ML20086L760

Safety Evaluation Supporting Amends 152 & 136 to Licenses NPF-04 & NPF-07,respectively

ML20086L760
Person / Time
Site:	North Anna
Issue date:	12/13/1991
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20086L749	List: ML20086L746 ML20086L760
References
NUDOCS 9112170059
Download: ML20086L760 (6)

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's,.....f SAFETY EVALUATION BY THE OFFICE OF kilCLEAR REACTCR REGUtATION RELATED TO AMEND!1ENT NOS.152 AND 136 TO FACILITY OPERATING LICENSE f:05. NPF-4 AND HPE-7 VIRGINTA ELECTRIC AND p0WER COMPANY OLD DOMINION ELECTRIC COOPERATIVE NORTH ANNA p0WER STATION, llHITS NO. 1 AND NO. ?

DOCKET NOS. 50 338 AND 50-339 1.0 INTRODilCT10N By letter dated October 3, 1991, the Virginia Electric and Power Company (the licensee) proposed changes to the Technical Specifications (TS) for the North Anna Power Station, Units No. 1 and No. 2 (NA-182). The proposed changes would revise the current NA-132 TS to ensure the design basis is met for the Service Water System (SWS).

The proposed changes are being made as a result of an NRC violation regarding the NA-1&2 SWS, in the Notice of Violation dated February 1, 1991, the NRC identified that the operating procedures for the SWS were inadequate by not ensuring design basis flows to the recirculation spray heat exc. hangers during periods when an SW pump is inoperable. This indicated that the licensee's control of the SWS design basis was inadequate.

In the licensee's response to the NRC Notice of Violation dated iiarch 1,1991, the licensee comitted to changes in the NA-1&2 TS to clarify the SWS operability requirements and, in the interim, to provide adequate administrative controls to ensure the SWS design basis is met. A description of the NA-182 SWS, discussie of the proposed changes and the staff's evaluation are provided below.

1.1 SWS Background The SWS is comon to both NA-182 and is designed for the simultaneous operation of various subsystems and components of both units. The purpose of the SWS is to provide long-term cooling after a loss-of-coolant accident (LOCA) and to supply cooling water to various safety-related components during normal plant operation.

The sources of cooling water for the SWS are the SW reservoir or Lake Anna.

l These two, independent sources of water form the ultimate heat sink for the units.

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F 2-The normal SW5 alignment consists of four normal SW pumps taking suction from the SW reservior, supplying various components through the supply header, and then returning to the SW reservoir through the return header to the spray arrays or bypass valves. A backup subsystem is available in the event of unavailability of the SW reservior.

This backup subsystem consists of two auxiliary SW pumps which take suction from Lake Anna, supplying various components through the alternate supply header, and then returning to Lake Anna through the alternate return header.

The cooling capacity of the SWS is based on the cooling requirements assuming one unit sustains a LOCA with a simultaneous loss of offsite power to both units. The SW cooling requirements following a LOCA on one unit dictate that two normal SW pumps operate to supply adequate cooling flow to the affected unit and unaffected unit heat loads.

In the event of the LOCA a safety injection would be initiated. To ensure that sufficient SW cooling is available to both units, the safety injection signal actuates the following, a.

All four normal SW pumps start on receipt of a safety injection signal from either unit or on a loss of reserve station service power. Operation of all four pumps provides maximum system cooling capacity and flexibility.

l b.

The SW spray header isolation valves automatically open and the bypass isolation valves automatically close af ter receipt of a safety injection signal. With all spray arrays in operation, the SWS can reject heat at the maximum rate.

During a design basis accident, the supply valves from both loops of SW to the affected unit's recirculation spray heat exchangers are opened automatically upon receipt of a containment depressurization signal. A safety injection signal will occur prior to the containment depressuritation signal.

With four normal SW pumps operable, the unthrottled head loss of the system to components other than the recirculation spray heat exchangers is such that design flows are achieved through the recirculation spray heat exchanger if a failure to a single pump or power supply occurs. With three normal SW puinps operable, the flow of the system to components other than the recirculation spray heat exchangers must be restricted to ensure that design flow will be i

available if a single pump or power supply failure occurs.

This is achieved I

hy reducing SW flow through the component cooling heat exchangers and must be I

done if either or both of the units are in operating modes 1 through 4.

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two normal SW pumps operable, design flows will not be achieved if a single normal SW pump failure occurs. With one normal SW pump operable, design flows are not achieved.

In the last two cases, more conservative actions are required by the specifications.

.0 015CllSS10H The proposed changes enhance the availability of the SWS and ensure design basis flows are available to the recirculation spray heat exchangers. The proposed changes further ensure the availability of shutdown cooling by requiring one operable SW loop when both units are in modes 5 or 6.

The Limiting Condition *, Operation of TS 3.7.4.1 is changed to define what constitutes an operable h loop.

Each SW loop must contain two operable SW pumps (excluding auxiliary SW pumps) with their associated normal and emergency power supplies, and an operable flow path capable of providing cooling for operable plant components and transferririg heat to the SW reservoir to ensure design basis ficws are achievable.

The applicability statement of TS 3.7.4.1 is changed to clarify that this applies if either unit is in mode 1 through 4 This change will ensure that sufficient cooling capacity is available for both units during power operation.

Action statement 3.7.4.1.a is added to require that if one of the four required normal SW pumps becomes inoperable, the component cooling heat exchanger SW flows must be throttled, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, to ensure thit the normal SU pumps remain capable of providing design basis flows to the recirculation spray heat exchangers.

This allows design basis flows to be delivered by two normal SW pumps with the failure of the third operable normal SW pump.

Action statement 3.7.4.1.b is added to require that if two of the four required SW pumps become inoperable, Action.3.7.4.1.a must be performed within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. Performing this action ensures the design basis flows can be met if no subsequent pump failures occur.

In addition, at least one SW pump must be restored to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, or both units shall be placed in hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

Action statement 3.7.4.1.c is modified to add the phrase "except as provided in 3.7.4.1.a" for clarification, in addition, this action statement is changed to clarify that the inoperable loop must be returned to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or both units will be placed in hot standby.

Action statement 3.7.4.1.d is modified to allow not having auto-start capability on the third normal SW pump and require two-out-of-two auxiliary SW pumps to be operable. Not requiring the third normal SW pump to have an auto-start capability is considered a clarification of the current TS and is needed to protect the normal SW pumps from a low flow condition with the three pumps are aligned to the same supply header. The probabi1Mic risk assessment that was performed for the original amendment on this issue only required that the pump be available for service.

Requiring two-out-of-two auxiliary SW pumps will provide for a complete backup system to be available and will ensure that a manually initiated backup system exists which can deliver design basis flows during an accident condition.

In addition, the footnote for tis action statement is modified to include the SW valve house l

components.

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4-Action statement 3.7.4.1.e is added to require that if both SW loops become iroperable, that buth units must be placed in hot shutdown within the next I?

hours and that actions be initiated to place both units in cold shutdown within the next hour and continue to cold shutdown. With two SW loops i

inoperable, the units are not prepared to respond to the design basis events for which the SWS is required.

The units must be placed in a mode in which the risk to the unit and the environment is minimized. Depending on the actual state of the SWS, the recirculation spray hi+t othangers may not have a safety-grade heat sink and the unit should be placed in hot shutdown, a condition where decay heat can be removed by the steam cenerators.

The action to place both units in hot shutdown and continue actions until both units are in cold shutdown addresses the condition if the SWS is unavailable to perform its intended function, in this situation, the unit may remain in hot shutdown until a method to further cool the units becomes available.

Survei11mce Requirement 4.7.4.1.c.) is changed to add that the automatic valve ser 4 icing safety-related equipment actuates on both an actual or simulated safety injection signal, in addition, Surveillance Requirement 4.7.4.1.c.2 is modified to clarify that the automatic SW valves should be verified to be in the correct position on a actual or simulated containment high-high signal.

Surveillance Requirement 4.7.4.1.d is added to specify surveillance testing for operability determination of the SW pumps in accordance with Specification 4.0.5, the ASME Section XI program.

TS 3.7.4.2 is added to support the Updated Final Safety Analysis Report (UFSAR) design basis for both units in modes 5 or 6.

When both units are in cold shutdown or refueling, the design hasis requires that the SWS be operable. This will ensure an adequate heat sink is maintained for the residual heat removal (RHR) system.

The requirements for modes 5 and 6 differ from TS 3.7.4.1 by requiring that one SW loop be operable.

SW is required to provide a heat sink for the RHR i

system to remove decay beat from the reactor core. Powever, there is a significant reduction in potential heat loading on the SWS. Therefore, only one SW loop is required to be operable. The components required for one loop to be operable are the same as defined in TS 3.7.4.1 except that credit for the operable auxiliary SW pump may be taken to satisfy the operability requirement of the LCO. This allows removing the SW reservoir from service for maintenance and utilizing the Lake Anna reservoir as the heat sink for core heat removal.

Requiring that two SW pumps he operable allows for a single pump or power failure while still providing the heat sink for the RHR system. This is consistent with the RHR system requirements.

Action Statement 3.7.4.2.a requires that if there is only one operable SW pump, at least one inoperable SW pump must be restored to operable status within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

This is consistent with the action requirements for a partial loss of RHR capability during shutdown conditions.

Action Statement 3.7.4.2.b requires that if no SW pumps are operable, all operations involving an increase in the reactor decay heat load or a reduction

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5-in boron concentration of the Reactor Coolant System (RCS) must be innediately suspended because of total loss of shutdown cooling may have occurred.

This is consistent with the action requirements for a total loss of RHR capability during shutdown conditions.

Surveillance requirements to demonstrate the operability of one SW loop are included in TS 3.7.4.2.

The existing bases section (B3/4.7-4) is expanded to provide a more detailed description of the SW system.

This bases section is also split to provice a description for operating and shutdown conditions (3/4.7.4.1 and 3/4.7.4.2, respectively).

3.0 EVAltlATION The proposed changes document the licensee's commitment to clarify the SWS operability requirements. The proposed changes modify the NA-182 TS to be consistent with the design basis and result in additional limitations not currently included in the NA-182 TS. Also, the proposed changes further

-ensure the availability of shutdown cooling by requiring one operable SW loop-when both units are in mode 5 or 6.

Finally, the proposed changes enhance the availability of the SWS and ensure l'FSAR design basis flows are available to the recirculation spray beat exchangers.

Based on all of the above, the staff finds the proposed changes to be acceptable.

4.0 STATE CONSULTAl f 0N in accordance with the Connission's regulations, the Virginia State official was notified of the proposed issuance of ths amendments.

The State official

- had no connent.

5.0 ENVIRONMENTAL CONSIDERATION

These amendments change a roirement with respect tc installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change surveillance requirements. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Connission has previously issued a proposed finding th61 the amendments involve no significant hazards coiideration and there has been no public connent on such finding (56FR55950). Accordingly, these amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR-51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact stet. ament or environmental assessment need be prepared in connection with the issuance of these amendments.

6.0 CONCLUSION

The Commission i s concluded, based on the considerations discussed above, that:

i not be endangered by operation in the proposed manner, (2) y of'the public wil (1) there is reasonable assurance that the health and safetsuch activities will

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6-i be conducted in comp'. lance with tht Courniktion's regulations, ahd (3) the issuance of the amendments will not be iniht.c.il to the contrico defense erd security or to the health and saftty of the public.

Priucipal Contributor: Leon B. Engic.

Date: December 13, 1991 4

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