ML19253C416
| ML19253C416 | |
| Person / Time | |
|---|---|
| Site: | Marble Hill |
| Issue date: | 11/20/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Shields S PSI ENERGY, INC. A/K/A PUBLIC SERVICE CO. OF INDIANA |
| References | |
| NUDOCS 7912050407 | |
| Download: ML19253C416 (1) | |
Text
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UNITt D ST ATE f.
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4 't NUCLE AR REGULATORN COYNISSION
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2 RE GION lli 2
y n,', m.ns n n 1 noan Docket No. 50-546 Docket No. 50-547 gg, Public Service of Indiana ATTN:
Mr. S. W. Shields Vice President - Electric System
?000 East Main Street Plainfield, IN 46168 Gentlemen:
The enclosed IE Bulletin No. 79-26 is forwarded to you for information.
No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, u db
/
- t. James G. Keppler Director
Enclosure:
IE Bulletin No. 79-26 cc w/ encl:
Mr. G. N. Brown, Project Director Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC
'IIC LeBoeuf, Lamb, Leiby & MacRae Mr. Dave Martin, Office of the 1502 341 Attorney General m20 so'07 i
UNITED STATES SSINS:
6820 NUCLEAR REGULATORY COMMISSION Accession No.
OFFICE OF INSPECTION AND ENFORCEMENT 7910250475 WASHIN'iTON, D. C.
20555 November 20, 1979 IE Bulletin No. 79-26 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 cuarter 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 pres =ures are sufficient to open the crack), boron is leached cut 10 of the tube at locations with more than 50 percent B local depletion (local depletion is considered to be twice the average depletion).
It was further found IO with similar cracking but with less than 50 percent local depletion of B
, t:,at 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.
According to the GE criteria the end of design life is reached when the reactivity 10 worth of the blade is reduced by 10 percent, which corresponds to 42 percent B depletion averaged over the top quarter of the control blade.
Because of the leaching mechanism, GE has reduced th, the top quarter of the control blade DUPLICATE DOCUMENT The safety significance of boron loss Entire document previously scram reactivity.
Although shutdown entered into system under:
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