ML25322A534
| ML25322A534 | |
| Person / Time | |
|---|---|
| Site: | 07007043 |
| Issue date: | 01/07/2026 |
| From: | Shana Helton Division of Fuel Management |
| To: | Turner F Subcritical Systems |
| References | |
| EPID L-2025-LLL-0015 | |
| Download: ML25322A534 (0) | |
Text
Fred Turner Chief Executive Officer Subcritical Systems, Inc.
900 Congress, Suite 500 Austin, TX 78701
SUBJECT:
U.S. NUCLEAR REGULATORY COMMISSION RESPONSE TO WHITE PAPER FROM SUBCRITICAL SYSTEMS, INC. ON ENERGY AMPLIFIER LICENSING STRATEGY (ENTERPRISE PROJECT IDENTIFICATION NUMBER L-2025-LLL-0015)
Dear Fred Turner,
By \
letter dated August 18, 2025, Subcritical Systems, Inc. (Subcritical Systems) submitted to the U.S. Nuclear Regulatory Commission (NRC) for review a white paper titled Subcritical Systems Inc. Energy Amplifier Whitepaper, (Agencywide Documents Access and Management System [ADAMS] Accession No. ML25246A727).
In the cover letter, Subcritical Systems stated that the white paper describes some of the potential regulatory frameworks for its subcritical energy amplifier system, which is an accelerator driven system (ADS), and requested NRC staff feedback on the licensing options outlined in the white paper. Attachment 1 contained an affidavit requesting the withholding of proprietary information. Attachment 2 contained a proprietary version of the white paper and licensing strategy. Attachment 3 contained a redacted version of the white paper, suitable for public disclosure.
Subcritical Systems outlined three options for potential licensing pathways under existing1 NRC regulations in its white paper:
1.
Subcritical Systems could request an NRC license for the integrated ADS (i.e.,
particle accelerator and energy amplifier) under Title 10 of the Code of Federal Regulations (10 CFR) Part 30, Rules of General Applicability to Domestic Licensing of Byproduct Material, and Part 70, Domestic Licensing of Special Nuclear Material. If the license application is determined to be acceptable, the NRC would use its existing regulations to issue a combined license for the particle accelerator under 10 CFR Part 30 and the energy amplifier - which contains the special nuclear material (SNM) - under 10 CFR Part 70.
2.
Subcritical Systems could request a license for only the particle accelerator under 10 CFR Part 30 using the NRCs Agreement State program. Prior to possession of the SNM, Subcritical Systems could incorporate its lessons learned into a separate license application and request an NRC license for the 1 As Subcritical Systems is or may be aware, the NRC is currently undergoing a substantial reformation of various existing regulations that are not yet published but which, depending on the timing of the intended application, may provide additional licensing pathways for consideration.
January 7, 2026
F. Turner 2
integrated ADS. If the license application is determined to be acceptable, the NRC would use its existing regulations to issue a combined license for the particle accelerator under 10 CFR Part 30 and the energy amplifier under 10 CFR Part 70.
3.
Subcritical Systems could request an NRC license for the integrated ADS under 10 CFR Part 50, Domestic Licensing of Production and Utilization Facilities, which may necessitate that the NRC perform an associated rulemaking.
Subcritical Systems suggests that, under existing regulations, the NRC would need to issue a rule of particular applicability to add the Subcritical Systems ADS to the definition of a utilization facility in 10 CFR 50.2 or perform a rulemaking to generically include subcritical assemblies within the scope of 10 CFR Part 50.
Also in its white paper, Subcritical Systems referenced the current regulatory definitions of:
utilization facility - see Section 11cc. of the Atomic Energy Act of 1954, as amended (AEA), and 10 CFR 50.2; production facility - see Section 11v. of the AEA and 10 CFR 50.2; and nuclear reactor - see 10 CFR 50.2.
The NRC staff has completed its review of the white paper and is basing its response on the following key assumptions:
The integrated ADS will be designed and operated as subcritical, so it does not meet the definition in 10 CFR 50.2 for a nuclear reactor because the ADS system is not designed or used to sustain nuclear fission in a self-supporting chain reaction.
The integrated ADS will be designed and operated for the sole purpose of generating electrical power; however, so it does not meet the current definitions in 10 CFR 50.22 for either a utilization facility or a production facility.
The particle accelerator portion of the ADS meets the 10 CFR 30.4 definition of a machine capable of accelerating electrons, protons, deuterons, or other charged particles in a vacuum and of discharging the resultant particulate or other radiation into a medium at energies usually in excess of 1 megaelectron volt.
Given these key assumptions presented in the white paper, 10 CFR Part 30 and Part 70 appear to be a viable licensing pathway. To determine the most efficient licensing pathway, the NRC staff encourages further preapplication engagement and believes it would be beneficial to meet in the near term to discuss the following:
Proposed possession limits for SNM - specifically, the amount of SNM expected to have 2 The NRC previously amended its regulations to add SHINE Medical Technologies, Inc.'s proposed accelerator-driven subcritical operating assemblies to the NRC's definition of a utilization facility.
(79 FR 62329).
F. Turner 3
enrichment levels of:
o less than 10 percent (%);
o from 10% to up to less than 20%, and o
from 20% and greater.
Aspects of nuclear criticality safety for the ADS, including potential accident scenarios that may impact the minimum margin of subcriticality, to ensure a common understanding of safety margins. Although the white paper postulated a maximum effective multiplication factor, maintaining an adequate margin of subcriticality could influence the most efficient licensing pathway for the integrated ADS. For example, natural phenomena hazards may impact the geometry of the ADS and impact safety margins. The guidance in NUREG-1520, Rev. 2, Standard Review Plan for Fuel Cycle Facilities License Applications (ML15176A258), states, in part, that for an SNM facility licensed under Subpart H to 10 CFR Part 70, in determining an appropriate MMS
[minimum margin to subcriticality], the reviewer should consider the specific conditions and process characteristics present at the facility in question. However, the MMS should not be reduced below 0.02. Although this guidance is specific to fuel cycle facilities, the NRC staff would consider similar specific conditions and factors to support the safety basis in the licensing of other facilities.
To determine the appropriate jurisdiction (i.e., NRC or Agreement State) over the ADS, the NRC staff encourages further preapplication engagement to discuss additional, specific technical details such as the amount of SNM and the location of the facility.
In accordance with 10 CFR 2.390, Public inspections, exemptions, requests for withholding, a copy of this letter will be available electronically for public inspection in the NRC Public Document Room (PDR) or from the Publicly Available Records component of the NRCs ADAMS. ADAMS is accessible from the NRC website at http://www.nrc.gov/reading-rm/adams.html. The PDR is open by appointment. To make an appointment to visit the PDR, please send an email to PDR.Resource@nrc.gov or call 1-800-397-4209 or 301-415-4737, between 8 a.m. and 4 p.m. eastern time (ET), Monday through Friday, except Federal holidays.
If you have any questions regarding this matter, please contact James Downs at 301-415-7744, or via email at James.Downs@nrc.gov.
Sincerely, Shana Helton, Director Division of Fuel Management Office of Nuclear Material Safety and Safeguards Docket No.: 07007043 Signed by Helton, Shana on 01/07/26
ML25322A534 OFFICE NMSS/DFM NMSS/DFM NMSS/MSST NRR/DANU NMSS/DFM NRR/DANU NAME JDowns JGoodridge AGiantelli MWentzel TGovan JGreives DATE 11/24/2025 11/24/2025 12/4/2025 12/4/2025 12/5/2025 12/5/2025 OFFICE NMSS/MSST NMSS/DFM OGC NLO NMSS Tech Editor NMSS NMSS/DFM NAME DSilberfeld SHelton RSiegman THerrera AKock SHelton DATE 12/8/2025 12/10/2025 12/26/2025 12/29/2025 01/6/2026 01/7/2026