ML20216D896
| ML20216D896 | |
| Person / Time | |
|---|---|
| Issue date: | 08/14/1997 |
| From: | Sheron B NRC (Affiliation Not Assigned) |
| To: | Terry C AFFILIATION NOT ASSIGNED, NIAGARA MOHAWK POWER CORP. |
| Shared Package | |
| ML20216D900 | List: |
| References | |
| TAC-M93925, NUDOCS 9709090455 | |
| Download: ML20216D896 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION
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t WASHINGTON. D.C. So66 Hoot
's,***** ,e Aug,,st 14, 1997 Carl Terry, BWRVIP Chairman Niagara Mohawk Power Company Post Office Box 63 Lycoming, NY 13093
SUBJECT:
TRANSHITTAL OF NRC STAFF'S INDEPENDENT ASSESSMENT OF THE BOILING
' WATER REACTOR VESSEL AND INTERNALS PROJECT BWRVIP-05 REPORT AND PROPRIETARY REQUEST FOR ADDITIONAL INFORMATION (TAC NO. M93925)
Dear Mr. Terry,
S
'6 d Thislettertransmitsthestaff'sindepende$tassessmentofthefrequencyof BWR reactor pressure vessel failure (Encloskre 1R a proprietary request for additional informatior, (Enclosure 2), and aqditibal guidance on information the staff will need to tssess requests for lieb from the inspection schedule in 10 CFR 50.55a(g)(6)(ii)(A) (Enclosure 3 - Tta staff's independent assessment was performed in response to the!Boinng Water Reactor Vessel and Internals Project (BWRVIP) submittal of the proMietary report, "BWR Vessel and Internals Project, BWR R Recommendations (BWRVIP-05)"gactor Pressure
." dated September VesW1,Shell 28, 1995, Weld Inspection as supplemented I
by letters dated June 24 and October 29, 1996, May 16, June 4, and June 13 1997. The staff's assessment, a preliminary, multi-disciplined, risk-informed review of the BWRVIP-05 report, drew upon the resources of the Offices of Nuclear Reactor Regulation (NRR), Nuclear Regulatory Research (RES), Analysis and Evaluation of Operational Data (AE00), and International Programs (OlP).
The staff has determined that, since the BWRVIP-05 report did not perform a risk-informed analysis, nor did it adequately consider beyond design basis transients (which appear to dominate the estimated frequency of BWR reactor \
vessel failure), the BWRVIP-05 report, as written and presently supplemented, \ \
is not sufficient for deferring permanently inspections of the circumferential \
welds. . However, based on the staff's independent assessment, any significant RPV vulnerabilities would not be expected until relatively late in life of the reactor vessels when higher levels of embrittlement are reached.
this observation, the staff will consider plant-specific requests, if technically justified, to delay inspections of the circumferential wclds for Based on
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up to 40-months. Further, based on the staff's assessment, the requested additional information should b6 sufficient to determine if permanently deferring inspections of the RPV circumferential welds is acceptable.
The SWRvlP 05 report proposed to redace the scope of inspection of the SWR reactor pressure vesset to pe ont t c r i r 9 to t f e 1 originst proposal to increase the examination of the axlat welds to 100 percent (frees 50 percent) while still proposing to inspect essentlatly zero percent of the circur.ferentist RPV shell welds (except that the intersections of the exist and circunferential welds would have been incitded; aproximately 2 3 percent of the circunferentist welds would be inspected trider this proposal).
q ()y0ll UY 9709090455 97 PDR TOPRP ENVGENE 14 h ' ' ' ' bbh C PDR
"., ,t C. Terry On May 12, 1997, the Commission was briefed by representatives of the BWRVIP and the staff on the issues related to the requirements for a full inspection of RPV shell welds. The Commission, in a Staff Requirements Memorandum (SRM
, dated May 30, 1997, requested that the staff consider a tiered M970512B)in approach gathering additional baseline information and/or implementing the Rule (10 CFR 50.55a(g)(6)(ii)(A)). The SRM recommended that the staff's assessment (a) should address the BWRVIP proposal to examine 100 percent of the axial welds which would include examinations of some circumferential weld lengths near the intersections of the weld types to determine if this proposal could provide an appropriato level of sampling of the circumferential welds, (b) should provide a comprehensive evaluation of the probabilistic analysis l
contained in the BWRVIP proposed alternative in determining the acceptability of a proposed technical alternative and/or in pursuing changes to the rule, and, (c) should receive appropriate review, including review by the Advisory Committee on Reactor Safeguards (ACRS).
l l In SECY 97-152, dated July 18, 1997, the staff reported to the Commission its preliminary results of a broader risk informed assessment it had initiated and described its proposed course of action in response to the SRM. In aarticular, the staff reported that )reliminary assessments indicated that seyond design basis transients, whici had not been considered in the BWRVIP-05 submittal, appeared to dominate the estimated frequency of BWR reactor vessel failure, it was further noted that, although additional studies were~
necessary in this area, any significant vulnerabilities would not be expected until relatively late in life of the reactor vessels when higher levels of embrittlement are reached. Based on this latter observation, the staff indicated that plant specific requests to delay inspections of the circumferential welds would be considered, if technically justified, by the staff. On August 7, 1997, the staff issued Information Notice (lN) 97-63,
" Status of NRC Staff's Review of BWRVIP-05 " regarding licensee requests for relief.
Since issuance of SECY 97-152, the staff has completed additional analyses of the potential for BWR RPV failure considering beyond design basis events.
These analyses were discussed with the BWR VIP and industry representatives during a meeting on August 3, 1997 and are documented in Enclosure 1. The additional work documented in Enclosure 1 supports the observations in SECY 97-152. However, these analyses are generic in nature and were performed utilizing more limited data than should be available to the industry.
Therefore, the staff requests that the BWRVIP supplement its original BWRVIP-05 submittal with a broader, risk-informed evaluation of the proposed change in RPV weld inspection requirements -
Enclosure 2 is a request for additional information (RAI) that is intended to
, provide guidance on the areas that should be addressed in the industry's assessment. As indicated in SECY 97-152, the staff plans to complete its final evaluation of this issue within six months. Meeting this schedule is, of course, dependent upon receiving the industry's evaluation. In order to meet this schedule, we request that you provide the additional information requested in Enclosure 2 within 90 days. Pl ase inform us within 30 days if J
., ,t C. Terry you can not meet this schedule. We are available for any meetings that would assist in facilitating this schedule.
With regard to plant specific relief requests Enclosure 3 provides some additional guidance on what information the staff will need to assess requests forrelieffromtheinspectionschedulein10CFR50.55a(g)(6)(ii)(A). As indicated in IN 97-63, the staff will consider delays in ins)ections of circumferential welds of up to 2 o)erating cycles or 40 montis (whichever is longer). The acceptability of suel requests will be based on )lant-specific information submitted by the licensee that demonstrates that tie expected frequency of beyond design basis events and the level of embrittlement of the DPV are low enough to assure low probability of vessel failure during the I
period of relief. It is the staff's expectation that granting relief for up to two operating cycles will allow sufficient time for the industry to complete its broader risk informed evaluation and for the NRC to reach a position on the acceptability of longer term relief from inspection of circumferential welds.
Also, a briefing of the ACRS subcommittee on this issue has been scheduled for August 26, 1997, which the industry has been invited to participate. A meeting with the main committee of the ACRS will be scheduled for early in 1998, after the industry has completed and submitted its risk informed evaluation, and the staff has completed its final Safety Evaluation.
Please contact C. E. (Gene) Carpenter, Jr., of my staff at (301) 415-2169 if you have any further questions regarding this subject.
Sincerely, Brian W. Sheron, irector Division of Engineering Office of Nuclear Reactor Regulation
Enclosures:
as stated cc: See next page
"o. .
C. Terry I
cc: ,
George Jones, Executive Chairman Robin Dyle, Technical Chairman BWRVIP Assessment Task BWRVIP Assessment Task Pennsylvania Power & Light Southern Nuclear Operating Co.
A6-1 Post Office Box 1295 Two North Ninth Street 40 Inverness Center Parkway Allentown, PA 18101 Birmingham, AL 35201 Joe Hagan, Executive Chairman Steve Leonard, Technical Chairman ,
BWRVIP Inspection Task BWRVIP Inspection Task Entergy Niagara Mohawk Power Company ESBl P. O. Box 756 Post Office Box 63 Waterloo Road Lycoming, NY 13093 Port Gibson, MS 39150 Paul Bemis, Executive Chairman Vaughn Wagoner, Technical Chairman BWRVIP Integration Task BWRVIP Integration Task Washington Public Power Supply Carolina Power & Light Company System One Hanover Square 8C1 P. O. Box 968 P.O. Box 1551 North Power Plant Loop Raleigh,.NC 27612 Richland, WA 99352-0968 Lewis Sumner, Executive Chairman John Wilson, Technical Chairman BWi: VIP Mitigation Task BWRVIP Mitigation Task Southern Nuclear Operating Co. Public Service Electric & Gas Co.
40 Inverness Center Parkway N51 Eirmingham, AL 35201 Post Office Box 236 Hancocks Bridge, NJ 08038 John Blomgren, Executive Chairman Bruce McLeod, Technical Chairman BWRVIP Re) air Task BWRVIP Repair Task Commonwealti Edison Co. Southern Nuclear Operating Co.
1400 Opus Place, Suite 600 Post Office Box 1295 Downers Grove, IL 6n515-5701 40 Inverness Center Parkway Birmingham, AL 35201 Warren Bilanin EPRI BWRVIP Robert Carter, EPRI BWRVIP Inspection Manager Assessment Manager Joe Gilman, EPRI BWRVIP Greg Selby, EPRI BWRVIP Mitigation Manager Inspection Manager Ken Wolfe, EPRI BWRVIP EPRI NDE Center Repair Manager P. O. Box 217097 Electric Power Research Institute 1300 W. T. Harris Blvd.
P. O. Box 10412 Charlotte, NC 28221 3412 Hillview Ave.
Palo Alto, CA 94301