ML26014A135

Letter and Enclosure 1 (Public) - Request for Additional Information for the Embrace II Transportation Package

ML26014A135
Person / Time
Site:	07109404
Issue date:	01/27/2026
From:	Nishka Devaser Storage and Transportation Licensing Branch
To:	Sloma-Delosier T Westinghouse
Shared Package
ML26016A560	List: ML26014A135
References
EPID L-2025-NEW-0003
Download: ML26014A135 (0)

Text

OFFICIAL USE ONLYPROPRIETARY INFORMATION OFFICIAL USE ONLYPROPRIETARY INFORMATION Tanya Sloma-DeLosier Package Licensing and Technology Manager, Westinghouse Electric Company LLC Columbia Fuel Fabrication Facility 5801 Bluff Road Hopkins, SC 29061

SUBJECT:

CERTIFICATE OF COMPLIANCE NO. 9404 FOR THE MODEL NO. EMBRACE II PACKAGE - REQUEST FOR ADDITIONAL INFORMATION

Dear Tanya Sloma-DeLosier:

By letter dated May 2, 2025 (Agencywide Documents Access and Management System Accession No. ML25122A209), you submitted an application to the U.S. Nuclear Regulatory Commission (NRC) for a certificate of compliance for the EMBRACE II transportation package.

In connection with our review, the NRC 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.

In accordance with Title 10 of the Code of Federal Regulations Part 2, Agency Rules of Practice and Procedure, 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. transmitted herewith contains proprietary information. When separated from the sensitive conditions in enclosure 2, this document and enclosure 1 are decontrolled.

January 27, 2026

T. Sloma-DeLosier OFFICIAL USE ONLYPROPRIETARY INFORMATION 2

OFFICIAL USE ONLYPROPRIETARY INFORMATION Please reference Docket No. 71-9404 and Enterprise Project Identifier No. L-2025-NEW-0003 in future correspondence related to this request. The NRC staff are 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. 71-9404 EPID L-2025-NEW-0003

Enclosures:

1. RAI (Public)

2. RAI (Non-Public)

Signed by Devaser, Nishka on 01/27/26

ML26016A560(pkg, non-public), ML26014A135(ltr & encl 1),

ML26016A561(encl 2, non-public)

OFFICE NMSS/DFM NMSS/DFM NMSS/DFM NAME NDevaser LHowe WWheatley DATE 1/14/26 1/15/26 1/16/26 OFFICE NMSS/DFM NMSS/DFM NMSS/DFM NAME JBorowsky JLopez JNguyen for YDiaz-Sanabria DATE 1/16/26 1/21/26 1/23/26 OFFICE NMSS/DFM NMSS/DFM NMSS/DFM NAME JPiotter LRegner NDevaser DATE 1/26/26 1/27/26 1/27/26

OFFICIAL USE ONLYPROPRIETARY INFORMATION OFFICIAL USE ONLYPROPRIETARY INFORMATION Request for Additional Information Docket No. 71-9404 Model No. EMBRACE II Package Certificate of Compliance No. 9404 Revision No. 0 Non-proprietary By letter dated May 2, 2025 (Agencywide Documents Access and Management System Accession No. ML25122A209), you submitted an application to the U.S. Nuclear Regulatory Commission (NRC) for a certificate of compliance (CoC) for the EMBRACE II transportation package. This request for additional information identifies information needed by the NRC staff in connection with its review of the application. The NRC 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 NRC staff for it to complete its review of the application and to determine whether the applicant has demonstrated compliance with regulatory requirements.

Chapter 2:

Structural Analysis RAI 2-1.

Regarding the lifting points on the outer container lid, describe how the four lifting points located on the outer container lid will be either: designed to meet the applicable lifting strength requirements, or rendered inoperable to prevent inadvertent use during transport, as required by Title 10 of the Code of Federal Regulations (10 CFR) 71.45(a) and Paragraph 609 of SSR-6.

Figure 1.7-1 of the Packaging Design Safety Report (PDSR) depicts four lifting points located on the outer container lid. The PDSR states that these lifting points may be rendered inoperable to prevent their inadvertent use during transport.

Additionally, the PDSR evaluates the combined shear and bending stresses induced by the transverse loading in the event the lifting points are not rendered inoperable. Based on this analysis and considering the possibility that the lifting points may remain operable during transport, it is unclear whether their design meets the strength requirements applicable to lifting attachments.

As specified in 10 CFR 71.45(a), Any lifting attachment that is a structural part of a package must be designed with a minimum safety factor of three against yielding when used to lift the package in the intended manner Furthermore, the regulation states that any other structural part of the package that could be used to lift the package must be capable of being rendered inoperable for lifting the package during transport, or must be designed with strength equivalent to that required for lifting attachments. Similarly, Paragraph 609 of SSR-6 requires that any other features on the outer surface of the package that could be used to lift it shall be designed either to support its mass in accordance with the requirements of para. 608 or shall be removable or otherwise rendered incapable of being used during transport.

This information is necessary to demonstrate compliance with the regulatory requirements in 10 CFR 71.45(a) and Paragraph 609 of SSR-6 with respect to

OFFICIAL USE ONLYPROPRIETARY INFORMATION 2

OFFICIAL USE ONLYPROPRIETARY INFORMATION rendering inoperable for lifting any other structural part of the package that could be used to lift the package.

RAI 2-2.

Regarding the loose fuel drop analysis, provide additional information to demonstrate that the mechanical behavior of loose fuel rods during transport has been appropriately considered and analyzed. Specifically, clarify how the analysis accounts for non-ideal orientations and eccentric loading scenarios, and justify that the assumptions used are conservative and representative of realistic transport conditions.

Section 2.1.3.10 of the PDSR states that loose rods are wrapped in plastic sleeves to prevent scratches, and that axial voids between the fuel rods and the inside Rod Box surface are filled with Ethafoam to also preclude movement which could lead to surface scratches. The report includes a buckling analysis intended to demonstrate structural integrity and leak-tightness following the hypothetical accident conditions (HAC) drop event.

However, it is unclear whether the analysis adequately represents the actual stress conditions that may occur under both normal conditions of transport (NCT) and HAC. The buckling analysis appears to assume idealized column behavior with some form of end restraint or connection. In contrast, loose fuel rods may not maintain a perfectly vertical orientation during a drop event and may instead be subject to eccentric loading. Such loading conditions can result in mechanical behavior that differs significantly from that of a centrally loaded column, potentially affecting the structural response and integrity of the rods.

This information is necessary to demonstrate compliance with the regulatory requirements of 10 CFR 71.73(c)(1) and Paragraph 727 of SSR-6, which ensure the mechanical integrity of the package containment boundary during and after the free drop test. Additionally, 10 CFR 71.71(c)(7) requires consideration of conditions that could affect the package contents under NCT.

RAI 2-3.

Regarding the material properties used to model fuel cladding in your LS-DYNA model, clarify/justify the material properties used to model fuel cladding. Update the LS-DYNA simulations, pertinent calculations, and the PDSR to properly describe the analyzed bounding conditions, as necessary.

Additional information is necessary to verify/validate the material properties used to model fuel cladding in LS-DYNA simulations for NCT and HAC drop scenarios (non-bundle runs).

{Proprietary}

Based on these references which consider multiple failure strains and different mechanical properties, it is unclear whether the most conservative values have been consistently selected for use in LS-DYNA simulations. Specifically:

The basis for the selected failure strain, yield strength, ultimate tensile strength, modulus of elasticity, and density used in LS-DYNA simulations as the bounding condition, is not clearly documented.

OFFICIAL USE ONLYPROPRIETARY INFORMATION 3

OFFICIAL USE ONLYPROPRIETARY INFORMATION The cladding type assigned to specific fuel assembly designs (e.g., SVEA, TRITON) is not clearly identified.

The material properties used in LS-DYNA simulations appear to be constant across all temperature conditions, despite the fact that NCT and HAC scenarios consider both: hot and cold temperatures (e.g., -29 °C or -40 °C).

Furthermore, references AA 263 293 E ZIRC 2 BWR and AA 302 723 E HiFi Cladding do not appear to provide material property data at these cold temperatures.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.33, 10 CFR 71.71 and 10 CFR 71.73.

These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

RAI 2-4.

Regarding the side/oblique drop analysis of your LS-DYNA model, provide the side/oblique drop analysis to address the issue described below. Update LS-DYNA simulations, pertinent calculations, and the PDSR, as necessary.

Section 3.0 of attachment 4.2.1 states, in part:

...BWR fuel assemblies are not modeled in detail. They are represented by homogeneous regions having the general shape of typical BWR fuel assemblies with an effective density assigned to the elements that give them the proper weight of 680 lb. Basis: The fuel assemblies are analyzed in detail in another calculation. By modeling them in this manner, their effect on the package during NCT and HAC can be evaluated without significantly increase the model size and solution time.

However, this referenced calculation that analyzes the fuel assemblies in detail cannot be located in the PDSR or supporting documentation. As currently modeled in LS-DYNA, the fuel assemblies are modeled as monolithic square tubes with uniform density and modulus of elasticity:

Figure 1: Illustration from 30-ft Slap Down Drop LS-DYNA simulation, only Target and Fuel tubes shown

OFFICIAL USE ONLYPROPRIETARY INFORMATION 4

OFFICIAL USE ONLYPROPRIETARY INFORMATION The depicted fuel assembly does not account for specific geometry/material/components of the fuel assemblies, such as thimble tubes, spacer grids, nozzles, internal hardware (e.g., springs, nuts, etc.).

Furthermore, it is unclear how the analyzed side/oblique drop orientations are the most challenging to the assemblies, as the lid down scenario shown above, rather than a lid up scenario could result in higher forces transmitted to the assemblies since the lid down scenario does not benefit from foam inserts located near the end of the assemblies (identified as Parts 39 and 45 in the licensing drawings).

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.71 and 10 CFR 71.73. These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

RAI 2-5.

Regarding your other material properties in your LS-DYNA model, for the issues described below, clarify/justify the material properties used in NCT and HAC LS-DYNA models/simulations, and clarify/justify how the discrepancies affect the results. Update the LS-DYNA simulations, any pertinent calculations, and the PDSR, as necessary.

Additional information regarding the material properties used in LS-DYNA simulations is necessary to address the following issues:

1.

Material properties used to justify fuel tube properties for NCT and HAC drop simulations described in the EMBRACE-II Fuel Bundle Impact Analysis (attachment 4.2.2).

{Proprietary}

2.

DELRIN material properties used in conjunction with fuel assemblies for LS-DYNA simulations.

Table 6-2 of attachment 4.2.2 lists Poissons ratio, modulus of elasticity, and density for high density polyethylene materials such as DELRIN (material ID 17/18 in LS-DYNA), among others. However, the material properties used in the LS-DYNA simulation for the e2_NCL_NT end drop run differ significantly from those listed in the table. Specifically:

The modulus of elasticity used in the simulation differs as much as a factor of three from the tabulated value.

The material is modeled as purely elastic and is not permitted to fail, which may not be representative of its actual behavior under impact conditions.

Additionally, there is a discrepancy in the modulus of elasticity for the fuel channel material (Material ID 23) in LS-DYNA, which differs by an order of magnitude from the values listed in table 6-1. The density values also appear inconsistent. These discrepancies raise concerns about the accuracy of the

OFFICIAL USE ONLYPROPRIETARY INFORMATION 5

OFFICIAL USE ONLYPROPRIETARY INFORMATION simulation results and their implications for the structural response of the fuel assemblies during end drop scenarios.

3.

Material properties used in LS-DYNA simulations compared to those assumed in the PDSR for Part Nos. 37, 39, 40, and 41.

LS-DYNA Parts 37, 39, 40, and 41 are described in the Impact Analysis Report as using Material ID 2 (stainless steel bolt-like material). However, the LS-DYNA simulation uses Material ID 1 (stainless steel), which has significantly different mechanical properties, including failure strain that does not permit failure.

Additionally, table 6-13 of attachment 4.2.1 states that LS-DYNA Parts 38 and 42 use Material ID 4. However, table 6-12 indicates that material ID 4 is not used in the analysis. This contradiction creates uncertainty regarding the actual material properties applied to these components.

Also, Part 121 (identified as a bolt) is assigned Material ID 1, whereas all other similar bolts in the model use Material ID 2. This inconsistency may result in non-conservative behavior or misrepresentation of bolt performance.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.33, 10 CFR 71.71 and 10 CFR 71.73.

These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during the HAC free drop.

RAI 2-6.

Regarding the fuel rods/assembly drawings, dimensions and material specifications of your LS-DYNA model, provide licensing drawings that properly describe dimensions and materials of construction of the rods/fuel assemblies intended to be transported by the EMBRACE II package and clarify the contents of the EMBRACE II. Update the PDSR and supporting documentation as necessary to ensure consistency and completeness in the description of package contents.

Additional drawings, dimensions and/or material specifications are necessary to verify/validate the model used for LS-DYNA simulations against the proposed contents for transport in the EMBRACE II package.

Section 1.2 of the PDSR states that the EMBRACE II package is intended to transport BWR 10x10 or 11x11 fuel assemblies, as well as loose BWR and PWR rods, but does not provide sufficient details regarding the specific fuel assembly designs or their physical characteristics. Furthermore, PDSR section 2.1.2.7.2 (NCT end drop evaluation) mentions TRITION11' [Nordic & Continental] BWR and briefly references SVEA-96 fuel bundles. Table 6-3 of attachment 4.2.1 lists several fuel assembly types, including SVEA-96 Optima2, F3 e30 LF A SVA-96 Optima3, TRITON11' BWR 6, TRITON11' 4-5 reactor assemblies.

While some calculations include partial drawings and component details, the PDSR does not provide a comprehensive and consistent description of the fuel assemblies intended for transport. The licensing drawings lack clear dimensional data, material specifications, and component callouts (e.g., rods, thimble tubes, spacer grids, end caps/nozzles, springs, nuts, and other structural hardware).

OFFICIAL USE ONLYPROPRIETARY INFORMATION 6

OFFICIAL USE ONLYPROPRIETARY INFORMATION Due to the lack of clarity and consistency, NRC staff cannot determine whether the fuel assembly configurations used in the NCT and HAC drop simulations are bounding or representative of the actual contents proposed for transport in the EMBRACE II package.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.33, 10 CFR 71.71 and 10 CFR 71.73.

These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

RAI 2-7.

Regarding the strain rate sensitivity of your LS-DYNA model, clarify/incorporate strain rate material properties, and cold material properties into the NCT and HAC drop simulations and update the PDSR and supporting calculations, as necessary.

Strain rate values in the fuel cladding have been noted to exceed 300 s-1 for several NCT/HAC LS-DYNA drop simulations such as for the two_part_continental_NCT scenario. It is unclear how strain rate sensitivity of the cladding material and supporting stainless steel has been incorporated into the analysis. High strain rate often reduces assumed failure strain and permits higher forces to develop in components such as the fuel assemblies. In addition, stainless steel properties appear to be invariant below 100 ºF according to tables 1.3-5 in the PDSR and table 6-5 in attachment 4.2.1 reference, which according to note b, say in part that:

Since this value is constant for -20 °F to 100 °F, it is conservative to use it for -40 °F, as these properties increase as temperature decreases However, higher material properties are not always conservative, as they allow more force to develop and transfer to other surrounding components in contact with them. In addition, ductility (permitted failure strain) tends to be less than at room temperature which may not be conservative.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.71 and 10 CFR 71.73. These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

RAI 2-8.

Regarding the package components drawings, dimensions and material specifications of your LS-DYNA model:

1.

Provide dimensions, materials of construction, and model name of the mounts on the licensing drawings; justify strain rate, cold/hot temperature rubber material properties, and adequacy of chosen rubber material (currently unidentified) to adequately represent LORDs damper. Update the PDSR, LS-DYNA simulations, and calcualtions as necessary.

2.

Provide dimensions and material specification for the latch assembly used to secure the inner container and clarify/justify the discrepancies/assumptions used to model them in the NCT and HAC drop simulation scenarios. Update the PDSR and/or the LS-DYNA simualtions, as necessary.

OFFICIAL USE ONLYPROPRIETARY INFORMATION 7

OFFICIAL USE ONLYPROPRIETARY INFORMATION 3.

Clarify how square tube parts (identified as bill of materials (BOM) Parts 25 and 26) for the outer container assembly are attached to the package.

For the following components, additional drawings, dimensions and/or material specifications are necessary to verify/validate the model used in LS-DYNA for the EMBRACE II package:

1.

The licensing drawings for the EMBRACE II package include transport dampers (identified as BOM Part 11, referred to as shock mounts in the PDSR) which are intended to transfer dampened impact forces to the fuel assemblies during NCT and HAC drop scenarios. However, several issues have been identified regarding the characterization and modeling of these components:

a) The licensing drawings do not include dimensional details or material specifications for the transport dampers, and the manufacturer of the dampers (if any) is not identified.

b) Section 1.8.2.4.3 of the PDSR states that the Lord Sandwich Shock Mount (Part Number J-5425-219) from LORD, or an engineering-approved equivalent, will be used. However, the PDSR does not define the criteria or methodology by which equivalence of alternative shock mounts would be determined, nor does it specify the mechanical performance requirements that must be met.

c)

The stress-strain curves used in LS-DYNA simualtions for the rubber material in the dampers was not provided by LORD. Instead, the applicant supplied a curve (figure 6-1 of attachment 4.2.1) reproduced from Reference 9 (Roland, 2006, figure 18). This introduces several concerns:

I.

Rolands figure 18 states the curve was for unfilled and unidentifed rubber which may not be representative of the actual damper material.

II.

It is unclear how temperature-dependent behavior was accounted for in the simulation, specifically for hot and cold temperatures

(-20 °F, -40 °F) relevant to NCT and HAC scenarios, and III.

The LS-DYNA simulations assume a strain rate of 80 s¹ from Rolands data, but do not select the LCSR (strain rate dependency) option in LS-DYNA. The selected strain rate may be inadequate when compared to cold/light oblique drop HAC simulations, which results in strain rate values that exceed 5,000 s-1 and in unrealstic failure behavior:

OFFICIAL USE ONLYPROPRIETARY INFORMATION 8

OFFICIAL USE ONLYPROPRIETARY INFORMATION Figure 2:Image from HAC oblique cold/lite simulation 2.

Licensing drawings for the EMBRACE II package depict latches (identified as BOM Part 14) that are intended to contain the fuel assemblies within the inner container and to minimize movement during drop scenarios. These latches correspond to LS-DYNA Parts 22, 23, 24, 25, 26, 36, 59, 60, 148 in the drop simulations.

However, several issues have been identified:

The licensing drawings or the manufacturer specification (if any) do not provide dimensional details or material callouts for the latches or associated components.

The licensing drawings indicate that the latches are rated for 1,000 lbs, but the type and style of latch depicted do not appear to match those modeled in LS-DYNA. This discrepancy raises concerns about the accuracy of the simulation inputs and whether the modeled latch behavior is representative of the actual components used in the package.

Figure 3: (Latches per the licensing drawings, right side)

OFFICIAL USE ONLYPROPRIETARY INFORMATION 9

OFFICIAL USE ONLYPROPRIETARY INFORMATION Figure 4: Latches modeled for LS-DYNA simulations 3.

LS-DYNA simulation models for the EMBRACE II package indicate that square tube components (identified as BOM Parts 25 and 26), which are part of the outer container assembly, are attached to the package using a method resembling stitch welding. These components appear to play a role in transmitting impact loads during NCT and HAC drop scenarios, as well as potentially loads during lifting operations.

However, the licensing drawings do not depict a clear method of attachment of these parts to the package. Without this information, NRC staff cannot confirm that the structural modeling assumptions are consistent with the actual package design.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.33, 10 CFR 71.71 and 10 CFR 71.73.

These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

RAI 2-9.

Regarding the coefficients of friction: unyielding surface, slap down angles of your LS-DYNA model, clarify the basis for the following assumptions and/or update the PDSR and LS-DYNA drop simulations, as necessary.

Friction values of FS=0.2 and FD=0.05 between the package and the target have been applied to contact surfaces in LS-DYNA (i.e.,

contact_auto_single_surface). Also, a slap down angle of 10 degrees has been used to simulate oblique (slap down) impact conditions in LS-DYNA simualtions.

However, the basis for the selected static and dynamic friction values and drop angle are unclear. These parameters significantly influence the dynamic response of the package during drop simulations, including impact forces, energy dissipation, and potential damage to the package and its contents. Without a clear technical basis, the NRC staff cannot determine whether the simulations adequately represent bounding conditions.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.71 and 10 CFR 71.73. These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

OFFICIAL USE ONLYPROPRIETARY INFORMATION 10 OFFICIAL USE ONLYPROPRIETARY INFORMATION RAI 2-10.

Regarding the amount of hourglass energy in your LS-DYNA model, justify/clarify the observed hourglass energy for parts that exceed 10% of energy distortion.

Update the PDSR and LS-DYNA simualtions for all NCT/HAC simulations as necessary.

Section 6.5.2 of attachment 4.2.1 states that distortion energy (hourglass energy/internal energy ratio) is considered acceptable when it remains below 10% for a given LS-DYNA simulation. However, this observation is made for the entire model rather than individual parts, which can obscure localized energy distortion at the part-level. For instance, fuel assemblies (identified as Part 145 in LS-DYNA models) experiences hourglass energy that exceeds 105% (see below), while other parts (identified as Part 148) approaches to 350%. These values suggest that individual parts may be experiencing unrealistic deformation behavior, which could significantly affect the accuracy of calculated quantities such as impact forces, accelerations, and stress distributions.

Figure 5 This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.71 and 10 CFR 71.73. These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

RAI 2-11.

Regarding the effective plastic strains for fuel cladding/plugs in your LS-DYNA models, justify/clarify the observed conditions of the fuel plugs when they experience effective plastic strains that far exceed their prescribed material failure strains during end drop simulations for NCT and HAC simulations, and the use of never fail scenarios for fuel cladding material. Update the PDSR and LS-DYNA drop simulations that exhibit such behavior as necessary.

{Proprietary}

In the e2_ECL_NT end drop HAC simulation, the effective plastic strain reaches 1.302.

OFFICIAL USE ONLYPROPRIETARY INFORMATION 11 OFFICIAL USE ONLYPROPRIETARY INFORMATION In the e2_NOM_NT drop simulation, the strain reaches 6.021.

Other material models used by the applicant for metallic materials induce element erosion once a failure strain is reached. However, the cladding material used in this application can never fail which is unrealistic.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.71 and 10 CFR 71.73. These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

RAI 2-12.

Regarding the physical gaps between fuel assemblies and other parts in your LS-DYNA models, clarify/justify the different initial gap assumptions used between the fuel assemblies and other parts for NCT and HAC drop scenarios. Update the PDSR, LS-DYNA simualtions, and calculations as necessary.

Section 6.3 of attachment 4.2.2 states that the outer container is not modeled in LS-DYNA fuel assembly end drop simulations because the inner container and support frame are decoupled from the rubber shock mounts. However, this assumption may not be valid for all drop scenarios, particularly those involving significant impact forces.

In the associated LS-DYNA end drop simulations described in attachment 4.2.2 (e.g., for Continental fuel assemblies), the model has an initial velocity of 527 in/sec (per HAC conditions) and a gap of 0.184 inches between components (between Part 233 and Part 16 and 17). In contrast, other LS-DYNA simulations such as HAC_EndDrop_ColdLite include a starting gaps of 2.13 inches with functioning shock mounts.

The NRC staff notes that the presence of large initial gaps between fuel assemblies and surrounding components can result in higher impact forces due to increased relative velocity and reduced energy absorption prior to contact. The omission of the outer container and shock mounts in certain simulations may therefore lead to non-conservative results, especially if the decoupling assumption is not adequately justified.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.71 and 10 CFR 71.73. These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

RAI 2-13.

Regarding the warning/error messages in your LS-DYNA models:

1.

Clarify whether the identified difference in material input curve and that used by LS-DYNA has any influence on the simulation results. Update applicable calculations and the PDSR, as necessary.

2.

Update/address the LS-DYNA simulations error messages identified below when executing the applicants LS-DYNA end drop simulations and update the PDAR as necessary.

LS-DYNA warnings:

OFFICIAL USE ONLYPROPRIETARY INFORMATION 12 OFFICIAL USE ONLYPROPRIETARY INFORMATION (1) When executing the applicants LS-DYNA simulations, the following warning message is generated:

MAT_PIECEWISE_LINEAR_PLASTICITY(ID: 1): Approximation (LCINT) of material curve ID 9 differ by 28.304287 percent This warning indicates that the approximate material curve used for this material in LS-DYNA models is different from what is input into the model.

Differences in the material input curve and that used by LS-DYNA may influence the results as most of the package is made of stainless steel material (Material IDs 1, 2, 3) and fuel assembly performance is dependent on surrounding stainless steel members.

(2) When executing the applicants LS-DYNA end drop simulations, two simulations ended prematurely with error messages:

(a) The first error was observed for the run FINAL-EndDrop-CONTINENTAL-HAC-3D-COLD-Nylon-Walled:

• • • Error 40024 (SOL+24)

• • • termination due to mass increase ***

added mass = 3.8671E+12 percent increase = 5.7040E+13 35829 t 1.4332E-02 dt 4.00E-07 write d3dump01 file 12/30/25 16:00:50 nodes with largest mass increase node id old mass new mass increase 15908584 3.26521E-07 9.66784E+11 9.66784E+11 15901962 2.17703E-07 9.66784E+11 9.66784E+11 15901663 7.12656E-08 9.66784E+11 9.66784E+11 15899107 4.05173E-07 9.66784E+11 9.66784E+11 15753980 3.84965E-06 1.42384E-05 1.03888E-05 15753979 3.84965E-06 1.42384E-05 1.03888E-05 15765420 3.84970E-06 1.42369E-05 1.03872E-05 15765419 3.84970E-06 1.42369E-05 1.03872E-05 15763080 3.84880E-06 1.42278E-05 1.03790E-05 15763079 3.84880E-06 1.42278E-05 1.03790E-05 15730814 3.84969E-06 1.42262E-05 1.03765E-05 15730813 3.84969E-06 1.42262E-05 1.03765E-05 15766200 3.84963E-06 1.42235E-05 1.03738E-05 15766199 3.84963E-06 1.42235E-05 1.03738E-05 15766252 3.84975E-06 1.42226E-05 1.03728E-05 15766251 3.84975E-06 1.42226E-05 1.03728E-05 15757022 3.84966E-06 1.42213E-05 1.03717E-05 15757021 3.84966E-06 1.42213E-05 1.03717E-05 15758036 3.84964E-06 1.42213E-05 1.03716E-05 15758035 3.84964E-06 1.42213E-05 1.03716E-05 total added mass for these 20 nodes = 3.86713E+12 35829 t 1.4332E-02 dt 4.00E-07 write d3plot file 12/30/25 16:00:50

OFFICIAL USE ONLYPROPRIETARY INFORMATION 13 OFFICIAL USE ONLYPROPRIETARY INFORMATION 35829 t 1.4332E-02 dt 4.00E-07 write d3plot file 12/30/25 16:00:50 E r r o r t e r m i n a t i o n 12/30/25 16:00:52 This error typically suggests that excessive amounts of mass were added to the model (often an attempt to speed up runtimes) but potentially inducing unrealistic behavior/response when too much mass is added.

(b) The second error was observed for the run, FINAL-EndDrop-COLD-Nordic-3D-2tenthsWalls, which had multiple negative solid volume errors such as:

• • • Error 40509 (SOL+509) negative volume in solid element # 7846556 cycle 47418 This error often occurs for foam/rigid plastic materials which experience large and unrealistic deformations due to meshing and low modulus of elasticity (technically, the Jacobian matrix calculation often has division by zero issues associated with this error). As a result, realistic package response and behavior from the LS-DYNA is unknown.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.71 and 10 CFR 71.73. These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

RAI 2-14.

Regarding the overall mass in LS-DYNA model, clarify/update the simulated model mass to address the discrepancy identified below. Update the PDSR and/or LS-DYNA simulations as necessary.

According to LS-DYNA output, the total simulated model mass is 4,085.3 lbs, while SAR table 1.3-3 of the PDSR specifies a total package mass of 4,660 lb, resulting in a discrepancy of approximately 12%.

Safety analysis report (SAR) table 1.3-3 indicates weights for the inner and outer container, but it does not clearly identify which LS-DYNA parts IDs correspond to each component. As a result, individual model and PDSR components can not be compared/verified to ensure that the NCT and HAC drop simulation results are valid/appropiate.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.33, 10 CFR 71.71 and 10 CFR 71.73.

These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

RAI 2-15.

Regarding the behavior of outer container lid bolts in your LS-DYNA models, clarify/update the simulated model to address the behavior discrepancies identified below for the outer container lid bolts and describe how the bolt stresses were determined. Update the PDSR and/or LS-DYNA simulations as necessary.

OFFICIAL USE ONLYPROPRIETARY INFORMATION 14 OFFICIAL USE ONLYPROPRIETARY INFORMATION The outer container lid bolts (LS-DYNA Part IDs 121-144) are critical components that help retain the fuel assemblies within the EMBRACE II package. Upon review of LS-DYNA output for NCT and HAC simulations, the following concerns have been identified:

1.

Simulation results show unexpected deformation patterns in the bolts (see figure below), where shear failure would be expected under the applied loading conditions. This suggests that the contact definitions between the bolts and their mating components may be inaccurate or incomplete, potentially affecting load transfer and stress distribution.

2.

The ultimate tensile strength of the bolt material is specified as 70,000 psi (see section 6.5.5 of attachment 4.2.1). However, effective stresses observed in the bolts during simulation appear to exceed this limit, indicating potential failure that is not captured by the current material model.

3.

Effective stresses in the bolts are also shown below (not found in attachment 4.2.1) and it is unclear how bolt stresses (e.g., SAR figure 6-63) were determined. Without this information, the NRC staff cannot confirm whether the bolts are modeled conservatively or whether failure criteria have been properly applied.

This information is necessary to demonstrate compliance with the regulatory requirements specified in 10 CFR 71.71 and 10 CFR 71.73. These regulations establish criteria to ensure the mechanical integrity of the package containment boundary under NCT and during HAC free drop.

Chapter 3:

Thermal Analysis RAI 3-1.

Provide the appendix A transient day-night temperature profile and temperature summary for the package components (e.g., foam, rubber, acetate, gaskets) so that a comparison with the allowable temperatures in SAR table 2.2-2 can be made. Individual component temperatures or bounding temperatures are important considering that results provided in SAR table 2.2-1 (for the transient constant insolation calculation) indicated there can be different temperatures associated with the Inner Container.

OFFICIAL USE ONLYPROPRIETARY INFORMATION 15 OFFICIAL USE ONLYPROPRIETARY INFORMATION a.

The day-night transient temperature profiles (figure A-1 and figure A-2) of the exterior Outer Container and the Inner Container surface provided in appendix A of the thermal calculation document CN-NFPE-24-015 (revision 1) appear to show that maximum temperature of the packages exterior surface reaches the maximum day transient result and that the maximum temperature of the Inner Container nearly approaches the maximum day temperature (i.e., within approximately 10 °C). This potentially indicates that the maximum temporal temperature reached by the various foams, polyethylene, rubber, acetate, and Inner/Outer Container gaskets during the transient diurnal cycle may reach or exceed the maximum allowable temperature of the foam and rubber reported in SAR table 2.2-2, recognizing that the non-metal components (e.g., rubber, gaskets) may degrade at the local high temperature regions. Although volumetric average temperatures of certain components were reported in SAR section 2.2 based on a transient calculation of a constant insolation boundary condition (but calculations were not provided), a volume average may not be appropriate if there is sufficient local degradation. It is noted that higher NCT temperatures would indicate the possibility of higher temperatures (and resulting pressures) during the fire HAC transient.

This information is needed to determine compliance with 10 CFR 71.35(a),

10 CFR 71.71, and 10 CFR 71.73.

RAI 3-2.

Provide calculations that consider the effects of package openings such that increased combustion air can result in reactions (e.g., combustion) of greater amounts of hydrogenous material (e.g., polyethylene, polyurethane, rubber, neoprene) than analyzed and, considering that fresh fuel packages exposed to fire have shown non-negligible combustion reactions occur from interior flammable components, further explanation of the hydrogenous material behavior within the package during the fire transient should be provided, including explaining whether fire test results have shown limited mass hydrogenous reactions within fresh fuel packages (e.g., 10 g of combustion). In addition, discussion and calculations should be provided to confirm that the thermal analysis considered combustion of flammable gas generated during fire HAC (i.e., due to radiolysis, thermolysis).

SAR section 1.2.3.3 stated that the quantity of hydrogenous material within the Inner Container can vary between 10 kg and 25 kg. Appendix B of the thermal calculation document addressed hydrogenous material combustion during the fire HAC. Assuming a fixed and limited quantity of combustion air, the analysis calculated thermal energy input and corresponding fuel rod temperature increase due to the combustion of a small fraction of hydrogenous material (i.e., on the order of 0.01 kg). However, SAR section 2.1.2.1.2 indicated that the package is not pressurized (i.e., is not air-tight), such that air exchange can occur during the fire and post-fire periods. This would indicate additional thermal input from solid material and flammable gas reactions (e.g., combustion) with resulting increases in fuel rod temperature and internal pressure.

This information is needed to determine compliance with 10 CFR 71.35(a) and 10 CFR 71.73.

OFFICIAL USE ONLYPROPRIETARY INFORMATION 16 OFFICIAL USE ONLYPROPRIETARY INFORMATION RAI 3-3.

Provide calculations for determining the fuel rod pressure (BWR and PWR) during NCT as well as the fire HAC fuel rod pressure, hoop stress, and allowable fuel rod pressure and hoop stress at the fire HAC fuel rod temperature (e.g., approximately 500 °C, per SAR section 2.1.3.4).

{Proprietary}

This information is needed to determine compliance with 10 CFR 71.35(a),

10 CFR 71.71, and 10 CFR 71.73.

RAI 3-4.

Provide the allowable temperatures of the neoprene, polyethylene, acetate plug, transport security device (TSD), and Inner and Outer Container gaskets and clarify that the component temperatures were within their allowable temperatures during normal and accident conditions (e.g., diurnal model discussed in appendix A of the thermal calculation document).

a.

SAR table 2.2-2 listed NCT and HAC allowable temperatures for certain package components (e.g., polyurethane foam, natural rubber, stainless steel, Zircaloy) but did not include the other components and, therefore, a comparison with calculated values could not be made.

b.

Although SAR section 2.1.2.2 noted that the packages steel components and the zirconium-based cladding will retain their integrity at -40 °C, there was no discussion about the performance of non-metal components (e.g., polyurethane, polyethylene, neoprene, acetate, rubber) at cold conditions.

This information is needed to determine compliance with 10 CFR 71.35(a),

10 CFR 71.43, 10 CFR 71.71, and 10 CFR 71.73.

RAI 3-5.

Provide justification and clarification that the thermal model and its results, including energy balances, residual convergence information, as well as spatial grid and temporal timestep convergence and sensitivity, demonstrate thermal model behavior is representative of transport conditions.

Section 6.6 of the thermal calculation document indicated that warning messages had impacts on the thermal evaluation.

a.

Information and discussion of thermal model convergence should be provided in order to understand that the model is representative of transport conditions.

b.

Clarify whether the Day Transient steady-state temperature of the Inner Container (per figure A-2 of thermal calculation appendix A) should be greater than a true steady-state temperature, or that the two values should asymptotically reach the same temperature over time.

This information is needed to determine compliance with 10 CFR 71.35(a),

10 CFR 71.71, and 10 CFR 71.73.

OFFICIAL USE ONLYPROPRIETARY INFORMATION 17 OFFICIAL USE ONLYPROPRIETARY INFORMATION RAI 3-6.

Clarify the polyurethane foam specific heat properties described in SAR section 1.8.1.5.1.

Although the material test acceptance criteria included polyurethane foam specific heat properties, the units (or values) are inconsistent with those provided in SAR section 1.3.9.2, possibly indicating a typographical error.

This information is needed to determine compliance with 10 CFR 71.33 and 10 CFR 71.35(a).

Chapter 4 Containment Analysis RAI 4-1.

Clarify that the radionuclides, total activity, and maximum allowable fuel weight (kgU) of the loose PWR and BWR fuel rods that can be transported in the Rod Boxes are consistent and bounded by the containment analysis discussed in the containment calculation document CN-LCPT-24-05.

The containment calculations performed in appendix A (e.g., section A.1, A.2, table A-2) of the containment calculation focused on the TRITON11 and SVEA96 fuel assembly content. However, a demonstration was not provided to show that this basis was bounding relative to the loose PWR and BWR fuel rods in the two Rod Boxes. In addition, there did not appear to be in the application a detailed content description that clearly defined the acceptable design parameters, radionuclides, and activities (including total content values) for the loose BWR and PWR fuel rods in the Rod Boxes. For example, whereas SAR section 1.2 stated that the nominal uranium fuel weight is 200 kgU per fuel assembly, SAR section 2.5.2.2 did not specify the maximum number of PWR/BWR fuel rods and the maximum amount of uranium content within the Rod Boxes.

This information is needed to determine compliance with 10 CFR 71.33 and 10 CFR 71.35(a).

Chapter 7 Materials Analysis RAI 7-1.

Justify the absence of a material specification (American Society of Mechanical Engineers [ASME], ASTM, SAE International, etc.) for important to safety components that do not comprise the containment boundary, to include the following:

SAR section 1.11.1, Drawing 10081E03, provides no material specification (e.g., ASME SA-240, Type 304) for the stainless-steel used to fabricate the draw latches of the inner container lid.

SAR section 1.11.1, Drawing 10081E03, provides no material specification (e.g., ASME SA-240, Type 304) for the stainless-steel used to fabricate the M10 screws that attach the lifting handles to the inner container body.

SAR section 1.11.1, Drawing 10081E03, provides no material specification (e.g., ASME SA-240, Type 304) for the stainless-steel used to fabricate the M20 cross member bolts that attach the crossmembers to the support frame.

OFFICIAL USE ONLYPROPRIETARY INFORMATION 18 OFFICIAL USE ONLYPROPRIETARY INFORMATION SAR section 1.11.1, Drawing 10081E03, provides no material specification (e.g., ASME SA-240, Type 304) for the stainless-steel used to fabricate the M12 damper mount bolts that attach the dampers to the support frame.

SAR section 1.11.1, Drawing 10006E59, provides no material specification (e.g., ASME SA-240, Type 304) for the stainless-steel used to fabricate the body, lid, and lid bolts that comprise the loose rod box.

This information is needed to confirm compliance with 10 CFR 71.31(c).

RAI 7-2.

Clarify what divisions and/or subsections of ASME Boiler and Pressure Vessel Code section III guide the design and evaluation of the fuel rods.

SAR section 1.2.1 states, [t]he ASME Boiler and Pressure Vessel Code, section III, is used as a guide in the mechanical design and stress analysis of the fuel rod.

The NRC staff notes that section III contains five divisions with numerous sections covering a wide breadth of component classifications and material categories and is overly broad for the NRC staff to make a safety evaluation as to the fabrication, evaluation, and testing of the fuel cladding. This information is needed to confirm compliance with 10 CFR 71.31(c).

RAI 7-3.

Justify the absence of an Acceptance Testing and Maintenance Program that governs quality assurance and the necessary quality control documents, key manufacturing procedures, and key testing protocols for the Nylon PA-12 3D printed material used to fabricate the TSD. These processes, controls, and quality assurance measures are needed for the NRC staff to access the acceptability of the material mechanical properties to ensure the TSD will perform its intended safety function over the 50-year period of use of the transportation package.

Appendix C of SAR attachment 4.2.2 provides material properties for Nylon PA-12 from the manufacture's data sheet; however, this data sheet states that these material properties are approximate and dependent on a number of factors, including but not limited to, machine and process parameters. The information provided is therefore not binding and not deemed to be certified.

This information is needed to confirm compliance with 10 CFR 71.33(a)(5),

10 CFR 71.35(a), 10 CFR 71.51(a) and 10 CFR 71.55(b), (d), and (e).

RAI 7-4.

Justify the exclusion of stress corrosion cracking as a credible aging mechanism.

What are the allowable stresses below which stress corrosion cracking is not a concern?

SAR section 1.4 states that... stressed components including pre-loaded outer container lid bolts, lifting bail bolts, and structural welds are less than allowable stresses and since the contact metals are similar, stress-corrosion cracking is not a concern.

This information is needed to confirm compliance with 10 CFR 71.35(a) and 10 CFR 71.43(d).

OFFICIAL USE ONLYPROPRIETARY INFORMATION 19 OFFICIAL USE ONLYPROPRIETARY INFORMATION RAI 7-5.

Justify the absence of an acceptable source/reference for the following materials properties:

Table 6-2 of SAR attachment 4.2.2 - Fuel Cladding and End Plugs Table 6-2 of SAR attachment 4.2.2 - Heavy Zircaloy-2 Cladding This information is needed to confirm compliance with 10 CFR 71.33(a)(5),

10 CFR 71.35(a), 10 CFR 71.51(a) and 10 CFR 71.55(b), (d), and (e).

RAI 7-6.

Please describe any national or international codes, standards, and/or other methods, programs, or procedures that are implemented to ensure that package maintenance activities (including visual inspections, screening and evaluation of visual indications, and corrective actions such as component repairs and replacements) are adequate to manage the effects of corrosion in stainless stee packaging components that would see long-term use, such that the package components are capable of performing their requisite safety functions throughout the period of use.

The NRC staff requests that this description address the following criteria:

1.

Inspection methods (e.g., bare metal visual exams and/or other types of nondestructive exams such as liquid penetrant exams or ultrasonic exams) for detection and characterization of localized corrosion and stress corrosion cracking (SCC) effects for stainless-steel components.

2.

Inspection equipment and personnel qualification requirements (e.g., lighting and visual acuity requirements for performing visual exams) to ensure reliable inspections that can adequately detect and characterize indications of localized corrosion and SCC prior to component failure or loss of safety function.

3.

Visual criteria for detection of the aging effects of localized corrosion (i.e.,

pitting and crevice corrosion) and SCC of stainless-steel components exposed to outdoor air during transport. Examples of visual indications that may indicate potential localized and SCC corrosion include the accumulation of atmospheric deposits such as salts, buildup of corrosion products, rust colored stains or deposits, and surface discontinuities or flaws associated with pitting and/or crevice corrosion.

4.

Describe any surface cleaning requirements that are implemented to ensure that bare metal visual inspections of component surfaces are capable of detecting surface flaws, and for ensuring adequate removal of atmospheric deposits such as salts or other chemical compounds that may contribute to localized and SCC corrosion of stainless-steel components.

5.

Describe any flaw evaluation methods (such as flaw sizing and flaw analysis methods) and associated flaw acceptance criteria that may be used to determine whether components containing flaws are acceptable for continued service.

OFFICIAL USE ONLYPROPRIETARY INFORMATION 20 OFFICIAL USE ONLYPROPRIETARY INFORMATION The NRC staff reviewed the applicants corrosion evaluation for the stainless-steel components in an outdoor environment and noted that stainless steel passivity may adequately inhibit general corrosion. But, stainless steel is susceptible to localized corrosion effects, including loss of material due to pitting and crevice corrosion, when exposed to aqueous air environments. During numerous package transport operations over a 50-year period, these chemical species may gradually degrade the protective passive oxide film on stainless steel surfaces leading to the formation of pits and crevice corrosion. Additionally, stainless steel components under high tensile stress (such as weld residual stress) exposed to aqueous outdoor air environments are also susceptible to the formation of cracks due to chloride-induced SCC. The NRC staff determined that localized corrosion and SCC are credible aging mechanisms for stainless steel components in outdoor environments and requires that adequate visual inspections performed by qualified personnel using qualified techniques are needed to detect and evaluate indications of corrosion so that personnel can reliably determine the need for remedial action, such as repair or replacement of components that show unacceptable indications. However, the NRC staff identified that the package handling and maintenance criteria described in sections 1.7 and 1.8 of the application does not include any specific provision for inspection of stainless-steel components to detect and evaluate indications of localized corrosion and SCC to ensure that stainless steel components with unacceptable localized corrosion and SCC are repaired or replaced prior to a loss of safety function.

Therefore, the information above is requested to ensure adequate inspection, flaw evaluation, mitigative measures, and corrective actions for managing localized corrosion and SCC of stainless-steel components.

This information is requested in order to verify compliance with requirements of the 2018 Edition of IAEA SSR-6, Paragraph 613A.