ML20084S247

AO 50-254/74-19:on 750805,reactor High Pressure Scram Switch 1-263-55A Was Isolated.Caused by Switch Left Isolated After Completion of Previous Month Testing.Establishment of Administrative Control Over Valves Initiated

ML20084S247
Person / Time
Site:	Quad Cities
Issue date:	08/15/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20084S252	List: ML20084S247 ML20084S254
References
AO-50-254-75-19, NJK-75-420, NUDOCS 8306160336
Download: ML20084S247 (3)

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Commogith Edison C

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\s August 15, 1975 ,

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

Re ference: Quad-Citles Nuclear Power St'ation Docket No. 50-254, DPR-29, Uni t 1 Appendix A, Sections 1.0.A.4, 3.1.A, 6.6.B.I.a Enclosed please find Abnormal Occurrence Report No. A0 50-254/75-19 for Quad-Ci ties Nuclear Power Station. This occurrence was previously reported to Region 111, Office of Inspection and Enforcement by telephone on August 5, 1975 and to you and Region li t, Office of Inspection and Enforcement by telecopy on August 5, 1975 This report is submitted to you in accordance with the requirements of Technical Specification 6.6.B.I.a.

Very truly yours, COMMONVEALTH EDISON COMPANY }

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' REPORT NUMBER: A0 50-254/75-19 .

REPORT DATE: August 15, 1975 OCCURRENCE DATE: August 5, 1975 -

FACILITY: Quad-Cities Nuclear Power Station Cordova, Illinois 61242

, IDENTIFICATION OF OCCURRENCE:

Reactor High Pressure scram sensor found isolated. g CONDITIONS PRIOR TO OCCURRENCE:

The uni t was operating et 1710 MWt and 512 .MWe. -

DESCRIPTION OF OCCURRENCE:

On August 5,1975 the Instrument Maintenance Department was doing routine surveillance testing of the Reactor High Pressure scram swi tches. When the instrument mechanic attempted to isolate pressure switch I-263-55A prior to the calibration, he discovered that it was already isolated. No

. additional operator actions were required to bring the situation under  ;

control.

1 DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

Operator Error The switch apparently had been left isolated after the completion of the previous month's testing, since no maintenance had been performed on the switch since then.

"~~"' ANALYSIS OF 6CCURRENCE:

l The safety significance of this occurrence was mininst because the re- i dundant pressure switches were operable during the time the subject switch l was isolated. The results of the surveillance testing of the switches  !

subsequent to the discovery of the isolated switch showed the other three  !

switches were operational and would have tripped within limits. The system redundancy was adequate to provide the trip function required. The effects j on the health and safety of the public were. thus minimal.

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August 15. 1975 CORRECTIVE ACTION:

The specific corrective action for this occurrence was to valve in the instrument upon completion of the surveillance test.

It is recognized that a predictable number of errors are inherent when people are performing routine tasks that are repetitive in nature such as the valving associated with instrument surveillance calibrations.

Nevertheless, the Station is attempting to develop a method that will preclude the possibility that such errors will occur in the future. Sev-eral alternative methods have been discussed. Most of the methods dis-cussed are aimed at establishing administrative control over the valves

• Involved between the Instrument Departnent supervisors and the Instrument Mechanics. The method deemed most feasible will be implemented expedi-tiously to attempt to minimize future occurrences of this type.

FAILURE DATA:

Tro occurrences of this type of valving error have been reported in the past. The safety implication of these occurrences based on cumulative experience is minimal. The controls described above should be adequate to prevent future occurrences.

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