ML20136J477

Forwards Safety Evaluation of Shroud Head Bolt Assembly Failures at Peach Bottom Atomic Station Unit 3, Prepared by Ge.Metallurgical Exam of Failed Bolt Revealed IGSCC Cause of Failure

ML20136J477
Person / Time
Site:	Peach Bottom
Issue date:	01/07/1986
From:	Daltroff S PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Muller D Office of Nuclear Reactor Regulation
Shared Package
ML20136J479	List: ML20136J477 ML20136J495
References
NUDOCS 8601130397
Download: ML20136J477 (2)

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l PHILADELPHIA ELECTRIC COMPANY 23ol MARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.191o1

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January 7, 1986 Docket No. 50-278 Mr. Daniel R. Muller, Director BWR Project Directorate #2 Division of Boiling Water Reactor Licensing U.S. Nuclear Regulatory Commission Washington, D.C. 20555

SUBJECT:

Peach Bottom Atomic Power Station Unit 3 Shroud Head Bolts

REFERENCE:

Meeting in Bethesda , MD, with NRC, Philadelphia Electric Company, and General Electric Company representatives dated December 19, 1985

Dear Mr. Muller:

During the current Unit 3 refueling outage, several of forty-eight shroud head bolts were found to be failed during shroud head installation. Metallurgical examination of one of the failed bolts indicates that the cause of the failures is Intergranular Stress Corrosion Cracking (IGSCC) .

This letter transmits two safety evaluations of the Peach Bottom Unit 3 shroud head bolt f ailures. Attachment 1, titled " Safety Evaluation of Shroud Head Bolt Assembly Failures at Peach Bottom Atomic Power Station Unit 3", was prepared by General Electric Company. Attachment 2, titled " Safety Evaluation for the Replacement of Twenty-Four Shroud Head Bolt Assemblies", was prepared by Philadelphia Electric Company. The evaluations, which address structural analysis considerations, the potential for additional failures, and loose parts considerations, conservatively demonstrate that twenty-four l

shroud head bolts will more than meet the plant licensing basis.

Twenty-four shroud head bolts l (every other one) have been replaced with new bolts.

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.Mr. Daniel R. Muller, Director January 7, 1986 Page 2 i

i These evaluations are being provided for review in response to an NRC request at the reference meeting.

If you have any questions or require additional information, please do not hes-itate to contact us.

Verytrulyzours,

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Attachments cc: Dr. T. E. Murley, Administrator, Region I, USNRC T. P. Johnson, Resident Site Inspector

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