ML24132A009
| ML24132A009 | |
| Person / Time | |
|---|---|
| Issue date: | 05/24/2024 |
| From: | Walter Kirchner Advisory Committee on Reactor Safeguards |
| To: | Raymond Furstenau NRC/EDO |
| Abdullahi Z | |
| References | |
| Download: ML24132A009 (1) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, DC 20555 - 0001 Mr. Raymond V. Furstenau Acting Executive Director for Operations U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
SUBJECT:
Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs
Dear Mr. Furstenau:
During the 715th meeting of the Advisory Committee on Reactor Safeguards, April 30 through May 2, 2024, we completed our review of Topical Report (TR) WCAP-18446-P/NP, Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs. We also reviewed the staff safety evaluation (SE) report approving the incremental burnup extension and staff Non-Concurrence related to this safety evaluation. Our Fuels, Materials, and Structures subcommittee reviewed this topic on April 2, 2024. During these meetings, we had the benefit of discussions with the NRC staff and representatives from Westinghouse Electric Corporation (WEC). We also had the benefit of the referenced documents.
CONCLUSIONS AND RECOMMENDATIONS 1.
The TR presents a methodology and evaluation of an increased burnup limit in WEC and Combustion Engineering (CE) fuel designs. The methodology mitigates the safety implications of Fuel Fragmentation, Relocation and Dispersal (FFRD) by limiting higher burnup assemblies to lower power peripheral positions in the core and imposing a no-burst criterion during a loss-of-coolant accident (LOCA) on rods in the extended burnup range.
2.
The SE report provides a thorough evaluation supporting the staffs approval of the requested extended burnup limit by addressing fuel assembly mechanical design, core and fuel rod performance, non-LOCA and LOCA safety analyses, and radiological consequences.
3.
The Non-Concurrence presents a thorough discussion of the importance of considering FFRD as a fuel performance issue. The SE report should be issued because the WEC methodology, with the imposed limitations and conditions, minimizes the potential for fuel dispersal when using higher burnup fuel assemblies in non-limiting peripheral core locations.
May 24, 2024
R. BACKGROUND Westinghouse Electric Company submitted licensing TR WCAP-18446-P/NP, Revision 0, Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs. The TR proposes allowing the maximum fuel rod-average burnup for certain WEC and CE Pressurized Water Reactor (PWR) fuel designs to be increased from the currently approved value of 62 GWd/MTU to a value stated in the proprietary version of the TR.
The TR presents extensive analysis to demonstrate that reactor safety is maintained at the proposed extended burnup in the following areas:
Fuel assembly mechanical design, Core and fuel performance, LOCA analysis methods, Non-LOCA analysis methods, and Radiological consequence analysis.
In all cases, WEC has shown that the extended burnup range is either circumscribed by existing data or is appropriately covered by approved codes and methods.
Recent evidence cited in Research Information Letter (RIL) 2021-13 suggests that fuel dispersal could occur if the cladding is breached during a LOCA event above a specific burnup. These conditions include: (1) pellet average burnup > 55 GWd/MTU, (2) cladding strain >3%, and (3) fuel cladding breach. Note that without cladding failure, even if conditions (1) and (2) are met and fuel fragmentation and relocation does occur, fuel dispersal cannot occur. A conservative no-burst criterion based on an extensive rod burst database is implemented in the methodology to ensure that cladding integrity is maintained in the extended burnup range.
DISCUSSION The WEC operational approach, plant-specific analysis requirements, and the experimental and analytical evidence presented supports the incremental burnup extension. Existing data bases adequately cover the proposed increased rod average burnup limit specified in the proprietary version of the topical report. The WEC analytical methods used are well validated to the new proposed limit for rod average burnup and have been reviewed previously by the staff. The WEC-provided analysis and the staffs audit review, combined with confirmatory and independent analyses, were exhaustive and extremely thorough in all areas. These analyses demonstrated that the proposed fuel management approach to achieve extended burnup will have a minimal effect on core performance. However, to provide for additional assurance, WEC and the staff each identified a number of Limitations and Conditions (LCs). Based on their analyses, the most important of these is LC Number 8 that states:
Only rods in peripheral assemblies (i.e., assemblies with at least one face towards the core baffles) may exceed a rod-average burnup of 62 GWd/MTU.
Fuel rods in assemblies with a half-face towards the baffles in CE-designed PWRs are limited to a maximum rod-average burnup of 62 GWd/MTU (similar to core interior assemblies).
This limitation will ensure that higher burnup assemblies will be in low power locations.
R. The WEC analysis focuses on demonstrating that FFRD will not be any more extensive for core loads using the higher fuel burnup limit than for fuel with the 62 GWd/MTU rod average burnup limitation. As noted above, the methodology requires that no cladding burst be predicted to occur in the higher burnup assemblies.
The FFRD issue and the necessity for its resolution was described in a thorough analysis presented in the Non-Concurrence that was submitted as a part of the staffs review. The Non-Concurrence authors properly point out that recent research (RIL 2021-13) suggests that FFRD can be an issue for fuel at pellet average burnups in excess of 55 GWd/MTU. The vulnerability above 55 GWd/MTU pellet average burnup has been accepted based on engineering judgment and has not been formally adjudicated by the Commission. The Non-Concurrence authors would prefer that the issue of FFRD vulnerability be formally addressed as part of approval to go beyond 62 GWd/MTU rod average burnup. NRC management decided that the TR should be approved because the WEC methodology, with the imposed LCs, shows no increase in the likelihood of fuel dispersal when using higher burnup fuel assemblies in non-limiting peripheral core locations. Further, the management position is that NRC processes, which include the ongoing increased enrichment rulemaking, will address FFRD. The Committee looks forward to participating in the rulemaking process.
SUMMARY
The TR presents a methodology and evaluation of an increased burnup limit in WEC and CE fuel designs. The TR methodology mitigates the safety implications of FFRD by limiting higher burnup assemblies to lower power peripheral positions in the core and imposing a no-burst criterion during a LOCA on rods in the extended burnup range. The SE report provides a thorough evaluation supporting the staffs approval of the requested extended burnup limit, addressing fuel assembly mechanical design, core and fuel rod performance, non-LOCA and LOCA safety analyses, and radiological consequences. The Non-Concurrence presents a thorough discussion of the importance of considering FFRD as a fuel performance issue. The SE report should be issued because the WEC methodology, with the imposed limitations and conditions, minimizes the potential for fuel dispersal when using higher burnup fuel assemblies in non-limiting peripheral core locations.
Sincerely, Walter L. Kirchner Chair REFERENCES 1.
The Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission Draft Safety Evaluation by The Office of Nuclear Reactor Regulation, Westinghouse Electric Company Topical Report WCAP-18446-P/WCAP-18446-NP, Revision 0, Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs, February 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23278A257 (Non-Public)).
Signed by Kirchner, Walter on 05/24/24
R. 2.
The Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Staff Non-Concurrence against the Preliminary Safety Evaluation of The Office of Nuclear Reactor Regulation, Westinghouse Electric Company Topical Report WCAP-18446-P/WCAP-18446-NP, Revision 0, Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs, February 2, 2024 (ADAMS Accession No. ML24053A348 (Public)).
3.
Westinghouse, "WCAP-18446-P, 'Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs'," December 14, 2020 (ADAMS Accession Nos.
ML20350B834 (Public), ML20349A273 (Non-Public)).
4.
Westinghouse, "Submittal of Voluntary Supplement to WCAP-18846-P / WCAP-18446-NP,
'Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs'," May 13, 2021 (ADAMS Accession Nos. ML21134A147 (Public), ML2113A149 (Public),
ML21134A148 (Non-Public)).
5.
U.S. NRC, "U.S. NRC Request for Additional Information (RAI) Questions for Topical Report WCAP-18446-P / WCAP-18446-NP, Revision 0, 'Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs'," December 15, 2021 (ADAMS Accession Nos. ML21344A024 (Public), ML21344A076 (Public), ML21344A077 (Non-Public)).
6.
Westinghouse, "Submittal of Set 1 of Responses to Requests for Additional Information on Westinghouse Topical Report WCAP-18446-P/NP, 'Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs'," February 4, 2022 (ADAMS Accession Nos. ML22038A161 (Public), ML22038A163 (Public), ML22038A162, (Non-Public)).
7.
Westinghouse, "Submittal of Set 2 of Responses to Requests for Additional Information on Westinghouse Topical Report WCAP-18446P/NP, 'Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs'," April 1, 2022 (ADAMS Accession Nos.
ML22094A120 (Public), ML22094A122 (Public), ML22094A121 (Non-Public)).
8.
Westinghouse, "Submittal of Set 3 of Responses and Clarifications to Requests for Additional Information on Westinghouse Topical Report WCAP-18446P/NP, 'Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs'," June 30, 2022 (ADAMS Accession Nos. ML22161A925 (Public), ML22161A927 (Public), ML22161A926 (Non-Public)).
9.
U.S. NRC, "Second Round of Requests for Additional Information for the Westinghouse Electric Company Topical Report WCAP-18446-P/WCAP-18446-NP, Revision 0, 'Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs'," September 21, 2022 (ADAMS Accession Nos. ML22262A323 (Public), ML22264A125 (Nonpublic)).
10.
Westinghouse, "Submittal of Set 1 of Responses to the Second Round of Requests for Additional Information on Westinghouse Topical Report WCAP-18446-P/NP, "Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs'," December 2, 2022 (ADAMS Accession Nos. ML22336A224 (Public), ML22336A226 (Public)).
11.
Westinghouse, "Submittal of Set 2 of Responses to the Second Round of Requests for Additional Information on Westinghouse Topical Report WCAP-18446-P/NP, "Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs'," February 2, 2023, and February 28, 2023 (ADAMS Accession Nos. ML23034A216 (Public), ML23034A218 (Public),
ML23034A217 (Non-Public)).
R. 12.
Westinghouse, "Submittal of Supplement to WCAP-18446-P/NP, Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs, to Extend AXIOMCladding," May 4, 2023 (ADAMS Accession Nos. ML23129A822 (Public),
ML23129A824 (Public), ML23129A823 (Non-Public)).
13.
Pacific Northwest National Laboratory, Fuel Performance Considerations and Data Needs for Burnup above 62 GWd/MTU; In-Reactor Performance, Storage, and Transportation of Spent Nuclear Fuel, November 2019 (ADAMS Accession No. ML19317D098 (Public)).
14.
U.S NRC, NRC's Methodology to Estimate Fuel Dispersal during a Large Break Loss of Coolant Accident, Andrew Bielen, James Corson, and Joseph Staudenmeier, April 26, 2023 (ADAMS Accession No. ML23116A214 (Public)).
15.
U.S. NRC, RIL 2021-13, Interpretation of Research on Fuel Fragmentation, Relocation, and Dispersal at High Burnup, December 2021 (ADAMS Accession No. ML21313A145 (Public)).
16.
Advisory Committee on Reactor Safeguards, Research Information Letter (RIL) 2021-13 on Interpretation of Research on Fuel Fragmentation, Relocation, and Dispersal at High Burnup, December 20, 2021 (ADAMS Accession No. ML21347A940 (Public)).
R.
SUBJECT:
Incremental Extension of Burnup Limit for Westinghouse and Combustion Engineering Fuel Designs Accession No: ML24132A009 Publicly Available (Y/N): Y Sensitive (Y/N): N If Sensitive, which category?
Viewing Rights:
NRC Users or ACRS only or See restricted distribution OFFICE ACRS SUNSI Review ACRS ACRS ACRS ACRS NAME ZAbdullahi ZAbdullahi LBurkhart RKrsek SMoore WKirchner DATE 05/13/24 05/13/24 05/13/24 05/16/24 05/17/24 05/24/24 OFFICIAL RECORD COPY May 24, 2024