ML20084U193

AO 50-254/75-7:on 750320,during Surveillance Calibr of Electro Hydraulic Control Fluid Pressure Sensors,One Tripped Below Tech Spec Limit.Caused by Worn Piston Assembly or O- Ring Seals.Piston & O-ring Replaced

ML20084U193
Person / Time
Site:	Quad Cities
Issue date:	03/27/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Oleary J Office of Nuclear Reactor Regulation
Shared Package
ML20084U194	List: ML20084U193 ML20084U197
References
AO-50-254-75-7, NJK-75-160, NUDOCS 8306270454
Download: ML20084U193 (3)

Text

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M8 Quad-Qties Nuclear Power Station Post Off.cc Box 216 -

Cordova, Ilknois 61242

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March 27, 1975 '" E ~

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Mr. John F. O' Leary, Di rector 7f,\'\

Directorate of Licensing Regulation S U. S. NUCLEAR REGULATORY COMMI.SSION Washington, D. C. 20545 RE FERENCE : Quad-Cities Nuclear Power Station Docket No. 50-254, DPR-29 Appendix A, Sections 3.1, 6.6.B.I.a.

Dear Mr. O' Leary:

Enclosed please find Abnormal Occurrence Report No. A0-50-254/75-7 for Quad-Ci ties Nuclear Power Station. This occurrence was previously reported to Region 111, Directorate of Regulatory Operations by telephone on March 21, 1975 and to you and Region ill, Directorate of Regulatory Operations by telecopy on March 21, 1975 This report is submitted to you in accordance with the requirements of Technical Specification 6.6.B.1.a.

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

// f N. J. Kallvianakis Station Superintendent NJK:RAR/dkp cc: Region ill, Directorate of Regulatory Operations J. S. Abel g6 P

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REPORT NUMBER: A0-50-254/75-7 REPORT DATE: March 27,1975 OCCURRENCE DATE: March 20, 1975 FACILI TY : Quad-Cities Nuclear Power Station Cordova, IL 61242 IDENTI FICATION OF OCCURRENCE:

Instrument setpoint drif t of an EHC Fluid Low Pressure sensor.

CONDITIONS PRIOR'TO OCCURRENCE:

The unit was in the RUN mode at 2472 MWt and 824 MWe.

DESCRIPTION OF OCCURRENCE:

On March 20, 1975, at 3:00 p.m. , while doing routine quarterly surveillance calibrations of the EHC Fluid Low Pressure sensors one of them tripped at 885 psig decreasing. This was less than the Technical Specifications limit of j> 900 psig. The three other switches were all within the Technical Specification limit. No operator actions were required.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE: ,

Component Failure - The apparent cause of the occurrence was a worn piston assembly or worn 0-ring seals. This was supported by the fact that the in-strument mechanic did not have to make any setpoint adjustments to bring the switch within limits; exercising the switch caused the setpoint to change to within the limit.

ANALYSIS OF OCCURRENCE:

The reactor protection system is arranged in a one out of two twice logic.

Although one sensor in the "B" channel was less than the limit, the other sensor was not; thus, the "B" channel would still have tripped before the lower' limit was reached. Since the "A" channel sensors were also within limits the unit would have scrammed before the Ilmit was reached. Therefore there are no safety implications arising from this occurrence.

CORRECTIVE ACTION:

When the occurrence was discovered, the switch was exercised and the setpoint went from the as-found value of 885 psig to 935 psig. On March 22, 1975 the piston assembly of the pressure switch was disassembled and inspected. Only a slight scoring of the piston was noted. As a precautionary measure the piston assembly and o-rings were replaced and the switch was recalibrated to 935 psis.

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FAILURE DATA:

Equipment identi fication -

Equipment Piece Number 1-5600-PS-2 Hanufacturer Barksdale Model C9612-2 Range 135-1500 pst Previous Failures -

DATE UNIT SWITCH NUMBER 8-22-72 1 1-5600-PS-l&4 8-31-72 2 2-5600-PS-2 11-9-72 1 1-5600-PS-4 12-20-72 2 2-5600-PS-1, 2, s 3 12-29-72 1 1-5600-PS-2 9-14-74 1 1-5600-PS-4 Most of the failures occurred before the setpoints of the switches were raised from 900 psig to 935 psig on January 12, 1973 Since this time there have been only two failures. Redundancy of the tripping circuit allows for occas-sional instrument failure or drift with minimal safety implications.

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