ML20084S753

AO 50-265/75-18:on 750522,single Valve Failure Made Standby Gas Treatment Sys Inoperable.Caused by Design Deficiency. Mod Request Has Been Initiated

ML20084S753
Person / Time
Site:	Quad Cities
Issue date:	06/20/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20084S754	List: ML20084S753 ML20084S762
References
AO-50-265-75-18, NJK-75-328, NUDOCS 8306170227
Download: ML20084S753 (2)

Text

i Commonwealth Edison {

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1 Director of Office of Nuclear Reactor Regulation "

U. S. Nuclear Regulatory Conmission ,

Washington, D. C. 20555 i

Reference:

Quad-Ci ties Nuclear Power Station Docket No.60-265, DPR-30, Unit 2 Appendix A, Sections 1.0.A.4, 3.7.B.1, 6.6.B.2.b Abnormal Occurrence Report No. 50-265/75-18 4

3 The purpose of this letter is to provide you with details concerning an un-usual event which occurred at quad-Cities Nuclear Power Station, Unit 2, on May 22, 1975 This report is being :,ubmi tted in accordance with the requi re-ments of Technical Specification 6.6.B.2.b.

Circumstances leading to the discovery of this event were reported to you on May 30, 1975 in Quad-Cities Nuclear Power Station Abnormai Occurrence Report No. 50-265/75-18.

Very truly yours, i

COMMONWEALTH EDISON COMPANY QUAD-ClTIES NUCLEAR POWER STATION f/}

N. J. Kalivicnakis

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!, Station Superintendent i

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, cc: . Region lII, Directorate of Regulatory Operations J. S. Abel 4 f E i

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,e' l REPORT NUMBER: Unusual Event Letter REPORT DATE: June 21, 1975 EVENT DALE: May 22, 1975 FACILITY: Quad-Ci ties Nuclear Power Station Cordova, 111. 61242 IDENTI FI CATION OF EVENT:

A single valve failure made the Standby Gas Treatment system inoperable.

CONDITIONS PRIOR TO EVENT:

Unit one was at 670 MWe and increasing at the rate of 3 MWe per hour. Unit two was at 495 MWe and increasing at the rate of 20 MWe per hour.

DESCRIPTION OF EVENT:

On May 22, 1975 a condition involving a single failure of a SBGT system inlet valve was discovered which could result in the loss of the capability of this system to perform i ts safety function. As the logic for the system is presently designed, an auto initiation signal for one uni t automatically closes the inlet valve to the SBGT system f rom the other unit. If a failure occurs on the inlet valve for the unit that auto initiates, the condition is such that no inlet valve at all is open to the system. This is a vio-lation of the " single failure" criteria for the SBGT system.

DESIGNATION OF APPARENT CAUSE OF EVENT:

Design Deficiency Due to a design deficiency, the SBGT system will not remain operable under all conditions with a single component failure.

_ ANALYSIS OF EVENT :

There are no safety implications from the event. Due to a previous abnormal occurrence both inlet valves have been taken out of service in the open direction and the conditions described above will not affect SBGT system operability.

CORRECTIVE ACTION:

A modifice- request has been initiated and routed to the Station Nuclear ,

Engineerir separtment. The modi fication request should result in a revision to the present logic scheme to preclude the possibility that a failure similar to that described above would render the system inoperable. Until the time that the modification is implemented, the inlet valves will remain positioned as described above.