ML19254E821

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Responds to Suppl to IE Bulletin 79-02.Oversize Bolt Holes for Concrete Expansion Bolts Found.Shear Washers Were Installed to Transfer Shear Loads on Nine Supports.Remaining 23 Temporarily Moldified.Insp Continuing
ML19254E821
Person / Time
Site: Peach Bottom, Limerick  Constellation icon.png
Issue date: 09/24/1979
From: Cooney M
PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To: Grier B
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
NUDOCS 7911020360
Download: ML19254E821 (2)


Text

, ffc, PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHI A. PA.19101 (2151 841-4o00 September 214, 1979 Mr. Boyce H. Grier Office of Inspection and Enforcement Region 1 United States Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406

Dear Mr. Grier:

As a result of the supplement to IE Bulletin 79-02, and our finding oversized bolt holes during a field inspection, our Mechanical Engineering Division has determined the effect on calculated bolt safety factors because of oversized bolt holes. By conservatively limiting the distribution of horizonta] forces to the bolts and utilizing potential friction forces developed by bolt preload, it was concluded that bolts with cal::ulated safety factors greater than four and with oversized holes would still have safety factors exceeding two.

Seismic supports with safety factors less than four were identified by Engineering and inspected. 'fhis revealed that 29 plates required field modification to assure a shear safety factor of greater than two. Consideration of the bolt hole gap criterion necessitated the installation of plate washers to transfer shear loads for approximately 2/3 of the bolts on these supports. In addition to the 29 supports referenced above, three one-plate supports were noninspectable. Therefore, shear washers were installed on these plates to assure both proper transfer of shear loading and a safety factor exceeding two.

In sumnry, nine of those supports requiring field modification because of the bolt hole gap criterion have been per=anently repaired (safety factor greater than 5).

1249 187 360 Q 7911o20

  • Mr. Boyce H. Grier Page 2 September 214, 1979 The reminirg 23 supports have been temporarily modified to provide a safety factor greater than two. These will be per=anently modified to obtain safety factors exceeding five at a later date.

Our inspection program is continuing in accordance with procedures and where necessary modifications will be made to restore the safety factors to meet the requirements of Bulletin 79-02.

Very truly yours,

  1. M. . Coone' perintendent GenerationDivision/ Nuclear cc: United Statrs Nuclear Regulatorf- Cocaission office of Inspection and Enfer'ement Division of Reactor Operations Inspection Washington, DC 20555 1249 188