ML20084S312
| ML20084S312 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 05/03/1984 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NCR-2734, NUDOCS 8405240313 | |
| Download: ML20084S312 (3) | |
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TENNESSEE VALLEY AUTHORITY CHATTA GA, TENNESSEE 37401 40 e t ut Street Tower II 1
i BLRD-50-438/841to$
sy May 3,1984 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 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.
Enclosed is our final report.
TVA does not now consider the subject nonconforming 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 truly 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 Atlanta, Georgia 30339 OFFICIAL cop ['
i 0405240313 040003 PDR ADOCK 05000430 1983-TVA SOTH ANNIVERSARY An Equal Opportunity Employer a
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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)
FINAL REPORT Descriptirn of Deficiency i.
While performing an inspection of attachment bolts on electrical conduit, conduit boxes, and cable trays, an electrical quality control (EQC) unit i
inspector found that some of the bolts had apparently been overtorqued.
j This was originally determined by measuring the necessary breakaway torque
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of the bolts (i.e., the torque necessary for the bolt to begin moving from its tightened-down position).
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i-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 maxirmam torquing limit on some drawings for bolts used to install conduits in safety-related areas when these bolts were originally installed some time ago. Sometime after the original installation, EN DES reissued the drawings with a maximum torquing limit. Some of those bolts were found l
to be overtorqued when measured by these new values.
i Safety Implications Since this concern was originally identified, EN DES has determined that i
the bolts can be used-as-is providing bolt failure does not occur during tightening.
(If bolt failure does occur, the bolts will be replaced.) This position. is based on technical manuals and references used by TVA (references 1 through 3 listed below). Maximum stress is seen only at the time of initial torquing. If bolt failure does not occur at initial torquing, it will not occur because the working load on the bolt will never
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exceed its prestress load. Provided that there is no material failure and all other parameters have been properly specified, the torqued-down bolt will continue to fbnction as designed. Therefore, this condition could not l
have adversely affected the safe operation of the plant. As such, TVA no l
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 l
indication of the real torque in a bo?.t and should not be used as a measurement. Torquing values should be determined during initial j
installation only.- Additional testing done by BLN Construction has resulted in the determination that breakaway torque cannot be used to l
confirm torque applied during installation. Based on this supporting i
information, BLN Constructior. is mvising quality control procedure (QCP) $
l 3 2, " Conduit Systems," to mnove the follow-up breakaway torque method'of checking conduit bolting. Thh: mvision will now require 100-percent inspection of conduit bolting during installation by quality control j
inspectors observing torque applied by craft.
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