ML24115A128
| ML24115A128 | |
| Person / Time | |
|---|---|
| Site: | 99902100 |
| Issue date: | 04/24/2024 |
| From: | Stephanie Devlin-Gill NRC/NRR/DANU/UAL1 |
| To: | TerraPower |
| References | |
| EPID L-2023-TOP-0057 | |
| Download: ML24115A128 (1) | |
Text
1 TERRAPOWER, LLC - AUDIT PLAN FOR TP-LIC-RPT-0006, STABILITY METHODOLOGY TOPICAL REPORT, REVISION 0 (CAC / EPID NO. 000431 / L-2023-TOP-0057)
Applicant:
TerraPower, LLC Applicant Address:
15800 Northup Way, Bellevue, WA 98008 Plant Name:
Natrium Project No.:
99902100
Background:
By letter dated November 30, 2023, TerraPower, LLC (TerraPower) submitted topical report (TR) Stability Methodology Topical Report, Revision 0 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23334A239) to the U.S. Nuclear Regulatory Commission (NRC) staff. The TR contains an overview and description of the model developed to evaluate reactor stability for the Natrium sodium fast reactor design. On February 20, 2024, the NRC staff found that the material presented in the TR provides technical information in sufficient detail to enable the NRC staff to conduct a detailed technical review (ML23355A072).
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.
TerraPower used RG 1.232, Guidance for Developing Principal Design Criteria for Non-Light-Water Reactors, Revision 0, (ML17325A611) to inform the development of its principal design criteria (PDC) for the Natrium reactor. The establishment of PDC is integral to the review of the nuclear facility design, and the development of its structures, systems, and components (SSC) design bases. These criteria aid in the NRC staffs evaluation of other regulations and allow the NRC staff to have reasonable assurance that the proposed nuclear reactor facility design will conform to the design bases with adequate margins for safety. The proposed Natrium PDCs are specified in TR NATD-LIC-RPRT-0002, Principal Design Criteria for the Natrium Advanced Reactor (ML23024A280), which is under review by the NRC staff.
Purpose:
The purpose of the audit is for the NRC staff to gain a more detailed understanding of TerraPowers reactor stability evaluation model presented in the TR. A secondary purpose of the audit is to identify any information that will require docketing to support the NRC staffs safety evaluation.
2 Regulatory Audit Basis:
Title 10 of the Code of Federal Regulations (10 CFR) 50.34(a)(3)(i) requires that an application for a construction permit include in its preliminary safety analysis report the PDC for the facility.
The NRC staff considered the following proposed Natrium PDCs from TR NATD-LIC-RPRT-0002 in its review of this TR:
Natrium PDC 10: Reactor design. The reactor core and associated coolant, control, and protection systems shall be designed with appropriate margin to assure that specified acceptable system radionuclide release design limits are not exceeded during any condition of normal operation, including the effects of anticipated operational occurrences.
Natrium PDC 12: Suppression of reactor power oscillations. The reactor core; associated structures; and associated coolant, control, and protection systems shall be designed to ensure that power oscillations that can result in conditions exceeding specified acceptable system radionuclide release design limits are not possible or can be reliably and readily detected and suppressed.
Regulatory Audit Methodology:
The regulatory audit will follow the guidance in the Office of Nuclear Reactor Regulation, Office Instruction LIC-111 Regulatory Audits, Revision 1 (ML19226A274), and focus on information provided by TerraPower in the electronic reading room (ERR).
Information and Other Material Necessary for the Regulatory Audit:
The NRC staff requests TerraPower to make available the information and/or subject matter experts necessary to respond to the audit inquiries included in the enclosure.
Team Assignments:
Ben Parks Senior Technical Advisor, Audit Lead Stephanie Devlin-Gill Senior Project Manager, Natrium Roel Brusselmans Project Manager, Audit Project Manager Deion Atkinson Project Manager, Audit Project Manager Reed Anzalone Senior Nuclear Engineer, Natrium Technical Lead Inseok Baek Reactor Engineer Logistics:
Entrance Meeting May 7, 2024, 4:00 PM Exit Meeting June 7, 2024, 4:00 PM Audit meetings will take place in a virtual format, using Microsoft Teams or another similar platform. Audit meetings will be scheduled on an as-needed basis after the entrance meeting and once the NRC staff has had the opportunity to review any documents placed in the online reference portal. The audit will begin on May 7, 2024, and continue as necessary, with activities occurring intermittently during the audit period. The audit period may be reduced or extended, depending on the progress made by the NRC staff and TerraPower in addressing audit questions.
3 Special Requests:
The NRC staff requests that TerraPower ensure that their technical staff are available to answer questions during the audit. The NRC staff also requests that TerraPower provide access to supporting documents via the TerraPower ERR.
Deliverables:
At the completion of the audit, the audit team will issue an audit summary within 90 days after the exit meeting but will strive for a shorter duration. The audit summary will be declared and entered as an official agency record in ADAMS and be made available for public viewing through the publicly available records component of ADAMS.
If you have questions about this audit, please contact me by phone at (301) 415-5301 or via email at Stephanie.Devlin-Gill@nrc.gov.
Sincerely,
/RA/
Stephanie Devlin-Gill, Senior Project Manager Advanced Reactors Licensing Branch 1 Division of Advanced Reactors and Non-Power Production and Utilization Facilities Office of Nuclear Reactor Regulation Project No.: 99902100
Enclosure:
As stated cc: TerraPower Natrium via GovDelivery
OFFICIAL USE ONLY - PROPRIETARY INFORMATION OFFICIAL USE ONLY - EXPORT CONTROLLED INFORMATION Enclosure OFFICIAL USE ONLY - EXPORT CONTROLLED INFORMATION OFFICIAL USE ONLY - PROPRIETARY INFORMATION Audit Questions Related to TP-LIC-RPT-0006 Stability Methodology Topical Report, Revision 0 Specific audit information needs and questions include:
- 1. TR Section 2.3, Important Phenomena states, Phenomena relevant to the stability of the Natrium reactor were identified and ranked using a categorization of low, medium, and high importance, and all phenomena with an importance of medium or higher are identified as important phenomena and included in Table 2-2.
- a. Provide documentation showing the additional phenomena considered and ranked as low.
- b. Briefly describe how the ranking was accomplished.
- 2. TR Chapter 3, Methodology Roadmap, ((
)).
- 3. Provide additional information to justify the uncertainty approach described in Section 3.3.3.1, Description of Selected Approach.
- 4. TR Chapters 4, Models, and 5, Technical Evaluation Process Description, provide descriptions of the models and stability evaluation process, respectively. TR Chapter 6, Fermi-1 Benchmark Calculation, provides a comparison of the calculated stability performance of the Enrico Fermi Unit 1 (Fermi 1) reactor to measured data from stability tests at Fermi 1. TR Chapter 7, Plant-Specific Application, provides an evaluation of Natrium stability at one statepoint. Provide calculation documentation (e.g., latest revisions of calculation notes or files) supporting the evaluations described in Chapters 6 and 7, including:
- a. for Chapter 6, material describing the treatment of experimental data;
- b. calculation of system reactivity coefficients and temperatures;
- c. calculation of the transfer functions; and
- d. description of the uncertainty analysis
- 5. Provide additional information describing the assessment of Fermi 1 benchmarking results, including a justification that reasonable agreement was achieved and that appropriate differences between measured and calculated parameters have been identified (e.g., ((
)) as displayed in TR Figures 6-2, Transfer Function Gain Plot, and 6-3, Transfer Function Phase Shift Plot).
- 6. As described in TR Section 6.1.3, ((
)) a ((
)) is determined based on a comparison of measured to calculated values. Provide a justification for the application of this ((
)) to predicted Natrium results as described in TR Section 7.2.1, Demonstration of Model Uncertainties Treatment.