ML12053A365
| ML12053A365 | |
| Person / Time | |
|---|---|
| Site: | Boiling Water Reactor Owners Group |
| Issue date: | 03/05/2012 |
| From: | Joe Golla Licensing Processes Branch (DPR) |
| To: | Schiffley F Exelon Generation Co |
| Golla J | |
| References | |
| TAC ME7649, BWROG-TP-11-022, Rev 1 | |
| Download: ML12053A365 (5) | |
Text
March 5, 2012 Mr. Frederick Schiffley BWROG Chairman Exelon Generation Co., LLC Cornerstone II at Cantera 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION RE: BOILING WATER REACTOR OWNERS GROUP LICENSING TOPICAL REPORT BWROG-TP-11-022, REVISION 1, PRESSURE-TEMPERATURE LIMITS REPORT METHODOLOGY FOR BOILING WATER REACTORS (TAC NO. ME7649)
Dear Mr. Schiffley:
By letter dated November 17, 2011, the Boiling Water Reactor Owners Group (BWROG) submitted for U.S. Nuclear Regulatory Commission (NRC) staff review, licensing topical report (LTR) BWROG-TP-11-022, Revision 1, Pressure-Temperature Limits Report Methodology for Boiling Water Reactors. Upon review of the information provided, the NRC staff has determined that additional information is needed to complete the review. On January 23, 2012, Lucas Martins, Project Manager for the BWROG, and I agreed that the NRC staff will receive your response to the enclosed Request for Additional Information (RAI) questions by June 13, 2012. If you have any questions regarding the enclosed RAI questions, please contact me at 301-415-1002.
Sincerely,
/RA/
Joseph A. Golla, Project Manager Licensing Processes Branch Division of Policy and Rulemaking Office of Nuclear Reactor Regulation Project No. 691
Enclosure:
RAI questions cc w/encl: See next page
ML12053A365 NRR-106 OFFICE PLPB/PM PLPB/LA EVIB/BC PLPB/BC PLPB/PM NAME JGolla DBaxely SRosenberg JJolicoeur JGolla DATE 02/27/2012 02/24/2012 03/1/2012 03/5/2012 03/5/2012 REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION LICENSING TOPICAL REPORT BWROG-TP-11-022, REVISION 1 PRESSURE-TEMPERATURE LIMITS REPORT METHODOLOGY FOR BOILING WATER REACTORS BOILING WATER REACTORS OWNERS GROUP PROJECT NO. 691
RAI-1
Section 2.5.3 of Licensing Topical Report (LTR) BWROG-TP-11-022 (SIR-05-044), Revision 1, Pressure-Temperature Limits Report Methodology for Boiling Water Reactors [(BWRs)],
provides a new equation (Equation (2.5.3-3a)), along with the existing equation (Equation (2.5.3-3b)), to calculate the thermal stress intensity factor (KIt) at the one-quarter thickness (1/4T) location of a postulated axial flaw in a nozzle corner. The LTR states that, either Equation 2.5.3-3a or 2.5.3-3b may be used for any nozzle configuration in a BWR. The LTRs stated reason for allowing applicants to choose either of the equations arbitrarily is that, the two formulations differ very little and in fact provide KI values which differ only by approximately 5%.
As indicated in the ORNL/TM-2010/246 report, Stress and Fracture Mechanics Analyses of Boiling Water Reactor and Pressurized Water Reactor Pressure Vessel Nozzles, Equation (2.5.3-3a) is for a nozzle with a sharp corner and Equation (2.5.3-3b) is for a nozzle with a rounded corner. Suggesting that applicants use either of the two equations arbitrarily and regardless of the nozzles geometry is not appropriate because the nozzles with a variety of geometries should not get the 5 percent advantage uniformly simply because it is valid for a nozzle of a specific geometry. Please provide adequate justification for this, or consider the following alternatives: (1) establish a guideline regarding use of these two equations for different nozzle types similar to the ORNL/TM-2010/246 report approach, or (2) use only one equation that always generates conservative results for all nozzles. Quantitative information should be used to support your choice. In addition, based on your choice, Equation (2.5.3-5a) and Equation (2.5.3-5b) need also to be revised accordingly.
RAI-2
Regarding the nozzle corner flaw stress intensity factor due to pressure (KIp), Section 2.5.3 of the LTR provides a new equation (Equation (2.5.3-5c)) based on Appendix 5 of Welding Research Council (WRC) Bulletin No. 175, PVRC Recommendations on Toughness Requirements for Ferritic Materials, as an alternative to calculate this value. Although the proposed alternative is based on a three dimensional finite element method (FEM) modeling of ENCLOSURE
F. Schiffley a nozzle, considerable progress has been made in fracture mechanics and FEM techniques since the publication of WRC-175 and could potentially make the WRC-175 approach on nozzles unacceptable in the future. Please clarify whether you elect to maintain your position in LTR SIR-05-044-A, or provide a comparison of results from all approaches, demonstrating that the WRC-175 nozzle approach can still provide conservative KIp results. If the BWROG decides to drop the new equation, a paragraph may be added to state that Appendix G of American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI currently permits use of the WRC-175 approach for nozzles.
RAI-3
Section 2.5.3 of the LTR addresses nozzles in the beltline region. One of the general guidelines regards disposition of the nozzle section with thickness equal to or less than 2.5 inches:
For those nozzle inserts which are ferritic the exemption given in ASME XI, Appendix G, paragraph G-2223(c) is generally applicable in which fracture toughness analysis to demonstrate protection against nonductile failure is not required for portions of nozzles and appurtenances having a thickness of 2.5 inches or less, provided the lowest service temperature is not lower than RTNDT plus 60 °F.
Based on the NRC staffs experience of reviewing license renewal applications, the NRC staff found that some applicants missed the second half of paragraph G-2223(c) regarding the lowest service temperature. Therefore, the NRC staff suggests the BWROG add some verbiage that would highlight the condition on the lowest service temperature. Please provide this in response to this RAI.
cc:
BWROG Chairman Frederick P. Schiffely Exelon Generation Co., LLC Cornerstone II at Cantera 4300 Winfield Road Warrenville, IL 60555 frederick.schiffley@exeloncorp.com BWROG Vice Chairman Michael H. Crowthers PPL Susquehanna, LLC 2 North Ninth Street Allentown, PA 18101-1179 mhcrowthers@pplweb.com BWROG Project Manager Lucas Martins GE-Hitachi Nuclear Energy PO Box 780 M/C F-12 3901 Castle Hayne Road Wilmington, NC 28402 Lucas.martins@ge.com BWROG Program Manager Craig J. Nichols GE-Hitachi Nuclear Energy PO Box 780 M/C F-12 3901 Castle Hayne Road Wilmington, NC 28402 craig.nichols@ge.com GEH Senior Vice President Jerald G. Head Senior Vice President, Regulatory Affairs GE-Hitachi Nuclear Energy PO Box 780 M/C A-18 Wilmington, NC 28401 jerald.head@ge.com