ML19296A469
| ML19296A469 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 03/08/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Gary R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| References | |
| NUDOCS 7903280008 | |
| Download: ML19296A469 (1) | |
Text
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'o NUCLE AR REGULATORY COMMISSION
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REGION IV n
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. 1 611 HYAN PLAZA DRIVE, SUITE 1000
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ARLINGTON, TEXAS 76011 5
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- a' March 8, 1979 In Reply Refer To:
RIV Docket flos.
50-445/IE Bulletin No. 79-02 50-446/IE Bulletin No. 79-02 Texas Utilities Generating Company ATTN:
Mr. R. J. Gary, Executive Vice President and General Manager 2001 Bryan Tower Dallas, Texas 75201 Gentlemen:
The enclosed Bulletin 79-02 is forwarded to you for action. A written response is required.
If you desire additional information regarding this..atter, please contact this office.
Sincerely,
- l.
~ k k "b
' Y Karl V. Seyfrit}-
Director
Enclosure:
IE Bulletin No. 79-02 7903280DO6
UNITED STATES NUCLEAR REGULATORY COMMISSION 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Bulletin No. 79-02 Date: March 8, 1979 Page 1 of 3 PIPF SUPPORT BASE PLATE DESIGNS USING CONCRETE EXPANSION ANCHOR BOLTS Description of Circumstances:
While perforrr.ing inspections during a March-April 1978 refueling outage at Millstone Unit 1, structural railures 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.
Deficie cy 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 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 p.'ctices and installation procedures which have been employed for the use
- s. 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 substantially 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 conc _ce 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 ancl.ar bolt loads.
In lieu of supporting analysis justifying the assumption of rigidity, the base plates
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