ML19254A661
| ML19254A661 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 05/31/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Eric Turner HOUSTON LIGHTING & POWER CO. |
| References | |
| NUDOCS 7907200354 | |
| Download: ML19254A661 (1) | |
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o UNITED STATES 8,%
NUCLEAR REGULATORY COMMISSION E
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AR LINGToN, TE X AS 7G012 611 RYAN PLAZA DRIVE.SulTE 1000 N,, ' b "
May 31, 1979 In Reply Refer To:
RIV Docket Nos. 50-498/IE Bulletin No. 79-12 50-499/IE Bulletin No. 79-12 Houston Lighting & Power Company ATTN:
Mr. E. A. Turner, Vice President Power Plant Construction and Technical Services Post Office Box 1700 Houston, Texas 77001 Gentlemen:
The enclosed IE Bulletin 79-12 is forwarded to you for information. No written response is required.
If you desi:e additional information regarding this matter, please contact this office.
Sincerely, tl Karl V. Seyfri Director
Enclosures:
1.
IE Circular No. 77-07 3.
List of IE Bulletins Issued in Last Twelve Months
( II 7907200367
UNITED STATES NUCLEAR R:
.ATORY COMMISSION _
0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Bulletin No. 79-12 Date:
May 31, 1979 Page 1 of 3 SHORT PERIOD SCPAMS AT BW 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 similar in most respects to events which were previously described by IE Circular 77-07 (copy enclosed). The recent recurrences cf 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 r. actor protective system high IRM flux scram.
Descripr. ion of Circumstances:
The follc, wing 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Oyster Creek - On December 14, 1978, the reactor experienced a scram as control rods were being withdrawn for approach to critical, following a scram from full power which had occurred about 15 hours1.736111e-4 days 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. Tl moderator temperature was 380 degrees F and the reactor pressure was 130 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 2.8 second period. The operator was attempting to reinsert the rod when the scram 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 Group 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 seconds, was experienced.
The operator was attempting to reinsert control rods when t DUPLICATE DOCUMENT Entire docunient previously entered into system under:
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