ML19225A813
| ML19225A813 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities  |
| Issue date: | 05/31/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Brian Lee COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 7907200296 | |
| Download: ML19225A813 (1) | |
Text
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?!C g>* me Cg UNITED STATES f
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NUCLEAR REGULATORY COMMISSION 8
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GLEN ELLYN, ILLINol5 60137 e'~
WAY 311979 Docket Nos. 50-10, 50-237, 50-249, 50-254 and 50-265 Commonwealth Edison Company ATIN:
Mr. Byron Lee, Jr.
Vice President Post Office Box 767 Chicago, IL 60690 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, oms $
James G. Kepp er Director
Enclosure:
IE Bulletin No. 79-12 cc w/ enc 1:
Mr. B. B. Stephenson, Station Superintendent Mr. N. Kalivianskis, Plant Superintendent Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Anthony Roisman, Esq., Attorney 4Ii 257 Mr. Dean Hansell, Office of Assistant Attorney General 190noo;zf6
U.S. NUCLEAR REGULATORY C0hMISSION OFFICE OF INSPECTION AND ENFCRCEMENT REGION III May 31, 19/9 IE Bulletin No. 79-12 SHORI PERIOD SCRAM.S AT BWR FACILITIES Eu==ary:
Reactor scra=s, resulting from periods of less than 5 seconds, have occurred recently at three Bk'R facilities. In each case the scra= vas 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 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.
Oy ster Creek - On December 14, 1978, the reactor experienced a scra as control rods were being withdrawn for approach to critical, following a scra= from full power which had occurred about 15 hours1.736111e-4 days 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 scra=
occurred. Failure of the "e=crgency 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 seconds, was experienced. The operator was attempting to reinsert control rods when the scram occurred.
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