ML19338D594
| ML19338D594 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 08/29/1980 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | John Miller GEORGIA POWER CO. |
| References | |
| NUDOCS 8009230525 | |
| Download: ML19338D594 (1) | |
Text
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- o, UNITED STATES 8'
NUCLEAR REGULATORY COMMISSION n
E REGION 11 6
r e
101 MARIETTA ST, N.W., SulTE 3100 o
ATLANTA, GEORGIA 3o303 AUG 2 01980 In Reply Refer To:
ITTJPO 50-321 50-366 w-Georgia Power Company ATTN:
J. H. Miller, Jr.
Executive Vice President 270 Peachtree Street Atlanta, GA 30303 Gentlemen:
The enclosed IE Bulletin No. 79-26, Rev. 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 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 (s) required by the Bulletin. Please estimate separately the manpower associated with corrective actions 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.
Sincerely, cw 0\\
James P. O'Reilly irector
Enclosures:
1.
IE Bulletin No. 79-26, Rev.
2.
List of Recently Issued IE Bulletins cc w/ encl:
M. hanry, Plant Manager C. E. Belflower, Site QA Supervisor W. A. Widner, Vice President ano General Manager-Nuclear Generation 8009230525 b
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s SSINS No.: 6820 Accession No.:
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 (CE) has informed us of a failure mode for control blades which can cause a loss of bocon 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 0
leached out of the tube at locations with more than 50 percent B 7,c,7 depletion (local depletion is considered to be twice the average depletion).
It was further found with similar cracking but with less than 50 percent local 0
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.
According to the GE criteria the end of dem n life is reached when the percent, which corresponds to DUPLICATE DOCUMENT quarter of the control blade.
Entire document previously ced the allowance for B deple-entered into system under:
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