ML19254A663
| ML19254A663 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 05/31/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Aswell D LOUISIANA POWER & LIGHT CO. |
| References | |
| NUDOCS 7907200357 | |
| Download: ML19254A663 (1) | |
Text
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UNITED STATES E ',", e, ( l S
- ' 1 NUCLEAR REGULATORY COMMISSION
' 5.bJkh ' 8 HEGION IV 611 HYAN PLAZA DRIVE, SUITE 1000 t
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,u ARLING TON, TEX AS 76012 May 31, 1979 In Reply Refer To:
RIV Docket No.
50-382/IE Bulletin No. 79-12 Louisiana Power and Light Co.
ATTN:
Mr. D. L. Aswell Vice President of Power Production 142 Delaronde Street New Orleans, Louisiana 70174 Gentlemen:
The enclosed IE Billetin 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.
Since:.ely,
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KarlV.Seyfrit/
Director
Enclosures:
1.
IE Circular No. 77-07 3.
List of IE Bulletins Issued in last Twelve Months 1-7907 2 003f7
UNITED STATES NUCLEAR REGULATORY C0t1 MISSION _
0FFICE OF INSPECTION AND EKFORCEMENT WASHINGTON, D.C.
20555 IE Bulletin No. 79-12 Date:
May 31, 1979 Page 1 of 3 SHORT.ZRIOD SCRAMS AT BWR FACILITIES Summary:
Reactor scrams, 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 simil y in most respects to events which were previously described by IE Circular 77-(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 IRM 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Oyster Creek - On December 14, 1978, the reactor experienced a scram as control rods were being withdrawn for approach to critical, following a scram from full power which had occurred about 15 hours1.736111e-4 days 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 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 .8 second period. The operator was attempting to reinsert the rc. when the scram occurred.
Failure of the
" emergency rod in" switch to maintain contact, due to a bent switch s'.,p, apparently ccatributed to the problem.
2.
Browns Ferry Unit 1 - On January 18, 1979, the r eactor experienced a scram during the initial approach to critical follow'.ug refueling. The operator was continuously withdrawing in " notch overriJe" the first control rod in Group 3 (a high worth rod) because the SMI count rate had led him to believe that the reactor was very subcrit: cal. A short reactor period, estimated at 5 seconds, was experienced. The operator was attempting to reinsert control rods when the ser occurred.
DUPLICATE DOCUMENT Entire document previously entered into system under:
ANO 7 WM p y 7 No. of pages:
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