IR 05000249/1975036

Report of Abnormal Occurrence 50-249/75-36 Per Section 6.6.A of the Technical Specifications Re Reactor High Pressure Sensor Setpoint Drift

ML17252A176
Person / Time
Site:	Dresden
Issue date:	09/02/1975
From:	Stephenson B Commonwealth Edison Co
To:	James Keppler NRC/RGN-III
References
50-249/75-36
Download: ML17252A176 (2)

Text

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Edison One First National Plaza, Chicago, Illinois Address Reply to: Post Office Box 76.7 Chicago, Illinois 60690 BBS Ltr. -#572-75 -------Dresden Nuclear RR #1 Morris, Illinois September 2, 1975 Mr. James G. Keppler, Regional Director Directorate of Regulatory Operation-Region III U. s. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 SUBJEm': REPORT OP ABNORMAL OCCURRENCE PER Sl!m'ION 6.6.A OF THE T&:HNI REACTOR HIGH PRESSURE SmiSOR SEl'POINT DR!ft. Referencesa 1) Regulatory Guide 1*.16 Rev. 1 Appendix A 2) NotificatiOn of Region III of U. S. "Nu.clear Regulatory Commission Telephones 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 Telegrams Mr. 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

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Report Numbers

_/. .** ',, I.' ; * Report Date: .September 2, 1975 *": I Occurrence Date: August 23, 1975 .

Facility:

Dresden Nuclear Power Station, Morris, IDENTIFICATION OF' OCCURBENCE Reactor high pressure sensors 263-55.A., -55B, and -55C were :tound with setpoints above the Technical Specification limit of 106o psig. CONDITIONS PRIOR TO OCCURRmCE Uiiit-3 was in the shutdown mode for a ref'ueling outage. DESCRIPl'ION OF' OCCURRENCE At apPJ:'().ximately 1300 hoUrs on August 23, 1975, a routine scheduled calibration of the reacto:J?-

• .high pressure sensors revealed that sensors 263-55A, -55B, and -55C had setpoints above the 1o60 psig limit. -8546

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G *. Keppler ** * September 2, 1975 DESIGNATION OP APPAREM' CAUSE OF OCCURRENCE (Unusual Service Conditions)

Setpoint-dri:f't on these by

• at zero pressur The swi tohes had not been *tested since April 7, a periOcl of nearly five months *. In each case the setpoint amounted to less than 5% of the operation range. ANALYSIS OF OCCURRENCE The reactor high pressure sensors initiate*a reactor scram upon sensing excessive .vessel I>ressur Had the unit been operating with the setpoints remaining Un.corrected, thi-ee of the four sensors would not have precipitated a reactor . scram at 1o6o psig. However, any such transient in reactor pressure would have . Jri,. been preceded by an increase in neutron activit Since the neµtt"on monitoring systen was always operable during .reactor operation, plant personnel and the general public were Jeopardized by* this .occurrenc CORRIDrIVE ACTION The switches 'WQre reset to within the station limits of 1055 psi. To prevent a recurrence of this nature, General Electric and the station are currently.evaluating*s'1itable replacements*

tor the.Meletron Model 372 switches presently in service. * -FAILURE DATA .Meletron Model 372 sensors have*had a history ot setpoint dri:f'ting on both' uni ts 2 and 3. . , BBS 1ARZ I amp File/NRC B *. B. ephenson *Sµperintendent