve.
Connect the relay hose and three pump discharge hoses to the 3-way distributor.
Start engines and prime pumps.
Open distributor valves and establish desired flow by adjusting engine / pump speed.
The detailed operating procedures are subject to review by the Office of Inspection and Enforcement.
The system will undergo prededication testing to ensure that the system design criteria have been met.
. Satisfactory completion of preoperational testing together with the periodic testing as specified in the Technical Specifications will ensure that the installed system can provide the necessary flow, and that the setup can be completed before flow is needed.
Based on these considerations, we consider that the proposed ESWSS design is acceptable.
2.1.5 Technical Specifications The licensee proposed Technical Specification Section 4/5 2.21, entitled,
" Emergency Service Water Supply System" in Reference 4.
This specification includes limiting conditions for operation as well as testing and surveillance requirements for the system.
The ESWSS shall De operable for plant operation other than cold shutdown or refueling.
The entire system is tested every 18 months to ensure that the t
system can be assembled under sinulated emergency conditions and deliver s
the required flow, inspection and maintenance on the pumps and inspection and testing of the hoses and other fittings at more frequent intervals provide added assurance that the system will function if needed.
The demonstration of operability requiremer:ts are consistent with those applicable for the systems whor e function 1 are performed by the ESWSS in the event of liquefaction.
Based on our review of the proposed Technical Specifications, we conclude that the Technical Specification changes are acceptable.
2.2 Primary Coolant System Pressure Isolation Valves (EVENT "V")
On the basis of information provided by DPC, our consultant, Franklin Research Center (FRC), cocpleted an evaluation of the LACBWR high pressure primary coolant system where separation from low pressure systems relied on two check valves in series or two check valves in series with a motor operated valve.
FRC in a Technical Evaluation Report (TER) (attached) " Primary Coolant System Pressure Isolation Valves" dated October 24, 1980 identified two check valves and a motor operated valve in series.
These valves provide the barrier between primary coolant syste. high pressures and the low pressure Alternate Core Spray System.
FRC concluded that changes to the LACBWR Technical Specifications are required for periodic testing of the
- wo check valves, valve number 38-26-001 and 38-26-002.
We agree with the
'RC finding that periodic testing of the subject valves is an acceptable neans of achievir; a reduction of risi' of an Event V type intersystem loss of coolant accider t
1
. Therefore, the technical specifications should be changed, as recommended by FRC, to require periodic tests.
DPC proposed a new technical specification, item 4/5.2.22 to satisfy this requi rement. We have discussed the new technical specification require-ments with DPC representatives and agree that the periodic testing criteria of the attached TER and are therefore, acceptable. Accordingly, we also find that the proposed technical specification change 4/5.2.22 is acceptable.
In addition to Event V valve configurations, we are continuing our e' forts to review other configurations located at high pressure / low pressure system boundaries for their potential risk contribution to an intersystem LOCA. Therefore, further activity regarding the broader topic of intersystem LOCA's may be expected in the future.
3.0 ENVIRONMENTAL CONSIDERATION
S We have determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 51.5(d)(4), that an environmental impact state-ment, or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
4.0 CONCLUSION
We have concluded, based on the considerations discussed above that:
(1) because the amendment does not involve a significant incredse in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Attachments:
1.
Technical Evaluation Report 2.
Figure 1 Date:
February 25, 1981
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REFERENCES:
i j
l 1.
LAC-7246, Dairyland Power Cooperative to NRC, November 2.
26, 1980.
LAC-7355, Dairyland Power Cooperative to NRC, February 2,-1981.
3.
Amendment No. 6 to Provisional Operating License No. DPR-45 for the i
Lacrosse Boiling Water Reactor, August I
12, 1976.
4.
L AC-7376 Dairyland Power Cooperative to NRC, February ~18,1981.
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