ML19254A669
| ML19254A669 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 05/31/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Goodwin C PORTLAND GENERAL ELECTRIC CO. |
| References | |
| NUDOCS 7907200370 | |
| Download: ML19254A669 (1) | |
Text
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- p SulTE 202, WALNUT CRFEK PLAZA W A LNUT CR EE K. C Allr ORN! A <>45'JG May 31,1979 Docket flo. 50-344 Portland General Electric Company 121 S. W. Salmon Streat Portland, Oregon 97204 Attention:
Mr. Charles Goodwin Assistant Vice President Gentlemen:
The enclosed Bulletin fio. 79-12 is fonvarded to you for information.
No written response is required.
If you desire additional information regard-ing this matter, please contact this office.
Sincerely,
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Enclosure:
IE Bulletin No. 79-12 with Enclosures cc w/ enclosures:
B. Withers, PGE F. C. Gaidos, PGE k
t 1907200976.
Util TED STATES f;UCLEAR REGULATORY COMMISSI0fl 0FFICE OF IllSPECTI0ft Afl0 Ef;FORCEMEflT WASHIt'GT0ft, D.C.
20555 fiay 31, 1979 IE Bulletin flo. 79-12 SHORT PERIOD SCRAMS AT BWR FACILITIES Sunmary:
Reactor scrans, resulting from periods of less than 5 seconds, have os.urred 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 in nost 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 system high IR'i flux scram.
Description of Circumstances:
The following is a brief account of each event.
1.
Oyster Creek - On December 14, 1978, the reactor experienced a scram as control rods were being withdrawn for approach to critical, following a scram from full power which had occurred about 15 hours1.736111e-4 days 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 330 degrees F and the reactor pressure was 190 psig.
Because of the high xenon concentration the operators had not made an accurate estirate of the critical rod pattern.
The operator at the controls was using the SRf1 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 becane 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 nair.tain 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 gritical 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 subcritical. A short reactor period, estimated at 5 seconds, was experienced.
The operator was attempting to reinsert control rods when the scram occurred.
DUPLICATE DOCUMENT Entire document previously entered into system under:
ANO 770 f 0 W MW No. of pages:
8