ML19246C069
| ML19246C069 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 05/31/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Stewart W FLORIDA POWER CORP. |
| References | |
| NUDOCS 7907200188 | |
| Download: ML19246C069 (2) | |
Text
{{#Wiki_filter:., i N3'l ^ .kh - >l', r [ Se nro UNITED STATES NUCLEAR REGULATORY COMMISSION l' .,_,gf't REGION 11 O ^^v/ E 101 MARIETT A ST.. N.W., SUIT E 31M PAY 31 1970 [ AT L ANT A, G Eo RGI A 30303 o, <g ss g EY 3 In Reply Refer To: RII:JPO 50-302 Florida Power Corporation Attn: W. P. Stewart, Manager Nuclear Operations P. O. Box 14042, Mail Stop C-4 St. Petersburg, Florida 33733 Gentlenen: No written The enclosed Bulletin 79-12 is forwarded to you for information.If yo response is required. matter, please contact this office. Sincerely, 5 4 ames P. O'Reilly J Director
Enclosure:
IE Bulletin No. 79-12 ^ L '37,7 3 i9052U f88
1 3 J E.; Florida Power Corporation ' cc w/ encl: G. P. Beatty, Jr. Nuclear Plant Superintendent Post Office Box 1228 Crystal River, Florida 32629 .'4, Jf y =f d') O. ? A fof..,
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 May 31, 1979 IE Bulletin No. 79-12 SHORT PERIOD SCRAMS AT BWR FACILITIES Sumary: Reactor scrams, resulting from periods of less than 5 seconds, have occurred In each case the scram was caused by high recently at three BVR facilities. flux detected by the IRM neutron monitors during an approach to critical. These events are similar in most respects to events which were previously The recent recurrences of described by IE Circular 77-07 (copy enclosed). 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 system high IRM flux scram. Description of Circumstances: The following is a brief account of each event. 14, 1978, the reactor experienced a scram as Oyster Creek - On December 1. control rods were being withdrawn for approach to critical, followingThe a scram from full power which had occurred about 15 hours earlier. moderator temperature was 380 degrees F and the reactor pressure was Because of the high xenon concentration the operators had not 190 psig. made an accurate estimate of the critical rod pattern. The operator at the controls was using the SRM count rate, which had changed only Control rod 10-43 slightly, (425 to 450 eps) to guide the approach. (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 The operator was attempting to reinsert the rod when the scram period. Failure of the "energency rod in" switch to maintain contact, occurred. due to a bent switch stop, apparently contributed to the problem. Browns Ferry Unit 1 - On January 18, 1979, the reactor experienced a 2. The scram during the initial approach to critical following refueling. operator was continuously withdrawing in " notch override" the first control rod in Group 3 (a high worth rod) because the SRM count rate had A short reactor led him to believe that the reactor was very suberitical. period, estimated at 5 seconds, was experienced. The operator was attempting to reinsert control rods when the scram occurred. c%"is r s u. a n_ ~ . DUPLICATE DOCUMENT
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