ML20084S713

AO 50-265/75-22:on 750716,two of Four High Drywell Pressure Switches Exceeded Tech Specs Limit.Caused by Instrument drift.PS-2-1001-88B & C Calibr to Trip at 1.90 Psi

ML20084S713
Person / Time
Site:	Quad Cities
Issue date:	07/24/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20084S715	List: ML20084S713 ML20084S724
References
AO-50-265-75-22, NJK-75-377, NUDOCS 8306170179
Download: ML20084S713 (2)

Text

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'[' . , Commonwe Edison (7 Quad Citi sG ting Station 'v Post Office Box 216 _u Cordova, Illinois 61242 Telephone 309/654-2241

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i Director of Office of Nuclear Reactor Regulation  ;

U.S. Nuclear Regulatory Commission Washington, D.C. 20555 p b

Re ference: Quad-Cities Nuclear Power Station j Docket No. 50-265, DPP-30. Unit 2 g Appendix A, Sections 3.1, Table 3.1.1, 6.6.B.I.a .

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4 Enciosed please find Abnormal Occurrence Report No. 50-265/75-22 for Quad-Cities Nuclear Power Station. This occurrence was previously reported to Region 111, Directorate of Regulatory Operations by telephone on July 17,

- 1975 and to you and Region Ill, Directorate of Regulatory Operations by il telecopy on July 17, 1975 (

This report is submitted to you in accordance with the requirements of Technical Speci fication 6.6.B. I .a . ,}

Very truly yours, COMMONWEALTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER STATION ,

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,67.puet, N.J. Kal ivianaki s Le Station Superintendent NJK/SRH/vmb cc: Region lit, Directorate of Regulatory Operations J.S. Abel

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4., o REPORT NUMBER: A0-50-265/75-22 O

REPORT DATE: July 25, 1975 OCCURRENCE DATE: July 16, 1975 I

FACILITY: Quad-Cities Nuclear Power Station Cordova, IL 61242 IDENTIFICAtl0N OF OCCURRENCE:

Two of the four high drywell pressure switches exceeded the Technical Specification limit of 2.0 PSI.

CONDITIONS PRIOR TO OCCURRENCE:

The Reactor mode switch was in RUN, with 1944 MWtand 602 MWe.

DESCRIPTION OF OCCURRENCE:

On July 16, 1975, while performing surveillance test number six, it was noted that PS-2-1001-888 and 2-1001-88C failed to meet the Technical Specification limit of 5 2 PSI. Both switches tripped at 2.05 PSI.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

The two pressure switches not meeting the Technical Specification requirement was apparently caused by instrument drift.

ANALYSIS OF OCCURRENCE:

The two pressure switches are located one in each logic system. Since the other two switches in each logic system tripped at the proper valves, the Rx protection system would have performed its intendend function within the limit of 12 PSI, therefore minimizing the safety implications. The health and safety of the public were not affected.

CORRECTIVE ACTION: .

PS-2-1001-88B & C were recalibrated 'to trip at 1.90 PSI and tested satisfactory.

FAILURE DATA:

The involved pressore switches are static-0-ring model 12N-AAS-PP, which have generally been quite stable. The exact cause of the instrunent drift is not known, but since the last setpoint drift involving these pressure switches reported was in January of 1974, the safety implication of this occurrence is considered to be minimal and no further corrective action is being considered.

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