ML19225A807
| ML19225A807 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, Zion, LaSalle File:ZionSolutions icon.png |
| Issue date: | 05/31/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Brian Lee COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 7907200287 | |
| Download: ML19225A807 (1) | |
Text
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NUCLEAR REGULATORY COMMISSION i{ ;
REGloN Hi 799 ROOSEVELT RO AD e
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CLEN ELLYN, ILLINOIS 60137 f
MAY 311979 Docket Nos. 50-456, 50-457, 50-454, 50-455, 50-373, 50-374, 50-295 and 50-304 Commenwealth Edison Company ATTN:
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 information. No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, b & An- __
James G. Keppbr Director
Enclosure:
IE Bulletin l
No. 79-12 cc w/ enc 1:
Mr. E. Cosaro, Project Mr. N. Wandke, Plant Superintendent Superintendent Mr. G. Sorensen, Site Central Files Project Superintendent Director, NRR/DPM Mr. L. J. Burke, Site Director, NRR/ DOR Project Superintendent PDR Mr. T. E. Quaka, Quality Local PDR Assurance Supervi.:or NSIC Mr. R. H. Holyoak, Station TIC Superintendent Mr. Dean Hansell, Office of Assistant Attorney General 411 255 1
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U.S. NUCLEAR REGULATORY COMMISSIOS OFFICE OF INSPECTION AND ENFORCEMENT REGION III May 31, 1979 IE Bulletin No. 79-12 SHORT PERIOD SCRAMS AT B G 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 scram was caused by high flux detected by the IRM neutron monitors during an approach to critical.
These events are similar is 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 'he reactor protective syste= high IRM flux scrat.
Description of Circunstances:
The following is a brief account of each event.
1.
Oyster Creek - On December 14, 1978, the reactor experienced a se' ts control rods were being withdrawn for approach to critical, folk a q a scra: from full power which had occurred about 15 hours1.736111e-4 days 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 /> earlie..
Ih a moderator tecperature was 380 legrees F and the reactor pressure m, 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 usit.; 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 an an esticated 2.8 second period. The operator was attempting to reinsert the rod when the scran 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 Grc,up 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 seconde, was experienced. The operator was atte=pting to reinsert control rods when the scram occurred. _ __ _ _ _
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