ML19246C083
| ML19246C083 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 05/31/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Hines E DETROIT EDISON CO. |
| References | |
| NUDOCS 7907200314 | |
| Download: ML19246C083 (1) | |
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etcN cttyn. stuNots 60M7 MAY 311979 Docket No. 50-341 The Detroit Edison Company ATTN:
Mr. Edward Hines, Assistant Vice President and Manager Quality Assurance 2000 Second Avenue Detroit, M1 48226 Gentlemen:
The enclosed IE Bulletin No. 79-12 is forwarded to you for information. No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, WA$
(/ James G. Kepp er Director
Enclosure:
IE Bulletin No. 79-12 cc w/ encl:
Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Ronald Callen, Michigan Public Service Commission Eugene B. Thomas, Jr.,
Attorney L; ~9 o 4 -n s a. ' 2..
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U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT REGION III May 31, 1979 IE Bulletin No. 79-12 SHORT PERIOD SCRAMS AT Bk'R FACILITIES Su==ary:
Reactor scra=s, resulting from periods of less than 5 seconds, have occurred recantly at three Bb'R f acilities. In each case the scram was caused by high fit.. 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 apprepriate to further reduce the number of challenges to the reactor protective syste= 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Oyster Creek - On December 14, 1978, the reactor experienced a scra: as control rods were being withdrawn for approach to critical, following a scra= from full power which had occurred about 15 hours1.736111e-4 days 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 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 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 ret" m%vmu nnher,:LLir.O
-A a barbreactor period, estimated at 5 seconds' DUPLICATE DOCUMENT attempting to reinsert control Entire document previously entered into system under:
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