ML19343C228

Ro:On 740610,investigation Re Valving Arrangement & Isolation Capability of Main Steam Line Drains Revealed That Valves V-1-110 & V-1-111 Failed to Meet Design Criteria. Caused by Design Error.Control Circuit Mods Underway

ML19343C228
Person / Time
Site:	Oyster Creek
Issue date:	07/10/1974
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8103040523
Download: ML19343C228 (2)

Text

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Jersey Central Power & Light C MADISON AVENUE AT PUNCH BOW 1. ROAD

• MORRISTOWN, N.J.07960

• 201-539-6111

.....m.,

General g,E PutWc utWties Corporation

,wa, July 10, 1974 pf ,k f Q it ,n d ll.f/f,) 'a Mr. A. Giambusso

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Deputy Director for Reactor Projects i3 - -

Directorate of Licensing "\ '

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United States Atomic Energy Commission  %

Washington, D, C. 20545 , -

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Subject:

Oyster Creek Station f j$.1 O Oy ,

Docket No. 50-219 - gpu / '

Main Steam Line Drain Valves *NTM5 y

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his is to renort an unusual event as defined in Technical &../ /

Specification 6.6.2.b.3 cohcerning the main steam line drain valves. "%F During our recent refueling outage, while preparation for the primary containment integrated leak rate test was under way, a condition was discovered which involved a possible single failure which, for a system designed against assumed single failures, could result in the loss of the capability of the system to perform its safety function. n e discovered condition was the inability of the main steam line drain valves, V-1-110 and V-1-111, located out-side the primary containment, to meet their design criteria as stated in the FDSAR.

On June 10, 1974, an investigation into the valving arrangement and isolation capability of ths main steam line drains was conducted and revealed that valves V-1-110 and V-1-111 do not isolate on a main steam isolation signal.

Investigation into the FDSAR, Table V-1-2, " Isolation Valve Requirements,"

indicated that the outside main steam line drain valves, V-1-110 and V-1-111, are listed as D-C motor operated isolation valves which close on a main steam line isolation. This was further confirmed in Amendment 15 to the FDSAR, Table III-1.

An investigation into the electrical control system for V-1-110 and V-1-111 revealed that the valves were not designed to close on an isolation signal as indicated in the FDSAR and operation of the valves was therefore under manual control from the station control room.

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Mr. Giambusso - July 10,1974 Preoperational startup tests were then reviewed to determine the condition of V-1-110 and V-1-111 during the initial plant startup. No reference to these valves was found in' the preoperatione.1 tests for the main steam system.

The apparent cause of this condition is a design error in the control circuit wiring for main steam line drain valves V-1-110 and V-1-111.

Main steam line drain valves V-1-106 and V-1-107 are connected to the A and B main steam lines on the reactor side of the main steam isolation valves NS03A and NS03B, respectively. Both main steam line drains then join into a single pipe and penetrate the drywell. The line then splits with isolation valves V-1-110 and V-1-111 going to the downstream side of the main steam lines (outside the second set of isolation valves) and to main condenser 1-A, respectively. During normal operation, valves V-1-106, V-1-107, V-1-110 and V-1-111 are closed.

It is this closed state during normal operation that has prevented discovery of this condition prior to this time. When the isolation signal was given during normal operation, no indication of the inability of these i valves to isolate was observable since they were closed.

Modification of the control circuits for V-1-110 and V-1-111 to close on main steam isolation signal (or remain closed) is currently under way as corrective action. Fu;cher investigation into the cause of this design error is also actively being p trsued.

Enclosed are forty copies of this letter.

Very truly yours,

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Donald A. Ross Manager, Nuclear Generating Stations es i

Enclosures cc: Mr. J. P. O'Reilly, Director Directorate of Regulatory Operations, Region I

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