ML19225A816
| ML19225A816 | |
| Person / Time | |
|---|---|
| Site: | Zimmer |
| Issue date: | 05/31/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Borgmann E CINCINNATI GAS & ELECTRIC CO. |
| References | |
| NUDOCS 7907200300 | |
| Download: ML19225A816 (1) | |
Text
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s**8800 UNITED STATES fs
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MAY 311973 Docket No. 50-358 Cincinnati Gas and Electric Cor.pany ATTN:
Mr. Earl A. borgmann Vice President Engineering Services and Electric Production 139 East 4th Street Cincinnati, OH 45201 Gentlemen:
The enclosed IE Bulletin No. 79-12 is forwarded to you for information.
No written respc'se is required.
If you desire additional information regarding this ma'ter, please contact this office.
Sincerely,
.hb James G. Keppler Director
Enclosure:
IE Bulletin No. 79-12 cc w/ encl:
Mr. J. R. Schott, Plant Superintendent Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC 415 332 TIC Harold W. Kohn, Power Siting Commission Citizens Against a Radioactive Environment Helen W. Evans, State of Ohio
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70,0'7 2 00 $ 00
U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND INFORCFuENT REGION III May 31, 1979 L" Bulle cin rio. 79-14 SHORT PERIOD SCRAMS AT BWR FACILITIES Su==ary:
Reactor scra s, resulting from periods of less than 5 aeconds, here occurred recently at three BWR facilities.
In each case the scram was caused by high flux detected by the IRM neutron monitore during an approach to critical.
These events are similar in cost respects to events which were previous]y described by IE Circular 77-07 (copy enclosed).
The recent re.currences of this event indicate an apparent loss of effectiveneas of the earlier Circular.
Issuance of this Bulletin is considered appropriate to further reduce the number of challenges to the reactor protective system high IRM flux scrat.
Description of Circumstances:
The following is a brief account of each event.
1.
Oyster Creek - On December 14, 1978, the reactor. nerienced a scra as control rods were being withdrawn for approach to critical, following a scra= from full power vnsch had occurred about 15 hours1.736111e-4 days 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 moderatur tecperature 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 :ritical rod pattern. The operator at the controls was using the SRM cosnt rate, which had changed only slightly, (425 to 450 cps) to guice the approach. Control rod 10-43 (first rod in Group 9) was being witHrawn in " notch override" t - notch position 10, when the reactor became critical on an esticated 2.8 second period. The operator was attecpting to refusert the rod when the scram occurred. Failure of the " emergency rod in' switch to maintait. 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 refuelinr,. The operator was continuously withdrawing in " notch override" the first control rod in Group 3 (a high worth red) 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 attempting to reinsert contre 14odswhenthescranoccurred.
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