ML24043A160
| ML24043A160 | |
| Person / Time | |
|---|---|
| Site: | 99902100 |
| Issue date: | 02/06/2024 |
| From: | Mallecia Sutton NRC/NRR/DANU/UAL1 |
| To: | George Wilson TerraPower |
| References | |
| EPID L-2023-TOP-0017 | |
| Download: ML24043A160 (1) | |
Text
Enclosure OFFICE OF NUCLEAR REACTOR REGULATION REGULATORY AUDIT
SUMMARY
REPORT TERRAPOWER, LLC TOPICAL REPORT FUEL AND CONTROL ASSEMBLY QUALIFICATION PROJECT NO. 99902100
1.0 BACKGROUND
By letter dated January 25, 2023, TerraPower, LLC (TerraPower) submitted topical report (TR)
NATD-FQL-PLAN-0004, Fuel and Control Assembly Qualification, Revision 0 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23025A409) to the U.S. Nuclear Regulatory Commission (NRC) staff. The TR provides TerraPowers plan to qualify fuel and control assemblies for the Natrium reactor design. In particular, the TR applies to Natrium Type 1 fuel, which is a metallic uranium-10 weight percent zirconium alloy fuel clad in HT9 steel, and control assemblies using boron carbide as a neutron absorber. The NRC staff finalized its completeness determination of the TR on March 31,2023, and found that the TR contained sufficient information such that the NRC staff could begin its detailed technical review of the TR (ML23086C087).
TerraPower requested the NRC staffs review and approval of its proposed qualification methodologies, acceptance criteria, manufacturing parameters, evaluation methods and models, use of legacy data, and planned testing, as described in the enclosed TR. The TR will be used by applicants of the TerraPower Natrium reactor design for future licensing submittals under Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, to design, license, construct, and operate the Natrium reactor.
TerraPowers overall licensing approach for the Natrium reactor design follows the Licensing Modernization Project (LMP) methodology described in Nuclear Energy Institute (NEI) 18-04, Revision 1, Risk-Informed Performance-Based Technology Inclusive Guidance for Non-Light Water Reactor Licensing Basis Development (ML19241A472). Regulatory Guide (RG) 1.233, Guidance for a Technology-Inclusive, Risk-Informed, and Performance-Based Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light Water Reactors, Revision0 (ML20091L698) endorses the LMP methodology described in NEI 18-04.
2.0 AUDIT REGULATORY BASES The audit regulatory bases are discussed in detail in the audit plan (ML23156A553) and include 10 CFR 50.43(e)(1)(i), 10 CFR 50.43(e)(1)(iii), 10 CFR 50.34(a)(1)(ii)(D), 10 CFR 50.34(a)(3)(i) and 10 CFR 50.34(a)(3)(ii). Relevant guidance that was considered during the audit included NUREG-2246, Fuel Qualification for Advanced Reactors (ML22063A131), NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants:
LWR Edition, (SRP) Section 4.2, Fuel System Design (ML070740002), and NUREG/CR-
2 7305, Metal Fuel Qualification: Fuel Assessment Using NRC NUREG 2246, Fuel Qualification for Advanced Reactors (ML23214A065).
3.0 AUDIT PURPOSE AND OBJECTIVES The purpose of the audit was for the NRC staff to gain a more detailed understanding of TerraPowers fuel and control assembly qualification efforts for the Natrium reactor and how the Natrium fuel and control assembly designs and qualification will support or demonstrate compliance with NRC regulations as discussed above. The audit was also performed to identify any information that will require docketing to support the NRC staffs safety evaluation. The audit plan, including the initial set of audit questions, was issued on June 7, 2023.
4.0 SCOPE OF THE AUDIT AND AUDIT ACTIVITIES The audit was conducted from June 26, 2023, to August 18, 2023, in a virtual format and followed the guidance in the Office of Nuclear Reactor Regulation Office Instruction LIC-111, Revision 1, Regulatory Audits (ML19226A274). TerraPower responded to the audit plan questions over the course of multiple audit meetings. To support addressing the NRC staff questions, TerraPower made the following documents available in its electronic Reading Room (eRR):
AFQM-LIC-RPT-0001, Regulatory Guidance Development Report AFQMG-ENG-PLAN-0001, Rev. 1, Type 1 Fuel Pin Qualification Report NATD-FQL-PLAN-0003, Rev. 0, Absorber Pin Qualification Plan NAT-2738, Rev. 0, Fuel and Control Pin Data Qualification Plan TP-ENG-PROC-0048, Rev. 1, Qualification of Existing Data NAT-2916, Rev. 0, Transient Testing in TREAT [Transient Reactor Test Facility] to Support Natrium Reactor Design Limits NAT-2917, Rev. 0, Fuel Performance Calculation to Support Transient Testing in TREAT for the Natrium Reactor Design Limits NAT-MDX-PLAN-0001, Rev. 0, Natrium Demonstration Project Methodologies Verification and Validation Test Plan ARMI-ENG-PRSNT-0004 ARMI MeV, The Advanced Reactor Modeling Interface (ARMI)
Framework Various drawings of control rod assembly components.
NAT-3098-P, Fuel and Control Assembly Qualification Presentations Materials NAT-3076, Fuel Slug (Type 1) Product Specifications NAT-3077, Fuel Pin Assembly NAT-3266, Rev. 0, Specification - HT9 Wire for Natrium NATD-ENG-SPEC-0008, Rev. 1, HT9 Raw Material NATD-ENG-SPEC-0009, Rev. 2, HT9 Duct Tube Specification NATD-ENG-SPEC-0010, Rev.1, HT9 Cladding Tube Specification NATD-ENG-SPEC-0022, Rev. 0, B4C Materials Spec to Support Testing In addition, TerraPower provided written summaries of its response to some of the NRC staff questions in the eRR. The NRC staff reviewed the written summaries provided by TerraPower but determined that none of the responses were necessary to support safety findings.
Members of the audit team included the NRC staff listed below:
3 Reed Anzalone Senior Reactor Engineer, Audit Lead Mallecia Sutton Senior Project Manager, Lead Natrium Project Manager Courtney Banks Project Manager, Lead Audit Project Manager Roel Brusselmans Project Manager, Audit Project Manager The primary participants from TerraPower for this audit included Patrick Donnelly, James Vollmer, Sam Miller, Brian Johnson, Javier Romero, Drew Mueller, Logan Smith, Jamie Getchius, and Ryan Christensen.
On August 18, 2023, the NRC staff held an audit exit meeting with TerraPower and summarized the audit purpose, activities, and high-level results. The NRC staff did not acquire any documents during the audit.
5.0
SUMMARY
OF OBSERVATIONS The audit plan included questions covering several categories related to the TR. Each category is provided here as a major bullet followed by a summary of the pertinent discussion and documentation from the audit.
Additional detail and context on the regulatory acceptance criteria, Natrium principal design criteria, and fuel system design criteria (including both damage and failure criteria), as well as the relationships between all of these criteria.
o TerraPower provided more detailed information on the regulatory acceptance criteria discussed in the TR by referencing a white paper (WP) entitled Advanced Fuel Qualification Methodology Report, which was submitted for the NRC staffs review on July 16, 2020 (ML20209A155).
o TerraPower clarified that the fuel design limits described in the TR support establishment of the specified acceptable system radionuclide release design limits (SARRDL). In the analysis, cladding integrity is evaluated against the fuel failure criteria unless there is a (predicted or assumed) cladding breach, at which point compliance with the SARRDLs is evaluated.
o TerraPower clarified the distinction between the fuel damage criteria provided in TR Table 4-1, Design Criteria to Prevent Fuel System Damage, and the fuel failure criteria provided in Table 4-2, Design Criteria to Prevent Fuel System Failure. TerraPower stated in Table 2-1 of the TR that fuel system damage criteria shall be establishedto ensure that fuel system dimensions remain within operational tolerances and that functional capabilities are not reduced below those assumed in the safety analysis. This is consistent with the definition of fuel system damage provided in SRP Section 4.2, which NUREG-2246 references as a basis.
Additional detail on the manufacturing process and how it affects key fuel system performance characteristics.
o TerraPower provided a discussion on the manufacturing processes for the fuel and which steps have a significant influence on the end state. Certain Natrium materials specifications were made available for the NRC staff during the audit.
4 The NRC staff was satisfied that the information provided in the TR was adequate.
Additional detail on radionuclide retention requirements, and associated retention and release modeling approach and validation o TerraPower indicated in public meetings held on July 11, 2023, and July 12, 2023, (ML23180A301 and ML23181A189, respectively) that radionuclide retention is not within the scope of the fuel and control assembly qualification TR and would be covered by the methodology for analyzing licensing basis events with fuel failure.
Additional detail on the phenomena identification and ranking table (PIRT) exercise(s) conducted by TerraPower.
o TerraPower made AFQMG-ENG-PLAN-0001, Type 1 Fuel Pin Qualification Report, Rev. 1, available to the NRC staff on the audit portal. This document contains a full discussion of the Natrium Type 1 fuel PIRT conducted by TerraPower. TerraPower requested feedback on Revision 0 of this report (at the time titled Type 1 Fuel Pin Qualification Plan) which was submitted to the NRC staff as a WP on February 26, 2021 (ML21057A008). The NRC staff verified that the PIRT information was consistent between the two versions of the report.
Additional detail on the evaluation model.
o TerraPower provided an overview of the codes discussed in the TR and role of the fuel performance models in steady-state and transient analyses. A detailed discussion was provided in NATD-MDX-PLAN-0001, Natrium Demonstration Project Methodologies Verification and Validation Test Plan, which was made available to the NRC staff on the eRR during the audit. TerraPower also provided a separate clarification on the means for analyzing duct deformation and control rod insertability criteria.
Additional detail on certain fuel phenomena.
o TerraPower and the NRC staff discussed several metallic fuel phenomena and how they are addressed by Natrium Type 1 fuel, including:
Burnup effects on the fuel Fuel constituent redistribution effects Fuel-cladding chemical interaction o TerraPower discussed phenomena to be addressed by planned transient testing.
Clarification on aspects of the fuel and control assembly design.
o TerraPower provided clarification on certain aspects of the Natrium Type 1 fuel assembly and control assembly designs, including:
Details on fuel assembly hold-down
5 Plans for manufacturing ducts Aspects of the control assembly design that were not clear in the TR Details on the planned process for welding fuel pin end caps General clarification of various subjects included in the TR.
o TerraPower provided a walkthrough of the historical data provided in the TR.
o TerraPower discussed plans for technical specifications related to fuel.
There were no deviations from the audit plan.
6.0 REQUESTS FOR ADDITIONAL INFORMATION RESULTING FROM AUDIT As a result of the audit, the NRC staff did not identify any specific items as requests for additional information related to this TR, nor did TerraPower identify a need to provide a voluntary revision or supplement to the TR.
7.0 OPEN ITEMS AND PROPOSED CLOSURE PATHS There are no open items resulting from this audit.