ML19210E563
| ML19210E563 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 11/20/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Leonard J POWER AUTHORITY OF THE STATE OF NEW YORK (NEW YORK |
| References | |
| NUDOCS 7912050269 | |
| Download: ML19210E563 (1) | |
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UNITED STATES
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,o KING OF PRUSSIA, PENNSYLVANIA 19406 Docket No. 50-333 G 2 0 1979 Power Authority of the State of New York James A. FitzPatrick Nuclear Power Plant ATTN:
Mr. J. D. Leonard Resident Manager P. O. Box 41 Lycoming, New York 13093 Gentlemen:
The enclosed IE Bulletin 79-26 is forwarded to you for action. A written response is required. If you desire additional information regaruing this matter, please contact this office.
Sincerely,
)f[,
[b oyce H. Grier rector
Enclosures:
1.
List of Recently Issued IE Bulletins CONTACT:
D. L. c phton a
(215-337-5266) cc w/encls:
George T. Berry, Executive Director P. W. Lyon, Manager - Nuclear Operations A. Klansmann, Director, Quality Assurance M. C. Cosgrove, Quality Assurance Supervisor J. F. Davis, Chairman, Safety Review Committee V. J. Cassan, Assistant General Counsel G. M. Wilverding, Licensing Supervisor 1500 156 soso 2(8
ENCLOSURE 1 UNITED STATES SSINS:
6820 NUCl. EAR REGULATORY COMMISSION Accession No.:
0FFICE OF INSPECTION AND ENFORCEMENT 7910250475 WASHINGTON, D.C.
20555 IE Bulletin No. 79-26 Date: November 20, 1979 Page 1 of 4 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 g nfined to locations in the poison tubes with more than 50 percent Boron-10 (B ) 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 B C as helium and lithium concentr3tions grow.
Once primary coolant penetrates thecladding(i.e.,thecrackinghasprogressedthroughthecladdingwalland thehelium-lithiumpressuresaresufficienttoopenthecrack),gronis leached out of the tube at locations with more than 50 percent B local depletion (local depletion is considered to be twice the average depletion).
Itwasfurtherfoundwithsimilarcrackingbutwithlessthan50percentlocal 1
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 controi blade.
According to the GE criteria the end of design life is reached when the reactivity w g th of the blade is reduced by 10 percent, which corresponds to 42 percent B
depletionaveragedoverthetopquarterofthecontrolglade.
Because of the leaching mechanism, GE has reduced the allowance for B depletion averaged over the top quarter of the control blade from the 42 percent value to 34 percent.
The safety significance of boron loss is its impact on shutdown capability and scram reactivity.
Although shutdown capability is demonstrated by shutdown margin tests after refueling, the calcula'
'~
tests are based on the assumption that no in scram reactivity due to boron loss cou Power Ratio (CPR) reductions during the p the consequences of control rod drop acc1 DUPLICATE DOCUMENT Entire document previously entered into system under:
1500 157 xNo 77/gpSo175-No. of pages: