ML19225A836
| ML19225A836 | |
| Person / Time | |
|---|---|
| Site: | Columbia, Washington Public Power Supply System, Satsop  |
| Issue date: | 05/31/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Strand N WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| References | |
| NUDOCS 7907200379 | |
| Download: ML19225A836 (1) | |
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UNITED S TATES
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NUCLEAR REGULATORY COMMISSION
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REGION V o, ' S2f} f 8
1990 N. CALIFORNI A BOUL EVARD
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WAL NUT CR EE K, CALIFORNI A 94596 May 31,1979 Docket Nos. 50-460 50-397 50-503 50-509 50-513 Washington Public Power Supply System P. O. Box 968 3000 George Washington Way Richland, Washington 99352 Attention:
Mr. N. O. Strand Managing Director Gentlemen:
The enclosed Bulletin No. 79-12 is forwarded to you for information.
No written response is required.
If you desire additional information regard-ing this matter, please contact this office.
Sincerely,
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Director Enclosure-IE Bulletin No. 79-12 with Enclosures cc w/ enclosures:
M. E. Witherspoon, WPPSS A. D. Kohler, WNP-2, WPPSS p
J. P. Ti.omas, WPPSS W. J. Talbot, WPPSS G. C. Sorensen, WPPSS e
366 001
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 May 31, ?979 IE Bulletin No. 79-12 SHORT PERIOD SCRAMS AT BWR FACILITIES Summary:
Reactor scrans, resulting frcm periods of less than 5 seconds, have occurred recently at three BWR facilities.
In each case the scram was caused by high flux detected by the IRM neutron monitors during an approach to critical.
These events are similar in c.~t roepects to events which were previously described by IE Circuler 77-0) (copy enclosed).
The recent recurrences of this event indicate an apparent loss of effectiveness of the earlier Circular.
Issuance of this Bulletin is considered appropriate to further reduce the number of challenges to the reactor protective systen high IPfl flux scram.
Description of Circumstances:
The following is a brief account of each event.
1.
Oyster Creek - On December 14, M78, the reacter experienced a scram as control rods were being withdrava for approach to critical, following a scran froa full power which had occurred about 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> earlier. The mcderator temperature was 330 degrees F and the reactor pressure was 190 psig.
Because of the high xenon concentration the operators had not made an accurate estinate of the critical rod pattern.
The operator at the controls was using the SPJ1 count rate, which had changed only slightly, (425 to 450 cps) to guide the approach.
Control rod 10-43 (first rod in Group 9) was being withdrawn in " notch override" to notch position 10, when the reactor becane critical on an estimated 2.8 second period.
The operator was attempting to reinsert the rod when the scram occurred.
Failure of the " emergency rod in" switch to maintain contact, due to a bent switch stop, apparently contributed to the problem.
2.
Browns Ferry Unit 1 - On January 18, 1979, the reactor experienced a scram during the initial approach to gritical following refueling. The operator was continuously withdrawing in " notch override" the first control rod in Group 3 (a high vorth rod) because the SRM count rate had led him to believe that the reactor was very subcritical. A short reactor period, estimated at 5 seconds, was experienced.
The operator was
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