ML19352A085

RO 50-219-77-9-1P:on 770423,during Transfer of Reactor Mode Switch,Shutdown Mode Inadvertently Selected,Resulting in Scram Signal.Cause of Occurrence Being Investigated

ML19352A085
Person / Time
Site:	Oyster Creek
Issue date:	04/25/1977
From:	Quintenz T JERSEY CENTRAL POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
RO-50-219-77-9, NUDOCS 8103040201
Download: ML19352A085 (2)

Text

. .

t

~

Initial Telephone Date of Report Date: April 23,1977 Occurrence: April 23, 1977 Initial Written Time of Report Date: April 25,1977 Occurrence: 0655 OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Reportable Occurrence Report No. 50-219-77-9-lP IDENTIFICATION OF OCCURRENCE: Violation of the Technical Specifications, paragraph 3.5. A.3 occurred when main steam line isolation valve NSO4A failed to close.

This event is considered to be a reportable occurrence as de-fined in the Technical Specifications, paragraph 6.9.2.a.(2).

CONDITIONS PRIOR TO OCCURRENCE: Steady State Power Routir;a Shutdown Operation Hot Standby Load Changes During Routine Power Cold Shutdown Operation XX Refueling Shutdown Other (Specify)

Routine Startup Operation Reactor cool down in progress and mode switch in " shutdown".

DESCRIPTION OF OCCURRENCE: On Saturday, April 23,1977 at 0655 the reactor mode switch was transferred from the "startup" mode to the " refuel" mode after all rods had been inserted and while a reactor cool down was in progress. During the transfer, the " shutdown" mode was in-advertently selected resulting in a scram signal. Also, in the

" shutdown" mode the main steam line low pressure relays 1Kil7, 1K118, 2K117, and 2K118 are not bypassed, therefore, a main steam line isolation valve closure signal was initiated because main steam line pressure was below the sensor's setpoint at the time of the incident. MSIV NSO4A failed to close upon re-ceiving the closure signal, while the other three MSIV's functioned p roperly. Following this occurrence NSO4A was manually actuated from the control room with its control switch, which also resulted in a failure to close. ,

APPARENT CAUSE OF OCCURRENCE: Design Procedure Manufacture Unusual Service Condition Inc.

Installation / Environmental Construction Component Failure Operator XX Other(Specify)

Occurrence is under investigation, no determination of cause'has h0]QfOQQ/ been found at this time.

,T

• Reportable Occurrence Report No. 50-219-77-991P Page Two ANALYSIS OF OCCURRENCE: The MSIV's provide a dual purpose: (1) reactor coolant isolation in the case of a mainsteam line break outside the drywell and (2) primary containment isolation should a pipe break occur inside the containment. Each steam line is provided with two redundant valves in series. Had a true isolation signal been initiated during power operation NS03A would have functioned properly to provide the necessary protection. Therefore, the safety significanc of this event is considered to be a loss of redundancy in those valves provided to maintain primary containment and reactor coolant isolation.

CORRECTIVE ACTION: After several attempts to close the valve, the valve did clase and was proven to be functional, although further investigation will be made to determine the cause of the failure.

FAILURE DATA: N/A Prepared by I /7^f '" > f Date: April 25,1977 T. E.-Quintenz 1

9

. .- .. - . _ . . - . - . . - .- - -.