ML19225A819
| ML19225A819 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 05/31/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Gerstner W ILLINOIS POWER CO. |
| References | |
| NUDOCS 7907200318 | |
| Download: ML19225A819 (1) | |
Text
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NUCLEAR REGULATORY COMMISSION REGION til
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A ctru ett vs. stusois sois7 MAY 311979 Docket No. 50-461 Docket No. 50-462 Illinois Power Company 6TTN:
Mr. W. C. Gerstner Executive Vice President 500 South 27th Street Decatur, IL 62525 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,
- A 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 Mr. Dean Hansell, Office of Assistant Attorney General 415 340 J
M0'2 2003/&.a
U.S. NUCLEAR REGULATORY CO5S!ISSION OFFICE OF INSPECi10N AND ENFORCEMENT REGION III May 31, 1979 IE Bulletin No. 79-12 SHORT PERIOD 2 CRAMS AT BWR FACILITIES Su==ary:
Reactor scra=s, resulting from periods of less
..an 5 seconds, hava occurred recently at three BWR facilities. In each case the scram was cai by high flux detected by the IRM neutron monitors during an approach to et zal.
These events are similar in cost respects to events which were prev 2 2 sly described by IE Circular 77-07 (copy enclos 1). The recent recur. nc, s of this event indicate an apparent loss of effectiveness of the earlier Circular.
Issuance of this Bulletin is considered apprapriate to further reduce t' e nutber 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Oyster Creek - On December 14, 1978, the reactor experienced a scra: as control rods were being withdrawn for approach to critical, following a scram from full power which had occurred about 15 hours1.736111e-4 days 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 hr.d not made an accurate estimate of the critical rod pattern. The operator at the controls was using the SRM count rete, 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 caintain 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 tne 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 rrae had led him to believe that the reactor was very suberitical. A short reactor period, estimated at 5 seconds, was experienced. The operator was atteepting to reinsert control reds when the scram Occurred.
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