ML17252A185
| ML17252A185 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/04/1975 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | James Keppler NRC/RGN-III |
| References | |
| BBS Ltr. #579-75 50-249/75-40 | |
| Download: ML17252A185 (3) | |
Text
{{#Wiki_filter:::;.> ,..., "4.f0. Com~alth Edison * ~ .* ~i.,, One Fir 0 s~al Plaza, Chicago, Illinois 'f *. Address Reply to: Post Office Box 767 \\.. _,....:* '-'Chicago, Illinois 60690 BBS Ltr. #579-75 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 6o450 September ~' 1975 Mr. James G. Keppler, Regional Director Directorate of Regulatory Operation-Region III
- u. s. Nuclear Regulatory Commission 799 Roosevelt Road
- Glen Ellyn, Illinois 6o137
- SUBJWr:
REPORT OF ABNORMAL OCCURRENCE PER SEX:TION 6.6.A OF THE TEX:HNICAL SPEX:IFICATIONS REACTOR PRESSURE 6oo PSI SWITCH*SE!'POINT DRD'l'
References:
1} Regulatory Guide 1.16 Rev. 1 Appendix A
- 2) Notification of Region III *of u. s. Nuclear Regulatory Commission Telephones _P. Johnson, 0920 hours on August 28, 1975 Telegrams* J. Keppler, 1045 hours on August 28, 1975 3}
Drawing Numbers 12E2465 Report Number: ~249/75;f40 Report Date: September 4, 1975 Occurrence Date: August 27, 1975
- Facility: Dresden Nuclear Power Station, Morris, *Ulinoie mmrIFICATION OF OCCURRENCE
,\\'\\all Section Docltot Clort . On August 27, 1975, during routine instrument. surveillance, pressure switches PS}-263-51A and.-51B were fo\\md with setpointe above the Technical Specification
- limit of ~6oo psi:'!
CONDITIONS PRIOR TO OCCURRENCE Uni t-3 was in the shutdown mode for a refueling outage. September 4, 1975 DESCRIPTION OF OCCURRENCE -~ - - Pressure switches 26.3-51A and -51B were found with setpoints of 605 psi and 615_ psi respectively. Th~ switches permit the Low Condenser Vacuum and Main Steam Line Valve Closure (~cram signals to be bypassed *when reactOr pressure is less than.6oo psi. DESIGNATION.OF APPAREm' CAUSE.OF OCCURRENCE (Unusual Service Conditions) Long periods at zero preas\\ire apparently allow inatrum~t setpoints to drift signif-icantly out 'of oaJ.ibration. *'l;'he defµiit~ve*.caU.S~:.of :setp0int drift has not been establish~d~:
- 1..;_*
ANALYSIS OF OCCURRENCE The setpointe of switches 263-51A and -51.B had l~at been.checked on March 8, 1975. Both switches were within the station limits at that time, five weeks before the unit Shutdown for retueling. Because* the switches have been demonstrably reliable between routine surveillances, it is considered unlikely that any. aigpificant aet:Point drif~&occurred during operation. In any event, the setpoint vai(l;l;e*~ "as found" woU.1.d. have provided a scram permissive at 6o5 psi. Consequently, the public was not endangered by this occurrence. CORREX:TIVE ACTION The switches were immediately reset to within the station limit of 58<> +/- 5 psi. Additional action will be taken as def'iriitive drift causes are.identified. FAILURE. DATA Pressure switches 26.3-51A and -51B are Meletron Model 372 pressure sensors with a range of 28-1~0 psi. These switches have had a history of setpoint drifting at Dresden. Station evaluation of replacement instrumentation is cont~;- . BBSs'WEH:smp File/NRC
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