ML19343C353

AO 50-219/74/33:on 740521,auto-depressurization Sys Initiation Timers 16M23A & 16M232B Failed to Complete Timing Cycle in Less than Two Minutes.Cause Under Investigation. Timers Reset & Timed Out in Less than Two Minutes

ML19343C353
Person / Time
Site:	Oyster Creek
Issue date:	05/31/1974
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:	US ATOMIC ENERGY COMMISSION (AEC)
References
AO-50-219-74-33, NUDOCS 8103120360
Download: ML19343C353 (2)

Text

. -

t j

.

-

, .

OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731

. - Abnormal Occurrence Report No. 50-219/74/33 Report Date May 31, 1974 Occurrence Date May 21, 1974 Identification of Occurrence Violation.of the Technical Specifications, paragraph 3.4.B.4, when it was observed that both auto-depressurization system initiation timers,16M232A and 16M232B, failed to complete their timing cycle in less than two minutes. This event is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15B, D, and G.

Conditions Prior to Occurrence The plant was shut down for refueling. The reactor mode switch was in the

" Refuel" position and the reactor cavity was flooded.

Description of Occurrence while performing the annual automatic initiation test of the auto-depressurization system, it was observed that both system initiation timers, 16M232A and 16M232B, completed their cycle in 169 seconds and 127 seconds, respectively, which is greater than the maximum allowable of 120 seconds. The timers act to delay the opening of the valves and the subsequent depressurization of the reactor vessel for a time period of 120 seconds after receiving coincident low reactor

'

water level, high drywell pressure, and core spray booster pump discharge pressure signals. The timers may be manually recycled by the operation of a keylock reset switch located on Panel IF/2F in the control room in the event of spurious initiation.

It should be noted that system initiation will occur as soon as any one timer completes its cycle.

Apparent Cause of Occurrence The cause of this occurrence is felt to be a lack of clarity in the procedure which did not specifically instruct the operator to time the cycle and verify this to be two minutes or less.

Tib SI A b3 coo

_ . -

. . . _. . - -

( -i

. .. .-

,

Abnormal Occurrence No. 50-219/74/33 Page-2

. -

Analysis of Occurrence The auto-depressurization system is required to depressurize the reactor vessel to less than 285 psig in the event of a small break design bases LOCA. In this event, it is possible for the reactor pressure to remain above the core spray permissive level with a continued loss of reactor coolant inventory until such time as the auto-depressurization system initiates. System initiation would have been delayed by approximately seven seconds had it.been_ required to function as part of the ECCS.

Corrective Action The timers were reset and were observed to time out in two minutes or less:

16M232A - 117 seconds 16M232B - 120 seconds The timers have been retested since they were reset and .found to repeat the times i as recorded above. However, in order to insure operation within two minutes,

,

the timers will be set at 105 seconds.

A study will be made to determine the significance of the 'seven seccnd delay for auto-depressurization system initiation.

The surveillance procedure will be revised to specifically instruct the operator to time the cycle and record same.

Failure Data Type: GE CR120 KT Delay Unit Model: 02241AA Range: 0-5 minute adjustable l

l 1

f f

!