ML25356A134
| ML25356A134 | |
| Person / Time | |
|---|---|
| Site: | 99902076 |
| Issue date: | 12/23/2025 |
| From: | Kevin Roche NRC/NRR/DANU/UAL2 |
| To: | Alissa Neuhausen Office of Nuclear Reactor Regulation |
| References | |
| EPID L-2025-TOP-0041 | |
| Download: ML25356A134 (0) | |
Text
MEMORANDUM TO:
Alissa Neuhausen, Chief Advanced Reactor Licensing Branch 2 Division of Advanced Reactors and Non-power Production and Utilization Facilities Office of Nuclear Reactor Regulation FROM:
Kevin Roche, Project Manager Advanced Reactor Licensing Branch 2 Division of Advanced Reactors and Non-power Production and Utilization Facilities Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF THE DECEMBER 11, 2025, PUBLIC MEETING WITH TERRESTRIAL ENERGY USA, INC., DISCUSSION ON THE STRATEGY FOR ESTABLISHING DEFENSE IN DEPTH FOR IMSR STRUCTURES, SYSTEMS AND COMPONENTS TOPICAL REPORT (EPID NO. L-2025-TOP-0041)
Meeting Information:
Applicant: Terrestrial Energy USA, Inc (TEUSA)
Docket/Project No.(s): 99902076 Public Meeting Notice Agencywide Documents Access and Management System (ADAMS)
Accession No.: ML25342A048 Meeting Attendees: See the enclosure for a list of meeting attendees.
CONTACT:
Michelle Vega Rodriguez, NRR/DANU 301-415-1170 December 23, 2025 Signed by Roche, Kevin on 12/23/25
ANeuhausen Meeting Summary:
The U.S. Nuclear Regulatory Commission (NRC) staff conducted the meeting in accordance with NRC Management Directive 3.5, Attendance at NRC Staff-Sponsored Meetings (ADAMS Accession No. ML21180A271). The main points of discussion during the meeting included:
Purpose and Scope of the Topical Report (TR)
The NRC staff asked about the intended use of the TR in future license applications and how the expected NRC staff findings on the TR would support this use.
TEUSA clarified that the TR is intended to show redundancy and diversity for accident categories (e.g., anticipated operational occurrences (AOOs), design basis accidents (DBAs), beyond-design-basis events (BDBEs)).
TEUSA clarified that the TR is intended to establish a defense-in-depth (DID) strategy for the Integrated Molten Salt Reactor (IMSR) design prior to a license application and that the methodology applies to the entire IMSR facility, not just the core unit.
Regulatory Basis The NRC staff discussed the potential benefits of white paper feedback compared to a safety evaluation for a TR given the NRCs existing DID philosophy and the lack of specific regulatory requirements addressing DID.
Clarifications NRC staff asked whether Table 1 in Section 6 of the TR, which has a list of specific structures, systems, and components (SSCs) (e.g., heat removal systems) is part of the defense-in-depth strategy or was intended to be an example.
TEUSA clarified that the SSCs listed are the minimum set required to perform the safety functions and central to the IMSR design. TEUSA stated that independence and diversity are addressed in the Principal Design Criteria TR, but full confirmation would come from the Probabilistic Risk Assessment in future submissions.
Next Steps:
NRC staff will conduct an acceptance review of the TR. Following its acceptance review, NRC staff will compile preliminary feedback on the TR to allow TEUSA to decide if an SE will support the intended use of the TR. A follow-up meeting will be coordinated for January 2026 to discuss NRCs review findings and determine the path forward.
No regulatory decisions were made as a result of this meeting.
Project [or Docket] No. 99902076
Enclosure:
List of Meeting Attendees cc: Terrestrial IMSR via GovDelivery dokeefe@terrestrialenergy.com
ANeuhausen
SUBJECT:
SUMMARY
OF THE DECEMBER 11, 2025, PUBLIC MEETING WITH TERRESTRIAL ENERGY USA, INC., DISCUSSION ON THE STRATEGY FOR ESTABLISHING DEFENSE IN DEPTH FOR IMSR STRUCTURES, SYSTEMS AND COMPONENTS TOPICAL REPORT (EPID NO. L-2025-TOP-0041).
DATED: DECEMBER 23, 2025 DISTRIBUTION:
PUBLIC RidsNrrDanuUal1 Resource RidsNrrDanuUal2 Resource RidsNrrDanu Resource ANeuhausen MVegaRodriguez KRoche HPhan GOberson ADAMS Accession Number: ML25356A134 NRR-106 OFFICE NRR/DANU/UAL2/PM NRR/DANU/UAL2/PM NRR/DANU/UAL2/BC NAME MVegaRodriguez KRoche ANeuhausen DATE 12/22/2025 12/23/2025 12/23/2025 OFFICE NRR/DANU/UAL2/PM NAME KRoche DATE 12/23/2025 OFFICIAL RECORD COPY
Enclosure List of Meeting Attendees For The December 11, 2025, Public Meeting with Terrestrial Energy USA, INC., Discussion on the Strategy for Establishing Defense in Depth for IMSR Structures, Systems and Components" Topical Report December 11, 2025 Name Organization Michelle E. Vega Rodriguez U.S. Nuclear Regulatory Commission (NRC)
Kevin Roche NRC Alissa Neuhausen NRC Greg Oberson NRC Hanh Phan NRC Matthew Gordon NRC David O'Keefe Terrestrial Energy USA, Inc. (TEUSA)
Darren Love TEUSA Francis Akstulewicz TEUSA William Smith TEUSA Zeke Thomason ZOHO Lisa LaBate Member of the public Sam McDonald Member of the public