ML19261C081
| ML19261C081 | |
| Person / Time | |
|---|---|
| Site: | Catawba, Perkins, Cherokee  |
| Issue date: | 03/08/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Dail C DUKE POWER CO. |
| References | |
| NUDOCS 7903140537 | |
| Download: ML19261C081 (1) | |
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MAR 81979 yy Y@/
In Reply Refer To:
RII:JPO yg 50-413, 50-414 50-488, 50-489 t/9.:3 50-490, 50-491 50-492, 50-493 Duke Power Company Attn:
Mr. L. C. Dail, Vice President Design Engineering P. O. Box 33189 Charlotte, North Carolina 28242 Gentlemen:
The enclosed Bulletin 79-02 is forwarded to you for action. A written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, u.6 ames P. O'Reilly D ector
Enclosure:
IE Bulletin No. 79-02 cc w/eacl:
D. G. Beam, Project Manager Catawba Nuclear Station P. O. Box 223 Clover, South Carolina 27910 J. T. Moore, Project Manager Chsrokee Nuclear Station P. O. Box 422 Gaffuey, South Carolina 293t0 7908140537
UNITED STATES NUCLT 't REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 March 8, 1979 hMe.-79-Oh PIPE SUPPORT BASE PLATE DESIGNS USING CONCRETE EXPANSION ANCHOR BOLTS Description of Circumstances:
While performing instavice inspections daring 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.
Def Aciency reports, in accordance with 10 CFR 50.55(e), filed by Long Island Lighting Company on Shoreham Unit 1, indicate that design of base plates using rigid plate assumptions has resulted in underestima-tion 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 installatiops 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 expan:ien en: hors.
The current trends in the industry are toward mora rigorous controls and verification of the installation of the bolts.
The data available on dynamic teating of the concrete expansion anchors shov f atigue failures can occur at loads substantially below the bolt stat?.c capacities due to material imperfections or notch type stress riser. 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 definad 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 1 of 3