ML19338D581
| ML19338D581 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 08/29/1980 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Dewitt R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 8009230489 | |
| Download: ML19338D581 (1) | |
Text
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N UNITED STATES o['n NUCLEAR REGULATORY COMMISSION cE REGION 111 6
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' 799 ROOSEVELT ROAD g
GLEN ELLYN. ILLINOIS 80137 106. 2.9. S80 Docket No. 50-155 Consumers Power Company
. ATTN:
Mr. R. B. DeWitt Vice President Nuclear Operations 212 West Michigan Avenue Jackson, MI.49201 Gentlemen:
The enclosed IE Bulletin No. 79-26, Revision 1, is forwarded to you for action.
The original IE Bulletin No. 79-26 has been revised to adjust the required completion date for. reporting the results of examination of an exposed control blade and to correct a typographical error. The revision is identified by use of "R1" in the right margin.
In order to assist the NRC.in evaluating the value/ impact of each bulletin'on i
licensees, it would be helpful if you would provide an estimate of the manpower expended in conduct of the review and preparation of the report required by the bulletin. Please estimate separately the manpower associated with corrective acti<us necessary following identification of problems through the bulletin.
A written response is required.
If you desire additional information regarding this matter, please contact this office.
l Sincerely, g
[JamesG.Keppler U Director i
Enclosure:
IE Bulletin No. 79-26, Revision 1 cc w/ encl:
Mr. D. P. Hoffman, Nuclear Resident Inspector, RIII Licensing Administrator PDR Mr. C. J. Hartman, Plant Local PDR l
Superintendent NSIC Central. Files TIC Director, NRR/DPM Ronald Callen, Michigan Director, NRR/ DOR Public Service Commission
.AEOD 8009230489 J
SSINS No.: 6820
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Accession No.:
- 1 UNITED STATES 8006190042 NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 August 29, 1980 IE Bulletin No. 79-26 Rev. 1 BORON LOSS FROM BWR CONTROL BLADES Description of Circumstances:
The General Electric Company _(GE) has informed us of a failure mode for control blades which can cause a loss of boron poison material.
Hot cell examinations of both foreign and domestic blades have revealed cracks near the upper end of stainless steel tubing and loss of boron from the tubes.
The cracks and boron loss have so far been confined to locations in the poison tubes with more than 50 percent Boron-10 (B10) local depletion.
Observed crack sizes range from a quarter to a half inch in length and from one to two mils in width.
GE has postulated that the cracking is due to stress corrosion induced by solidification of boron carbide (B C) particles and swelling of the compacted 4
B C as helium and lithium concentrations grow.
Once primary coolant penetrates 4
the cladding (i.e., the cracking has progressed through the cladding wall and the helium-lithium pressures are sufficient to open the crack), boron is 10 leached out of the tube at locations with more than 50 percent B local depletion (lochi depletion is considered to be twice the average depletion).
It was further found with similar cracking but with less than 50 percent local 10 depletion of B
, that leaching did not occur even though primary coolant had penetrated the cladding.
The cracking and boron loss shorten the design life of the control blade.
j According to the GE criteria the end of design life is reached when the reactivity worth of the blade is reduced by 10 percent, which corresponds to e top quarter of the control blade, 10 s reduced the allowance for B deple-DUPLICATE DOCUMENT control blade from the 42 percent Entire document previously entered into system under:
nNo 8amesW No. of es.
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