ML20083P814

Ro:On 840307,during Drainage of RCS to Holdup Tanks,Rhr Containment Sump B Suction Valves MOV 851 a & B Opened Before Valve 850 a Closed,Causing Drainage of RCS Into Sump B

ML20083P814
Person / Time
Site:	Ginna
Issue date:	03/20/1984
From:	Snow B ROCHESTER GAS & ELECTRIC CORP.
To:	Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
NUDOCS 8404200183
Download: ML20083P814 (2)

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3 ROCHESTER GAS AND ELECTRIC CORPORATION . 89 EAST AVENUE, ROCHESTER, N.Y.14649 A TF s E PetOpel a.a coon 7 e 546-2700 March 20, 1984 Dr. Thcmas E. Murley, Regional Administrator U.S. Nuclear Regulatory Con. mission Region I 631 Park Avenue King of Prussia, Pennsylvania 19406

Subject:

Potential Loss of Residual heat Ren. oval (RHR) Capability R. E. Cinna Nuclear Foker Plant, Unit No. l' Docket No.56-244 Ecar Er. Murley:

This is a preliminary notification of an cvent that occurred on March 7, 1984, that will be followed by a. Licensee Event Rcport.

While at Cold Shutdown condition the following actions were in prcgress: draining the Reactor Coolant System (RCS) to the CVCS hold up tanks, and preparing to shift fron. draining the BCS via the Reactor Coolant Drain Tank Pump to the low pressure purification pump. During this process Valves MOV 851 A and B (Containment Sunp E suction to RHR) were opened prior to shutting valve MOV B50A (Downstream of MOV 851A and Upstream of RCDT pump suction).

The Cperator's first acticn was to turn the switch for McV-850A to the " Closed" position. Approximately 30 seconds later the Sump B level alarm was actuated and the 8" level indicator lights were actuated. The operator then noticed that the RCS lccp level ncnitor indicated zero. The running RHR pump was then stopped. Tc this point the RHR flow had remained at a steady 900 GFM. After h0V-650A was shut, the RHR pump was restarted and 9C0 GFM flow indicated. Approxin ately one minute later MOV-856 ( Refueling Water Storage Tank to RHR Pump Euction and to RCS Hotleg Locp A) was opened to restore RCS loop level, then closed. The final pressurizcr level indication was 150".

Delaying the opcning cf MOV-856 until after the RHR pump was restarted and indicating steady flow, showed that at no tin.e was RHR inoperable.

The RHR ten perature prior tc the event was approximately 100 0F.

khen the purrp was stopped the RhR tenperature indicated approximatelg 1150F. khen MOV E56 was opencd the tenperatur e decreased to ,y approximately 600F. khen RHR flow was reestablished' the temperature returned to 1000F. 8404200183 840320

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Both CAM's (continuous air acnitors) in the Containment Vessel Basement were alarming on High Gaseous Activity. R-12 (Containment Vent Gaseous Monitor) indication in the Control Foom did not increase significantly above the pre-event reading. Containment evacuation alarm was sounded and personnel inside containment evacuated.

One hour or four hcur. notification of the event to the NRC was evaluated and it sas determine 6 that none of the criteria established in the Ginna Procedure O-9.3, which covers all 10 CFR 50.72 reporting criteria were applicable.

Subsequent investigation revealed that a total of 31 inches of water was drained into the Sump B (Sump B discrete light indications are at 8 inches and 78 inches). This was verified by actual measurement. This volume of approximately 2000 gallons is consistent with the calculation of ECS loop level change from 20 inches to zero inches. The evaluation further showed that after opening valves MOV-851A and B the RHR pumps were still operable and operating.- The event that could have caused loss of RHR capability was the closing of MOV-850A with essentially zero inches loop level indication. Had the RHR pumps operated in this mode for greater than or equal to one minute withcut MGV-856 open they could have beccme air bound and hence inoperatic.

It should be noted that the travel time for 851A, 851B, 850A, and 856 is approximately two minutes and calculations show that it would take less than 30 seconds to drain the volume of water frcm RCS (20" loop level to zero) to Sump B.

Further evaluation and discussions revealed that this event is reportable under 10 CFR 50.73 (a) (v) which thus implies it is reportable within four hours of occurrence, in that the event alone could have prevented the fulfillment of the safety function of system needed to remove residual heat, without operator action.

Very truly yours, Bruce A. Snow Plant Superintendent L__________-__-_______--__-_. . _ _ _ - - _ - _ _ -