ML17252A186
| ML17252A186 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/04/1975 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | James Keppler NRC/RGN-III |
| References | |
| BBS Ltr. #580-75 50-249/75-38 | |
| Download: ML17252A186 (2) | |
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- com~ealth Edison One Fir.s'llllrtional Plaza, Chicago, Illinois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 BBS Ltr. #580-75 Dresden Nuclear Power Station Mr. James G. Keppler, Regional Director Directorate of.Regulatory Operation-Region III
- u. s. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 6o137 R. R. #1 Morris, Illinois September 4, 1975 References s 1 ) Regulatory Guide 1
- 16 Rev. 1 Appendix A
- 2) Notification of Re~on III of u. s. Nuclear Regulatory Comnission Telephones R. Knop, 1.710 hours0.00822 days <br />0.197 hours <br />0.00117 weeks <br />2.70155e-4 months <br /> on August 26, 1975 Telegrams 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 12E3430/12E34*37" Report Number:
50-249/75-38 Report Date: September 4, 1975 Occurrence Date: August 26, 1975 Facility: Dresden NU.clear Power Station, ~rris,.Illinois mmrIFICATION OF OCCURRm-CE 1i,,;...i: Section Oockot Clorir.
Pressure switches }-26}-52A1 and -S:aA2 were found with setpoints greater than the Technical Specification "band" of 300 psi~ P~ 350 psi.
CONDITIONS PRIOR TO OCCURRENCE Unit-3 was in the shutdown mode for a refueling.outage.
DF.SCRIPrION OF OCCURRmCE 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 found with setp;~§."lJgreater than 350 psi. Sl4tches 26}-52A1 and-52A2 had setpoints of 365 psi and 366 psi respectively.
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/~ James G~ Kepple~ w e September. 4, 1975
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- ' DESIGNATION OF APPARENT CAUSE OF OCCURRENCE.(Unusual Service Conditions)
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. ~e. Mel~tr_Q~ pre~sure s.~_sors.. appear to be e:~eoially suscept:i!:eJ:"e to.. setpoint. -
- drift during long periods *.o.f inactivity. Minor setpoint variations (which are*
routinely corrected during operation) tend to be aggravated by extended outage conditions~ The cause of setpoint drift.is.unknmm*
.ANALYSIS OF OCCURRENCE.
. The switches :.had last been checked* for setpoint drift on April. 7, 1975, nine days before the unit's refUel:lng outage began. All four switches had setpoints within: the station limits *.,It is considered improbable that significant drift occurred }(,D."these' 'sWi tclle~ '.before the unit shutdown.
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. The setpoin~. dri~. on ~tohe~.. ?63-5.2A1.~.-;..52A2 )las,in.~e c~ervative direction~.,:: :If ;*~he.. 8-e~Po.int di*sc~epalicy 'iia<l:*exfate~' dl.ir:ing: reactOr operation in conjun~t;o~. ~th."*~ ~ose~,f~c~].~t e:ccii.~erit~ ~t
&11d~ co~e,.. ~pray initiation would have actual~~ be~ even* earl.~.er tlWl: '.necessary. 1,'herefore,***'this occurrence* did not threaten the safety of plant personnel or the public.*
CORRECTIVE ACTION The immediate *corrective action. was to reset switches 263-52.A* and ~52A2 to: withiri the Technical Specification.limits.
. The station is currently evaluating eui table replacements for the Meletron Model 372 switches* presently in service..
FAILURE DATA.
Meletron Model 372 pressure sensors.have *mad a history of setpoint drifting.at..
Dresden.
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Superintendent.
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Fi_le/NRC