ML25021A202

Memo - Summary of Meeting with TRISO-X LLC, on ISA Likelihood Definitions

ML25021A202
Person / Time
Site:	Triso-X
Issue date:	02/10/2025
From:	Matt Bartlett NRC/NMSS/DFM/FFLB
To:	Lav S NRC/NMSS/DFM/FFLB
References
EPID L-2022-PMP-0005
Download: ML25021A202 (1)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 MEMORANDUM TO:

Samantha Lav, Chief Fuel Facility Licensing Branch Division of Fuel Management Office of Nuclear Material Safety and Safeguards FROM:

Matthew Bartlett, Sr. Project Manager Fuel Facility Licensing Branch Division of Fuel Management Office of Nuclear Material Safety and Safeguards

SUMMARY

OF MEETING HELD ON DECEMBER 16, 2024, WITH TRISO-X LLC, TO ALIGN ON THE INTEGRATED SAFETY ANALYSIS DEFINITIONS OF UNLIKELY AND HIGHLY UNLIKELY, (ENTERPRISE PROJECT IDENTIFIER L-2022-PMP-0005)

The U.S. Nuclear Regulatory Commission (NRC) staff conducted a closed Microsoft Teams meeting with TRISO-X, LLC (TRISO-X) on December 16, 2024, from 3:00 p.m. until 5:00 p.m. to align on the Integrated Safety Analysis (ISA) update from the December 3-4, 2024 Audit Visit.

The purpose of the call was to discuss the options for resolution of the definitions of unlikely and high unlikely.

The TRISO-X original application was received April 5, 2022 (Agencywide Documents Access and Management System [ADAMS] Accession No. ML22101A200 - package) and was supplemented by letters dated October 13, 2022 (ML22286A144 - package), November 4, 2022 (ML22308A251 - package) and February 29, 2024 (ML24060A239).

The following options were discussed during the call.

Commitment: No sole items relied on for safety (IROFS).

Commitment: The definitions of highly unlikely and unlikely in Section 9 of the ISA Summary will remain -4 (highly unlikely) and -3 (unlikely).

Commitment: In addition to the statements on hierarchy of controls, TRISO-X will document a justification for relying only on administrative controls as IROFS, which demonstrates the alternatives to achieve the design criteria are not practicable (e.g.,

consistent with Title 10 of the Code of Federal Regulations (10 CFR) 70.64(b) and NUREG-1520, Revision 2, Standard Review Plan for Fuel Cycle Facilities License Applications, page 3-21).

CONTACT: Matthew Bartlett, NMSS/DFM 301-415-7154 February 10, 2025 Signed by Bartlett, Matthew on 02/10/25

S. Lav 2

Commitments for License Chapter 3 for demonstration of compliance with 10 CFR 70.61:

1.

Criticality accident sequences: Use the double contingency principle (DCP) with the criteria presented in the three bullets shown in NUREG-1520 p. 5-A-7 and 5-A-8 (i.e., DCP +3). Use -4 (risk-indexed highly unlikely) for risk indexing.

2.

Non-criticality accident sequences: Intermediate and high consequence accident sequences will be documented with a likelihood index of at least

-5 (risk-indexed highly unlikely) and -4 (risk-indexed unlikely).

The NRC staff and TRISO-X agree in principle that the options identified above would resolve the definitions of unlikely and highly unlikely. The NRC and TRISO-X staff agree they need to work through the implementation of these options in the revised license application to be submitted in December 2024 or January 2025.

The TRISO-X staff asked if the implementation for the options should go in Chapter 3 of the license application or in the ISA Summary. The NRC staff said that the information should be placed in the license application with a description of how the thresholds demonstrate compliance. This would facilitate development of the NRCs safety and safeguards evaluation report. TRISO-X pointed out the regulations indicate the likelihood definitions should be in the ISA Summary.

Docket No. 07007027 License: Not Applicable

Enclosure:

Attendee List

ML25021A202 (memo)

Enclosure LIST OF ATTENDEES DECEMBER 16, 2024, MEETING WITH TRISO-X LLC, TO ALIGN ON THE INTEGRATED SAFETY ANALYSIS DEFINITIONS OF UNLIKELY AND HIGHLY UNLIKELY Name Organization Jennifer Wheeler TRISO-X, LLC (TRISO-X)

Burns Cunningham TRISO-X Bob Maurer TRISO-X Matt Bartlett U.S. Nuclear Regulatory Commission (NRC)

Steve Poy NRC Joseph Rudd NRC Jonathan Marcano Lozada NRC Jeremy Munson NRC Dante Johnson NRC Langston Lewis NRC Lisa Dimmick NRC Mike Call NRC