ML20084S639

AO 50-254/75-15:on 750728,electro-hydraulic Control Sys Fluid Pressure Sensor 1-5600-PS-3 Setpoint Exceeded Tech Spec Setting.Caused by Instrument Drift.Pressure Switch 1-5600-PS-3 Recalibr

ML20084S639
Person / Time
Site:	Quad Cities
Issue date:	06/06/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20084S642	List: ML20084S639 ML20084S652
References
AO-50-254-75-15, NJK-75-311, NUDOCS 8306170143
Download: ML20084S639 (3)

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.I' '.h Commonwrith Edison Outd-CF'qG:neraung Station

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Telephone 3D9/654-2241 NJ K-75-31 I b1 i

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Director of Office of Nuclear Reactor Regulation U. S. NUCLEAR REGULATORY COMMISSION Washington, D. C.

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REFERENCE:

quad-Cities Nuclear Power Station Docket No. 50-254, DPR-29, Unit i Appendix A, Sections 1.0.A.2, 3.1, 6.6.B.I.2 Enclosed please find Abnormal Occurrence Report No. 50-254/75-15 for Quad-Cities Nuclear Power Station. This occurrence was previously reported to Region lil, Directorate of Regulatory Operations by telephone on May 29. 1975 and to you and Region lil, Directorate of Regulatory Operations by telecopy on May 29, 1975 This report is submitted to you in accordance with the requirements of Technical Specification 6.6.B.1:a.

Very truly yours, COMMONWEALTH ED1SOff COMPANY QUAD-CITIES NUCLEAR POWER STATION

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f N. J. Kalivianakis Station Superintendent NJK:SH/dkp I

cc: Region 111, Directorate of Regulatory Operations

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.a 8306170143 750606 PDR ADOCK 05000254 S

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-_E. PORT NUMBER: A0-50-254/75-15 R

REPORT DATE: June 5, 1975 OCCURRENCE DATE: May 28, 1975 FACILITY: QUAD-CITIES NUCLEAR POWER STATION Cordova, IL 61242 IDENTIFICATl0rl 0F OCCURRENCE:

Electro-hydraulic control (EHC) system fluid pressure sensor 1-5600-PS-3 setpoint exceeded its Technical Specification setting.

CONDITION PRIOR TO OCCURRENCE:

The unit one reactor mode switch was in "RUN", the uni t was operating at 1604 MWt and 470 MWe.

g DESCRIPTION OF OCCURRENCE:

At 11:00 a.m. on May 28, 1975, while doing routine weekly surveillance, it was noted that pressure switch 1-5600-PS-3 tripped below the Technical Specification limit of j>. 900 PSIG by 10 PSIG.

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DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

Eauipment Failure - Instrument drift was the apparent cause of this occurrence.

f, ANALYSIS OF DEVIATION:

The safety implications are minimal since this this is an anticipatory scram signal; the core would be protected by the APRM and high reactor pressure scrams if all switches would fail.

In addition, the control valves would not start

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closing on loss of EHC fluid pressure until 600 PSIG; therefore the scran set-

~k point of jt 900 is in the conservative direction.

The reactor protection system would have received a trip on low EHC pressure be-cause the other pressure switch in the same channel tripped at 933 PSIG; the.re-fore had a low EHC pressure condition existed, the reactor would have scrammed.

Since safe plant operation was not jeopardized, the health and safety of the public were not affected.

CORRECTIVE ACTION:

The pressure swtich 1-5600-PS-3 was innediately recalibrated to trip at 935 PSIG.

Action item Record has previously been initiated to investigate this problem and find a suitable replacement switch or system to prevent continual recurrence of instrument drif t.

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o FAILURE DATA:

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So far this year there have been two previous instances where the Technical Specification limit has not been rnet by EHC pressure switches.

This is the first failure involving 1-5600-PS-3

?This pressure switch, manufactured by Barkdale, is a model C9612-7 with an adjustable range of 13c to 1500 PSI.

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