ML19225A822
| ML19225A822 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 05/31/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Wachter L NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 7907200328 | |
| Download: ML19225A822 (1) | |
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ctc~ tttvs. e tisois soi n MAY 311979 Docket No 50-282 Docket No.50-30f; N^ rthe : n States Power Company A'
Mr. Leo Wachter Vice President Power Production and System Operation 414 Nicollet Mall Minneapolis, riN 55401 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, Ypf 'k%
James G. Keppfer Director
Enclosure:
IE Bulletin No. 79-12 cc w/ encl:
Mr. F. P Tierney, Jr.,
Plant Manager Central Files Director, NRR/DPM Director, h1R/ DOR PDR Local FDR NSIC TIC John W.
Ferman, Ph.D.,
Nuclear Engineer, HPCA 7,74 440 J'
7907200 T
U.S.
'nCLEAE REGULATOF' C OEI F 510' OFFICE OF ISSFECTIC' AND E.TOFCEMENT
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R FG I D' III
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31, 1979 IE Bulletin No. 79-12
$ HOR 7 PERIOD SCP>dS AT BkT FACILITIES S um ry.
Reactor scrats, resulting froc periods of less than 5 seconds, have occurred recently at three Eb'R f acilities.
In each case the scrat was caused by high flux detected by the IFM 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 nutber of challenges to the reactor protective syst e= high IRM flux scrat.
Description of Circumstances:
The follovirg 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Oyster Creek - On December 14, 1978, the reactor experienced a scra as control rods were being withdrawn for approach to critical, following a scra: from full power which had occurred about 15 hours1.736111e-4 days 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 360 degrees F and the reactor pressure was 190 psig.
Because of the high xenon concentration the operators had not made an accurate esti= ate of the critical rod pattern. The operator at the controls sas 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 ca an estimated 2.8 second period. The operator was attempting to reinsert the rod when the scrat occurred.
Failure of the "ecergency rod in" switch to caintain contact, due to a bent switch stop, apparently contributed to the proble=.
2.
Browns Ferry Unit 1 - On January 18, 1979, the reactor experienced a scra= 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 hic to believe that the ra-*^*
"or "am _anker1 Hen 1, A nhnrt reactor period, estimated at 5 second DUPLICATE DOCUMENT attempting to reinsert contro e
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