ML24361A072
| ML24361A072 | |
| Person / Time | |
|---|---|
| Site: | 99900003 |
| Issue date: | 03/12/2025 |
| From: | Glisan J NRC/NRR/DNRL/NLIB |
| To: | Hayes M NRC/NRR/DNRL/NLIB |
| Shared Package | |
| ML24361A071 | List: |
| References | |
| Download: ML24361A072 (12) | |
Text
March 12, 2025 MEMORANDUM TO:
Michelle W. Hayes, Chief New Reactor Licensing and Infrastructure Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation FROM:
Jordan D. Glisan, Project Manager /RA/
New Reactor Licensing and Infrastructure Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF PUBLIC MEETING TO DISCUSS PRE-APPLICATION LICENSING TOPICAL REPORT ON SOURCE TERM METHODOLOGY FOR THE BWRX-300 SMALL MODULAR REACTOR On December 11, 2024, an Observation Public Meeting / Partially Closed Proprietary meeting was held between the U.S. Nuclear Regulatory Commission (NRC) staff and GE-Hitachi Nuclear Energy Americas, LLC (GEH) concerning the expected submittal of the license topical report on BWRX-300, Source Term Methodology.
The topic discussed during this meeting included the following:
Public / Closed Pre-Application meeting concerning the GEH proposed licensing topical report (LTR) on source term methodology for the BWRX-300 small modular reactor (SMR) for Establishment of emergency planning zone (EPZ)
The NRC issued the public meeting notice (Agency Documents Accession Management System (ADAMS) Accession No. ML24304A931) on October 30, 2024, and posted it on the NRC public website. Prior to the meeting, GEH submitted presentation slides for the open session (ML24330A258).
CONTACT: Jordan Glisan NRR/DNRL 301-415-3478
M. Hayes 2
Enclosed are the meeting agenda (Enclosure 1), list of participants for the meeting (Enclosure 2), and summary (Enclosure 3).
Docket No. 99900003
Enclosures:
- 1. Meeting Agenda
- 2. List of Attendees
- 3. Meeting Summary
- via email NRR-106 OFFICE NRR/DNRL/
NLIB: PM NRR/DNRL/
NRLB: LA NRR/DNRL/
NRLB: PM NRR/DNRL/
NRLB: BC NRR/DNRL/
NRLB: PM NAME JShea*
SGreen*
JShea*
MHayes*
JGlisan*
DATE 12/23/2024 01/08/25 01/30/25 03/10/25 03/12/25
U.S. NUCLEAR REGULATORY COMMISSION
SUMMARY
OF THE DECEMBER 11, 2024, OBSERVATION PUBLIC MEETING TO DISCUSS PRE-APPLICATION LICENSING TOPICAL REPORT ON SOURCE TERM METHODOLOGY FOR THE BWRX-300 SMALL MODULAR REACTOR Meeting Agenda Time Topic Speaker 10:00 am - 11:00 am GEH Public Presentation of Technical Topics U.S. Nuclear Regulatory Commission (NRC)/ GE-Hitachi Nuclear Energy Americas, LLC (GEH) 11:00 am - 11:10 am Public Comment Period 11:10 am -12:30 pm GEH Proprietary Presentation of Technical Topics NRC/GEH
U.S. NUCLEAR REGULATORY COMMISSION
SUMMARY
OF THE DECEMBER 11, 2024, OBSERVATION PUBLIC MEETING TO DISCUSS PRE-APPLICATION LICENSING TOPICAL REPORT ON SOURCE TERM METHODOLOGY FOR THE BWRX-300 SMALL MODULAR REACTOR List of Attendees Public Proprietary Name Organization x
x Jim Shea NRC x
x Jordan Glisan NRC x
x Michelle Hayes NRC x
x Carolyn Lauron NRC x
x Donna Williams NRC x
x Hossein Esmaili NRC x
x Zhe Yuan NRC x
x Shawn Campbell NRC x
x Edward Robinson NRC x
x Elijah Dickson NRC x
x Anne-Marie Grady NRC x
x Marie Pohida NRC x
x Stacy Rosenberg NRC x
x Edward Robinson NRC x
x Kevin Hsueh NRC x
x Todd Smith NRC x
x Keith Miller NRC x
x Michelle Hart NRC x
x George Wadkins GEH x
x Richard Montgomery GEH x
x Suzanne Karkour GEH x
x David Hinds GEH x
x George Malone GEH x
x Luis Hinojosa GEH x
x Michael Norwood GEH x
x Sarah Davis GEH x
x Michael Norwood GEH
2 Public Proprietary Name Organization x
x Christer Dahlgren GEH x
x Alexandre Seguin GEH x
x David Hindera GEH x
x Justyna Salachna GEH x
x Home Deepayan GEH x
x Elana Sorin GEH x
x Samantha Smelley GEH x
x Jakub Zychowicz GEH x
x Michelle Catts GEH x
x Kelli Banks GEH x
x Chantal Morin GEH x
x Brian McDermott TVA x
x Ray Schiele TVA x
x Jesse Morson TVA x
x Scott Owen TVA x
x Edward Schulte TVA x
x David Daigle TVA x
x James Thornton TVA x
x James Ashe TVA x
x Alex Fife ONR x
x Adrian Chewter ONR x
x Joel Robinson ONR x
x Michael Xu CNSC x
x Thambiayah Nitheanandan CNSC x
x Douglass Miller CNSC x
x Sara Mostofian CNSC x
x Jana Ene CNSC x
x Tomasz Gulinski CNSC x
x Thuy Nguyen CNSC x
x Abderrazzaq Bounagui CNSC x
x Geoff Pihl Duke x
x Christie Taylor Duke x
x Leon Mohorovic OPG x
x Adam Jaroszek PAA
3 Public Proprietary Name Organization x
Bartosz Kowalczyk ORLEN Synthos Green Energy x
Wiktor Saczawa ORLEN Synthos Green Energy x
Eleonora Skrzypek National Centre for Nuclear Research (NCBJ) x Yue "Joy" Jiang Breakthrough Institute
U.S. NUCLEAR REGULATORY COMMISSION
SUMMARY
OF THE DECEMBER 11, 2024, OBSERVATION PUBLIC MEETING TO DISCUSS PRE-APPLICATION LICENSING TOPICAL REPORT ON SOURCE TERM METHODOLOGY FOR THE BWRX-300 SMALL MODULAR REACTOR Meeting Summary On December 11, 2024, commencing at 10:00 am, an observation public and partially closed meeting was held between the U.S. Nuclear Regulatory Commission (NRC) staff and GE-Hitachi Nuclear Energy Americas, LLC (GEH) regarding their proposed accident source term methodology to demonstrate compliance with Title10 of the Code of Federal Regulations (10 CFR) 50.34(a)(1) or 10 CFR 100.21(c)(2) and for establishment of its emergency planning zone (EPZ) License Topical Report (LTR) NEDC-33913P. GEH provided a public pre-application presentation dated November 25, 2024, and a proprietary presentation ((Agency Document Accession Management System (ADAMS) Accession No. ML24330A258 (public)
ML24330A257 (proprietary)) for NRC staff review prior to the meeting.
Upon receipt of the meeting presentation the NRC staff provided pre-meeting initial feedback dated December 6, 2024 (ML24341A047) that requested clarification on how the proposed methodology met specific core melt design basis accident (DBA) regulations. Specifically, the NRC staff pointed to requirements for the deterministic design basis substantial core-melt source term. This source term meets different regulatory requirements than those typically assessed in NUREG 0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, (SRP) Chapter 15, Transient and Accident Analyses, which assess a spectrum of DBAs and the development of their respective source term.
The substantial core-melt DBA source term is consistent with the requirements of 10 CFR Part 50.34(a)(1)(ii)(D).and 10 CFR 100.21(c)(2), which are the specific NRC requirements for source term determination for light-water nuclear reactor (LWR) designs that provide adequate protection of public health and safety. Per footnote [6] in 10 CFR 50.34, the fission product release assumed for this evaluation should be based upon a major accident, hypothesized for purposes of site analysis or postulated from considerations of possible accidental events. Such accidents have generally been assumed to result in substantial meltdown of the core with subsequent release into the containment of appreciable quantities of fission products.
The following information was not included in the preliminary feedback but is provided here for additional background.: In the statements of consideration for 10 CFR 50.34, as outlined in 61 FR 65457, the Commission emphasizes its use of the exclusion area boundary (EAB) and low population zone (LPZ) dose acceptance criteria of 25 rem, based on a postulated deterministic core melt source term, as a fundamental aspect of evaluating plant design features and site characteristics that mitigate radiological consequences of accidents. This criterion ensures that, even under severe accident conditions, the public remains at low risk, aligning with the Commissions defense-in-depth approach to reactor siting for public safety. Over time, the Commissions experience with this criterion and subsequent radiological consequence analyses has influenced key design considerations, such as containment leak rates and the performance of engineered filtration systems, enhancing overall plant safety by reinforcing multiple barriers to radiation release. By maintaining this conservative dose threshold, the NRC continues to integrate both deterministic safety principles and probabilistic risk insights, ensuring reactor siting and design remain robust in protecting public health.
2 Probabilistic risk assessments provide useful insights into system performance and suggest changes in how the desired defense-in-depth is achieved. The 1995 Commission PRA Policy Statement (60 FR 42622, August 16, 1995) on the use of probabilistic risk assessment methods calls for the use of probabilistic risk assessment technology in all regulatory matters in a manner that complements the Commissions deterministic approach and supports the traditional defense-in-depth philosophy. Based on this policy, the NRC staff provided its positions related to use of the core melt source term for passive and evolutionary LWR design concepts In NRC SECY-94-302, Source term-related Technical and Licensing Issues Pertaining to Evolutionary and Passive Light-water-reactor Designs. (ADAMS Accession No. ML003708141) In this policy paper, the NRC staff outlined its specific use of the accident source terms for the evolutionary and passive LWR designs for equipment qualification, control room habitability, engineered safety features as well as other design considerations where an accident source term would be applied.
The meeting commenced with a brief introduction by the NRC licensing project manager, who explained the purpose of the meeting, provided background on pre-application engagement with GEH on the BWRX-300 since 2019 including a previous October 5, 2022 (ML22294A006) public meeting on this topic and briefly introduced the NRC staff participating in the meeting and described the meeting logistics. All GEH staff participated in this public meeting remotely. NRC staff participated in the meeting at the designated conference room and also remotely. In addition, the NRC introduced the Canadian Nuclear Safety Commission (CNSC) and the United Kingdom Office for Nuclear Regulation (ONR) staff as part of a March 12, 2024 (ML24066A026) trilateral Memorandum of Cooperation (MOC) with the NRC to collaborate on the assessment of small modular reactor (SMR) and advanced reactor designs. Therefore, as an integral part of the meeting, the CNSC and the ONR could ask and participate in discussions with GEH during the public portion and during the closed portion of todays meeting.
During the meeting, GEH provided its source term methodology overview and described the BWRX-300 source term methodology as, The combination of the robust, systematic process required by the BWRX-300 Safety Strategy (NEDC-33934P), along with the inherent safety features of the BWRX-300 design [that] makes the likelihood of significant nuclear fuel failure including core melt not credible.
GEH also noted that their presentation only included the proposed source term methodology and that they plan to have more pre-application engagements in the future on specifics of the source term application to issues such as the EPZ, environmental qualification, control room habitability and containment source term prior to the submittal of the LTR for review.
GEH stated as part of their presentation and subsequent discussions that, the BWRX-300 currently does not have any full power, internal events within the event selection approach criteria that result in a core melt, so no core-melt accidents would be included in the spectrum of events for the BWRX-300.
GEH also quoted a section of the NRC Regulatory Guide (RG) 1.183, Revision 1, Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors, October 2023, (ML23082A305), stating that the GEH approach is consistent with this definition accident whose consequences, as measured by the radiation exposure of the surrounding public, would not be exceeded by any other accident whose occurrence during the lifetime of the facility would appear to be credible.
3 GEH concluded its presentation and discussions stating that, the BWRX-300 currently has no full power, internal events within the [source term] evaluations proposed cut-off frequency that have subsequent release into containment of appreciable quantities of fission products, and that the design of the BWRX-300 is such that events are successfully mitigated to prevent an accident resulting in core meltdown whose occurrence during the lifetime of the facility would appear to be credible, as described in RG 1.183.
As a result of these discussions the NRC staff provided prospectives on these topics including a description of the purpose of the deterministic substantial core melt source term as described in RG 1.183. The NRC staff noted that the proposed methodology as described by GEH in their presentation uses a risk-based accident cut off approach, which is not consistent with the selection of major accident as described in RG 1.183. The NRC staff explained that accident source terms specified in RG 1.183, Revisions 0 and 1, are specifically designed for applicants to comply to the requirements of 10 CFR 100.21(c)(2) and 10 CFR 50.34(a)(1)(ii)(D).
The NRC staff specifically noted that the Commissions "defense in depth" philosophy is not risk based but refers to a strategy of creating multiple, independent, and redundant layers of protection within nuclear power plants to prevent and mitigate accidents, ensuring that no single layer is solely relied upon to safeguard against potential failures, including human error, and minimize the risk of radiation release to the public; essentially, it means implementing various overlapping safety measures to compensate for potential failings in any one system. 10CFR Part 50 regulatory requirements provide the minimum level of defense-in-depth through processes that include design, construction, regulatory oversight and operating activities; additional defense-in-depth shall be provided through the application of deterministic design and operational features for events that have a high degree of uncertainty with significant consequences to public health and safety. Adequate protection of public health and safety is presumptively assured by compliance with NRC requirements.
The NRC staff noted the use of the term cut-off frequency(s), as inconsistent with the 1995 Commission PRA Policy Statement (60 FR 42622, August 16, 1995), which specifically states that, The use of PRA technology should be increased in all regulatory matters to the extent supported by the state of the art in PRA methods and data, and in a manner that complements the NRC's deterministic approach and supports the NRC's traditional defense-in-depth philosophy. The Commission also specified that a risk-informed approach explicitly identifies and quantifies sources of uncertainty in the analysis (NRC, NUREG-1855, Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decision Making, Revision 1, March 2017, (ML17062A466)). The NRC staff also explained to GEH that risk informed approaches consider all modes and all hazards not just full power internal events and that the NRC does not have a quantitative definition of the term credible. However, the core melt source term that meets the requirements of 10 CFR 100.21(c)(2) and 10 CFR 50.34(a)(1)(ii)(D) are based on internal events.
During further discussions, the NRC staff pointed to the proposed RG 1.183 (DG-1425),
Revision 1, Alternative Radiological Source Terms for Evaluating Design Basis Accident at Nuclear Power Reactors, Section 2, Attributes of an Acceptable Accident Source Term, which identifies attributes of an acceptable accident source term for use in new power reactor applications. This guidance provides that could include additional flexibility and additional mitigation credit that GEH could leverage to develop a BWRX-300-specific accident source term. The NRC staff provided that the BWRX-300 design could have design features that limit
4 the accident progression and subsequent extent of core damage than what is traditionally assessed for Generation 2 large light water reactors.
GEH also requested examples of accident source terms. The NRC staff provided examples of core melt source terms designed to meet the 10 CFR 100.21(c)(2) and 10 CFR 50.34(a)(1)(ii)(D) requirements. They include: NUREG-1465 which was discussed above; SAND2011-0128, Accident Source Terms for Light-Water Nuclear Power Plants Using High-Burnup or MOX Fuel, issued January 2011 (ML20093F003) which is endorsed in RG 1.183 Revision 1; and SAND2023-01313, High Burnup Fuel Source Term Accident Sequence Analysis, Albuquerque, issued April 2023 (ML23097A087) which is endorsed in Draft Guidance 1425 (RG 1.183 Revision 2). The NRC staff also elaborated that NuScale took a similar design-specific approach to developing their accident source term to meet the requirements under a Part 52 license which are equivalent to those in 10 CFR 100.21(c)(2) and 10 CFR 50.34(a)(1)(ii)(D). See the NRC staffs safety evaluation report at (ML19297G520). To address the regulatory requirements, the NuScale topical report proposed a methodology to develop a core damage source term based on several severe accident scenarios that result in core damage, taken from the design-specific probabilistic risk assessment.
At the conclusion of the open portion of the meeting the public was invited to make comments or ask questions of the NRC staff. There was a question from a member of the public who was interested in additional background information related to source term policy and specific guidance used by the NRC staff to develop its safety determinations on this topic. The member of the public was directed to the NRC public website, Nuclear Power Reactor Source Term, that included the history and current applications and guidance used for determining adequacy of an applicants source term including a reference for application of source terms applied to advanced and passive LWR designs, SECY-94-302, "Source Term-Related Technical and Licensing Issues Pertaining to Evolutionary and Passive Light-Water-Reactor Designs."
There were no further comments or questions from members of the public, therefore the NRC staff continued the meeting in a closed session continuing the discussions of the GEH proposed source term methodology which they stipulate as a risk-informed, performance-based (RIPB) method for selecting limiting accident event sequences and then utilizes a mechanistic approach for determining radiological release source terms and timing. This proposed method would assume no internal event sequences that result in core-melt for the BWRX-300 within its RIPB event sequence selection approach, and therefore, the mechanistic radiological analyses use reduced source terms including specific RIPB cut off values that are used to determine its limiting accident sequences that do not lead to any core-melt sequence for any DBA.
Given what was presented and discussed by GEH the NRC staff did suggest that GEH could pursue an exemption to the 10 CFR Part 50 requirements of substantial core-melt, however, it could be a difficult option to pursue given that there is no model of an exemption that has ever been approved for an LWR design.
While GEH stated that the EPZ aspects of the future LTR would be discussed at future meetings,NRC staff did point to recently approved RG 1.242, Performance-Based Emergency Preparedness for SMRs, non-LWRs, and non-power production or utilization facilities, Revision 0, November 2023 (ML23226A036) concerning these issues for guidance on implementing a performance-based emergency planning (EP) program to comply with 10 CFR 50.160. The requirements in 10 CFR 50.160 afford a performance-based, technology-inclusive, risk-informed, and consequence-oriented approach to EP for these specific technologies as an alternative to the EP requirements under 10 CFR 50.47(b) and Appendix E to 10 CFR
5 Part 50. Applicants and licensees choosing to comply with 10 CFR 50.160 also need to comply with the applicable provisions in 10 CFR 50.47.
There were no regulatory decisions made as a result of this public meeting.
The meeting was then adjourned at approximately 12:30 pm.