ML092881119
| ML092881119 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 11/02/2009 |
| From: | Lisa Regner License Renewal Projects Branch 2 |
| To: | Gallagher M Exelon Generation Co, Exelon Nuclear |
| Doyle D., NRR/DLR/RPB2, 301-415-3748 | |
| References | |
| Download: ML092881119 (8) | |
Text
November 2, 2009 Mr. Michael P. Gallagher Vice-President, License Renewal Exelon Nuclear 200 Exelon Way Kennett Square, PA 19348
SUBJECT:
AUDIT
SUMMARY
REGARDING THE OYSTER CREEK NUCLEAR GENERATING STATION CONTAINMENT DRYWELL LINER 3-D FINITE ELEMENT ANALYSIS
Dear Mr. Gallagher:
By letter dated January 22, 2009, Exelon Nuclear submitted the results of a three-dimensional finite element analysis using modern methods to determine the margin of the containment drywell liner of the Oyster Creek Nuclear Generating Station, as compared to the requirements of the American Society of Mechanical Engineers Code. By letter dated September 9, 2009, Exelon Nuclear submitted an addendum to the January 22 report, incorporating results from an updated analysis which modifies two items related to an analytical assumption. On September 18, 2009, the Nuclear Regulatory Commission staff completed an audit of the analysis results described in the addendum. The audit summary is enclosed.
If you have any questions, please contact me at 301-415-1906 or by e-mail at Lisa.Regner@nrc.gov.
/RA/
Lisa M. Regner, Senior Project Manager Projects Branch 2 Division of License Renewal Office of Nuclear Reactor Regulations Docket No. 50-219
Enclosure:
As stated cc w/encl: See next page
November 2, 2009 Mr. Michael P. Gallagher Vice-President, License Renewal Exelon Nuclear 200 Exelon Way Kennett Square, PA 19348
SUBJECT:
AUDIT
SUMMARY
REGARDING THE OYSTER CREEK NUCLEAR GENERATING STATION CONTAINMENT DRYWELL LINER 3-D FINITE ELEMENT ANALYSIS
Dear Mr. Gallagher:
By letter dated January 22, 2009, Exelon Nuclear submitted the results of a three-dimensional finite element analysis using modern methods to determine the margin of the containment drywell liner of the Oyster Creek Nuclear Generating Station, as compared to the requirements of the American Society of Mechanical Engineers Code. By letter dated September 9, 2009, Exelon Nuclear submitted an addendum to the January 22 report, incorporating results from an updated analysis which modifies two items related to an analytical assumption. On September 18, 2009, the Nuclear Regulatory Commission staff completed an audit of the analysis results described in the addendum. The audit summary is enclosed.
If you have any questions, please contact me at 301-415-1906 or by e-mail at Lisa.Regner@nrc.gov.
/RA/
Lisa M. Regner, Senior Project Manager Projects Branch 2 Division of License Renewal Office of Nuclear Reactor Regulations Docket No. 50-219
Enclosure:
As stated cc w/encl: See next page DISTRIBUTION: See next page ADAMS Accession Number: ML092881119
- via e-mail OFFICE LA:DLR SL:DLR PM:RPB2:DLR BC:RPB2:DLR NAME SFigueroa AHiser LRegner*
DWrona (Robert Kuntz for)
DATE 10/21/09 10/23/09 10/26/09 10/23/09 OFFICE BC:RASB:DLR OGC PM:RPB2:DLR NAME RAuluck BHarris (NLO)
LRegner DATE 10/26/09 11/02/09 11/02/09 OFFICIAL RECORD COPY
ENCLOSURE U.S. NUCLEAR REGULATORY COMMISSION (NRC)
OFFICE OF NUCLEAR REACTOR REGULATION - DIVISION OF LICENSE RENEWAL AUDIT
SUMMARY
REGARDING THE OYSTER CREEK NUCLEAR GENERATING STATION CONTAINMENT DRYWELL LINER 3-D FINITE ELEMENT ANALYSIS Docket No:
50-219 License No:
DPR-16 Licensee:
Exelon Generation Company, LLC Location:
Exelon 101 Constitution Avenue, NW Suite 400 East Washington, DC 20001 Dates:
September 18, 2009 NRC Staff:
A. Hiser, Senior Technical Advisor, DLR K. Manoly, Senior Technical Advisor, DE Licensee Staff:
J. ORourke, Exelon Nuclear C. Wilson, Exelon Nuclear Approved By:
David Wrona, Chief Projects Branch 2 Division of License Renewal Office of Nuclear Reactor Regulation Rajender Auluck, Chief Aging Management of Structures, Electrical, and Systems Division of License Renewal Office of Nuclear Reactor Regulation
Introduction On January 22, 2009, Exelon Nuclear submitted the results of a three-dimensional finite element analysis (3-D FEA) using modern methods to determine the margin of the containment drywell shell of Oyster Creek Nuclear Generating Station, as compared to the requirements of the American Society of Mechanical Engineers (ASME) Code (Agencywide Documents Access and Management System (ADAMS) Accession Number ML091830077). This 3-D FEA was reviewed by the NRC staff as part of a license renewal inspection, as documented in the inspection report (ADAMS Accession Number ML091380379). On September 9, 2009, Exelon Nuclear submitted an addendum to the January 22 report, incorporating results from an updated analysis which modified two items related to an analytical assumption (ADAMS Accession Number ML092540596). Exelon provided this information to ensure the NRC staff and the Advisory Committee on Reactor Safeguards (ACRS) have the latest relevant information on the 3-D FEA.
The NRC staff conducted a one-day audit of the addendum report on September 18, 2009. The audit focused on an assessment of the 3-D FEA described in the addendum. The staff reviewed the proprietary addendum calculations and supporting documentation to ensure that the analysis was based on realistic, but conservatively biased assumptions and that it was conducted using good engineering practices and judgment.
In performing this audit, the NRC staff reviewed the proprietary calculations, including modeling and simplifying assumptions, and documents used to develop or support the calculations. The NRC staff also interviewed Exelon representatives to obtain additional clarification related to the calculations. This summary documents the NRC staff activities during this audit.
Audit Findings The NRC staff reviewed the calculations described in the addendum report submitted on September 9, 2009. The NRC staffs review focused on the modeling and simplifying assumptions used in the addendum report that were updated from those used in the 3-D FEA submitted on January 22, 2009. The NRC staff reviewed the following documents during this audit:
DOCUMENT TITLE REVISION Addenda to Structural Integrity Associates Report No.
0006004.403 Structural Evaluation of the Oyster Creek Drywell Summary Report Revision 0 Structural Integrity Associates Report No.
0006004.403 Structural Evaluation of the Oyster Creek Drywell Summary Report Revision 0 Structural Integrity Associates Report No.
0006004.404 Oyster Creek Drywell Sandbed Region Wall Thinning Sensitivity Analyses Summary Report Revision 0 Exelon stated that the modification to the modeling assumptions and the re-calculation was at the recommendation of Dr. Clarence Miller, an industry expert on structural buckling analysis and the developer of the ASME Code cases that pertain in this area. In particular, Dr. Miller recommended that (1) the length between supports used in the calculation of the capacity reduction factor for the spherical shell should be based on the arc lengths between the supports instead of the elevation differences, and (2) the lower support beam, which was excluded in the 3-D FEA should be used as a contributing stiffener for the lower spherical and sandbed regions.
Exelon clarified that the modeling assumption changes did not result in changes to the finite element results for the drywell shell (e.g., the finite element model was not reanalyzed), but did impact the post-processing aspects of the calculations to determine safety factors.
Exelon staff illustrated the modeling assumption changes using the attached figure (the drawing and safety factor identified as Original are from the January 22, 2009, 3-D FEA, and those identified as Updated are from the September 9, 2009, addendum). As illustrated, the support lengths in the lower spherical and the sandbed regions decrease with the inclusion of the lower support beam. Consequently, the safety factors for the middle and lower spherical locations and the sandbed region increase from those provided in the original 3-D FEA. Conversely in the upper spherical region, the safety factor decreases for the addendum calculation from that provided in the 3-D FEA because the support lengths increase in this area. As expected, the safety factor in the cylindrical portion of the drywell does not change in the addendum calculation since there are no modeling assumption changes that affect this area.
The limiting safety factors from both the original 3-D FEA and the addendum calculation are in the sandbed and lower spherical regions of the drywell shell. With implementation of the modeling assumption changes recommended by Dr. Miller, the safety factor increases in these regions, indicating higher margins in the critical areas of the drywell shell.
The NRC staff reviewed other aspects of the calculations to determine whether any other changes to the assumptions and inputs were made from those used in the 3-D FEA, and the staff identified no changes.
The NRC staff identified no concerns with the analyses and results reported in the September 9, 2009, addendum.
The State of New Jersey participated in the exit briefing via teleconference.
Letter to M. Gallagher from L. Regner, Dated November 2 2009 DISTRIBUTION:
SUBJECT:
AUDIT
SUMMARY
REGARDING THE OYSTER CREEK NUCLEAR GENERATING STATION CONTAINMENT DRYWELL LINER 3-D FINITE ELEMENT ANALYSIS HARD COPY:
DLR RF E-MAIL:
PUBLIC A. Hiser B. Pham RidsNrrDlr RidsNrrDlrRpb1 RidsNrrDlrRpb2 RidsNrrDlrRer1 RidsNrrDlrRer2 RidsNrrDlrRerb RidsNrrDciCvib RidsNrrDciCpnb RidsNrrDraAfpb RidsNrrDeEmcb RidsNrrDeEeeb RidsNrrDssSrxb RidsNrrDssSbpb RidsNrrDssScvb RidsOgcMailCenterResource RidsOpaMailResource L. Regner D. Doyle D. Tifft, RI N. McNamara, RI D. Scenci, RI R. Conte, RI B. Harris, OGC
Oyster Creek Nuclear Generating Station cc:
Site Vice President - Oyster Creek Nuclear Generating Station AmerGen Energy Company, LLC P.O. Box 388 Forked River, NJ 08731 Senior Vice President-Operations Support AmerGen Energy Company, LLC 4300 Winfield Road Warrenville, IL 60555 Kathryn M. Sutton, Esquire Morgan, Lewis, & Bockius LLP 1111 Pennsylvania Avenue, NW Washington, DC 20004 Patrick Mulligan, Chief Bureau of Nuclear Engineering New Jersey Department of Environmental Protection 25 Arctic Parkway Ewing, NJ 08638 Vice President - Licensing and Regulatory Affairs AmerGen Energy Company, LLC 4300 Winfield Road Warrenville, IL 60555 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406-1415 Mayor of Lacey Township 818 West Lacey Road Forked River, NJ 08731 Manager Regulatory Assurance Oyster Creek Generating Station AmerGen Energy Company, LLC P.O. Box 388 Forked River, NJ 08731 Senior Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 445 Forked River, NJ 08731 Director - Licensing and Regulatory Affairs AmerGen Energy Company, LLC Correspondence Control P.O. Box 160 Kennett Square, PA 19348 Manager Licensing - Oyster Creek Exelon Generation Company, LLC Correspondence Control P.O. Box 160 Kennett Square, PA 19348 Ron Bellamy, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406-1415 Correspondence Control Desk AmerGen Energy Company, LLC 200 Exelon Way, KSA 1-N-1 Kennett Square, PA 19348 Plant Manager Oyster Creek Nuclear Generating Station AmerGen Energy Company, LLC P.O. Box 388 Forked River, NJ 08731 Associate General Counsel Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Chief Operating Officer (COO)
AmerGen Energy Company, LLC 4300 Winfield Road Warrenville, IL 60555 Senior Vice President - Mid-Atlantic Operations AmerGen Energy Company, LLC 200 Exelon Way, KSA 3-N Kennett Square, PA 19348