ML19296A467
| ML19296A467 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 03/08/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Humphreys L GULF STATES UTILITIES CO. |
| References | |
| NUDOCS 7903280004 | |
| Download: ML19296A467 (1) | |
Text
7t94 pa "'o iq^>*
r UNITED STATES g
NUCLEAR HEGULATORY COMMISSION
[ f *.
E o HEGION IV 7.
E G11 RYAN PLAZA DRIVE, SUITE 1000 o.,f.['4]
ARLINGTON, TEXAS 76011
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ur f4 arch 8, 1979 In Reply Refer To:
RIV Docket flos.
50-458/IE Bulletin fio. 79-02 50-459/IE Bulletin flo. 79-02 Gulf States litilities Attn: fir. L. L. Humphreys Senior Vice President, Energy Development Post Office Box 2951 Beaumont, Texas 77704 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,
/
1/
U.
- f,l.lll: <j.j!.f Karl V. Seyfrit Director
Enclosure:
IE Bulletin fio. 79-02 790328 0 0 0 4
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 PIPE SUPPORT BASE PLATE DESIGNS USING CONCRETE EXPANSION ANCHOR BOLTS Description of Circumstances:
While performing 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 Compar.y 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 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 an'chors
~
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 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 790314003S DY