ML20084N794

AO 50-249/75-36:on 750823,reactor High Pressure Sensors 263-55A,55B & 55C Found W/Setpoints Above Tech Spec Limit. Apparently Caused by Extended Periods at Zero Pressure. Switches Reset

ML20084N794
Person / Time
Site:	Dresden
Issue date:	09/02/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084N797	List: ML20084N794 ML20084N802
References
572-75, NUDOCS 8306090077
Download: ML20084N794 (2)

Text

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'. # .. . C C mm^02ith Edison One First(jonal Haza. Chicago. Ilhnois ,

5 bv Of Address Reply to: Post Office Box 767 Chicago, Ilknois 60690 4.

BBS Ltr. #572-75 Dresden Nuclear Power Station M #1 Morris, Illinois 60450 September 2, 1975 - ~~ , S

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Mr. James G. Keppler, Regional Director  : p 4 8 p //) .'o ,

Directorate of Regulatory Operation-Region III 7.99p  ;

U. S. Nuclear Regulatory Comatission 799 Reosevelt Road \

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Glen Ellyn, Illinois 60137

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SUBJECT:

REPORT OF ABNORMAL OCCURRENCE PER SECTION 6.6.A 0F THE TECHNI SPECIFICATIONS REACTOR HIGH PRESSURE SENSOR SETPOINT DRIPP

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A

2) Notification of Region III of U. S. Nuclear Regulatory Comunission Telephone: Mr. R. Knop at 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> on August 24, 1975 Telegram: Mr. J. Keppler at 1235 hours0.0143 days <br />0.343 hours <br />0.00204 weeks <br />4.699175e-4 months <br /> on August 25, 1975

3) Drawing Number 12E3465/12E3466 Report Number 50-249/75-36 Report Date: September 2, 1975 Occurrence Date: Aug1st 23, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinoie IDENTIFICATION OF OCCURREUCE Reactor high pressure sensors 263-55A, -55B, and -550 were found with setpoints above the Technical Specification limit of 1060 psig.

CONDITIONS PRIOR TO OCCURRENCE Unit-3 was in the shutdown mode for a refueling outage.

DESCRIPTION CF OCCURRENCE At approximately 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> on August 23, 1975, a routine scheduled calibration of the reactor high pressure senors revealed that sensors 263-55A, -55B, and l -55C had setpoints above the 106G psig limit.

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Mr. Jamea 0. K ppl Siptemb:r 2, 1975 DESIGNATION OP APPARENT CAUSE OP OCCURRENCE (Unusual Service Conditions)

Setpoint drift on these sensors appears to be aggravated by extended periods at zero pressure. The switches had not been tested since April 7, a period of nearly five months. In each case the setpoint error amounted to less than 55 of the operation range.

ANALYSIS OP OCCURRENCE The reactor high pressure sensors initiate a reactor scram upon sensing exceceive vessel pressure. Had the unit been operating with ths setpoints remaining uncorrected, three of the four sensors would not have precipitated a reactor scram at 1060 psig. However, any such transient in reactor pressure would have been preceded by an increase in neutron activity. Since the neutron monitoring system was always operable during reactor operation, plant personnel and the general public were not jeopardized by this occurrence.

CORRECTIVE ACTION The switches were imediately reset to within the station limits of 1055 -5 psi.

To prevent a recurrence of this nr.ture, General Electric and the station are currently evaluating suitable replacements for the Meletron Model 372 switches presently in service.

PAILURE DATA Meletron Model 372 pressure sensors have had a history of setpoint drifting on both units 2 and 3 m ;.

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B.B.S(ephenson Superintendent BBS:ARZ smp File /MtC

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