ML081650141

RAI Related to Summary of Design and Analyses of Weld Overlays for Pressurizer and Hot Leg Nozzle

ML081650141
Person / Time
Site:	Davis Besse
Issue date:	06/20/2008
From:	Thomas Wengert NRC/NRR/ADRO/DORL/LPLIII-2
To:	Allen B FirstEnergy Nuclear Operating Co
Goodwin, Cameron/DORL, 415-3719
References
TAC MD8105
Download: ML081650141 (8)

Text

June 20, 2008 Mr. Barry S. Allen Site Vice President FirstEnergy Nuclear Operating Company Davis-Besse Nuclear Power Station Mail Stop A-DB-3080 5501 North State Route 2 Oak Harbor, OH 43449-9760

SUBJECT:

DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 - REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE

SUMMARY

OF DESIGN AND ANALYSES OF WELD OVERLAYS FOR PRESSURIZER AND HOT LEG NOZZLE LARGE BORE DISSIMILAR METAL WELDS FOR ALLOY 600 MITIGATION (MD8105)

Dear Mr. Allen:

By letter to the Nuclear Regulatory Commission (NRC) dated February 8, 2008, FirstEnergy Nuclear Operating Company submitted a summary of design and analyses of the weld overlays for pressurizer and hot leg large bore dissimilar metal welds for Alloy 600 mitigation to satisfy commitments provided in the February 15, 2007, letter which requested NRC approval of a proposed alternative to American Society of Mechanical Engineers Code Section XI requirements in support of weld overlay repairs, for the Davis-Besse Nuclear Power Station, Unit No. 1.

The NRC staff is reviewing your submittal and has determined that additional information is required to complete the review. The specific information requested is addressed in the enclosure to this letter. During a discussion with your staff on June 16, 2008, it was agreed that you would provide a response within 30 days from the date of this letter.

The NRC staff considers that timely responses to requests for additional information help ensure sufficient time is available for staff review and contribute toward the NRC=s goal of efficient and effective use of staff resources. If circumstances result in the need to revise the requested response date, please contact me at (301) 415-4037.

Sincerely,

/RA/

Thomas J. Wengert, Project Manager Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-346

Enclosure:

Request for Additional Information cc w/encl: See next page

Mr. Barry S. Allen June 20, 2008 Site Vice President FirstEnergy Nuclear Operating Company Davis-Besse Nuclear Power Station Mail Stop A-DB-3080 5501 North State Route 2 Oak Harbor, OH 43449-9760

SUBJECT:

DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 - REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE

SUMMARY

OF DESIGN AND ANALYSES OF WELD OVERLAYS FOR PRESSURIZER AND HOT LEG NOZZLE LARGE BORE DISSIMILAR METAL WELDS FOR ALLOY 600 MITIGATION (MD8105)

Dear Mr. Allen:

By letter to the Nuclear Regulatory Commission (NRC) dated February 8, 2008, FirstEnergy Nuclear Operating Company submitted a summary of design and analyses of the weld overlays for pressurizer and hot leg large bore dissimilar metal welds for Alloy 600 mitigation to satisfy commitments provided in the February 15, 2007, letter which requested NRC approval of a proposed alternative to American Society of Mechanical Engineers Code Section XI requirements in support of weld overlay repairs, for the Davis-Besse Nuclear Power Station, Unit No. 1.

The NRC staff is reviewing your submittal and has determined that additional information is required to complete the review. The specific information requested is addressed in the enclosure to this letter. During a discussion with your staff on June 16, 2008, it was agreed that you would provide a response within 30 days from the date of this letter.

The NRC staff considers that timely responses to requests for additional information help ensure sufficient time is available for staff review and contribute toward the NRC=s goal of efficient and effective use of staff resources. If circumstances result in the need to revise the requested response date, please contact me at (301) 415-4037.

Sincerely,

/RA/

Thomas J. Wengert, Project Manager Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-346

Enclosure:

Request for Additional Information cc w/encl: See next page DISTRIBUTION:

PUBLIC LPL3-2 R/F RidsNrrDorlLpl3-2 RidsNrrPMTWengert RidsNrrLAEWhitt RidsAcrsAcnw&mMailCenter RidsOgcRp RidsRgn3MailCenter RidsNrrDorlDpr ADAMS Accession Number: ML081650141 OFFICE LPL3-2/PM LPL3-2/PM LPL3-2/LA LPL3-2/BC NAME CGoodwin TWengert EWhitt RGibbs DATE 6/18/08 6/19/08 6/18/08 6/20/08 OFFICIAL RECORD COPY

Davis-Besse Nuclear Power Station, Unit No. 1 cc:

Manager, Site Regulatory Compliance President, Board of County FirstEnergy Nuclear Operating Company Commissioners of Ottawa County Davis-Besse Nuclear Power Station Port Clinton, OH 43252 Mail Stop A-DB-3065 5501 North State Route 2 President, Board of County Oak Harbor, OH 43449-9760 Commissioners of Lucas County One Government Center, Suite 800 Director, Ohio Department of Commerce Toledo, OH 43604-6506 Division of Industrial Compliance Bureau of Operations & Maintenance The Honorable Dennis J. Kucinich 6606 Tussing Road United States House of Representatives P.O. Box 4009 Washington, D.C. 20515 Reynoldsburg, OH 43068-9009 Resident Inspector The Honorable Dennis J. Kucinich U.S. Nuclear Regulatory Commission United States House of Representatives 5503 North State Route 2 14400 Detroit Avenue Oak Harbor, OH 43449-9760 Lakewood, OH 44107 Stephen Helmer Joseph J. Hagan Supervisor, Technical Support Section President and Chief Nuclear Officer Bureau of Radiation Protection FirstEnergy Nuclear Operating Company Ohio Department of Health Mail Stop A-GO-19 35 East Chestnut Street, 7th Floor 76 South Main Street Columbus, OH 43215 Akron, OH 44308 Carol OClaire, Chief, Radiological Branch David W. Jenkins, Attorney Ohio Emergency Management Agency FirstEnergy Corporation 2855 West Dublin Granville Road Mail Stop A-GO-15 Columbus, OH 43235-2206 76 South Main Street Akron, OH 44308 Zack A. Clayton DERR Danny L. Pace Ohio Environmental Protection Agency Senior Vice President, Fleet Engineering P.O. Box 1049 FirstEnergy Nuclear Operating Company Columbus, OH 43266-0149 Mail Stop A-GO-14 76 South Main Street State of Ohio - Transportation Department Akron, OH 44308 Public Utilities Commission 180 East Broad Street Manager, Fleet Licensing Columbus, OH 43266-0573 FirstEnergy Nuclear Operating Company Mail Stop A-GO-2 Principal Assistant Attorney General 76 South Main Street Environmental Enforcement Section Akron, OH 44308 State Office Tower 30 East Broad Street, 25th Floor Columbus, OH 43215

Davis-Besse Nuclear Power Station, Unit No. 1 cc:

Director, Fleet Regulatory Affairs FirstEnergy Nuclear Operating Company Mail Stop A-GO-2 76 South Main Street Akron, OH 44308 Jeannie M. Rinckel Vice President, Fleet Oversight FirstEnergy Nuclear Operating Company Mail Stop A-GO-14 76 South Main Street Akron, OH 44308 Paul A. Harden Vice President, Nuclear Support FirstEnergy Nuclear Operating Company Mail Stop A-GO-14 76 South Main Street Akron, OH 44308 James H. Lash Senior Vice President of Operations and Chief Operating Officer FirstEnergy Nuclear Operating Company Mail Stop A-GO-14 76 South Main Street Akron, OH 44308

REQUEST FOR ADDITIONAL INFORMATION DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 DOCKET NO. 50-346 By letter dated February 8, 2008, FirstEnergy Nuclear Operating Company (FENOC) submitted a summary of design and analyses of the weld overlays for pressurizer and hot leg dissimilar metal welds. The submittal is part of the licensees commitment provided in its Relief Request, RR-A30, Revision 2, which was submitted by letters dated February 15, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML071020195),

June 28, 2007 (ADAMS Accession No. ML071840039), September 28, 2007 (ADAMS Accession No. ML072750034), and November 19, 2007 (ADAMS Accession No. ML073180505), for the Davis-Besse Nuclear Power Station, Unit No. 1 (DBNPS). The NRC staff has determined that the following information is needed in order to complete its review:

1. In Table 2-3, the licensee shows that the time for a postulated circumferential flaw to reach the design basis flaw size for the hot leg surge nozzle weld and hot leg decay heat nozzle weld are 2.58 years (31 months) and 6 years, respectively. The postulated flaw is 75 percent through wall and the design basis flaw is 100 percent through wall of the original alloy 82/182 weld. RR-A30, Revision 2, requires that the overlaid dissimilar metal welds be inspected during the first or second refueling outage after the overlay installation. If no indication is detected, the weld will be included in a sample population.

Twenty-five percent of the sample population will be inspected every 10 years. The NRC staff notes that once the weld overlay is installed, the current ultrasonic examination is not qualified to inspect the inner 75 percent of the wall thickness of the dissimilar metal weld.

(a) The NRC staff is concerned that the 10-year inspection interval may be inadequate (i.e., too long) to monitor the structural integrity of the hot leg surge nozzle weld and hot leg decay heat nozzle weld. If an actual flaw exists, it may grow to the design basis flaw size (i.e, 100 percent through wall of the weld) in less time than the inspection interval. If the actual flaw is caused by fatigue, the 100 percent through wall flaw may grow into the weld overlays of the subject welds. If the flaw is caused by primary stress corrosion cracking, it may be blunt by the weld overlays. If not blunted, it may grow into the weld overlays also.

Discuss the adequacy/effectiveness of the 10-year inservice inspection frequency for these two welds.

(b) Because the postulated circumferential flaw is predicted to reach the design basis flaw size in less time than the inspection interval, discuss whether an analysis was performed to predict how far that flaw would grow into the weld overlay at the end of the 10 year inspection period. If not, provide the technical basis to support the structural integrity of the subject welds.

(c) Table 2-3 shows that the time for the postulated circumferential flaw and axial flaw to reach the design basis flaw size for the two pressurizer relief nozzles (i.e.,

Enclosure

the 3-inch nozzle and 2.5-inch nozzle) is the same (> 60 years). However, for other nozzles (e.g., pressurizer surge and spray nozzles, hot leg surge and decay heat nozzles) the time for the circumferential flaw and axial flaw to reach the design basis flaw size is much different. Discuss why for the pressurizer 2.5 and 3-inch relief nozzles the time period is the same.

(d) Discuss the analytical input parameters and degradation mechanisms that cause the circumferential flaw to reach the design basis flaw size for the pressurizer surge nozzle, pressurizer spray nozzle, hot leg surge nozzle, and hot leg decay heat nozzle. Discuss why the time for the circumferential flaw to reach the design basis flaw size is a much shorter time than the axial flaw in the hot leg surge nozzle, hot leg decay heat nozzle, pressurizer surge nozzle, and pressurizer spray nozzles.

(e) In a letter dated February 5, 2008, the licensee reported an axial flaw that caused leakage in the hot leg decay heat nozzle during welding of the overlay. Discuss whether this flaw was used in the stress analysis. If not, provide the reason for not modeling the actual flaw in the analysis.