ML25044A487

Enclosure 1: Brr Package (Docket 71-9341) Amendment Request RAI Responses

ML25044A487
Person / Time
Site:	07109341
Issue date:	02/13/2025
From:	Orano Federal Services
To:	Office of Nuclear Material Safety and Safeguards
Shared Package
ML25044A485	List: ML25044A486 ML25044A487 ML25044A489
References
EPID L-2023-LLA-0090, FS-25-0018
Download: ML25044A487 (1)

Text

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 1 of 16 Structural Evaluation RAI 2.1 Provide detailed technical justifications for not performing the structural analyses with free drop orientations [i.e., center-of-gravity-over (CG-over) corner drop and oblique angle drops] for the RITC and RITC basket under NCT and demonstrate or explain how the RITC and RITC basket comply with Title 10 of the Code of Federal Regulations (10 CFR) 71.71(c)(7).

The applicant performed the structural analyses of the RITC and RITC basket with two free drop orientations (end drop and side drop) under NCT (Reference 1). However, the applicant did not perform the structural analyses with other free drop orientations (i.e., CG-over corner drop and oblique angle drops) for the RITC and RITC basket under NCT. As required by 10 CFR 71.71(c)(7) a package needs to be demonstrated for structural adequacy by a free drop through the distance specified in 10 CFR 71.71(c)(7) onto a flat, essentially unyielding, horizontal surface, striking the surface in a position for which maximum damage is expected (Reference 2). In general, the drop orientations of 90° (vertical end), 0° (horizontal side), oblique angles (30°,

45°and 60°) and CG-over corner are considered in the structural analyses to find the location and magnitude of the maximum damage expected in the structural package system. Therefore, the applicant is requested to provide detailed technical justifications for not performing the structural analyses of the RITC and RITC basket with oblique angle drops including the CG-over corner drop under NCT and demonstrate or explain how the RITC and RITC basket meet the requirements of 10 CFR 71.71(c)(7).

This information is required to determine compliance with 10 CFR 71.71(c)(7).

Structural Evaluation RAI 2.1 Reply Both the center-of-gravity-over (CG-over) corner drop and oblique angle drops are considered in the overall performance of the package and the baskets, including the new RIT, RITC basket and RITC and their components, in order to maximize potential damage. In SAR Section 2.12.2.3.3 during the certification tests, the governing impact cases on the package are identified as cold, 15° slapdown and secondary impact. Also, SAR Section 2.12.2.3.3 identifies that the C.G.-over-corner impact at 68° from horizontal gives the governing crush deformations for the impact limiter foam, but otherwise is bounded by impact accelerations of the other drop orientations.

In accordance with SAR Section 2.12.5.2.2, the NCT free drop results show that the maximum impact acceleration occurs in the 90° end drop orientation. For NCT, from Table 2.12.5-15, the maximum overall impact acceleration is equal to 32.9g which is for the end drop case. This value bounds the accelerations at all other impact angles, including the acceleration in the secondary impacts of Table 2.12.5-16. As a result of the 32.9g acceleration, a bounding 40g acceleration is used in all NCT drop cases and orientations, which is 21.5% higher than that required under the bounding case (the end free drop cold case) and 54.4% higher than the next highest oblique angle drop, the 45° drop orientation. Similar bounding results for the HAC maximum 120g acceleration field are indicated in the tables listed in Section 2.12.5.2.1. Indeed, the bounding impact acceleration is kept constant in all drop orientations (40-g NCT and 120-g HAC) which is a very conservative assumption, since for example in the CG over corner HAC case, the actual acceleration was 58.5-g during CTU testing and 69.6-g from the analysis results (see Table 2.12.5-24), which is approximately 1/2 of the applied 120-g acceleration.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 2 of 16 Confirmation for this is provided in SAR Section 2.12.4.2.2, which states that, A bounding impact deceleration field of 40g is applied for the NCT cases as discussed in Section 2.6.7, Free Drop, and 120g is applied for the HAC cases as discussed in Section 2.7.1, Free Drop. As shown in Section 2.7.1, the governing orientations for stress analysis are the end drop (top end down and bottom end down), and the side drop.

Regarding the use of the side drop case to bound the oblique drop cases, SAR Section 2.6.7.2 describes this as follows, The NCT side free drop is evaluated using the same finite element model which was used for the end drop case. The quasi-static acceleration of 40g also applies to the side drop, since it bounds the calculated side drop impact as discussed in Appendix 2.12.5, Impact Limiter Performance Evaluation. The side drop orientation is governing over the slapdown orientation as discussed in Section 2.7.1.4, Oblique Drop.

Section 2.7.1.4, Oblique Drop states, For the HAC free drop, the BRR package can strike the ground in any primary orientation. As shown in the following discussion, the cask stresses for all oblique drop orientations are conservatively bounded by the side drop (horizontal) orientation when performed using an impact of 120g.

The BRR package can strike the ground in any primary orientation and thus SAR Section 2.7.1.4 for oblique drop orientations explains the rationale how the side drop load case is bounding for all oblique cases that might be considered. This is shown via an analysis of the inner shell axial and shear forces along with bending moment at the highest HAC side drop magnitude of 120g. SAR page 2.7-15 summarizes as follows, The resulting cask shell forces and maximum combined stress intensities are shown in Table 2.7-3. Since only the inner shell properties are used, the stress intensity is relative, and is used for comparison between the different cases only. The stress values in the table therefore do not represent actual inner shell stress intensity. As shown, the stress intensity is greatest in the horizontal side drop case at the bounding value of 120g. This technical evaluation shows that a side drop with the bounding higher acceleration magnitude governs over the worst case oblique free drop shallow angle slapdown orientation at a primary impact angle of 15°.

It concludes by stating that the actual impacts in the oblique drop cases are bounded by the higher HAC side drop impacts of the governing accelerations. This same rationale is also extended to the NCT drop cases by the statements in SAR Section 2.6.7.2 discussed above, since the governing 40g side drop would envelope the oblique drop angles at lower acceleration magnitudes. This precedent of evaluating the side and end drops with bounding acceleration magnitudes has been previously extended to every basket in the BRR package, as summarized in the subsections of SAR Section 2.7.1.5. SAR Section 2.7.1.5.1 states Each of the five stainless steel fuel baskets and the loose plate box are evaluated for structural integrity in the governing end and side free drop orientations. Hence, this precedent includes the new RIT, RITC, RITC basket and their hardware and subcomponents.

In conclusion, the RIT, RITC and RITC basket structural analysis considers this bounding 40g acceleration (for NCT) and 120g acceleration (for HAC) on the loading condition of these components to maximize potential damage. Limiting cases would be for bending in the side drop and buckling in the end drop, so limiting analyses on structures of significance are analyzed in SAR Section 2.12.8.9. For side drop cases and loading directions, component bending analyses compute the allowable stress margins due to bending between any unsupported structures. For the end drop cases, axial buckling stresses are calculated for the most susceptible components as well.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 3 of 16 Considering the RIT, RITC and RITC basket at the limiting accelerations for both end and side drop orientations bounds the evaluation of possible structural failures at other oblique drop angle orientations, including the CG-over-corner impact. Nonetheless, as shown below, SAR Appendix Section 2.12.8.9 will be strengthened with these justifications cross-referencing to SAR Section 2.7.1.4, Oblique Drop for how other drop orientations are bounded by the side drop case.

SAR Section 2.12.8.9 RAI 2.1 - RAI 2.3 changes (updates shown in red font)

The RITC Basket structural analysis includes the basket itself, the RITC, and the RITs. These component details are depicted in SAR Drawing 1910-01-05-SAR from Appendix 1.3.3, Packaging General Arrangement Drawings. In accordance with Section 5.10.4.1, Methods, these components maintain adequate physical separation of the fuel rod segments within the RITs for radioactive shielding purposes during NCT. Therefore, the RIT, RITC and RITC basket are checked for failure along the structural load paths for both end and side free drop loading. As reference, as previously addressed in Section 2.7.1.4, Oblique Drop, the RITC basket and other RIT sub-components evaluated in this section consider consistent justifications for using the side drop load case as bounding oblique drop load cases. The loads are derived from the bounding NCT 40g acceleration from Section 2.6.7, Free Drop. Unlike the RIT, the RITC and RITC basket are not required to control the separation of the fuel rod segments during an HAC event. This is stated in Section 5.10.4.1, Methods with the statement: For HAC, movement of the source cylinders within the cavity is conservatively not restricted, indicating that the RITC and RITC basket perform no shielding positioning function under HAC. Therefore, only the RIT is evaluated for the bounding HAC 120g free drop load found in Section 2.7.1.1, Impact Forces and Deformations.

RAI 2.2 Provide detailed technical justifications for not performing the structural analyses for the RITC and RITC basket under the hypothetical accident conditions (HAC) and demonstrate or explain how the RITC and RITC basket comply with 10 CFR 71.73(c)(1).

The applicant performed the structural analyses of the RITC and RITC basket for two free drops (end drop and side drop) under NCT, but did not perform the structural analyses under HAC. The applicant provided a brief statement in section 2.12.8.9, RITC Basket, RITC, and RIT, of the safety analysis report (SAR), in which it states, The RITC and RITC basket are not required to control the separation of the fuel rod segments during an HAC event. Therefore, only the RIT is evaluated for the bounding HAC 120g free drop load. However, no justification was provided for this statement. Therefore, the staff requests to: (i) provide detailed technical justifications for not performing the structural analyses of the RITC and RITC basket under HAC, and (ii) demonstrate or explain how those justifications comply with 10 CFR 71.73(c)(1), which requires a free drop of a package through a distance of 30 ft. onto a flat, essentially unyielding, horizontal surface, striking the surface in a position for which maximum damage is expected.

This information is required to determine compliance with 10 CFR 71.73(c)(1).

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 4 of 16 Structural Evaluation RAI 2.2 Reply The new RITC and RITC basket are not important to safety (NITS) components during the HAC case, as they are not considered in the shielding analysis for any shielding positioning assumptions, and they have no other intended safety function. Their role would only be as uncredited defense-in-depth structures in the protection of the RIT under HAC tests. SAR Section 2.1.2.2 states the following: However, the RITC and RITC basket are only credited in the NCT evaluations and are thus evaluated to Service Level A allowable criteria of Subsection NF [9] per Table 2.1-4 for aluminum.

Specifically, SAR Figure 5.10-1 shows the NCT shielding model for the irradiated rod segments.

SAR Figure 5.10-2 shows the BRR package model for the irradiated rod segments payload for HAC. These two graphics along with the SAR Section 5.10.4.1, Methods narrative describes the shielding positioning assumptions made for the RIT, RITC and RITC basket. SAR Section 5.10.4.1 states the following, with emphasis added via the underlined portion: The encapsulation tubes, RITCs, and RITC basket are not modeled. The encapsulation tubes are credited for maintaining structural integrity such that rod segments remain stacked during NCT and HAC. For NCT, credit is taken for the RITCs keeping RITs stacked and the RITC basket in limiting the movement of RITs. Up to two RITCs may be shipped per basket opening and thus the reduction in source length for HAC represents the possible decoupling of stacked RITs.

The source cylinders are grouped together and shifted towards the package side wall to maximize side dose rates. For NCT, radial movement of the source cylinders is conservatively restricted by only the basket openings. For HAC, movement of the source cylinders within the cavity is conservatively not restricted. No axial shifts of the source cylinders are analyzed for NCT as any axial movement of the RITs will be relatively small.

Therefore, for NCT, three full length irradiated rod segments are preferentially bundled along one sector of each RITC basket opening. The basket opening keeps the RITs from moving outside of this region. For the RITCs under NCT shielding assumptions, the RITC base plates keep the RITs from an upper RITC from preferentially rearranging next to the lower set of three RITs. This is provided by the SAR Section 5.10.4.1 statement: For NCT, credit is taken for the RITCs keeping RITs stacked and the RITC basket in limiting the movement of RITs.

As such, SAR Section 2.12.8.9.2, RITC for the RITC NCT structural analyses states, The RITCs prevent side-by-side doubling up next to each other of RITs in a stacked upper and lower RITC arrangement. Meanwhile, for the RITs themselves under NCT shielding assumptions, the RIT maintains confinement of the fuel segments within the tubes. As such, all three components: the RIT, RITC and RITC basket have been included in the NCT basket structural analyses of SAR Section 2.12.8.9, RITC Basket, RITC, and RIT. However, as indicated in the SAR shielding section 5.10.4.1, the RITC and RITC basket performs no shielding positioning assumptions during HAC. This is confirmed by the SAR Section 5.10.4.1 statement, For HAC, movement of the source cylinders within the cavity is conservatively not restricted. Hence, those two components have no intended safety function under HAC and their only role is as uncredited defense-in-depth assurance during the HAC performance tests. Therefore, no further structural evaluation of the RITC and RITC basket are performed in Chapter 2. As shown in reply to RAI 2.1, SAR Section 2.12.8.9 statement about the intended safety function of these components is expanded to reiterate these facts.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 5 of 16 RAI 2.3 Provide detailed technical justifications for not performing the structural analyses with free drop orientations [i.e., CG-over corner drop and oblique angle drops] for the Rods-In-Tubes (RITs) under NCT and HAC and demonstrate or explain how the RITs comply with 10 CFR 71.71(c)(7) and 71.73(c)(1).

The applicant performed the structural analyses for two RITs (A3 and A4 assemblies) in section 2.12.8.9.1, RIT, of the SAR. The A3 assembly was analyzed with two orientations (end drop and side drop) under NCT and HAC, while the A4 assembly was analyzed with only one orientation (end drop) under NCT and HAC. The applicant explained that the A4 assembly was not analyzed for the side drop because the A4 assembly is supported by the RITC tube over its full length, which is acceptable to the staff.

However, the applicant did not perform the analyses for both A3 and A4 assemblies with other free drop orientations [i.e., CG-over corner drop and oblique angle drops) under NCT and HAC.

Since both 10 CFR 71.71(c)(7) and 71.73(c)(1) require that a package needs to be demonstrated for structural adequacy by a free drop through a specified distance onto a flat, essentially unyielding, horizontal surface, striking the surface in a position for which maximum damage is expected, the applicant would need to consider evaluating the RITs with other free drop orientations (i.e., CG-over corner drop and oblique angle drops) under NCT and HAC. Therefore, the applicant is requested to provide detailed technical discussions and information to demonstrate compliance with the NCT requirements of 10 CFR 71.71(c)(7) and HAC requirements of 10 CFR 71.73(c)(1).

This information is required to determine compliance with 10 CFR 71.71(c)(7) and 71.73(c)(1).

References:

Orano Federal Services LLC Letter to U. S. Nuclear Regulatory Commission, Submittal of BEA Research Reactor Package CoC Amendment and CoC Renewal Request, Docket No. 71-9341, EPID L-2023-LLA-0090, dated August 26, 2024, with: - BEA Research Reactor Package Safety Analysis Report, Rev. 19, and - BEA Research Reactor Package Table of Changes for BRR SAR, Rev. 19.

Structural Evaluation RAI 2.3 Reply Please refer to RAI 2.1 response for justification of how the NCT and HAC CG-over corner and oblique angle drops are bounded by the side and end drops with a governing acceleration magnitude (40-g for NCT and 120-g for HAC) on the RIT. Nonetheless, as shown in response to RAI 2.1, SAR Appendix Section 2.12.8.9 will be strengthened with justifications which will cross-reference to SAR Section 2.7.1.4, Oblique Drop for how other drop orientations are bounded by the side drop load case.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 6 of 16 Thermal Evaluation RAI 3.1 Provide calculations (e.g., Excel file) to show derivation of the thermal properties (thermal conductivity and specific heat) of the MURR HEU Fuel Plate for verification.

The applicant provided thermal properties of the fuel element materials of MURR HEU Fuel Plate, MITR-II HEU Fuel Plate, ATR HEU Fuel Plate 1, ATR HEU Fuel Plate 2 to 18, and ATR HEU Fuel Plate 19 in SAR table 3.2-2. The applicant noted, in SAR table 3.2-2, that these material properties are determined based on composite value of aluminum cladding and fuel core material (see SAR appendix 3.5.3.9, Determination of Composite Thermal Properties for HEU Fuel Plates, and SAR table 3.5-1 for ATR HEU Fuel Plate, table 3.5-2 for MITR-II HEU Fuel Plate, and table 3.5-3 for MURR HEU Fuel Plate).

The applicant needs to provide calculations (e.g., Excel file) to show derivation of the thermal properties of the MURR HEU Fuel Plate, mentioned above, for staffs review verification. The calculations (e.g., Excel file) should include parameters of the MURR HEU Fuel Plate, such as x1, x2, k1, k2, cp1, cp2, 1 and 2.

This information is required to determine compliance with 10 CFR 71.35.

Thermal Evaluation RAI 3.1 Reply Fundamental thermal properties of the fuel element materials are provided in SAR Table 3.2-2.

Each fuel type references a specific table source citation footnote, with a reference to SAR Appendix 3.5.3.9, Determination of Composite Thermal Properties for HEU Fuel Plates, for the specific MURR HEU fuel plate composite properties, as provided in SAR Table 3.5-3. While the MURR HAC evaluation was rerun in the current SAR revision, the material properties in the MURR HEU model have remained consistent between SAR revisions, going back to the original SAR revision. Therefore, the data in Table 3.5-3 has not changed since the initial issue of the SAR. The thermal properties in all rows of SAR Table 3.5-3 are straightforward and require simple mathematical operations to deduce. The MURR HEU fuel plate values were based on these simple computations. The values were generated and checked by hand using the equations and parameters as defined in the initial discussion of SAR Appendix 3.5.3.9.

The calculated values and formulations for requested verifications are shown here:

= x11 + 22

= (0.05 0.03 ) x (191 11) + 0.03(14.47 11) 0.05

= 85.1 11

= 11 + 22

= (0.05 0.03 ) x (2702 3) + 0.03 (3680 3) 0.05

= 3288.8 3

= 111 + 222

= (0.05 0.03 ) x (1034 11)(2702 3) + 0.03 (708 11) (3680 3) 0.05 x 3288.8 3

= 815.1 11

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 7 of 16 These example MURR HEU fuel plate equations and formulations are added to SAR Appendix Section 3.5.3.9 on SAR page 3.5-31 as an example of such computations for all the HEU Fuel plates.

RAI 3.2 (A) Clarify, in the application, whether a personnel barrier is required for installation on the BRR package when transporting each payload of MURR HEU fuel, MITR-II HEU fuel, ATR HEU fuel, RITC payload, MURR LEU fuel, MITR-II LEU fuel, and ATR LEU fuel.

(B) Define Note (1) in Max. Accessible Surface (1) of SAR table 3.8.1-1.

The applicant performed the NCT thermal analysis with an ambient 100 °F and no solar heat when packaging the MURR HEU fuel with a bounding heat load of 1,264 W among HEU fuels.

The applicant included thermal barrier in thermal model and predicted a maximum accessible package surface temperature of 185 °F (see SAR table 3.3-1). The applicant also performed NCT thermal analyses of MITR-II HEU fuel with a maximum heat load of 1,200 W per shipment and ATR HEU fuel with a maximum heat load of 240 W per shipment, as described in SAR section 3.2.

The applicant performed NCT thermal analysis without thermal barrier in thermal model when packaging the rod-in-tube canister (RITC) payload with a maximum heat load of 180 W, as described in SAR section 3.7.

The applicant performed thermal analysis for NCT with thermal barrier in thermal model when packaging MURR LEU fuel (1,264 W), MITR-II (1,200 W), or ATR LEU fuel (960 W). The applicant predicted the maximum accessible package surface temperatures of 183 °F for MURR LEU fuel (SAR table 3.8.3-1), 183 °F for MITR-II LEU fuel (SAR table 3.8.3-2) and 155 °F for ATR LEU fuel (SAR table 3.8.3-3).

With analyses, mentioned above, either including or not including personnel barrier in the thermal model, the applicant needs to clarify, in SAR Chapter 3, Thermal Evaluation or Chapter 7, Package Operation, whether a personnel barrier is required when transporting each payload of MURR HEU fuel, MITR-II HEU fuel, ATR HEU fuel, RITC payload, MURR LEU fuel, MITR-II LEU fuel, and ATR LEU fuel.

This information is required to determine compliance with 10 CFR 71.43(g).

Thermal Evaluation RAI 3.2 Reply There was some confusion over the nomenclature used to describe the packaging components.

The BRR Package design does not include a component described as a thermal barrier. There is a thermal shield that is an integral component of the cask body (e.g., welded component). In addition, there is an optional personnel barrier which is only included with the isotope target payloads (refer to SAR Section 3.1, Description of Thermal Design and SAR Section 7.1.4, Preparation for Transport, step 8). Also, the glossary section of the SAR, Section 1.3.2, Glossary of Terms and Acronyms, provides a description of these two components.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 8 of 16 As stated in the first paragraph of SAR Section 3.1, the personnel barrier is only required when shipping the Isotope production target basket discussed in SAR Section 3.6, Thermal Evaluation of Isotope Production Target Payloads. There are no other payloads that require a personnel barrier, and the personnel barrier is only included in the Isotope production target analysis in Section 3.6 and in no other portion of Chapter 3.

The maximum accessible package surface temperature is found in Table 3.3-1 and is discussed in the sixth paragraph of Section 3.3.1.1, Maximum Temperatures. This was previously discussed when addressing RAI 3-4 with respect to the original revision 0 of the SAR (see NRC Accession Number ML12090A3170) and the changes were accepted per Section 3.3 of the Safety Evaluation Report (SER) (see NRC Accession Number ML100260364).

The LEU fuel payload results regarding the maximum accessible surface temperature remained consistent with the HEU fuel results in Table 3.3-1 and are bounded by those results in a revised SAR Table 3.8.1-1. Regarding footnote 1 to SAR table 3.8.1-1, this should read Maximum accessible surface temperature is modeled with no insolation and occurs at the upper cask impact limiter attachment lugs at the interface of the thermal shield. This footnote was inadvertently deleted during editing and is added back into SAR Table 3.8.1-1.

RAI 3.3 Provide the requested information on items (A) and (B) below for clarification on maximum normal operating pressure (MNOP) calculations.

The applicant calculated MNOPs for package loaded with MURR HEU fuel (SAR section 3.2.2) and ATR LEU fuel (SAR section 3.8.3.2) by assuming that the cavity gas reaches a bulk average temperature that is equal to the mean of the average inner shell temperature and the average fuel basket temperature.

The staff needs to verify whether a mean of the average inner shell temperature and the average fuel basket temperature is appropriate for MNOP calculations when there are differences in mass and structure configuration between inner shell and fuel basket.

(A) Provide the cask cavity bulk gas temperature, directly computed for fill gas from the thermal model, for each of MURR HEU fuel and ATR LEU fuel loaded in the package. This request is to confirm that use of the mean of the average inner shell temperature and the average fuel basket temperature is appropriate for MNOP calculation.

(B) Provide the average inner shell temperature and the average fuel basket temperature in SAR tables 3.3-1 (MURR HEU fuel), 3.3-2 (MITR-II HEU fuel), 3.3-3 (ATR HEU fuel), 3.8.3-1 (MURR LEU fuel), 3.8.3-2 (MITR-II LEU fuel), and 3.8.3-3 (ATR LEU fuel) under NCT.

The applicant calculated the MNOP for package loaded with RITC payload by predicting the cask cavity bulk gas temperature from the gas sub model (SAR sections 3.7.3.2 and Note 1 on SAR table 3.7-1).

(C) Provide explanation of the gas sub model in SAR.

This information is required to determine compliance with 10 CFR 71.71.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 9 of 16 Thermal Evaluation RAI 3.3 Reply The fill gas in the MURR HEU and ATR LEU is modeled as contacts between the thin gaps between the modeled components. When the gaps are represented by thermal resistors in the model, then the volumes, elements and nodes are not requisite in representations of the gas.

However, since there is no heat generation in the cavity gas, there is a linear temperature drop through the air gaps between the components. Therefore, taking the average between the basket and inner shell will provide the average gas temperature which is deemed appropriately conservative for the MNOP calculations.

The average temperature of the inner shell and fuel basket are shown in RAI Table 3.3-1 below.

These values will be added to their respective table in the SAR. The average gas temperature, also shown in the table, is the computed average value.

RAI Table 3.3-1: Average Temperatures, °F Payload Inner Shell Fuel Basket Gas MURR HEU Fuel 224 293 259 MITR-II HEU Fuel 220 288 254 ATR HEU Fuel 140 188 164 MURR LEU Fuel 225 293 259 MITR-II LEU Fuel 221 295 258 ATR LEU Fuel 198 355 276 While the helium components are described in the SAR, the term sub model is not explicitly used. The gas sub model is only found in the Isotope Production Target and RITC Payload models. The gas sub model fills up the large open volumes within the cask cavity with these two payloads. This sub model is shown in SAR Figure 3.6-13 for the isotope production model and in SAR Figure 3.7-6 for the RITC Basket Model.

The gas in the RITC analytical thermal model is identified in SAR Section 3.7.5.1, Description of Thermal Model, and is identified as being helium. As such, the voids between the RITC basket, RITCs, RITs and fuel segments are backfilled with helium. The helium is modeled using a combination of finite difference objects, finite element objects, and thermal contactors as appropriate.

As discussed above, changes to the SAR include incorporating the average NCT temperatures for the MURR, MITR-II and ATR HEU fuel baskets and inner shells to SAR Tables 3.3-1, 3.3-2, and 3.3-3, respectively. Further SAR changes include incorporating the average NCT temperatures for the MURR, MITR-II and ATR LEU fuel baskets and inner shells to SAR Tables 3.8.3-1, 3.8.3-2, and 3.8.3-3, respectively. The maximum pressure during helium backfill in Section 3.8.3.5 of the SAR and Table 3.8.3-4 were also updated because of this RAI. In addition, SAR Section 3.8.4.3 was updated regarding a statement regarding cavity gas HAC temperature. MURR LEU and HEU HAC average temperatures of the shell and basket were added in Table 3.8.4-1 and Table 3.4-1, along with Figure 3.8.4-3 and Figure 3.4-3 for the cavity gas temperature added. ATR LEU HAC average temperatures of the fuel, shell and basket were added in Table 3.8.4-2, along with Figure 3.8.4-6 for the cavity gas temperature added.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 10 of 16 RAI 3.4 Provide the rationale (or base) of the assumptions (underlined below) and their impact to thermal evaluation of the package transporting the RITC payload.

The applicant listed, in SAR section 3.7.5.1, five assumptions to highlight their importance for RITC analytical thermal model. The applicant needs to explain rationale (or base) and/or their impact to thermal evaluation on two assumptions: (1) the thermal properties of the aluminum materials are assumed in the annealed condition, and (2) the material properties of the fuel segment material properties are calculated using an assumed irradiation burnup of 62 GWd/MTU and a pellet density of 95 percent which results in reasonable values for the pellet conductivity and specific heat.

Note - Aluminum in an annealed condition is a metal that has been through a heat-treating process to restore its crystalline grain structure and make it easier to shape.

This information is required to determine compliance with 10 CFR 71.71 and 71.73(c)(4).

Thermal Evaluation RAI 3.4 Reply For assumption #2 in SAR Section 3.7.5.1, Description of Thermal Model, this statement is intended to denote the fact that the temper of the aluminum is not considered in defining the thermal properties used in the SAR for aluminum alloys. It is not intended to require annealing of the material prior to use. This assumption is reworded to provide this distinction.

As for assumption #4 in SAR Section 3.7.5.1, any minor adjustment to the pellet conductivity will only marginally change the thermal results in the analytical thermal model. The relationships used to calculate the specific heat is not dependent on these values. Also, while the pellet conductivity is dependent on these values, the variation is insignificant. Due to the pellet stacks relatively small diameter and the large temperature margins seen in the results of SAR Table 3.7-1, a large variation in conductivity will not invalidate the overall conclusions from the model. Therefore, the assumption is valid for the model but is clarified accordingly.

In summary, as shown in revised SAR text below, the assumptions in SAR Section 3.7.5.1 are revised to clarify these points.

SAR Section 3.7.5.1 RAI 3.4 assumption changes (updates shown in red font)

The following assumptions are stated herein to highlight their importance. Other assumptions are justified as used.

1. The thermal conductivity of the polyurethane foam in the impact limiters varies based on its density. Conservatively, the lower thermal conductivity, based on the lowest allowable density, is used in the NCT models.

2. For analysis purposes, the effect of temper on the aluminum materials is assumed to be negligible and will not significantly affect the thermal properties.

3. All void spaces within the BRR cask cavity are assumed to be filled with helium at atmospheric pressure following the draining and drying process.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 11 of 16

4. The material properties of the fuel segment material are calculated using an assumed irradiation burnup of 62 GWd/MTU and a pellet density of 95% which, due to the pellet stacks relatively small diameter and the large temperature margins seen in the results in Table 3.7-1, provides reasonable values for the pellet conductivity and specific heat.

5. The UO2 is assumed to be in direct contact with the cladding, and the material of the cladding is predicted to be stainless steel. Therefore, the emissivity of 0.30 for stainless steel is applied to the rod segments.

RAI 3.5 Provide a source book or Reference #51, as shown in SAR section 3.8.2.2 (page 3.8-5), to illustrate that Equation (Tb = 3.25 x 107 f-0.2282) and a peak fission density of 8 x 1021 fissions/cm3 are appropriate for determining the LEU fuel plate temperature limit of 620 °F during vacuum drying.

The applicant stated, in SAR section 3.8.2.2, that the maximum allowable temperature limits for LEU fuel plate are 400 °F, 1100 °F, and 620 °F during NCT, HAC, and vacuum drying, respectively. The applicant noted that the aluminum fuel plate is not relied upon for structural strength of the fuel during vacuum drying operations, and therefore an allowable temperature based on the foil material may be used.

The applicant used a peak fission density of 8 x1021 fissions/cm3 to derive the lower bounding permissible cladding temperature limit of 620 °F, based on Equation (Tb = 3.25 x 107 f-0.2282).

The applicant needs to provide pages from the source book or the Reference #51 which is shown in SAR page 3.8-5 to support and illustrate Eqn. (Tb = 3.25 x 107 f-0.2282) and a peak fission density of 8 x 1021 fissions/cm3 are appropriate for determining the LEU fuel plate temperature limit of 620

°F during vacuum drying.

This information is required to determine compliance with 10 CFR 71.35.

Thermal Evaluation RAI 3.5 Reply Reference 51 is an Idaho National Laboratory (INL) preliminary report on U-Mo monolithic fuel for research reactors (INL EXT-17-40975, Revision 4). Chapter 10 of this reference presents preliminary safety limits. Equation 95 from the reference is used to compute the lower bounding temperature for the fuel blister threshold temperature.

The peak power densities for the various reactors are shown in the Executive Summary of reference 51, specifically Figure E-1. Also shown in the reference is an Executive Summary via Figure E-4 showing an operating limit of 7.8x1021 fissions/cm3. Based on the upper limit of the Peak Fission Density axis of Figure E-1, a value of 8 x1021 fissions/cm3 is considered appropriate to calculate a lower bounding temperature for this thermal evaluation, which is 326.7°C (620°F).

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 12 of 16 The reference source information INL EXT-17-40975 has been provided onto the docket and is available via ADAMS at NRC Accession Number ML25017A403. In addition, improvements to the SAR Section 3.8.2.2, Technical Specifications of Components, have been made to the second paragraph on page 3.8-5 and are shown here:

SAR Section 3.8.2.2 RAI 3.5, page 3.8-5 changes (updates shown in red font)

The peak power densities for the various reactors are shown in Figure E-1 of the Executive Summary of reference [51]. In addition, Figure E-4 of the Executive Summary of reference

[51] shows an operating limit of 7.8x1021 fissions/cm3. Based on the upper limit of the Peak Fission Density axis of Figure E-1, a value of 8 x1021 fissions/cm3 may be deemed appropriate to calculate a lower bounding temperature for this evaluation. Conservatively, this evaluation uses the lower bounding permissible cladding temperature limit of 620 °F at the peak fission density of 8x1021 fissions/cm3.

RAI 3.6 Explain how the indefinite operation for vacuum drying of the LEU fuels is determined and whether a time duration limit is needed to ensure the fuel temperature will not continue heating up to reach 620 °F limit.

The applicant used the ATR LEU fuel as the bounding LEU fuel and stated, in SAR section 3.8.3.3, that the computed peak fuel plate temperature of 552 °F, under steady-state conditions, will require a total of approximately 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> to achieve (see SAR figure 3.8.3-14), and therefore, with the peak fuel temperature of 552 °F well below the 620 °F limit established in SAR section 3.8.2.2, indefinite operation under either air (or nitrogen gas) filled conditions or vacuum drying is permissible for in-facility operations.

The staff reviewed SAR figure 3.8.3-14 and noted that the ATR fuel temperature continues to increase after 480 minutes and a time duration limit is still needed to ensure the vacuum drying is completed before reaching the 620 °F limit, based on extrapolation of the transient trend shown in SAR figure 3.8.3-14.

The applicant needs to explain how the indefinite operation for vacuum drying for LEU fuels is determined and whether a time duration limit is needed to ensure the fuel temperature will not continue heating up to reach 620 °F limit.

This information is required to determine compliance with 10 CFR 71.35 and 70.71.

Thermal Evaluation RAI 3.6 Reply The 510 minutes identified on the x-axis of SAR Figure 3.8.3-14 is erroneous. The chart x-axis should be identical to that of SAR Figure 3.3-10. The last part of the chart occurs well after 510 minutes, as it is run as a steady-state loading condition, shown by the horizontal lines at the end of the chart in SAR Figure 3.8.3-14. The temperatures do not rise above the 620 °F limit. SAR Figure 3.8.3-14 chart has been corrected in the revised SAR, and due to other unrelated changes is now labeled as SAR Figure 3.8.3-16.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 13 of 16 RAI 3.7 Explain the phrase of one-hour time period in SAR section 3.6.3.4 and assess whether a tracking of the elapsed time is required to take six hours to cool down the peak fuel plate temperature below 400 °F.

The applicant stated, in SAR section 3.8.3.4, that the one hour time-period following helium gas backfill required to reduce the peak fuel plate temperature below 400 °F is so short compared with the time to complete preparation of the cask for transport that no specific tracking of the elapsed time will be required.

The staff noted, from SAR figure 3.8.3-15, that it will take six hours (360 minutes), instead of one hour, to reduce the peak fuel plate temperature below 400 °F. Therefore, the applicant needs to explain the phrase of one-hour time-period and assess whether a tracking of the elapsed time is required to take six hours to cool down the peak fuel plate temperature below 400 °F.

This information is required to determine compliance with 10 CFR 71.35 and 70.71.

Thermal Evaluation RAI 3.7 Reply This should be six hours in the third paragraph of SAR Section 3.8.3.4, Cask Cavity Backfill with Helium Gas. The second paragraph in this section already states six hours, but the one hour in the third paragraph is erroneous and therefore SAR Section 3.8.3.4 will be corrected. Since it takes tens of man hours to complete shipping preparations due to the numerous successive steps including leak testing and cask closure along with the transport preparation steps of Section 7.1.4, this is still a negligible timeframe to consider the need for tracking operational hours.

Prior to transportation, the cask must be subjected to leak tests of the main containment O-ring seal, the drain port sealing washer, and the vent port sealing washer. Following leak testing, the cask is prepared for transport. The cask preparation steps include installing both the lower and upper impact limiters, moving the package to the transportation vehicle, and securing the package for transport. As confirmed by all BRR package operational groups, it takes tens of man hours (or multiple workdays) to complete all closure and shipping preparation activities together with the required 10 CFR 71.87, Routine Determinations, including recording package contamination and radiation levels. It is reasonably credible that performance of these tasks, in addition to the expected transition intervals between tasks exceeds the required six-hour time to allow the fuel adequate cooling to meet the temperatures computed for the NCT Hot without solar condition.

Therefore, no changes to the thermal or structural analyses for transport are necessary as a result of the elevated fuel cladding temperature potentially achieved under vacuum drying operations.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 14 of 16 As a result of this RAI, the last two paragraphs of Section 3.8.3.4 are revised as follows:

SAR Section 3.8.3.4 RAI 3.7 2nd and 3rd paragraph changes (updates shown in red font)

Figure 3.8.3-17 illustrates the cool down transient after helium backfill assuming an initial temperature distribution of steady-state operations with an air or nitrogen atmosphere in the cask cavity. As seen from the figure, less than six hours is required to lower the peak fuel plate temperature to below 400ºF. Approximately eight hours are required to lower the fuel and cask component temperatures to those reported in Section 3.8.3.1.1.3, ATR Fuel Element Payload.

Prior to transportation, the cask must be subjected to leak tests of the main containment O-ring seal, the drain port sealing washer, and the vent port sealing washer. Following leak testing, the cask will be prepared for transport, including installation of both the lower and upper impact limiters, moving the package to the transportation vehicle, and securing the package for transport.

It takes tens of man hours (or multiple workdays) to complete all these closure and shipping preparation activities together with the required 10 CFR 71.87, Routine Determinations, including recording package contamination and radiation levels. Therefore, it is reasonably credible that performance of these tasks, in addition to the expected transition intervals between tasks exceeds the required time to allow the fuel adequate cooling time to achieve those temperatures computed for the NCT Hot without solar condition. Due to the short six-hour cooldown time interval requirement compared to the cask preparation time needed prior to commencing transport, no changes to the thermal or structural analyses for transport are necessary as a result of the elevated fuel cladding temperature potentially achieved under vacuum drying operations.

In conclusion, the results presented above demonstrate that steady-state operations under cask draining and vacuum drying conditions are permissible without exceeding the maximum allowable component temperature limits. The six-hour period following helium gas backfill required to reduce the peak fuel plate temperature below 400ºF and the eight-hour period to drop below the maximum NCT temperatures is within the time required to complete preparation of the cask for transport and that no specific tracking of the elapsed time will be required. Once filled with the helium gas, and cooled appropriately, the package temperatures are bounded by those presented in Section 3.8.3.1.1, Maximum Temperatures, for NCT conditions.

Criticality Evaluation RAI 5.1 Provide more information regarding the use of Whisper in determining the bias and bias uncertainty, and the calculation of the upper subcritical limit (USL).

Guidance recommends the usage of a methodology consistent with American National Standards Institute/American Nuclear Society-8.1. Insufficient information was included in the application for staff to make this determination.

This information is required to determine compliance with 10 CFR 71.55.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 15 of 16 Criticality Evaluation RAI 5.1 Reply Additional information and details regarding the usage of Whisper in determining the bias and bias uncertainty and the calculation of the USL have been provided on the BRR Package docket 71-9341. This information is available via ADAMs at NRC Accession Numbers ML25008A214 (Questions and Answers on Whisper USL calculations and Whisper Theory paper),

ML25008A215 (Whisper Orano FS Software Commercial Grade Dedication Plan), and ML25008A216 (Whisper Orano FS Software Commercial Grade Dedication Report).

Package Operations RAI 7.1 Add package surface temperature survey in SAR chapter 7 (e.g., section 7.1.4, Preparation for Transport) for an exclusive-use shipment of BRR package loaded with each fuel type of MURR HEU fuel, MITR-II HEU fuel, MURR LEU fuel and MITR-II LEU fuel in compliance with 10 CFR 71.43(g).

The maximum accessible surface temperature for BRR packaging with each fuel type of MURR HEU fuel (SAR table 3.3-1), MITR-II HEU fuel (table 3.3-2), MURR LEU fuel (table 3.8.3-1) and MITR-II LEU fuel (table 3.8.3-2), under NCT without solar heat, could be close to 185 °F limit in an exclusive-use shipment.

The applicant needs to add package surface temperature survey in SAR section 7.1.4, Preparation for Transport, to ensure that the maximum package surface temperature is below 185 °F for an exclusive-use shipment of BRR package loaded with each fuel type of MURR HEU fuel, MITR-II HEU fuel, MURR LEU fuel and MITR-II LEU fuel.

This information is required to determine compliance with 10 CFR 71.43(g).

Package Operations RAI 7.1 Reply The addition of a package surface temperature survey in SAR Section 7.1.4, Preparation for Transport, is preventable and would consistently show acceptable results. This is since the conditions required by 10 CFR 71.43(g) during preparation for transport (i.e., maintaining an ambient temperature of 100 °F) at the package facilities will not approach this temperature extreme.

With the changes to the LEU fuel No Insolation thermal models described below, the BRR package already addresses the 10 CFR 71.43(g) regulatory limit and demonstrates the limit has been met. The BRR package maximum accessible surface temperature is found in SAR Table 3.3-1 and is discussed in the sixth paragraph of Section 3.3.1.1, Maximum Temperatures. The new LEU fuel payload results regarding the maximum accessible surface temperature remained consistent and bounded by the HEU fuels, as shown in revised SAR Table 3.8.3-1 and SAR Table 3.8.3-2. However, further refinements of the new LEU fuel thermal models for the NCT No Insolation case as shown below denote that the values of maximum accessible surface temperature have been slightly reduced further due to minor upgrades to the thermal model.

Although the maximum accessible surface temperatures approach the 185 °F exclusive-use shipment limit under the extreme ambient temperature of 100 °F, they continue to comply with this regulatory limit. Therefore, imposing a package surface temperature survey is redundant and would provide no commensurate safety benefit.

BRR Package (Docket 71-9341) Amendment Request RAI Responses 2/13/2025 Page 16 of 16 Furthermore, a temperature survey was previously discussed when addressing RAI 3-4 with respect to the original revision 0 of the SAR (see NRC Accession Number ML12090A3170) and the changes were accepted per Section 3.3 of the revision 0 CoC Safety Evaluation Report (see NRC Accession Number ML100260364). Hence, by using these revised LEU fuel thermal models for the No Insolation case, consistency is maintained with both previous licensing actions and BRR package operations and observance of 10 CFR 71.43(g) is affirmed by validating the accessible surface temperature of the package is below 185°F for an exclusive-use shipment with no insolation. Further discussion follows of the SAR enhancements made.

Chapter 3.0 of the SAR provides a comprehensive thermal analysis that demonstrates compliance with 10 CFR 71.43(g). The text in SAR Section 3.3.1.1, Maximum Temperatures, refers to a limited area on the impact limiter attachment lugs that approaches the 185 °F criteria. This assessment is based on a less refined thermal model in the region of the attachment lugs. As described in SAR Section 3.5.3.1, Description of BRR Packaging Thermal Model for NCT Conditions, the increased number and size of the re-designed impact limiter attachment lugs was not implemented in the NCT thermal model of the HEU fuels. As such, the NCT thermal model for the HEU fuels provides a conservatively high estimate of the NCT package temperatures.

To corroborate the 10 CFR 71.43(g) criteria and improve the results, the accessible surface temperature model for the LEU fuels thermal model was amended by increasing both the size and quantity of attachment lugs. As noted in SAR Section 3.3.1.1:

an earlier cask design that used 6 instead of the current 8 attachment lugs per limiter, cask lug plates that are 0.38-inches thick by 2.75-inches wide vs. the current 0.5-inches thick by 3.63-inches...

Therefore, the revised NCT No Insolation LEU fuel thermal models used for calculating the surface temperatures incorporate the increased number of attachment points from the earliest HEU thermal model and correct the size of the lugs to their actual size. These revised models also include credit for the seal welded joints between the thermal shield and the upper attachment lugs (shown on sheet 4 of SAR drawing 1910-01-01-SAR). For the MURR LEU fuel, the resulting temperature distribution is shown in the revised SAR Figure 3.8.3-6 and SAR Figure 3.8.3-7 for the exterior areas of the package and the thermal shield, respectively. For the MITR LEU fuel, the resulting temperature distribution is shown in the new SAR Figure 3.8.3-11 and SAR Figure 3.8.3-12 for the exterior areas of the package and the thermal shield, respectively. The results show that no accessible exterior package surface exceeds 185 °F.

It should be noted that the revised thermal model still contains the following conservatisms: 1) the potential for convective heat transfer from the inside surface of each attachment lug is ignored due to the assumed flow blockage by the blade portion of the impact limiter attachment (a nominal 1/8-inch gap will exist on either side of the blade) and 2) no credit is taken for conduction into the attachment pin and then dissipation to the ambient via convection and radiation from the attachment pins. As such, the actual peak temperature is expected to be lower.

Due to the LEU thermal model changes for the NCT Hot without Solar case, the text in SAR Section 3.8.3.1.1.1, MURR LEU Fuel Element Payload and SAR Section 3.8.3.1.1.2, MITR Fuel Element has been updated. In addition, the temperature results in SAR Tables 3.8.1-1, 3.8.3-1 and 3.8.3-2 and Figure 3.8.3-10 have been updated to reflect the results of the revised NCT thermal model. No changes have been made to the NCT Hot results since, since as explained earlier, the base NCT thermal model generates conservatively high package temperatures.