ML19296A487
| ML19296A487 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 03/08/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| NUDOCS 7903280040 | |
| Download: ML19296A487 (1) | |
Text
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8 UNITED STATES NUCLEAR REGULATORY COMMISSION
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$31 PARK AVENUE KING OF PRUSSI A, PENNSYLVANI A 19406 March 8, 1979 Docket Nos. 50-245 50-336 50-423 Northeast Nuclear Energy Company ATTN: Mr. W. G. Counsil Vice President - Nuclear Engineering and Operations P. O. Box 270 Hartford, Connecticut 06101 Gentlemen:
The enclosed IE Bulletin No. 79-02 is forwarded to you for action.
A written response is required.
If you desire additional information regarding this matter, please contact this offica.
Sincerely, g Boyce H. Grier Director
Enclosures:
1.
Listing of IE Bulletins Issued in Last Twelve Months cc w/encls:
J. F. Opeka, Station Superintendent D. G. Diedrick, Manager of Quality Assurance J. R. Himelwright, Licensing Safeguards Engineer K. W. Gray, Construction Quality Assurance Lead H. R. Nims, Director of Nuclear Projects A. Z. Roisman, Natural Resources Defense Council 790328 OOVo
UNITED STATES NUCLEAR REGULATORY C0fiMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Bulletin No. 79-0E Cate: March 8, 1979 Page 1 of 3 PIPE SUPPORT BASE PLATE DESIGNS USING CONCRETE EXPANSION ANCHOR BOLTS Description of Circumstances:
While performing inservice inspections during a March-April 1978 refueling outage at Millstone Unit 1, structural failures of piping supports for safety equipment were observed by the licensee.
Subsequent licensee inspections of undamaged supports showed a large percentage of the concrete anchor bolts were not tightened properly.
Deficiency reports, in accordance with 10 CFR 50.55(e), filed by Long Island Lighting Company on Shoreham, indicate that design of base plates using rigid plate assumptions has resulted in underestimation of loads on some anchor bolts.
Initial investigation indicated that nearly fifty percent of the base plates could not be assumed to behave as rigid plates.
In addition, licensee inspection of anchor bolt installations at Shoreham has shown over fifty percent of the bolt installations to be deficient.
Vendor Inspection Audits by NRC at Architect Engineering firms have shown a wide range of design practices and installation procedures which have been employed for the use of concrete expansion anchors. The current trends in the industry are toward more rigorous controls and verification of the installation of the bolts.
The data available on dynamic testing of the concrete expansion anchors show fatigue failures can occur at loads substar.tially below the bolt static capacities due to material imperfections or notch type stress risers. The data also show low cycle dynamic failures at loads below the bolt static capacities due to joint slippage.
Action to be Taken by Licensees and Permit Holders:
For pipe support base plates that use concrete expansion anchor bolts in Seismic Category I systems as defined by Regulatory Guide 1.29, " Seismic Design Classification" Revision 1, dated August 1973 or as defined in the applicable FSAR.
1.
Verify that pipe support base plate flexibility was accounted for in the calculation of anchor bolt loads.
In lieu of supporting analysis justifying the assumption of rigidity, the base plates 700314003 8 OdP6