ML20084S596

AO 50-265/75-16:on 750516,reactor Vessel Low Pressure Alarm Received.Caused by Operator Error.Pressure Switch Was Valved in & Alarm Cleared

ML20084S596
Person / Time
Site:	Quad Cities
Issue date:	05/23/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20084S600	List: ML20084S596 ML20084S611
References
AO-50-265-75-16, NJK-75-290, NUDOCS 8306170128
Download: ML20084S596 (3)

Text

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. Director of Of fice of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Reference:

Quad-Ci ties Nuclear Pcraer Station Docket No. 50-265, DPR-30, Unit 2 Appendix A, Sections 1.0. A.4, 3 2.0, 6.6.B. I .a Enclosed please find Abnormal Occurrence Report No. A0 50-265/75-16 for Quad-Ci ties Nuclear Power Station. This occurrence was previously re-ported to Region 111, Directorate of Regulatory Operations by telephone on May 19, 1975 and to you and Region lil, Directorate of Regulatory Operations by telecopy on May 19, 1975 This report is submitted to you in accordance wi th the requi rements of Technical Speci fication 6.6.B. l .a.

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

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N.'J. Kallvianakis ,.

Station Superintendent ' /. * " < . . ,

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'cc: Region 111, Directorate of Regulatory Operations J. S. Abel-1 l

'8306170128 750523 PDR ADOCK 05000265 S PDR

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O REPORT NU't1BER: ' A0 50-265/75-16 REPORT DATE: May 23, 1975 OCCURRENCE DATE: May 16,1975 IDENTI FICATION OF OCCURRENCE:

l Received " Reactor Vessel Low Pressure" alarm while operating U-2 at normal pressure. Pressure swi tch PS-2-263-52A was found to be valved out.

CONDITIONS PRIOR TO OCCURRENCE:

Reactor in RUN mode, 2254 MWt, 717 nwe DESCRIPTION OF OCCURRENCE:

1 At 6:50 p.m. on May 16.1975 the U-2 operator received a " Reactor Vessel Lov Pressure" alarm. The actual reactor pressure was normal at the time.

DESIGNATION OF APPARENT CAUSE: ,

Operator Error The apparent cause of this occurrence is designated as operator error. On J!

the afternoon of May 16, 1975, surveillance testing was performed whicli [;

required isolation of pressure swi tch PS 2-263-52A. Upon completion of the  !!

1 surveillance, the instrument Mechanic inadvertantly lef t the switch valved out.

ANALYSIS OF OCCURRENCE:

The isolation of pressure switch 2-263-52A caused an erroneous signal to one half of the Core Spray and RHR systems; however, because of the logic arrangement of the redundant pressure switch and the respective relay con-tacts, both systens would have properly functioned if needed in the event of an ECCS initiation signal.

Had an initiation occurred while the reactor pressure was above the low pressure set point, with the isolated switch actuated, a false injection

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signal would have been present to both lav pressure ECCS systems. However, the low pressure piping of these systems would have been protected against overpressurization by the reverse flow check valves in the injection lines.

- Had an initiation occurred with reactor pressure below the low pressure

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set point, and the isolated switch nac actuated, the redundant pressure switch would have properly allowed injection from both loops of the'ECCS systems.

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o A0 50-265/75-16 May 23, 1975 There were thus no safety inplications from this occurrence; the re fo re ,

the health and safety of the public were not endangered.

CORRECTIVE ACTION:

The pressure swltch was valved in and the alarn cleared. ,

FAILURE DATA:

This is the first time this pressure switch has been inadvertantiv iso-lated. No safety implications based upon previous data exist.

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