ML20236Q173
| ML20236Q173 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 11/17/1987 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML20236Q176 | List: |
| References | |
| NUDOCS 8711190223 | |
| Download: ML20236Q173 (7) | |
Text
n-TENNESSEE VALLEY AUTHORITY CH ATTANOOG A, TENNESSEE 374o1 SN 157B Lookout Place NOR/171987 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - UNITS 1 AND 2 - ADDITIONAL INFORMATION REQUESTED BY NRC ON FUSE REPLACEMENT
References:
1.
Letter from R. L. Gridley to NRC dated September 16, 1987, "Sequoyah Nuclear Plant (SQN) - Follow-up to the Part 21 Report on Bussman Corporation MIS-5 Fuses" 2.
Letter from L. M. Nobles to NRC dated July 21, 1987,
" Tennessee Valley Authority - Sequoyah Nuclear Plant Unit 1 -
Docket No. 50-327 - Facility Operating License DPR Reportable Occurrence Report SQRO-50-327/87030" This letter provides NRC with additional information concerning the SQN Fur.e Replacement Program, associated with the Littlefuse FLAS-5 fuse failures of lots 2 and 3.
The request for additional information was telecopied to the site by NRC on October 2,1987. NRC expressed the need for more information than was provided in reference 1 to permit them to provide a technical evaluation and resolution of the fuse replacement problem originally identified to NRC in reference 2.
Although TVA addressed these questions in a telephone conversation with NRC on October 6, 1987, this letter will provide NRC the information requested to allow them to resolve this issue. containa the questions transmitted to TVA by NRC and TVA's response. Also included in enclosure 1 are the TVA laboratory test reports associated with the testing performed by TVA on these fuses. TVA believes this information will aid NRC in their evaluation of this problem and allow them to successfully close this issue.
If there are any additional questions concerning this issue, please telephone M. R. Harding at (615) 870-6422.
Very truly yours, TENNESSEE VAL EY AUTHORITY 8711190223 871117 DR ADOCK 05000 7
R. Gridley, D ector Nuclear Licensing and Regulatory Affairs
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Enclosures cc:
see page 2 I \\
An Equal Opportunity Employer
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o U.S.-Nuclear Regulatory Commission
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cc (Enclosures):
l Mr. G. G. Zech,' Assistant Director for Inspection Programs Office of Special Projects U.S. Nuclear Regulatory Commission 101 Marietta Street, NW, Suite 2900 1
Atlanta, Georgia' 30323 j
Mr. J. A. Zwol.inski, Assistant Director for Projects Division of TVA Projects i
j Office of Special Projects U.S. Nuclear Regulatory Commission 4350 East-West Highway.
1 EWW 322
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Bethesda, Maryland 20814 j
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Sequoyah Resident Inspector Sequoyah Nuclear Plant j
2600 Igesu Ferry. Road l
Eoddy Daisy, Tennessee 37379 l
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ENCLOSURE 1 3
FUSE REPLACEMENT - REQUEST FOR ADDITIONAL INFORMATION i
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4 ENCLOSURE 1 SEOUOYAH NUCLEAR PLANT UNITS 1 AND 2
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i TENNESSEE VALLEY AUTHORITY j
l FUSE REPLACEMENT - RLOUEST FOR ADDITIONAL INFORMATION The following additional information is provided in response to a request from NRC on the Sequoyah Nuclear Plant Fuse Replacement Program.
Request:
"The LER 87-030 submitted by the TVA on July 21, 1987, states that. extensive testing is being done by TVA to determine the root cause of the failure.
l Provide the test reports documenting test plan, test results and resolution'of any anomalies for staff review."
Response: details elevated temperature and mechanical tests done at TVA's Central Laboratories Services Branch (CLSB) to investigate the cause of FLAS-5 fuse failure (lots 2 and 3).
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l Request:
"Also, the LER 87-030 submitted by TVA on July 21, 1987, states that extensive testing is being done by Littlefuse. Inc., and TVA regarding the acceptability I
of the subsequent lots of FLAS-5 fuses.
Provide the test reports documenting
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test plan, test result and resolutions of any anomalies for staff review.
Also provide details of changes (material and process) made on subsequent lots of FLAS-5 fuses and explain how these changes improve the reliability of the fuses."
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Response
Tests were performed on FLAS-5 fuses (lots 4 and higher) by the fuse manufacturer in accordance with requirements of Underwriters Laboratories (UL) i standards and TVA's procurement documents.
In addition, tests were also l
performed on the above fuses.at TVA's Singleton' Materials Engineering Laboratories and CLSB.
These tests were performed to establish the expected life of the solder junction and to measure the fuse solder joint temperature i
rise ovet ambient temperature for various load currents.
Attachments 2 and 3 3 detail the results of these tests.
Based on this information (the expected life test 3 and fuse temperature rise tests) together with knowledge of fuse loading and ambient temperature, a basis is provided for predicting service l
life of the solder junction to be 80-month average and 23-month minimum.
Regarding the material, the solder material composition was [ hanged from bismuth to cadmium on fuse lots 4 and higher by the manufacturer as part of l
his product development. This change was made to improve the fuse characteristics; creep failure had not been experienced at this time.
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O Request:
"Does Littlefuse agree with TVA on the failure analysis on the FLAS-5 (lots 2 and 3) fuses? Has TVA checked with.Littlefuse about the application and experience of other utilities with the FLAS-5 (lots 2 and 3) fuses?"
Response
TVA informally discussed the failure analysis of the lots 2 and 3 FLAS-5 fuses i
with Littlefuse, and they are in general agreement with TVA on the root cause for the failure.
As discussed on October 6,1987, with NRC on this subject, FLAS-5 fuses are unique to TVA; and application / experience review from other utilities on these fuses is not necessitated.
Request:
" Update the failure of FLAS-5 fuses (all lots) since the LER was issued on July 21, 1987 and explain if these failures have any effect on the fuse replacement program."
Response
Subsequent to the replacement of FLAS-5 fuses (lots 2 and 3) with lots 4 and higher, it has been found that these cadmium fuses have blown because of short-circuit conditions and not creep failure as experienced with lots 2 and 3.
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Attachments - " Elevated Temperature Test Report and Mechanical Pull Test Report for Littlefuse FLAS 5, 5 Amp Fuses Lot Nos. 002, 003, 004, and 006" (E13 871013 001) - "Sequoyah Nuclear Plant Littlefuse Type FLAS-05 Fuses Predicted Service Life SME-MET-87-901" (B46 870928 001) - " Temperature Measurement Report for the Long Term Current Test on Littlefuse, FLAS-5, 5 Amp Fuses" (E13 871001 167) i
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" Elevated Temperature Test Report and Mechanical Pull Test Report for Littlefuse FLAS-5, 5 ' Amp Fuses Lot Nos.- 002, 003, 004, and 006" Na a
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871013 001 es.mm srurus anvenswer El3 Memorandum TENNESSEE VALLEY AUTHORITY W. S. Raughisy, Chief. Electrical En61neuring Branch, DNE, W8C165 C.K 70 l
Richard L. Morley, Chief. Central Laboratories Services Branch, LA PSC 1-C FROM DATE
.: October 13, 1967 t
SUBJECT:
SPECIAL TESTS ON'LITTELPUSE FLAS-5 FUSES Pursuant to your request, attached is the intermediate report containint l
the results of the elevated temperature and mechanical pull test that l
Central Laboratories servicen Branch (CLSB) performed on Littelfuse type PLAS-5 fuses for Sequoyah Nuclear Plant.
We hope that the report will assist you and look forwarc to continuing to i
support your future needs.
Should you have any questions or additional needs, please feel free to contact CLSB.
RLM:EC Attachment l
cc (Attachtnent):
RIMS, HR 4N 72A-C Xen Greene, WB Clat C-X W. G. Jones. LA PSC 1-C l
J. A. Wormaley, LA PSC 1-C 0658E-2 4
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