ML20209J427
| ML20209J427 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 10/10/1985 |
| From: | Hufham J TENNESSEE VALLEY AUTHORITY |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8511140007 | |
| Download: ML20209J427 (3) | |
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t; TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 37401 400 Chestnut ! treet,. Tower II 85 0CT 16 P, :.ID October 10, 1985 BLRD-50-438/85-02 BLRD-50-439/85 U.S.' Nuclear Regulatory Commission
- Region II Attn:
Dr. J. Nelson Grace, Regional: Administrator 101 Marietta Street, NW, Suite 2900 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 FINAL REPORT-The subject.defici6ncy was initially reported to NRC-0IE 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 interim reports dated January 7 and July 11,
. 1984. Enclosed is our final report.
If'you have any questions, please get in touch with R. H. Shell at
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FTS 858-2688.
Very truly yours, TENNESSEE VALLEY AUTHORITY J. v. M.-,
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J. W. Hufham, MaNa 7
Licensing and Risk Protection Enclosure cc: 'Mr. James Taylor, Director (Enclosure)
Office of Inspection and Enforcement-U.S. Nuclear Regulatory Commission 2 Washington, D.C.
'20555 4
Records Center (Enclosure)'
Institute of Nuclear Power Operations 1100 circle-.75 Parkway, Suite 1500 Atlanta, Georgia 30339 8511140007 851010 PDR ADOCK 05000438
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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 NCR BLE CEB 8421 10 CFR 50.55(e)
FINAL REPORT Description of Deficiency TVA's drawing 36A0059-00-12,- revision 4, Note III.1, provides TVA's Office of
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Construction.(OC) with several tolerances for fabrication and modification of Lhaseplates and installation of anchor bolts (excluding TVA typical supports
- which are not modified by field variances). These tolerances were'primarily J
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 4
I considered in the design of the various supports. Subsequently, construction
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tolerances were incorporated into the 3GA0059-00 notes by-design personnel, without considering.the effects on support design stresses.
Y This condition was discovered due to nonconfhrmance report (NCR) WBN CEE 8419 (WBRD-50-390/84-48, WBRD-50-391/84-43) which documented a similar problem on
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Watts Bar Nuclear Plant (WBN).
Safety Implications Failure to consider the potential cumulative effects of modifying supports F
within the approved tolerance envelopes could result in an "as built" support configuration that does not meet design requirements. This condition could result in failure of the affected support (s) under. design loads and, therefore, adversely affect the safe operation of the plant.
Corrective Action
_In_ order to address-the potential impact of this deficiency on future support designs, a study has been completed which assesses the detrimental! effects of' the cumulative application of baseplate tolerances as described in the subject LNCR.
As a resultiof this study, Civil Design Standard DS-C1.7.1--which establishes current design practice--has been modified by a' Quality.
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Information Release (QIR) 1to provide _ an acceptable methodology to be used to account for permitted support attachment and anchor. location tolerances.
All TVA and current contractor support designers have'been trained to this.
-standard to assure that-the appropriate methods for' consideration of baseplate tolerances are used in the future.
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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 wore 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 require-ments.. Based on the sample results, modification of existing supports is not required.
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