ML19253C365
| ML19253C365 | |
| Person / Time | |
|---|---|
| Site: | 05000516, 05000517, Shoreham File:Long Island Lighting Company icon.png |
| Issue date: | 11/20/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Wofford A LONG ISLAND LIGHTING CO. |
| References | |
| NUDOCS 7912050243 | |
| Download: ML19253C365 (1) | |
Text
CfQ / ft/J nt 8[} ). Rtcy)o UNITED STATIES
((g NUCLEAR REGULATORY COMMISSION g
agg%j.
REGION I o,, 'fg6 g
631 PARK AVENUE
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,o XtNG OF PRUSSIA, PENNSYLVANIA h406 Docket Nos. 50-322 EDV 2 4 is3 50-516 50-517 Long Island Lighting Company ATTN:
Mr. Andrew W. Wofford Vice President 175 East Old Country Road Hicksville, New York 11801 Gentlemen:
The enclosed IE Bulletin 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, NM, b
oyce H. Grier
[Trector
Enclosures:
1.
List of Recently Issued IE Bulletins CONTACT:
D. L. Caphton (215-337-5266) cc w/encls:
J. P. Novarro, Project Manager Edward M. Barrett, Esquire Edward J. Walsh, Esquire T. F. Gerecke, Manager, Engineering QA Department 1503 027 7912050 2 9-3
ENCLOSURE 1 UNITED STATES SSINS:
6820 NUCLEAR 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 B0RON LOSS FROM BWR CONTROL BLADES Description of Circumstances:
The Ge...ral 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 losshavesofarbeenggnfir.edtolocationsinthepoisontubeswithmorethan 50 percent Borond 0 (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 compac.ed g
B C as helium and lithium concentrHtions grow.
Once primary coolant penetrates g
tne cladding (i.e., the cracking has progressed through the cladding wall and thehelium-lithiumpressuresaresufficienttoopenthecrack),ggronis 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).
Itwasfurtheryoundwithsimilarcrackingbutwithlessthan50percentlocal 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 af the control blade.
Accoroing to the GE criteria the end of design life is reachta when the reactivity wggthofthebladeisreducedby10 percent,whichcorrespondsto42 percent B
depletionaveragedoverthetopquarterofthecontrolflade.
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 demonstratad by snatdown margin tests after refueling, the cal tests are based on the assumption tha in scram reactivity due to boren loss Power Rallo (CPR) reductions during t DUPLICATE DOCUMENT the consequences of control rod drop Entire document previously entered into system under:
ANO d
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