ML19225A810
| ML19225A810 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 05/31/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Wright G COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 7907200292 | |
| Download: ML19225A810 (1) | |
Text
7tc pa naco UNITED STATES f
'[0, NUCLEAR REGULATORY ' 7MMISSION y
' r-o REGION 111 5 "'
a otts Ettvs.ittisons soisi jf JUNi 1979 State of Illinois Department of Public Health ATTN:
Mr. Gary N. Wright, Chief Division of Nuclear Safety 535 West Jefferson Street Springfield, IL 62761 Gentlemen:
The enclosed IE Bulletin No. 79-12 titled "Short Period Scrams At BWR Facilities" was sent to the following licensees on May 31, 1979, far action and information:
ACTION Commonwealth Edison Company Dresden 1, 2, 3 (50-10, 50-237, 50-249)
Quad Cities 1, 2 (50-2J' 50-265)
Consumers Power Company Big Rock Point (50-155)
Iowa Electric Light and Power Company Duane Arnold (50-331)
Northern States Power Company Monticello (50-263)
INFORMATION American Electric Power Service Corporation IcJi Ja and hichigan Power Company D. C. Cook 1, 2 (5C-315, 50-316)
Cincinnati Gas & Electric Company Zimmer (50-358)
Cleveland Electric Illuminating Company Perry 1, 2 (50-4'+0, 50-441) 366 3,11) f 190n0026
JUN 1 1979 State of Illinois -
Ccmmonwealth Edison Company Braidwood 1, 2 (50-456, 50-457)
Byron 1, 2 (50-454, 50-455)
La Salle 1, 2 (50-373, 50-574)
Zion 1, 2 (50-295, 50-304)
Consumers Power Company Midland 1, 2 (50-329, 50-330)
Palisades (50-255)
Dairyland Power Cooperative LACBWR (50-409)
Detroit Edison Company Fermi 2 (50-341)
Illinois Power Company Clinton 1, 2 (50-461, 50-462)
Northeca Indiana Public Service Company Bailly (50-367)
Northern States Power Company Prairie Island 1, 2 (50-282, 50-306)
Tyrone Energy Park 1 (50-484)
Public Service of Indiana Marble Hill 1, 2 (50-546, 50-547)
Toledo Edison Company Davis-Besse 1 (50-346)
Union Electric Company Callaway 1. 2 (50-483, 50,485)
Wisconsin Electric Power Company Point Beach 1, 2 (50-266, 50-301) 366 320
M1 M
State of Illinois
_3_
Wisconsin Public Service Corporation Kewaunee (50-305)
Sincerely, d Yft f d Y l
Helen Pappas, Chief Administrative Branch
Enclosure:
IE Eulletin No. 79-12 cc w/ encl:
Mr. D. W. Kare, Sargent & undy Central Files Reproduction Unit h7C 20b Local PDR NSIC TIC 366 321
U.S. NUCLEAR REGULATORY CO.91ISSION OFFICE OF INSPECTION AND ENFORCEMENT REGION III May 31, 1979 IE Bulletin No. 79-12 SHORT PERIOD SCRAMS AT 3WR FACILITIES Su==ary:
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 tigh flux detected by the IRM neutron monitors during an approach to critical.
These events are imilar 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 number of challenges to the reactor protective system high IRM flux scram.
Description of Circumstances:
The follovig 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 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 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 becare criM c33 rr. ers cct h ud 2.0 second pc P,d. The c,parator 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 tne 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 North rod) because the SRM count rate had led him to believe that the reactor was.yern nuberig gal. _A short reactor.
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period, estimated at 5 ceconds,i L j
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DUPLICATE DOCUMENT attempting to reinsert control rc j
lEntire docr. ment previously entereo linto system under:
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ANO No. of pages:
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