ML19246C080
| ML19246C080 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 05/31/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Dewitt R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 7907200310 | |
| Download: ML19246C080 (1) | |
Text
T1C gne asog UNITED STATES
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NUCLEAR REGULATORY COMMISSION e
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occu ettvu. ictmois sour MAY 311979 Docket No. 50-155 Consumers Power Company ATTN:
Mr. R. B. DeWitt Manager of Nuclear Plant Operations 212 West Michigan Avenue Jackson, MI 49201 Gentlemen:
The enclosed IE Bulletin No. 79-12 is forwarded to you for action.
A written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, gA-y amesG.Kepp$er Director
Enclosure:
IE Bulletin No. 79-12 cc w/ encl:
Mr. C. J. Hartman, Plant Superintendent Central Files Director, hM /DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Ronald Callen, Michigan Public Service Commission Anthony Roisman, Esq., Attorney LOf}1E t007aco3/o,
U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT 9EGION III May 31, 1979 IE Bulletin No. 79-12 SHORT PERICD SCRAMS AT BWR FACILITIES Su==ary:
Reactor scra=s, resulting from periods of less than 5 seconds, have occurred recently at three BWR facilities.
In each case the scrac was caused by high flux detected by the IRM neutron monitors during an approach to critical.
These events are similar in most respects to events which were previously described by IE Circular 77-07 (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 nu=ber of challenges to the reactor protective system high IRM flux scra=.
Description of Circumstances:
The following is a brief account of each event.
1.
Oyster Creek - On December 14, 1978, the reactor experienced a scra: as control rods were being withdrawn for approach to critical, following a scra= from full power which had occurred about 15 hours1.736111e-4 days 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 moderator temperature was 380 degrees F and the reactor pressure was 190 psig. Because of the high xenon concentration the operators had not made an accurate estimate of the critical rod pattern. The operator at the controls was using the SRM 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 became critical on an estimated 2.8 second period. The operator was atte=pting 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 critical following refueling. The operator was continuously withdrawing in " notch override" the first control rod in Group 3 (a high worth rod) because the SRM count rate had led him to believe that the reactor was very suberitical. A short reactor period, estimated at 5 second#;
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