ML25356A104

Enclosure, Staffs Criticality Safety Question, Telephone Call to Discuss a Criticality Safety Request for Additional Information Related to Water Inclusion, Model No. Npc (Docket No. 71-9294, CAC No. 001029/EPID No. L-2025-LLA-0079)

ML25356A104
Person / Time
Site:	07109294
Issue date:	11/20/2025
From:	Garcia-Santos N Global Nuclear Fuel, Storage and Transportation Licensing Branch
To:
Shared Package
ML25356A102	List: ML25356A103 ML25356A104 ML25356A105
References
001029, EPID L-2025-LLA-0079
Download: ML25356A104 (0)

Text

Model No. New Powder Container Docket No. 71-9294 GLOBAL NUCLEAR FUEL - AMERICAS, LLC NRC Staff Question Regarding Water Exclusion Assumption in NEDE-33881P. Rev. 8 In Section 6.1 of NEDE-33881P, Revision 8 of the NPC Safety Analysis Report, it is stated:

Water exclusion from all but two of the ICCAs is required for this package design. Each cylindrical inner container within the package was analyzed in both undamaged and damaged container arrays under optimal moderation conditions. The most reactive configuration of the ICCAs for the packages was identified.

The criticality analysis included in the report follows this approach. However, NRC staff (the staff) has identified a potential regulatory concern with this methodology.

Specifically, this approach may not align with the requirements of 10 CFR 71.55(b), which states the following:

Except as provided in paragraph (c) or (g) of this section, a package used for the shipment of fissile material must be so designed and constructed and its contents so limited that it would be subcritical if water were to leak into the containment system, or liquid contents were to leak out of the containment system so that, under the following conditions, maximum reactivity of the fissile material would be attained:

(1) The most reactive credible configuration consistent with the chemical and physical form of the material; (2) Moderation by water to the most reactive credible extent; and (3) Close full reflection of the containment system by water on all sides, or such greater reflection of the containment system as may additionally be provided by the surrounding material of the packaging.

NRC staff believes that the most reactive credible extent of moderation would involve all ICCAs being fully flooded, not just two. This interpretation is consistent with current regulatory expectations and with the methodology used in the previous revision of the SAR for this package.

To assess the potential safety implications, staff conducted preliminary calculations using the input files provided by the licensee as a starting template. These calculations indicate that, under conditions where all ICCAs are fully flooded and loaded with 8 wt.% U-235, using the Heterogeneous Optimal Particle Size Fuel model, there is a potential to exceed the Upper Subcritical Limit (USL) and a keff of 0.95 for a single package.

The staff requests that the applicant reviews this issue and provide clarification or revised analysis demonstrating compliance with 10 CFR 71.55(b).