ML19225A820
| ML19225A820 | |
| Person / Time | |
|---|---|
| Site: | Bailly |
| Issue date: | 05/31/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Shorb E NORTHERN INDIANA PUBLIC SERVICE CO. |
| References | |
| NUDOCS 7907200322 | |
| Download: ML19225A820 (1) | |
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- i MAY 311979 IM k t t No S u 'it i Northern Indlar; Public Service Company ATTN
Mr. Eugene M. Shorb Senior Vice President 5265 Hohman Averme Hammond, IN 46325 Gentlemen:
The enclose (: TE Bulletin No. 79-12 is forwarded to you for information.
No writte, response is required.
If you desire
.Jditional inf ormation regarding t his matter, please ccntact this office Sincerely, S?
James G. Keppier Director
Enclosure:
IE bulletin No. 79-12 cc w/ encl:
Central Files Di rector, NRR/LP1 Director, NRh/ DOR PDR Local PDR NSIC TIC Mr. Dean Hansell, Office of Assistant Attorney General t} " n 7,
336 79072003 2 2
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RFCULATJEY COMMISSIO5 OFFICE OF INSPLCT105 AND ESTORCEMENT RTGInt III Ly 31, 1979 IE Bulletin No. 79-12 SHORT PERIOD SCRAMS AT BWR FACILITIES Su ry:
Reactor scrats, resulting fro = periods of less than 5 seconds, have occurred recently at three BWR facilities. In each case the scra= was caused by high flux detected by the IRM neutron monitors during an approach to critical.
These events are similar in cost 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 syster high IRM flux scrat.
Dascription of Circumstances:
The follovirg is a brief account of each event.
1.
Oyster Creek - On December 14, 1978, the reactor experienced a scrat as control rods were being withdrawn for approach to critical, following a scra from full power which had occurred about 15 hours1.736111e-4 days 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 terperature was 380 degrees F and the reactor pressure was 190 psig.
Because of the high xenon cencentration 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, (l.25 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 en an esticated 2.8 second period. The operator was attempting to reinsert the rod when the scrat occurred.
Failure of the "e=ergency rod in" switch to maintain 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 (o 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 secondl atte=pting to reinsert contro f DUPLICATE DOCUMENT
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