ML20133P604
| ML20133P604 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 07/11/1985 |
| From: | Hufham J TENNESSEE VALLEY AUTHORITY |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| BLN-CEB-8421, NUDOCS 8508140385 | |
| Download: ML20133P604 (2) | |
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374o1 1630 Chestnut Street Tower II July 11, 1985 BLRD-50-438/85-02 BLRD-50-439/85-02 U.S. Nuclear Regulatory Commission Region II Attn:
Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 g
Atlanta, Georgia 30323
Dear Dr. Grace:
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - SUPPORTS MAY BE DEGRADED BY USE OF INSTALLATION TOLERANCES - BLRD-50-438/85-02, BLRD-50-439/85 SECOND INTERIM REPORT The subject deficiency was initially reported to NRC-OIE Inspector S. Weise on December 6, 1984 in accordance with 10 CFR 50.55(e) as NCR BLN CEB 8421. This was followed by our first interim report dated January 7, 1985.
Enclosed is our second interim report. We expect to submit our next report on or about September 6, 1985.
If you have any questions, please get in touch with R. H. Shell at FTS 858-2688.
Very truly yours, TENNESSEE VALLEY AUTHORITY pystLA.
. W. Hufham, Manager Licensing and Risk Protection Enclosure cc:
Mr. James Taylor, Director (Enclosure)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Records Center (Enclosure)
Institute of Nuclear Power Operations 1100 circle 75 Parkway, suite 1500 Atlanta, Georgia 30339 hD q
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An Equal Opportunity Employer
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ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 SUPPORTS MAY BE DEGRADED BY USE OF INSTALLATION TOLERANCES BLRD-50-438/85-02, BLRD-50-439/85-02 BLN CEB 8421 10 CFR 50.55(e)
SECOND INTERIM REPORT Description of Deficiency TVA's drawing 36A0059-00-12, revision 4, Note III.1, provides TVA's Office of Construction (OC) with several tolerances for fabrication and modification of baseplates and installation of anchor bolts (excluding TVA typical supports which are not modified by field variance). These tolerances were primarily given to allow OC to resolve problems with interference of expansion anchor bolts with reinforcing steel. The cumulative effects of the use of these tolerances may result in significant increases in baseplate stresses and anchor bolt loads. The potential increases due to cumulative effects were not considered in the design of the various supports.
Interim Progress In accordance with the approach outlined in our first report, a study has been completed which assessed the detrimental effects of the cumulative application of baseplate tolerances. As a result of this study, current design practices are being revised to account for the use of these tolerances on future pipe support designs.
For supports already installed, a statistical sampling of existing field installation was made to determine actual field use of baseplate tolerances and existing factors of safety. Ninety-eight expansion anchored pipe supports were randomly selected and inspected. Supports which utilized installation tolerances were reanalyzed. Factors of safety for all 98 supports are consistent with design requirements (self-drilling expansion anchor factor of safety greater than 5; wedge bolt factor of safety greater than 4).
This sample provides a 95-percent confidence level that less than 3-percent of the supports have factors of safety less than design requirements. Based on the sample results, modification of existing supports is not required.
TVA will provide further information in our next report expected to be submitted on or about September 6,1985.