ML17252A176
| 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) | |
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Commonwe* Edison One First National Plaza, Chicago, Illinois Address Reply to: Post Office Box 76.7 Chicago, Illinois 60690 BBS Ltr. -#572-75 --- -
-- - Dresden Nuclear PowerSta'timf~ -~
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 SP~IPICATIONS 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 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 Telegrams 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 Numb~~?12E3465/12E3466
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Report Numbers 50-249/7~36
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- Report Date:.September 2, 1975
~ I Occurrence Date:
August 23, 1975
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Facility: Dresden Nuclear Power Station, Morris, Ill~*w.111.
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. -
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- It.'* ~SJIJfJS G *. Keppler
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- September 2, 1975 DESIGNATION OP APPAREM' CAUSE OF OCCURRENCE (Unusual Service Conditions)
Setpoint-dri:f't on these sensors.appears~tO'be-~wavated by extended~rlods.
- at zero pressure. The swi tohes had not been *tested since April 7, a periOcl of nearly five months *. In each case the setpoint ~r 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>ressure.
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 activity. Since the neµtt"on monitoring systen was always operable during.reactor operation, plant personnel and the general public were ~t Jeopardized by* this.occurrence.
CORRIDrIVE ACTION The switches 'WQre immedia~ely reset to within the station limits of 1055 +/-.~5 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 pres~e 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