ML20003C721

Ao:On 740309,during Shutdown to Perform Maint on Six Torus to Drywell Vacuum Breaker Valves,Recirculation Loop Temp Recorder Indicated 160 F,Then Jumped to 250 F When Bumped. Caused by Equipment Malfunction & Operator Error

ML20003C721
Person / Time
Site:	Oyster Creek
Issue date:	03/18/1974
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:	US ATOMIC ENERGY COMMISSION (AEC)
References
AO-50-219-74-19, NUDOCS 8103160321
Download: ML20003C721 (3)

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Fifa Cy OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. 50-219/74/19 Report Date

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g'MbN Identification of Occurrence Violation of the Technical Specifications, paragraph 3.5. A.1, failure to main-tain primary containment integrity with reactor water temperature above 212*F and fuel in the reactor vessel. This event is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15B.

Conditions Prior to Occurrence lhe plant was shut down with reactor coolant <212*F.

Description of Occurrence At' 1000 on March 8,1974, an orderly shutdown of the plant commenced to perform uaintenance on six of the fourteen torus to drywell vacuum breaker valves.

Although thirteen of the valves were considered to be operable at this time, j

the plant was shut down in order to effect more permanent repairs on the valves.

(See Abnormal Occurrence Report No. 50-219/74/16 dated March 15, 1974).

In accordance with the requirements of paragraph 3.5. A.1 of the Tee.hnical Specif-ications, maintenance on these valves did not begin until reactor coolant tem-perature was below 212*F.

At approximately 0500 on March 9,1974, the control room operator noticed that the reactor vessel head metal temperature was increasing at a rate of 10*F/hr after being stable at 231*F for about a 3-hour period. A check of the recirculation loop temperature recorder, which was being used as the primary indication of reactor water temperature, showed the recorder trace to be constant at 160*F.

While this inconsistency was being investigated, a radiation protection technician reported to the shift foreman that water vapor appeared to be issuing from a special manometer which had been installed for monitoring of the pressure difference between the drywell and reactor vessel. The shift foreman's investi-gation revealed that the reactor side of the manometer was hot. The recirculation loop temperature recorder was then rechecked and again indicated a temperature of 160*F.

However, the indication jumped to approximately 250*F when the recorder was bumpe6. Since two of the torus to drywell vacuum breaker valves were undergoing maintenance at this time (0531 on March 9,1974), primary

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Abnormal Occurrence No. 50-219/74/19 Page 2 containment integrity was not in effect. Shutdown cooling system flow was then increased to decrease the reactor water temperature.

Reactor water temperature was reduced to less than 212*F within approximately 30 minutes.

Within approxi-mately 130 minutes, a reactor water temperature of 160*F was established and maintained.

Apparent Cause of Occurrence This abnormal occurrence is attributed to equipment malfunction and operator error. The recirculation loop recorder did stick and give a false indication of reactor coolant temperature. However, the control room operator failed to react properly to indications that reactor water temperature was increasing.

Specifically, a review of the chart paper from the recorder monitoring shutdown cooling system temperatures showed that the "C" loop heat exchanger inlet temperature was increasing at a rate of about 10*F/hr during the 3-hour period prior to 0230 on March 9,1974. At this time, the control room operator secured flow in this loop and thereby contributed to the rise in reactor water temperature.

Analysis of Occurrence The primary containment system provides a barrier against uncontrolled release of fission products to the environs in the event of a break in the reactor coolant systems. Whenever the reactor coolant water temperature is above 212*F, failure of the reactor coolant system could cause rapid expulsion of the coolant from the reactor with an associated pressure rise in the primary containment.

Primary containment is required, therefore, to contain the thermal energy of the expelled coolant and fission products which would be released from any fuel failures resulting from the accident.

The safety significance of this event is that primary containment integrity was not maintained during the period that the reactor coolant temperature was in excess of 212*F due to the maintenance being performed on the vacuum breaker valves. At the condition that existed, the safety significance is considered minimal.

Corrective Action

'lhe following corrective actions will be taken:

1. - The operator retraining program will emphasize that all available indications are to be used when critical parameters such as reactor water temperature are being monitored.

In additon, the operators will be instructed in their retraining to regard extremely straight recorder traces as suspect and to view confirming indications whenever such suspicious recorder traces are encountered, both while operating and shut down.

Abnormal Occurrence No. 50-219/74/19 Page 3 2.

The shutdown log will be reviewed and modified to require the recording of additional system temperatures related to the reactor coolant tem-perature.

- Failure Data Basic recorder data are as follows:

Manufacturer:

General Electric Company Type:

GE/MAC 551

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Span:

4 inches i

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