ML19338D584
| ML19338D584 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 08/29/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Finfrock I JERSEY CENTRAL POWER & LIGHT CO. |
| References | |
| NUDOCS 8009230493 | |
| Download: ML19338D584 (1) | |
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-- UNtTED STATES o
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' NUCLEAR REGULATORY COMMISSION 4 *
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J 831 PARK AVENiJE.
KING ' F PRUSSIA, PENNSYLVANIA 19406 -
O August 29, 1980
- D:cket No.'50-219 Et~
ifp l Jersey Central. Power and Light Company.
ATTN:
Mr. Ivan R. 'Finfrock, Jr.
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Vice President Madison /; venue ~at Punch Bowl-Road-Morristown, New Jersey. 07960
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Gentlemen:
$.A Enclosed is 'IE, Bulletin No. 26, LRevision 1, which requires actNri by you with respect;to your nuclear power facility (ies).
The original 1E Bulletin
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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
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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 u ch Bulletin on licensees, it would be helpful if your.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 following identification of problems.through the Bulletin.
Sho.uld you.have any questions regarding the Bulletin or actions required by b
you, please contact this office.
Sincerely,
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A yce H. Grier
' ector
Enclosures:
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IE Bulletin' No.;79-26,' Revision.1 2.
. List of!Recently Issued-IE' Bulletins j3 1
CONTACT:
D. L. Caphton (215-337-5266)
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6;:: 7 Jersey-Central Power and 2
Light Company l
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.J.'T.-Carroll,. Station Manager
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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 (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 bcron from the tubes.
The cracks and boron loss have so far been gnfined to locations in the poison tubes with more than 50 percent Boron-10 (B ) local depletion.
Observed crack sizes range frcm 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) carticles and swelling of the compacted B C as helium and lithium ccocer' grow.
Once primary coolant penetrates 4
tne cladding (i.e., the crackir gogressed through the cladding wall and the helium-lithium pressures are afficient to open the crack), gron is 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).
Itwasfurtherfoundwithsiteilarcrackingbutwithlessthan50percentlocal y
depletion of 8
, that leaching did not occur even though primary coolant had penetrated the cladding.
The cracking and boron loss shorten the de;ign life of the control blade.
According to the GE crite>ia the end of design life is reached when the reactivitywgthofthebladeisreducedby10 percent,whichcorrespondsto 42 percent B depletionaveragedoverthetopquarterofthecontrolglade.
y Because of the leaching mechanism, GE has reduced the allowance for B deple-tion averaged over the top quarter of the control blade from the 42 percent value tc 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 calculated control blade worths used in the tests are based on the assumption that no boron loss has occurred.
Reduction in scram reactivity due to boron loss could increase the severity of Critical ant tiansients and could increase ents.
DUPLICATE DOCUMENT Entir'e document previously entered into system under:
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