ML20133P007
| ML20133P007 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 06/25/1985 |
| From: | Hufham J TENNESSEE VALLEY AUTHORITY |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8508140101 | |
| Download: ML20133P007 (2) | |
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i TENNESSEE VALLEY AUTHORITY CH AT TANOOGA, TENNESSEE 37401 400 Chestnut Street Tower II June 25, 1985 BLRD-50-438/81-56 05 JUL 2 ej:07
.BLRD-50-439/81-58 U.S. Nuclear Regulatory Comission 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 A" 2 - REACTOR COOLANT SYSTEM SUPPORTS AND RESTRAINTS - BOLT TORQUES - BLha-50-438/81-56, BLRD-50-439/81 FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector R. V. Crlenjak on August 24, 1981 in accordance with 10 CFR 50.55(e) as NCR BLN NEB 8111. This was followed by our interim reports dated September 24 and December 7,1981; March 10, June 7, and December 13, 1982, June 29, 1983; and June 24, 1985. Enclosed is our final report. The report concludes that TVA no longer considers 10 CFR 50.55(e) applicable to this item.
If you have any questions concerning this matter, please get in touch with R. H. Shell at FTS 858-2688.
Very truly yours, T
SEE VALLEY AUTHORI J. W. Hufham, Manager Licensing and Risk Protection Enclosure oc (Enclosure):
Mr. James Taylor, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Comission Washington, D.C.
20555 Mr. H. B. Barkley 205 Plant Project Services P.O. Box 10935 Lynchburg, Virginia 24505 Records Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 8508140101 850625 PDR ADOCK O y8
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S i t 16MG An Equal Opportunity Employer g
ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 REACTOR COOLANT SYSTEM SUPPORTS AND RESTRAINTS - BOLT TORQUE NCR BLN NEB 8111 BLRD-50-438/81-56, BLRD-50-439/81-58 10 CFR 50.55(e)
FINAL REPORT Description of Deficiency Babcock and Wilcox (B&W), Lynchburg, Virginia, specified ASME SAS40 classes 1 and 2 material and a preload of 70 percent of ultimate tensile strength for many of the reactor coolant system (RCS) anchor bolts for supports and restraints. These materials have a minimum yield strength of 150 kai and 140 kai, respectively. However, it has been documented that stress corrosion cracking (SCC) is a potential failure mode for high-yield strength (120 ksi) low-alloy steel bolting material subjected to appreciable steady-state loads (generally preload in the case of supports and restraints) and typical reactor containment corrosive environments (humid air or borated water on occasion) for extended periods of time.
When the Bellefonte Nuclear Plant (BLN) supports were being designed (the early 1970s), the general philosophy of support design (basically an AISC approach with relatively large preloads) did not take into account SCC as a potential failure mode.
Safety Implications The Atomic Industrial Forum / Metals Property Council (AIF/MPC) Task Group on Bolting developed a screening criteria for component support bolting which established that bolting with a minimum specified yield strength of 180 ksi or less did not require further evaluation (this information was submitted to the NRC as Appendix I, Task 14 of the Task Group's bolting program enclosed with Richard M. Eckert's letter from the AIF to R. H. Vollmer dated July 19, 1983). Based on this criteria, TVA concluded that a generic evaluation of the support and restraint bolting is not warranted at BLN since the minimum specified yield strength of the material at BLN is not greater than 150 kai.
Also, since TVA has not experienced failures of the support and restraint bolting, case-by-case evaluation via a plant-specific plan was similarly not warranted. However, because the minimum specified yield ~ strength of the SAS40 class 1 bolting is at the dividing line of 150 kai, TVA performed a case-by-case review of class 1 bolting using the certified material test records (CMTRs) of each heat of the SAS40 class 1 bolting used and a seven-point CMTR review criteria established by APTECH Engineering Services. Each heat met all seven of the criteria and again demonstrated that the bolting material is acceptable for use "as is." Therefore, TVA concludes that there is ne condition which could adversely affect plant safety. As such, TVA no longer considers 10 CFR 50.55(e) applicable to this item.
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