ML15218A142
| ML15218A142 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 07/28/1995 |
| From: | Berkow H NRC (Affiliation Not Assigned) |
| To: | Hampton J DUKE POWER CO. |
| References | |
| TAC-M92779, NUDOCS 9508040272 | |
| Download: ML15218A142 (4) | |
Text
M411TED STATES LA REGAULATORY COMMISSION WASHINGTON, D.C. 20555-001 July 28, 1995 Mr. J.
. Hampton Vice Prcsiden't, Oconse Site Duke Power Company P. 0. Rox 1439
- Seneca, SC 296790
SUBJECT:
REQUEST FOR RELIEF 95 OCONEE UNIT 3 (TAC NO. M92779)
Dear Mr. Hampton:
On July 5, 1995, you submitted, for NRC approval, a relief request seeking a delay for one outage in performing the code-required reactor vessel nozzle examinations. This request can be traced back to your two original relief requests made on September 13, 1984, to use ultrasonic examination of the reactor vessel nozzles from the inside diameter instead of from the outside diameter as required by Table IWB-2500-1 of Section XI of the American Society of Mechanical Engineers Code. The NRC granted the relief requests with the condition that Duke Power Company (DPC) demonstrate the capability to detect surface cracks using this alternate technique. The NRC has not found the demonstration of this alternate technique acceptable pending the resolution of a few technical concerns.
A series of activities involving the NRC, DPC, and the Babcock and Wilcox Owners Group (B&WOG) took place since then, leading to the recent NRC approval of a B&WOG Topical Report, BAW-2228, "Fracture Mechanics Assessment of Postulated Outer Surface, Semi-elliptical Circumferential RV Nozzle-to-Pipe Weld Flaws" on December 2, 1994. This Topical Report demonstrated that an adequate margin exists between the bounding allowable flaw size and the minimum detectable flaw size for several nozzle welds and resolved the last technical issue in this effort. The NRC requires each licensee that references BAW-2228 as the basis for the requesting relief from the external surface examination to confirm the plant-specific applicability of BAW-2228 to its plant by demonstrating (1) the input stresses under normal/upset and emergency/faulted conditions shown in Table 1 (BAW-2228) for its plant are the result of using the bounding transient in the analysis, and (2) the material in its inlet, outlet, and core flood nozzles is either A508 Class 2 carbon steel or SA 336 (316) stainless steel.
The plant-specific applicability of BAW-2228 was submitted by you for the Oconee units on June 12, 1995. It was mentioned in a B&W letter attached to your June 12 submittal that, "a more appropriate, but still conservative, fracture mechanics solution methodology was determined to be applicable to the analysis.',' Based on this information and the magnitude of the change in the maximum allowable flaw depth for at least one case listed there, the staff decided that the approved Topical Report BAW-2228 is no longer applicable and 9508040272 950728 PDR ADOCK 05000287 P
Mr. J. W. Hampton, J ri
-2 staff review is required for BAW-2228, Revision 1. Considering the time needed for Revision 1 finalization and the needed time for staff review, you made this new request for relief from performing the code-required surface examinations until the next scheduled outage for Unit 3 scheduled for November 1996.
The NRC staff has completed its review of your request and supporting information. The staff reviewed the revised fracture mechanics methodology attached to your July 5 submittal and found it is more rigorous than the previous one. The B&WOG reexamined Assumption 4 regarding gross-section membrane and bending stresses in BAW-2228 and removed it from the fracture mechanics analysis in the revised version. As a result, the stress-intensity factor solutions used by the B&WOG to generate the applied K, have been changed from Raju Newman's work related to a pipe model to that related to a plate model.
Since one simplification has been removed from BAW-2228, this revised methodology represents an upgrade and should give more realistic results. For Oconee 3, the revised maximum allowable flaw depths for nozzle to-safe end weld (core flood nozzle), safe end-to-pipe weld (core flood nozzle), and nozzle-to-pipe weld (outlet nozzle) are 79% for all three welds, as opposed to 93%, 100%, and 65% generated by the old methodology. Although the new value represents less margin, it is still higher than the bounding allowable limit reported in BAW-2228. Hence, the revised results are acceptable. The NRC staff has determined that the performance of the alternate testing provides an acceptable level of quality and safety for the interim period specified (End-of Cycle 16 outage). Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), your request to delay the surface examinations for Oconee Unit 3 is authorized. If you have questions regarding this matter, contact me at (301) 415-1495.
Sincerely, rig neT 's ned by:
Hert N. Berkow, Director Project Directorate 11-2 Division of Reactor Pro4netsT/II Office of Nuclear Reactor Regulation Docket No. 50-287 cc: See next page DISTRIBUTION Docke OGC PUBLIC E. Jordan PD22 Reading File G. Hill (2)
W. Russell/F. Miraglia ACRS (4)
R. Zimmerman G. Tracy R. Spessard E. Merschoff RII J. Lieberman J. Zwolinski S. Varga R. Crlenjak, RH1 T. Sullivan S. Sheng K. Wichman DOCUMENT NAME: G:\\OCONEE\\9503LTR To receive a copy of this docume Indicate In the box: "C" = Copy without attachmentlephsue "E"
Copy with attachmentlenclosure "N" = No copy OFFICE LA:PD22:D E
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Mr. J. W. Ilaigqtorf., Jr.-
staff reviev2 is required for BAW-2228, Revision 1. Considering the time needed for Revision 1 finalization and the time needed for staff review, you made this new: request for relief from performing the code-required surface examinations until the next scheduled outage for Unit 3 scheduled for November 1996.
The NRC staff has completed its review of your request and supporting information. The staff reviewed the revised fracture mechanics methodology attached to your July 5 submittal and found it is more rigorous than the previous one. The B&WOG reexamined Assumption 4 regarding gross-section membrane and bending stresses in BAW-2228 and removed it from the fracture mechanics analysis in the revised version. As a result, the stress-intensity factor solutions used by the B&WOG to generate the applied K, have been changed from Raju Newman's work related to a pipe model to that related to a plate model.
Since one simplification has been removed from BAW-2228, this revised methodology represents an upgrade and should give more realistic results. For Oconee 3, the revised maximum allowable flaw depths for nozzle to-safe end weld (core flood nozzle), safe end-to-pipe weld (core flood nozzle), and nozzle-to-pipe weld (outlet nozzle) are 79% for all three welds, as opposed to 93%, 100%, and 65% generated by the old methodology. Although the new value represents less margin, it is still higher than the bounding allowable limit reported in BAW-2228. Hence, the revised results are acceptable. The NRC staff has determined that the performance of the alternate testing provides an acceptable level of quality and safety for the interim period specified (End-of Cycle 16 outage).
Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), your request to delay the surface examinations for Oconee Unit 3 is authorized. If you have questions regarding this matter, contact me at (301) 415-1495.
Sincerely, Herbert N. Berkow, Director Project Directorate 11-2 Division of Reactor Projects-I/II Office of Nuclear Reactor Regulation Docket No.
50-287 cc: See next page
Mr. J. W. Hampton Duke Power Company Oconee Nuclear Station cc:
A. V. Carr, Esquire Mr. Ed Burchfield Duke Power Company Compliance 422 South Church Street Duke Power Company Charlotte, North Carolina 28242--0001 Oconee Nuclear Site P. 0. Box 1439 J. Michael McGarry, III, Esquire Seneca, South Carolina 29679 Winston and Strawn 1400 L Street, NW.
Ms. Karen E. Long Washington, DC 20005 Assistant Attorney General North Carolina Department of Mr. Robert B. Borsum Justice B&W Nuclear Technologies P. 0. Box 629 Suite 525 Raleigh, North Carolina 27602 1700 Rockville Pike Rockville, Maryland 20852-1631 Mr. G. A. Copp Licensing -
ECO50 Manager, LIS Duke Power Company NUS Corporation 526 South Church Street 2650 McCormick Drive, 3rd Floor Charlotte, North Carolina 28242-0001 Clearwater, Florida 34619-1035 Dayne H. Brown, Director Senior Resident Inspector Division of Radiation Protection U. S. Nuclear Regulatory Commission North Carolina Department of Route 2, Box 610 Environment, Health and Seneca, South Carolina 29678 Natural Resources P. 0. Box 27687 Regional Administrator, Region II Raleigh, North Carolina 27611-7687 U. S. Nuclear Regulatory Commission 101 Marietta Street, NW. Suite 2900 Atlanta, Georgia 30323 Max Batavia, Chief Bureau of Radiological Health South Carolina Department of Health and Environmental Control 2600 Bull Street Columbia, South Carolina 29201 County Supervisor of Oconee County Walhalla, South Carolina 29621