ML20010E221

Interim Deficiency Rept Re Vol Control Tank Level Instrumentation Control Sys Interaction W/Protection Sys, Initially Reported 810522.Plant Procedures Being Reviewed to Assure Operator Alert.Rept to Follow

ML20010E221
Person / Time
Site:	Farley
Issue date:	05/26/1981
From:	Hairston W ALABAMA POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
10CFR-050.55E, 10CFR-50.55E, FNP-81-0647, FNP-81-647, NUDOCS 8109030214
Download: ML20010E221 (2)

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?!ay 26, 1981 FNP-81-0647 11 r . J. P. O'Reilly, Director C. S. Nuclear R2gulatory Commission 101 ?!arietta Street, N.W.

Atlanta, Georgia a0303

Dear ?Ir. O'Reilly:

This is to confirm the telephone call to NRC Region II I&E by Mr. J. D. Woodard (APCo) at appro.<imately 1S00 hours on ?!ay 22, 1981.

Westinghouse notified Alabama Power Company that the Westinghouse Water Reactor Division's Safety Review Committee has identified a potential control and protection system interacticn concern involving the Volume Control Tank (VCT) level instrumentation control system. This situation represents a '.131ation of the Nerlear Regulatory Commission regulations related to separation of protection and control systems and single failure criteria as delineated in GDC-24 and IEEE-279. Engineering review of this notification resulted in a determination on ?!ay 22, 1981, that this situation is potentially reportable under Technical Specification 6.9.1.S.i (Unit 1) and 6.9.1.12.i (Unit 2). This situation is being evaluated for reportability under 10CFR Part 21 and will be addressed in the follow-up report.

Westinghouse does not see this item as one with serious safety implications, but rather, as one which violates current Regulatory requirements. The postulated event is as follows:

Assume the plant is operating with a centrifugal charging pump performing the normal charging function. The failure of the VCT level control system (LT-115 or LT-112 failing high) causes the let-down flow to be divert"d t a the Recycle Holdep Tanks. The VCT liquid inventory is reduced (,ue to no mal c!.arging without any make-up to the VCT due to letdown. Assumag LT-115 or LT-112 fails high, charging pump -uction is not transferred to the R'aST, and without operator intervention the VCT could empty causing the centrifugal charging pump to be damaged due to loss of suction fluid. The second centrifugal charging piunp is then taken to be the assu: red active 810903o214 8105 ' 8

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failure. The RCS inventory decreases due to normal letdown flow and, following letdown isolation, due to RCP seal leakage. However, bor-ated water cannc* be injected into the RCS from the centrifugal charg-ing pumps. The operator must find a means to restore the primary inve; tory lost via letdown and RCP seal leakage. In addition, the operator must be capable of borating the RCS prior to going to a cold shutdown condition.

This scenario assumes that during normal plant operation, one charging pump is running with another on standby. Actually, three charging pumps exist, although the Technical Specifications require only two.

Following the failure in the VCT level control system, the operator would have approximately 10 minutes to transfer the charging pump suction f rom the VCT to the RWST, simply stop te pump, or restore letdown to the VC'i If no operator action occurs at this time, then the pump in operation could be damaged due to loss of suction, and the plant would continue to lose inventory due to letdown. However, this is a slow loss in water inventory. Automatic letdown isolation should occur. Even without letdown isolation or operator intervention, approximately two days would elapse prior to core uncovery. The operator would have considerable time to align the standby pump to tne RWST.

Timely operator action can negate this scenario and positively add-ress the identified concern. FNP is equipped with instrument read-outs which would indicate the presence of this situation and numerous alarms would be actuated at various times in the event.

FNP plant procedures are being reviewed to assure that the operator would be properly alerted to this situation and would take the appcopriate action necessary to assure an adequate water supply to the charging pumps.

l Further details will be furnished in the 14-day follow-up report.

i Sincerely yours, 1

l 7T G. Hairston, !II Plc t Manc;er WGH/DWH:sjs cc: H. O. Thrash R. D. Hill K. W. McCracken File