ML20084N777

AO 50-249/75-38:on 750826,pressure Switches 3-263-52A1 & 52A2 Found W/Setpoints Above Tech Spec Limit.Apparently Caused by Setpoint Drift Due to Long Periods of Inactivity. Switches Reset

ML20084N777
Person / Time
Site:	Dresden
Issue date:	09/04/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084N756	List: ML20084N769 ML20084N774 ML20084N777
References
BBS-580-75, NUDOCS 8306090071
Download: ML20084N777 (2)

Text

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Commo mith' Edison

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BBS Ltr. #580-75 Dresden Nuclear Power Station R. R. #1 Morris. Illinois 60450 , ' ' p b' N September 4, 1975 '*

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Mr. James G. Keppler, RcAinnal Director 1- 6

Directorate of Regulatcry Operation-Region III Y 'Nbt 'O

'h ' 'N'y U. S. Nuclear Regulatory Cocznission -

y 799 Roosevelt Road , _ .. . c s' Glen Ellyn'. Illinois 60137 M _/N l.1 ' \

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SUBJECT:

REPORT OF AthCU4AL OCCITQ8.NCE PER SETION 6.6.A 0F 'mE TEHNICAL S?TIFICATII'.'.2 REACTOR FRESSURE ECCS INITIATION SWITCH SETPODiP DRIFT

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A

2) Notification of Region III of U. S. Nuclear Regulatory Cocanission Tehphones R. Anop, 1710 hours0.0198 days <br />0.475 hours <br />0.00283 weeks <br />6.50655e-4 months <br /> on August 26, 1975 Teletram: J. Keppler, 1347 hours0.0156 days <br />0.374 hours <br />0.00223 weeks <br />5.125335e-4 months <br /> on August 27, 1975

3) Drawing Number 12E3430/12E3437 ReportNumbei 50-249/75-38 Report Date: SeptembeP 4, 1975 Occurre$ce Dates August 26, 1975 Facility: Dresden h clear Power Station, Morris, Illinois j IDENTIFICATICN OF OCCURRE!CE Pressure switches >263-52A1 and -52A2 were found with setpoints greater than the Technical Specification " band" of 300 psif PA 350 psi.

l CONDITIONS PRIOR 'IU OCCURRE!CE l

l Unit-3 was in the shutdown mode for a refbeling outage.

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DESCRIPTION OP OCCURRE;CE On August 26, 1975, during the routine scheduled calibration of the 350 psi reactor pressure switches for the LPCI and core spray systems, two of the four switches were I

found with setpoints greater than 350 pai. Switches 263.-52A1 and-52A2 had setpoints of 365 psi and 366 psi respectively.

8306090071 750909 PDR ADOCK 05000249 S PDR

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.. ptember 4, 1975 DESIGNATION OF APPARENT CAUSE OF OCCURRDICE (Unusual Service Conditions) - - --

The Meletron pressure sensors appear to be especially susceptible to setpoint ~

drift during long periods of inactivity. ICnor setpoint variations (which are , -

routinely corrected during operation) tend to be aggravated by extended outege conditions. The cause of setpoint drift is unknown.

ANALYSIS OF OCCURRENCE The switches had last been checked for setpoint drift on April 7, 1975, nine ' '

days before the unit's refueling outage began. All four switches had setpointe "

within the station limits. It is considered improbable that significant drift occurred on these switches before the unit shutdown.

The setpoint drift on switches 263-52A1 and -52A2 was in the conserva,_ve direction. If the setpoint discrepancy had existed during reactor operation in conjunction with a loss-of-coolant accident,LPCI and core spray initiation would have actually begun even earlier than necessary. Therefore, this occurrence did not threaten the safety of plant personnel or the public.

CORRECTIVE ACTION '

The ic:nediate corrective action was to reset switches 263-52A1 and -52A2 +4 within the Technical Specification limits.

The station is currently evaluating suitable replacements for the Meletron Fodel 372 switches presently in service.

FAILURE DATA Meletron Model 372 pressure sensors have had a history of setpoint drifting at Dresden.

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