ML25337A407
| ML25337A407 | |
| Person / Time | |
|---|---|
| Site: | 07109225 |
| Issue date: | 12/22/2025 |
| From: | Nishka Devaser Storage and Transportation Licensing Branch |
| To: | Baldner H NAC International |
| References | |
| EPID L-2025-LLA-0108 | |
| Download: ML25337A407 (0) | |
Text
Heath Baldner Licensing Manager NAC-International 2 Sun Court, Suite 220 Peachtree Corners, GA 30092
SUBJECT:
REVISION 78 OF CERTIFICATE OF COMPLIANCE NO. 9225 FOR THE MODEL NO. NAC-LWT PACKAGE - REQUEST FOR ADDITIONAL INFORMATION
Dear Heath Baldner:
By application dated July 7, 2025 (Agencywide Documents Access and Management System Accession No. ML25189A260), NAC International applied for amendment to Certificate of Compliance No. 9225 for the Model No. NAC-LWT package.
In connection with our review, the U.S. Nuclear Regulatory Commission needs the information identified in the enclosure to this letter. Additional information requested by this letter should be submitted in the form of revised pages. Please provide your response within 30 days from the date of this letter.
Please reference Docket No. 71-9225 and Enterprise Project Identifier No. L-2025-LLA-0108 in future correspondence related to this request. The staff is available to meet to discuss your proposed responses. If you have any questions, I may be contacted at (301) 415-5196.
Sincerely, Nishka Devaser, Project Manager Storage and Transportation Licensing Branch Division of Fuel Management Office of Nuclear Material Safety and Safeguards Docket No. 71-9225 EPID L-2025-LLA-0108
Enclosure:
Request for Additional Information December 22, 2025 Signed by Devaser, Nishka on 12/22/25
ML25337A407 OFFICE:
NMSS/DFM NMSS/DFM NMSS/DFM NMSS/DFM NAME:
NDevaser SFigueroa BPatel JBorowsky DATE:
12/5/2025 12/5/2025 12/8/2025 12/8/2025 OFFICE:
NMSS/DFM NMSS/DFM NMSS/DFM NMSS/DFM NAME:
LRegner JPiotter TLiu for YDiaz-Sanabria NDevaser DATE:
12/10/2025 12/17/2025 12/22/2025 12/22/2025
Enclosure Request for Additional Information Docket No. 71-9225 Model No. NAC-LWT Package Certificate of Compliance No. 9225 Revision No. 78 By application dated July 7, 2025 (Agencywide Documents Access and Management System Accession No. ML25189A260), NAC International submitted an application for amendment to Certificate of Compliance (CoC) No. 9225 for the Model No. NAC-LWT package. This request for additional information identifies information needed by the U.S. Nuclear Regulatory Commission staff (NRC or the staff) in connection with its review of the application. The staff used guidance provided in NUREG-2216, "Standard Review Plan for Transportation Packages for Spent Fuel and Radioactive Material, in its review of the application.
The questions below describe information needed by the staff for it to complete its review of the application and to determine whether the applicant has demonstrated compliance with regulatory requirements.
Chapter 3:
Thermal Analysis RAI 3-1.
Provide clarification and justification of the WESF capsule UCS configuration thermal model and its results, including energy balances, residual convergence information, grid sensitivity discussion, consistent property values (e.g., differences in SrF2 salt thermal conductivity values in SAR section 3.4.1.22 and thermal calculation document table 4-7), and content decay heat inputs, that demonstrate thermal behavior representative of transport conditions.
a.
Thermal calculation document 50088.02-3010 Rev. 0 Thermal Evaluation of UCS with SrF2 Loaded in NAC-LWT Cask indicated a volumetric heat generation rate of 27.5 Btu/in3 for a 400 W capsule, which has a 2.625 inch diameter and an approximate 20-inch length, according to SAR figure 1.2.3-23. However, the calculation for the 27.5 Btu/in3 heat generation should be provided, considering that the 400 W (1364 Btu/hr) decay heat is in units of energy per unit time (e.g., power units of J/sec or Btu/hr) whereas the thermal calculation documents heat generation is in units of energy per unit volume (e.g., energy unit of Btu/in3). In addition, it was not certain how the modeled volumetric heat generation (27.5 Btu/in3) accounted for the half-symmetric 180° aspect of the model (per SAR figure 3.4-33), which would indicate a 1.2 kW total modeled decay heat, recognizing that the actual package can transport 2.4 kW.
b.
SAR table 3.4-29 indicates a large temperature gradient between the salt interface temperature and the WESF outer capsule temperature during NCT. In addition, the two temperatures are much different from the preceding WESF capsule container configuration (i.e., a previous amendment) reported in table 3.4-29 even though the decay heat source is the same for each configuration. Considering that thermal calculation document section 6.1 appeared to indicate the thermal model was an agglomeration of multiple thermal models that need to be appropriately joined, sufficiently accurate model representation is important to ensure components do not exceed allowable temperatures.
2 For example, SAR section 3.5.3.20 presented the calculation of package component temperatures during the fire HAC, which relied on similar behavior and temperature differences of components between the current WESF capsule UCS configuration model and the previous WESF capsule container configuration model. The calculation assumption used an aluminum insert temperature difference (between fire HAC and NCT aluminum insert temperatures) of an earlier amendments WESF container configuration even though the current amendments WESF UCS configuration aluminum basket does not appear to be the same component (per SAR table 3.4-29 note 5 and SAR table 3.5-7 description). In addition, the UCS salt interface/inner capsule temperature is approximately 120°°F higher than the previous WESF capsule container configuration, thus indicating there is a different thermal resistance for each WESF configurations heat transfer path toward the packages exterior.
There is a need for confidence in the analysis because the UCS aluminum component has only a 58°°F margin with the allowable temperature.
This information is needed to determine compliance with 10 CFR 71.71 and 10 CFR 71.71.
RAI 3-2.
Clarify that interior and package cavity gas temperatures and pressures during the fire HAC and NCT when transporting WESF capsules within the UCS configuration are bounded by previously reviewed contents.
Interior and cavity gas temperatures and pressures should be provided because, although SAR table 3.5-7 provided salt interface and aluminum basket content temperatures during the fire HAC that showed they were below allowable values, content temperatures (e.g., 921°°F) are much higher than previously reviewed content temperatures, which could impact interior gas cavity temperatures.
Similarly, interior temperatures and pressures for NCT should be addressed (also see RAI 3-1 issue for both NCT and HAC).
This information is needed to determine compliance with 10 CFR 71.71 and 10 CFR 71.73.
RAI 3-3.
Clarify that content and package temperatures would not be greater than NCT allowable values during the loading procedures vacuum drying process described in SAR section 7.1.23.
a.
The loading procedure indicated there is a vacuum drying period that potentially can be open-ended. It is possible for a vacuum within the package to result in higher temperatures than normal transport conditions because of the vacuums lower thermal conductivity relative to backfilled helium gas during transport. However, the temperatures reported in SAR table 3.4-29 were based on the transport condition with helium gas within package cavity and between interior package gaps.
b.
Clarify the helium backfill pressure in step 32 of section 7.1.23 (0 psig (1 atmosphere, absolute), +1, -0 psi). For example, it is uncertain whether this indicates the backfill pressure range would be 14.7 psia to 15.7 psia (i.e., no lower than 14.7 psia).
This information is needed to determine compliance with 10 CFR 71.71.