ML19332B317

LER 80-032/01T:on 800724,GE SIL 299 Review Revealed Higher Drywell Ambient Temp than Used for Original Safeguard Yarway Calibrs.Caused by High Temp Due to Inadequate Drywell Cooling.Recalibr & Survey of Drywell Ventilation Conducted

ML19332B317
Person / Time
Site:	Pilgrim
Issue date:	09/22/1980
From:	Mathis C BOSTON EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19332B312	List: ML19332B311 ML19332B317
References
LER-80-032-01T, LER-80-32-1T, NUDOCS 8009260485
Download: ML19332B317 (1)

Text

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISt!ON (7 77)

O LICENSEE EVENT REPORT u-(PLEASE *RINT OR TYPE ALL REQUIRED INFORMATION)

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7 4 60 61 DOCKET NUMBER 68 69 EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h 1o12l l Review of G.E. SIL 299, as pertaining to Pilgrim Nuclear Power Station, revealed l io i3 j l higher drywell ambient temperatures than used for original safeguard Yarway cali- l io l4 ; l brations. Therefore the potential existed that had automatic actions been l loj5l l necessary, they might not have been initiated within the limits imposed by l )

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42 lAl@ lBl5l1l5l@ l 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS I i, j o; j Drywell temperatures higher than design were the cause of this event. The reason  ;

i, ,,,l for these temperatures is inadequate drywell cooling. The Yarways were re-cali- l g

brated to compensate for the existing conditions and an engineering evaluation of l

,,, , y drywell ventilation is being conducted.  ;

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c BOSTON EDISON COMPANY PILGRIM NUCI. EAR POWER STATION DOCKET NO. 50-293 Attachment to LER 80-032/01T-0 At 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on July 24, 1980, PNPS personnel received a preliminary copy of a memo from the SECo. Nuclear Engineering Department to the Nuclear Operations Manager which addressed recommended calibration changes to safety related Yarway level instrumentation. These calibration changes were necessary to correct for higher reference leg temperatures than initially used to derive calibration data.

This memo was a result of a series of events which began in October of 1979 when PNPS personnel requested an in-depth study of G.E. SIL#299 be conducted by the NOD Plant Support Group. In the review of SIL#299, the possibility that conditions existing at PNPS warranted further investigation and evaluations of the real potential for " flashing" to occur.

The preliminary review indicat d that even without the small break LOCA condition identified in SIL#299, there app. eared to be higher drywell ambient temperatures than used for original Yarway calibration. Set point changes were recommended and a Plant Design Change Request was generated to instrument the water level columns to obtain actual operating conditions. PNPS was conducting 4 refueling outage at this ti=e and it was decided not to make any unsubstancia:ted changes in set points until actual operating conditions were verified, since the potential for inadvertant cold water injections as a result of increasing the i

set point would create undue ther=al stresses.

PNPS Instrument and Control personnel gathered infor=ation from the sensors installed during the outage and forwarded the data to the Plant Support Group.

The results of the review of this data was presented to PNPS in draf t form without Nuclear Operations Manager concurrence on July 17, 1980. Since independent review by the Nuclear Engineering Department and concurrence by the Nuclear Operations Manager had not been conducted, no action was taken at this time.

On July 7.4, 1980 a.'ter independent review by NED and confir=ation with Yarway represer.tatives, a w mo was forwarded to the Nuclear Operations Manager recom-

=ending a zero adjust of five (5) inches. It was a copy of this me=o which was forwarded to the Instrument and Control Supervisor that initiated actions to re-calibrate the level instruments.

PNPS calibration procedures were revised, reviewed and approved on July 25, 1980 and the zero adjust calibrations were commenced on July 26, 1980. The station had been shut down on July 25, 1980 to conduct scram testing per II Bulletin 80-17.

While re-calibrations were in progress, the reactor was brought critical and a power ascension was commenced to perform the automatic scram portion of IE Bulletin 80-17. Calculations were made to determine maximum drywell temperatures that would not violate Yarway setpoints and recording of these temperatures every half hour were commenced.

At approximately 1730 on July 26, the drywell temperature exceeded the calculated maximum values. The Watch Engineer was not (fied at 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> that the reference leg average temperature had been exceeded d that three of the safeguard yarways were still'not calibrated.

The reactor was scra==ed at 1832 and drywc 1 temperatures below calculated =axi=um

• by 1930. The re-es11bration of remaining arways was completed prior to return to power.