ML20092A198
| ML20092A198 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 06/12/1984 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8406190083 | |
| Download: ML20092A198 (2) | |
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 37401 400 Chestnut Street Tower II June 12, 1984 BLRD-50-438/84-10 BLRD-50-439/84-09 U.S.~ Nuclear Regulatory Commission Region II Attn:
Mr. James P. O'Reilly, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303
Dear Mr. O'Reilly:
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 -0VERTORQUED CONDUIT AND CONDUIT BOX SUPPORT BOLTS - BLRD-50-438/84-10, BLRD-50-439/84 REVISED FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector P. E. Fredrickson on January 24, 1984 in accordance with 10 CFR 50.55(e) as NCR 2734.. This was followed by our interim report dated February 17, 1984 and our final report dated May 3,1984. Enclosed is our revised final repor t.
TVA does not now consider the subject renconforming condition adverse to the safe operation of the plant. Therefore, we will amend our records to delete the subject nonconformance as a 10 CFR 50.55(e) item.
If you have any questions, please get in touch with R. H. Shell at FTS 858-2688.
Very ter y yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, nager Nuclear Licensing Enclosure cc:
Mr. Richard C. DeYoung, 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 gp Atlanta, Georgia 30339 PDR ADOCK 05000438 OiTN 8406190083 840612 8
PDR 1
1983-TVA 5OTH ANNIVERSARY g
g An Equal Opportunity Employer
ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 OVERTORQUED CONDUIT AND CONDUIT BOX SUPPORT BOLTS BLRD-50-438/84-10, BLRD-50-439/84-09 NCR 2734 10 CFR 50.55(e)
REVISED FINAL REPORT Description of Deficiency While performing an inspection of attachment bolts on electrical conduit, conduit boxes, and cable trays, an electrical quality control (EQC) unit inspector found that some of the bolts had apparently been overtorqued.
This was originally determined by measuring the necessary breakaway torque of the bolts (i.e., the torque necessary for the bolt to begin moving from its tightened-down position).
This appears to' be due to the fact that TVA's Division of Engineering Design (EN DES) did not supply Bellefonte Nuclear Plant (BLN) Construction
. with a maximum torquing limit on some drawings for bolts used to install conduits in safety-related areas when these bolts were originally installed Sometime after the original installation, EN DES reissued some time ago.
the drawings with a maximum torquing limit. Some of these bolts were found to be overtorqued when measured by these new values.
Safety Implications Since this concern was originally identified, EN DES has determined that the bolts can be used-as-is providing bolt failure does not occur during (If bolt failure does occur, the bolts will be replaced.) This tightening.
position is based on technical manuals and references used by TVA (references 1 through' 3 listed below). Maximum stres. is seen only at the If bolt failure does not occur at initial time of initial torquing.
torquing, it will not occur because the working load on the bolt will never exceed its prostress load. Provided that there is no material failure and all other parameters have been properly specified, the torqued-down bolt will continue to function as designed. Therefore, this condition could not As such, TVA no have adversely affected the safe operation of the plant.
longer considers this item to be reportable under 10'CFR 50.55(e).
In addition, breakaway torque has been determined not to be an adequate indication of the real torque in a bolt and should not be used as a Torquing values should be determined during initial measurement.
installation only. Additional testing done by BLN Construction has resulted in the determination that breakaway torque cannot be used to confirm torque applied during installation. Based on this supporting information, BLN Construction will no longer utilize the follow-up breakaway torque method of checking conduit bolting.
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"Halpful Hinta... on Partening with Screws, Nuts, cnd Bolta' by Rur. coll, Burdsall, and Wird Bolt and Nut Company, Third Editien, pago 7 2.
" Structural Steel Design" by Lambert Tall, Second Edition, pages 608-610 3
1979 Annual Book of ASTM Standards l
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