ML20080H061
| ML20080H061 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 02/03/1984 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NCR-2182, NUDOCS 8402140071 | |
| Download: ML20080H061 (2) | |
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TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 37401 h00 Chestnut Street Tower II February 3,1984 BLRD-50-438/83-17 BLRD-50-439/83-13 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 - CANNOT IDENTIFY GRADE OF NUTS i
BECAUSE OF ORIENTATION - BLRD-50-438/83-17, BLRD-50-439/83 FINAL REPORT The subject deficiency was initially mported to NRC-0IE Inspector P. E. Fredrickson on January 26, 1983 in accordance with 10 CFR 50.55(e) as NCR 2182. This was followed by our interim reports dated February 24, June 14 and September 26, 1983 Enclosed is our final report.
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, Manager Nuclear Licer.;ing Enclosure oc (Enclosure):
Mr. Richard C. DeYoung, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Records Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 COM OFFICIA 8402140071 e40203 DR ADOCK 05000 38 y
gg An Equal Opportunity Employer
ENCLOSURE a
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 CANNOT IDENTIFY GRADE OF NUTS BECAUSE OF ORIENTATION BLRD-50-438/83-17, BLED-50-439/83-13 NCR 2182 10 CFR 50.55(e)
FINAL REPORT Description of Deficiency The grade of nut on approximately 50 percent of all high strength bolted connections installed _ in the plant cannot be idsstified since the nuts were installed with the grade markings faced against the structural member.
Nuts were installed by craft personnel without any attempt being made to place markings outward for easy identification. The procedures do not specifically state that the nuts are to be turned outward for identifica-tion, although this must be done in order to verify the grade of material.
The high strength nuts in question are very similar to a heavy-hex low strength nut which has no identifying markings and is in use at the project. Because of a lack of segregation in the field, the possibility exists that low strength nuts have been installed in place of high strength nuts. The cause of this deficiency has been determined to be the lack of procedural guidance for the installation of high strength nuts.
Safety Implications Since the nuts which have been installed cannot be positively identified as high strength due to their orientation, the possiblity exists that some are low strength. The possible use of low-strength nuts renders the integrity of safety-related connections questionable. Failure of these connections during a seismic event would adversely affect safe plant operations.
o Corrective Action TVA's Division of Construction (CONST) and Singleton Materials Laboratory have completed a random sampling of over 600 high-strength connections in Category I structures. The sampling indicated that less than 10 percent (a total of 60) of the high-strength nuts were turned with their grade markings inward rather than the 50 percent originally estimated. Further investigation of the unidentifiable nuts found only one of the nuts rejectable based on it not being of the specified material. The nut was a 7/8 inch A325 bolted connection. This nut was tested and found to fail at a value of 143 KSI, only slightly less than the 144 KSI minimum required.
The minimum tensile strength of a 7/8 inch A325 bolt is 120 KSI.
Therefore, the A325 bolted connection from which the rejected nut was taken was not unsafe since failure would have, by design values, taken place in the body of the bolt and not the nut. Based on this information, the nonconformance report (NCR) was revised and resubmitted to TVA's Division of Engineering Design (EN DES) for disposition. EN DES resolved the revised NCR as follows:
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1.
Ths random sampling results indicata with a 95-psroent confidenca level that tha as-specified high-strength nuts htva been installed.
2.
All remaining unmarked nuts are acceptable as installed.
3 No further sampling is required.
NCR 2182 has been closed. To prevent recurrence of this deficiency, BNP-QCP-2.15, " Structural Steel Installation," has been revised to clearly state that the grade of nut must be identifiable when installed.-
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