ML25155A086

CoC No. 5797 Rev. 24 RAI Response Enclosure

ML25155A086
Person / Time
Site:	07105797
Issue date:	05/20/2025
From:	US Dept of Energy, Office of Packaging and Transportation
To:	Yoira Diaz-Sanabria Storage and Transportation Licensing Branch
Shared Package
ML25155A082	List: ML25155A085 ML25155A086
References
EPID L-2023-LLA-0156
Download: ML25155A086 (1)

Text

Enclosure - Response to Request for Additional Information, Certificate of Compliance No. 5797, Docket No. 71-5797, May 2025

RAI-1

Provide the location and magnitude of the maximum deformation of the package measured from the model tests and calculated by the finite element (FE) structural analyses for the vertical end, horizonal side and center-of-gravity-over-top (CGT) corner drops under the normal conditions of transport (NCT). If the results of the FE structural analyses do not bound the results of the model tests, justify how the results of the FE structural analyses are accurate and conservative. Additionally, provide a deformation contour view of the FE analyses and model test results of each drop orientation in the vicinity of impact for a comparison.

In 1991, the applicant performed structural analyses of the package under NCT using the DYNA FE codes (DYNA2D and DYNA3D) and submitted safety evaluations based on the results of the structural analyses from Inner HFIR Unirradiated Fuel Element Shipping Container and Outer HFIR Unirradiated Fuel Element Shipping Container Certificate of Compliance No. 5797 Revision No. 9, dated May 30, 1991. The staff reviewed the applicants safety analysis report (SAR) and issued SAFETY EVALUATION REPORT: Inner HFIR Unirradiated Fuel Element Shipping Container and Outer HFIR Unirradiated Fuel Element Shipping Container Certificate of Compliance No. 5797, Revision No. 9, dated July 13, 1992. In 2023, the applicant performed the full-scale model tests of the package to demonstrate compliance with the requirements of 10 CFR 71. The applicant performed external visual and dimensional inspections on each package prior to and following the model tests. The visual inspection provided limited data (i.e., measured deformation) that could be used for qualitative safety evaluations. However, the applicant made quantitative safety evaluations (i.e.,

calculated stress vs. yield stress) based on the results of the FE structural analyses performed in 1991. The staff needs to assess the impacts of the results of the model tests on the structural analyses, evaluate the relationship between them, and determine the accuracy and acceptability of the quantitative results.

This information is needed by the staff to determine compliance with 10 CFR 71.71(c)(7).

The location and magnitude of the maximum deformations for the horizontal side, CGT, and vertical end drops, as determined through analysis and observed from physical testing, are presented in Table 1 below. Where possible, the accompanying figures illustrate a comparison between the analyzed deformation and the maximum physical damage at the point of impact. In some instances, test package impact positions do not fully replicate the analyzed four-foot drop orientation.

The initial HFIR fresh fuel shipping package SAR, in lieu of testing, used finite element analysis (FEA) (DYNA) and Energy Balance (EB) calculations to evaluate package performance to 10 CFR Part 71 (prior to the crush requirement). The physical drop tests performed in 2023 were selected to maximize package damage when addressing the sequential crush, not to benchmark previous analysis. However, when comparing physical deformations, the analyzed conditions are reasonably comparable and conservatively bound the measured physical NCT drop deformations. The analysis methods used when comparing the results with the physical tests are listed in the table.

The HFIR fresh fuel shipping package FSAR utilizes a combination of testing, analyses, and calculations to demonstrate compliance with the 10 CFR 71 requirements. DYNA2D and DYNA3D computer models were used to evaluate performance of the package in the end drop (bottom down) orientation. Side-drop and corner-drop orientations were studied via the EB method (FSAR Reference 2.12.10). The physical tests performed in 2023 evaluated NCT free drops in horizontal, corner, and end drop (top down) attitudes. The DYNA programs have been utilized to evaluate free drop conditions for the HFIR package in support of a previous application. Contour views of the DYNA model results are available in FSAR References 2.12.12 and 2.12.13 for the bottom-down end drop; however, no FEA contour plots were produced for the side and corner drop orientations. Table 1 lists the NCT free drop test results.

Page 1 of 19

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 Page 2 of 19 Table 1: NCT Free Drop Results NCT Free Drop (4 feet)

Package Orientation Package Model (Test Unit)

Primary Damage Location(s)

Approximate Deformation (inches)a Energy Balance Method Finite Element Analysis (DYNA)

Physical Test Results b Side Inner Projected portions of the lid; packaging body and support structures 1.13 Outer (O-2) 1.78 1.1 Corner Inner (I-1)

Lid closure and support structures 0.55 (plywood) c Outer (O-1) 0.80 (plywood) c End Inner d (I-2)

Lid and supporting structures; packaging bottom and channel 0.25 Outer e 0.75 a: For NCT free drops, reported deformation includes steel lid, body, and support structures unless otherwise noted.

b: Assessments of deformation from physical testing are based on pictures and videos following free drop tests.

c: Test results show complete collapse of lid flange at point of impact. Observations indicate continued progression of lid flange collapse was mitigated by the plywood impact limiter. Based on the lid deformation, its reasonable to assume the amount of plywood deformation is bounded by corner drop EB analyses.

d: Test unit Inner-2 was dropped in a top-down orientation.

e: An outer package was analyzed in the bottom-down free drop orientation using the DYNA computer code.

Figure 1 details the drop orientations performed during the 2023 physical test program for the HFIR package.

Figures 2 through 5 show the damage sustained by each test package for the NCT free drop. The methods employed to study package performance during NCT free drop tests (i.e., FEA, EB, or physical testing) indicate that the requirements of §71.43(f) will be satisfied for any package orientation.

Response to Request for Additional Information, Certificate of Compliance No. 5797, Docket No. 71-5797, May 2025 Page 3 of 19 Figure 1: NCT Physical Test Free Drop Orientations

Response to Request for Additional Information, Certificate of Compliance No. 5797, Docket No. 71-5797, May 2025 Page 4 of 19 Figure 2: Inner-1 NCT Free Drop Damage Comparison

Response to Request for Additional Information, Certificate of Compliance No. 5797, Docket No. 71-5797, May 2025 Page 5 of 19 Figure 3: Outer-1 NCT Free Drop Damage Comparison

Response to Request for Additional Information, Certificate of Compliance No. 5797, Docket No. 71-5797, May 2025 Page 6 of 19 Figure 4: Inner-2 NCT Free Drop Damage

Response to Request for Additional Information, Certificate of Compliance No. 5797, Docket No. 71-5797, May 2025 Page 7 of 19 Figure 5: Outer-2 NCT Free Drop Damage Comparison

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025

RAI-2

Provide detailed technical justifications for not performing the model tests of the package under the hypothetical accident conditions (HAC).

The applicant stated that the purpose of the safety evaluations of the package submitted in this application is to demonstrate compliance with the NCT and HAC requirements of 10 CFR 71 by performing a series of the full-scale model tests. The applicant performed the model tests for the end and side drop orientations under NCT.

However, the applicant did not perform the model tests for the end and side drop orientations under HAC. The end and side drop model tests under HAC are important model tests to understand the behavior of the package under the 30-ft. accident drop and to demonstrate compliance with the requirements of 10 CFR 71.73(c)(1).

In section 2.7 of the SAR, Safety Analysis Report for the HFIR Unirradiated Fuel Element Shipping Package, ORNL/RRD/INT-180, Rev. 0, dated July 30, 2024, the applicant briefly provided its general qualitative engineering assumptions/judgements for not performing the HAC model tests. The applicant stated that the end drop test was not performed under HAC because damage from a 30-ft. vertical end drop will not challenge the package, with typical damage being a slight reduction in the overall height of the package from drum side wall buckling. The localized buckling would not be greater than the axial spacing above and below the fuel element. The applicant also stated that the side drop test was not performed under HAC because damage from a 30-ft. horizontal side drop does not challenge the package based on other similar packages (i.e.,

DT-20 and DT-23 packages). However, 10 CFR 71.73(c)(1) requires that a package needs to be demonstrated for structural adequacy by a free drop through a distance of 30 ft. onto a flat, unyielding, horizontal surface in a position for which maximum damage is expected. The structural responses of a package under HAC, including interactions among the components in the package, are quite complex and involve non-linear plasticity. Therefore, the applicant is requested to provide more detailed quantitative technical information to demonstrate compliance with the HAC requirements of 10 CFR 71.

This information is needed by the staff to determine compliance with 10 CFR 71.73(c)(1).

ORNLs approach to demonstrating compliance with the regulations is by a combination of the methods described in 49 CFR §173.461. In 1992, calculations and analyses were presented that demonstrated compliance with the regulations in place at the time. In August of 2023, the HFIR fresh fuel shipping package was subjected to physical NCT and HAC tests to demonstrate compliance with -96 regulations, and specifically to address the dynamic crush test. The bases for testing were documented in ORNL/RRD/INT-173, Revision 1, Test Plan for Normal Conditions of Transport and Hypothetical Accident Condition Tests, and ORNL/RRD/INT-174, Revision 0, Test Plan for Normal Conditions or Transport and Hypothetical Accident Condition Tests, Oak Ridge National Laboratory Package Design USA/5797/B(U)F-96: Bases for Selecting Tests, Orientations, and Test Conditions, both of which were acceptable to NRC staff per Project Manager email dated December 28, 2021.

HAC end and side drop orientations were studied via FEA and EB methods in FSAR References 2.12.13 and 2.12.10, respectively, to demonstrate compliance with 10 CFR §71.73(c)(1). Detailed technical information regarding the package response to a 30-foot free drop in the orientations in question can be found in FSAR Section 2.7.1.1 and Reference 2.12.13 for the end drop, and FSAR Section 2.7.1.2 and Reference 2.12.10 for the side drop. The results of these drops are provided for comparison with other HAC drops in Table 2, in response to RAI-3. The model tests performed supplement earlier technical evaluations for HAC drops and in combination demonstrate the package meets the performance requirements of 10 CFR §71.73(c)(1).

Page 8 of 19

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 Page 9 of 19

RAI-3

Justify the use of the energy balance (EB) method over the FE method to analyze the performance of the package for the side drop under NCT and HAC, while the FE method was used to analyze the package for end drop under NCT and HAC.

In sections 2.6 and 2.7 of the SAR, Safety Analysis Report for the HFIR Unirradiated Fuel Element Shipping Package, ORNL/RRD/INT-180, Rev. 0, dated July 30, 2024, the applicant indicated that the EB method was used to analyze the performance of the package for the side drop under NCT and HAC. However, the applicant indicated that the FE method was used to analyze the package for end drop under NCT and HAC. The applicant is requested to justify the use of the EB method over the FE method to analyze the performance of the package for the side drop under NCT and HAC and explain how the EB method accurately analyzes the component interactions and nonlinear behavior of the components during the 30-ft. drop dynamic impacts.

This information is needed by the staff to determine compliance with 10 CFR 71.71(c)(7) and 71.73(c)(1).

The use of the EB method to analyze side and corner drop orientations is consistent with the quasi-static method of impact analysis described in NUREG/CR-3966, Methods for Impact Analysis of Shipping Containers. The method utilized in FSAR Reference 2.12.10 considers the dissipation of the drop energy primarily through plastic deformation of the metallic structural members and crushing of the plywood impact limiter while ignoring energy dissipation in the 11-gauge steel body of the cask and in the elastic deformation of the plywood.

The NUS Corporation benchmarked the methodology used in the FSAR Reference 2.12.10 calculations during development of its Computerized Energy Balance Analysis (CEBA) code, which was designed to calculate decelerations and forces due to the side, end, and corner impact of radioactive waste packages. The methodology NUS corporation employed for the HFIR fresh fuel package utilizes small crush deflection increments of 0.0625 inches to ensure that any errors between steps are insignificant. The text in FSAR Reference 2.12.10 (p 2-3) provides the iterative procedure adhered to for the analysis.

The results of CEBA calculations were compared to the drop test results for a half-scale model package and the results of calculations from another computer code. The half-scale model tested was the Beneficial Uses Shipping System (BUSS) cask, developed by Sandia National Laboratory, and certified by NRC Certificate No. 9511. A comparison between these methods is shown below in Figure 6. Note that the unbacked and backed cases indicate whether the foam was backed by the steel shell of the cask or not.

Figure 6: BUSS Cask Drop Testing Comparison Comparisons to calculational results for the NuPac Model 10-142 SAR (NRC Certificate No. 9208) were made between corner, side, and end drop orientations with both backed and unbacked foam. The results are shown in Figure 7.

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 Figure 7: NuPac Cask Drop Testing Comparison The methods conservatism may also be demonstrated through comparison between physical test results and EB analytical results for the HFIR fresh fuel shipping package. A direct comparison between the EB method and physical test results may be made for a center of gravity over top (CGT) orientation for the inner package. FSAR Reference 2.12.10 predicts plywood deflection and deformation of 0.55 inches and 2.13 inches for the NCT and HAC free drop tests, respectively. NCT testing of test unit Inner-1 in CGT orientation showed plastic deformation of the 11-ga. steel lid, 1/4-inch-thick steel top brace angle, and 1/8-inch-thick steel flange angle; however, no physical plywood damage could be confirmed (see Figure 8), but based on the observed physical damage it is reasonable to conclude that some small amount of damage to the plywood (i.e., < 0.55 inches) did occur, as predicted by the EB method.

HAC CGT testing of Inner-1 targeted the area damaged by the NCT free drop testing and resulted in further plastic deformation of the previously damaged steel members. Some plywood deformation would have occurred but could not be physically observed during the test sequences; however, the observed deformation is bounded by that predicted in the EB evaluation (2.13 inches) for the 30-ft. CGT drop (see Figure 9). These experimental results also support the assertion that the EB methods employed for previous analysis of this package are conservative and provide assurance of satisfactory package performance during the prescribed normal and accident condition tests. Tables 1 (RAI-1) and 2 (below) provide comparison between FEA, EB, and physical test results tabulated from FSAR References 2.12.4 (physical testing), 2.12.10 (EB), 2.12.12 (FEA), and 2.12.13 (FEA).

Page 10 of 19

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 Page 11 of 19 Figure 8: NCT CGT Free Drop Test Damage to Test Unit Inner-1 Figure 9: HAC CGT Free Drop Test Damage to Test Unit Inner-1

Response to Request for Additional Information, Certificate of Compliance No. 5797, Docket No. 71-5797, May 2025 Page 12 of 19 Table 2: HAC Free Drop Results HAC Free Drop (30 feet)

Package Orientation Package Model (Test Unit)

Primary Damage Location(s)

Approximate Plywood Deformation (inches)

Fuel Element Response b Energy Balance Method Finite Element Analysis (DYNA)

Physical Test Results a Side Inner Projected portions of the lid; packaging body and support structures 2.26 Plate bending occurs Outer 2.36 Plate bending occurs Oblique Inner Lid closure and packaging body and bottom interface N/A Outer (O-2) 1.75 c (TSD)

Negligible d Corner e Inner (I-1, I-2)

Lid closure and support structures 2.13 (CGT)

Negligible Negligible d Outer (O-1) 2.66 (CGT) 3.0 (CGB)

Negligible d End Inner Lid and supporting structures; packaging bottom and channel N/A Outer Not quantified f Buckling of end adapter a: Plywood deformation from physical testing is estimated based on pictures and videos following HAC free drop tests since it was not practical to remove the lid and disassemble the constituent components of the packaging for inspection following each impact.

b: For fuel element response to CGT drops, the physical test results are reported.

c: Test unit Outer-2 was subjected to a top slap down (TSD) oblique angle drop of approximately 13 degrees. The initial impact site at the lid area experienced significant flattening of a lid segment with a chord (damage) length of about 18 inchessee Figures 10 and 11. The damaged area on the outside of Outer-2 indicates deformation into the lid plywood area of approximately 0.75 inches. Minor deformation and bulging of the 11-ga. steel sheet metal and displacement of less than one inch was observed at the secondary (bottom) impact site. These measurements have been added together to give a conservative approximation of total plywood deformation.

d: Negligible indicates minimal deformation occurred between plates, as measured by pre-and post-test go/no-go gauge.

e: Three units were tested in a corner drop orientation. The Outer-1 free drop orientation was with the center of gravity over the bottom (CGB) corner, with the impact site in the free area between sections of bottom channel. Vertical displacement of the container bottom and body in the middle of the damage segment is estimated to be three inches. Note that the CGB damage location is not reinforced by steel flanges and angles; thus, these results cannot be directly compared with predicted CGT orientation damage.

f: DYNA2D is used to model end drop in bottom-down orientation (FSAR Reference 2.12.13). The quantification of damage is not expressed in an amount of plywood crushing at the impact site but rather is focused on fuel element response. The result of the analysis is that the maximum shear stress of the fuel element plates remains well below the critical shear buckling stress for aluminum.

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 Page 13 of 19 Figure 10: HAC TSD Free Drop Test Damage to Test Unit Outer-2

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 Figure 11: HAC TSD Free Drop Test Damage to Test Unit Outer-2

RAI-4

Clarify how assumed material emissivity values used to perform the thermal analysis of the HFIR shipping package would result in realistic or conservative results.

Table 3.3 of the SAR provides material properties used in the thermal analysis. It is stated in this table that all emissivity values are assumed. The staff needs to have assurance the assumed values are realistic or conservative to make a determination of the adequacy of the analysis results.

This information is necessary to determine compliance with 10 CFR 71.71 and 71.73.

FSAR Table 3.3, Material Properties Used in Thermal Analysis, provides assumed emissivity values that are utilized in the analysis. These values were compared against available references and have been determined to be representative and/or conservative against published and/or test data. See Table 3, below.

Page 14 of 19

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 Page 15 of 19 Table 3: Package Material Emissivities Used in FSAR Thermal Analysis Package Emissivities Comparison Material FSAR Table 3.3 value Comparison Comparison Reference Fir Plywood 0.9 0.9 Wood Handbook (2021), Table 18-2, p. 18-13 Polyethylene Foam 0.9 0.9 Testing a Steel 0.6 b 0.2 - 0.32 J.P. Holman, Heat Transfer, 8th Ed., p. 651 Aluminum 0.7 0.039 - 0.31 J.P. Holman, Heat Transfer, 8th Ed., p. 651 a Test conducted on site at ORNL using a calibrated precision thermocouple and thermal imaging camera.

b The previous value of 0.6 was identified as an error and will be updated to the correct value, 0.8.

Surface emissivity values for polyethylene foam were not readily referenceable. As such, a sample of 2.2 pound per cubic foot polyethylene foam (Ethafoam) was procured for testing. A calibrated precision thermocouple (Beamex MC6) and a thermal imaging camera (Flir E95) were used to measure the emissivity of the polyethylene foam. The thermocouple was connected to the Ethafoam sample, and the foam temperature was allowed to equilibrate (see Figure 12). The emissivity setting on the thermal imaging camera was then adjusted until the foam temperature measurement closely matched that of the precision thermocouple, and the corresponding emissivity value was recorded.

The temperature value of the foam as measured on the thermal camera most closely matched that of the thermocouple readings when the emissivity value was set at 0.90. Table 4 and Figure 13 provide the results.

While many factors can impact these measurements, the test demonstrates that a value of 0.9 is a reasonable approximation for Ethafoam 220 used in the HFIR package.

Table 4: Ethafoam Emissivity Test Results Ethafoam Emissivity Camera Emissivity Setting Ethafoam Temp. (Thermocouple)

Average Temp. (Camera) 1.00 71.3 71.6 0.90 71.4 0.85 70.9 For clarity, it is proposed to revise FSAR Table 3.3 notes to include specific references for the above emissivity values. The Al-air material from FSAR Table 3.3 has a given value of 1.0 and is considered sufficiently conservative without further justification.

The emissivity value for steel in Table 3.3 is listed as 0.6 in error. The package external surface emissivity identified in the text on page 3-14 of the FSAR and analysis from FSAR Reference 3.5.12 for the HAC thermal transient is 0.8; therefore, Table 3.3 will be updated to reflect this value. A note for the steel material will be added to clarify that the NCT insolation analysis from FSAR Section 3.3.1.1 utilizes an emissivity value of 1.0.

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 Page 16 of 19 Figure 12: Thermocouple, Thermal Camera, and Ethafoam Sample

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 Figure 13: Temperature of Ethafoam at Various Emissivities (left) vs. Temperature of Ethafoam as Measured by Thermocouple (right)

RAI-5

Justify the heat transfer coefficient value used to perform the analysis of the 30-minute regulatory fire test.

SAR Section 3.4.2 states that for the convective condition for a fire be a forced convection coefficient a value of about 1.8 BTU/hr-ft2-°F can be used based on M. H. Burgess, Heat Transfer Boundary Conditions in Pool Fires, IAEA-SM-286/75P, Proceedings of PATRAM 86, IAEA, Vienna, 1987. During the 30-minute fire regulatory test, the NRC staff have accepted values provided in Gregory, J.J., R. Mata, and N.R. Keltner, Thermal Measurements in a Series of Large Pool Fires, SAND85-0196, TTC-0659, UC-71, Sandia National Laboratories, Albuquerque, NM, August 1987. The values provided in this reference for the fire test conditions are more than twice the value used by the applicant for performing the fire thermal analysis.

This information is necessary to determine compliance with 10 CFR 71.73(c)4.

Page 17 of 19

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 The FSAR utilizes experimental convection coefficient values used by Burgess for a 2-meter cube in a pool fire.

This value will be compared with the convection coefficient of a cylinder in a vertical and horizontal orientation, calculated herein. FSAR Reference 3.5.7 (p. 242) provides a method for determining the average forced convection heat transfer coefficient (h) for a flat plate in laminar flow conditions, i.e., with a Reynolds number less than 2.0 x 105. This equation is given as:

=

0.664 1/21/3 The Reynolds number was calculated using the below equation.

=

Where is density, is free stream gas velocity, is the characteristic length of the cask, and is the dynamic viscosity of the gas at the film temperature.

A document published in Volume 111 of the Journal of Heat Transfer (pp. 446-454), by the authors of the paper referenced by the NRC staff in RAI-5, entitled Thermal Measurements in Large Pool Fires,1 provides a measured gas velocity of 4.8 m/s at a distance of 1.4 m above the fuel source to calculate h values in its experiments. This value was used as an input to approximate the Reynolds number for the HFIR package and, subsequently, to find the h value. The results are 94,199 and 7.2 W/m2 K (or about 1.3 BTU/hr ft2 F), respectively.

Note that the HFIR package was assumed to be upright during the HAC thermal event. However, for comparison, the convection coefficient for a cylinder in cross flow was calculated, assuming the HFIR package is on its side during the HAC thermal event. The equation for average convection coefficient for a cylinder in these conditions (from FSAR Reference 3.5.7, p. 302) is given below.

= ()

1/3 Values of constants and are provided in Table 6-2 of FSAR Reference 3.5.7 and are based on the Reynolds number (which was recalculated for the different orientation). A film (f) temperature of 700 K was assumed for deriving parameter values, as it is roughly the average between the initial temperature of the cask at the start of the HAC thermal event, i.e., 169 °F, and the 1475 °F regulatory fire temperature. The above assessment would indicate a convection coefficient of 10.5 W/m2 K (about 1.85 BTU/hr ft2 F) for the outer HFIR fuel element package and 10.9 W/m2 K (about 1.92 BTU/hr ft2 F) for the inner HFIR fuel element package.

From a direct comparison of the coefficient used in the FSAR Section 3.4.2 and the paper referenced by the NRC staff, the major difference is the assumed flame temperature of 1850 °F compared to the minimum of 1475 °F, which would satisfy 10 CFR 71.73(c)4. The difference in temperature (relative to the regulatory fire), atmospheric conditions, and differing geometry and orientation of the test subjects will have a considerable impact on the heat transfer variables. Assessing the value of a convective heat flux 1.0 Btu/ft2 s (page 35) cited for the large 56.5-in calorimeter with a flame temperature of 1850 °F the convective heat transfer coefficient would be 2.32 Btu/hr ft2 °F. Assuming the driving temperature is 1475 °F the coefficient obtained is 1.76 Btu/hr ft2 °F. The slight difference in convective heat transfer coefficient values (i.e., between what is computed here or determined from the referenced data corrected for fire temperature) will have a negligible impact on the outcome of the HAC thermal test for the HFIR package.

HFIR fuel elements are constructed of fuel plates coupled between concentric aluminum cylinders. The inner and outer HFIR fuel elements have 171 and 369 fuel plates, respectively. The fuel matrix within each fuel plate contains aluminum with U3O8 as its radioactive contents. The fuel matrix is clad with 6061 aluminum, forming Page 18 of 19

Response to Request for Additional Information, Certificate of Compliance No.

5797, Docket No. 71-5797, May 2025 Page 19 of 19 the containment boundary of the HFIR package. As such, the fuel elements are a quality assurance (QA) Category A item.

Figure 14, below, illustrates the heat up and cool down of various packaging components monitored during the analysis. Points A-D, J, and K are near the package exterior and heat up quickly during the fire. However, the interior packaging materials near the fuel (Points E-I) respond much more slowly due to the thermal insulation provided by the Douglas fir plywood. Thus, the performance of the fuel during the fire is not significantly impacted by the convection coefficient utilized in the analysis.

Figure 14: Inner HFIR Package HAC Temperature Curves As stated in FSAR, Section 3.4.2, the HEATING6 model used to analyze the HAC transient was run up to a time of 2.33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br />, at which time the temperature at the bottom piece of plywood in the package had peaked. Since the unirradiated HFIR fuel elements generate a negligible amount of heat (i.e., less than 0.02 watts), the transient was stopped at this point. Table 3.5 of the FSAR provides the maximum HAC temperatures for the packaging components, accounting for NCT insolation. The maximum calculated fuel element temperatures under HAC are 359 °F and 357 °F for the inner and outer packages, respectively. Since the solidus temperature of the cladding that serves as the fuel containment boundary is approximately 1080 °F, a margin of over 700 °F exists, ensuring fuel integrity and no release of radioactive material resulting from hypothetical accident thermal conditions.

References 1.

Gregory, J. J., Keltner, N. R., and Mata Jr. R. (1989). Thermal Measurements in Large Pool Fires, Journal of Heat Transfer, Volume 111, pp. 446-454.

ORNL/RRD/INT180,Rev.0, July 2024 Draft Change Pages, May 2025 2-5 recommended. Therefore, the guidance provided in those documents related to codes and standards was not factored into the original packaging design and fabrication. Codes and standards applied to the design and fabrication of the packagings are specified on the applicable drawings included in Chapter 1, General Information. The maximum curie content of HFIR unirradiated fuel is significantly less than the limits for Category III shipping packages as defined in Table 2-1 of Regulatory Guide 7.9 (see Section 4.1).

Evaluations and test results included in this document demonstrate compliance with the applicable regulatory requirements for NCT and HAC. Therefore, the codes and standards used for design and fabrication of the HFIR unirradiated fuel shipping packages satisfy the intent of the guidance provided in both Regulatory Guide 7.9 and NUREG/CR-3854.

2.2 MATERIALS 2.2.1 Material Properties and Specifications Tables 2.3 through 2.5 provide a description of the packaging and fuel materials, along with the material mechanical properties used in the structural analyses. A comparison between design specifications for the legacy, test unit, and contemporary packaging designs is provided in Reference 2.12.8. The primary load-bearing material is the 11-gauge CS body and bottom, along with the 11-gauge CS lid that forms the drum-shaped packaging. The body is reinforced with four CS rib angles, and the bottom is supported on a skid structure composed of CS channels and 11-gauge CS base end. Within the package, exterior grade fir plywood provides thermal insulation and energy-absorption capability. A 1-inch-thick layer of polyethylene foam that lines the inside of the cavity provides padding and shock resistance during normal transport. The structural portions of the fuel elements (i.e., non-fueled region), excluding the cladding that forms the primary containment of the radioactive material, are constructed of alloy 6061-T6 aluminum.

The mechanical properties used in the structural analyses and calculations performed for the original SAR (Reference 2.12.9) were taken to be the same as those used in the original calculations, provided that the values were traceable to an authoritative standard or appeared to be reasonable with existing data. The hot-rolled carbon steel sheet used for the drum and lid plate having a carbon content of approximately 0.1% is most likely AISI 1010. The yield strength of this material typically ranges from 30,000 to 40,000 psi, so use of a value of 30,000 psi is reasonable. The steel angles, channels, and plates are most likely ASTM A36 having a yield strength of 36,000 psi, so use of a yield strength of 30,000 psi for this material is also reasonable.

The material properties given in Table 2.5 for plywood are based on in-plane data. That is, tests were performed with loads applied in the direction of the plywood laminates. For Douglas fir plywood the modulus of elasticity and compressive strength vary somewhat depending upon the geographic area in which the wood product was taken. The in-plane compressive strength (yield or crush strength) referenced in the original SAR fell within the range of values given in the Wood Handbook (Table 2.5, Ref. e), so that the value of 3250 psi was judged reasonable and was used in the calculations for side and corner drop orientations of the packages in Reference 2.12.10.

For the end-drop evaluation of the package, the plywood placed above and below the fuel element cavity absorbs the impact forces by loading perpendicular to the plywood laminates. A report has been issued (Reference 2.12.11) in which Douglas fir plywood was tested by application of compressive loading perpendicular to the laminates. These data have been evaluated for use in the analysis of the package for the end-drop conditions in References 2.12.12 and 2.12.13. Also, additional references on wood and timber design have been reviewed (References 2.12.14 - 2.12.17) for comparison of data for loading in-plane and out-of-plane of the wood grain. Generally, these references indicate that, for wood, properties

ORNL/RRD/INT-180, Rev. 0, July 2024 Draft Change Pages, May 2025 2-6 perpendicular to the grain (laminate) direction are significantly reduced from properties in the direction of the grain (laminate). For example, Reference 2.12.16 indicates that for Douglas fir wood the proportional limit perpendicular to the grain is 800 psi, whereas the proportional limit parallel to the grain is 3500 psi.

Reference 2.12.18 indicates that the modulus of elasticity perpendicular to the grain is approximately 0.05 times the modulus of elasticity for loading parallel to the grain. Therefore, based on this review of wood and plywood data, it was deemed appropriate to investigate a range of values for Douglas fir plywood yield stress of 300 to 1500 psi for loading perpendicular to the laminates. The data from actual tests (Reference 2.12.11) support this assumption.

Because the polyethylene foam does not provide appreciable energy absorption capability, its contributions during analyzed drop scenarios were not considered in the analysis.

The minimum yield strength of alloy 6061-T6 aluminum from Reference 2.12.19 is 35,000 psi.

Reference 2.12.19 also gives a corresponding value for ultimate tensile strength of 42 ksi.

Table 2.3 Packaging Design Description Material Description Functional Criteria Steel body (outer shell and base)

Carbon steel, ASTM A1011 CS Type B Structural integrity is maintained during normal transport & accident conditions Plywood Douglas fir, exterior grade Thermal insulation during fire test; shock absorber during normal and accident conditions Foam Polyethylene foam, 2.2 lb./ft3 density Shock absorber during normal transportation Gasket Neoprene rubber Weather seal during NCT Wood Post Pine Blocks placement of inner and outer fuel element in outer fuel element package Steel Lid Carbon steel, ASTM A1011 CS Type B Structural integrity is maintained during normal transport & accident conditions Lid Closure Bolts Carbon steel, ASTM A449, Type 1 Hold lid to body during normal and accident condition Lid Closure Nuts Carbon steel, ASTM A563, Gr. D Hold lid to body during normal and accident condition Lid Washers 300 Series SST Hold lid to body during normal and accident condition Table 2.4 Fuel Design Description Material Description Functional Transportation Criteria Fuel plate fuel matrix clad U3O8-Al Aluminum alloy type 6061 Provide containment

[10 CFR §71.51(a)(1) & (2)]

Side plates Tube aluminum alloy Maintain spacing of fuel plates (criticality)

Protects fuel plates from structural damage

ORNL/RRD/INT-180, Rev. 0, July 2024 Draft Change Pages, May 2025 2-7 Table 2.5 Mechanical Properties Used in Analysis Property Steel Plywood Aluminum Bolting Material

1. Yield strength, psi Static 30,000a 3,250b (in-plane) 35,000 92,000 (lid bolts)h

2. Ultimate, psi 600-1,000g ( to plane) 120,000 (lid bolts)h

3. Proof load, psi 77,500c 144,000 (lid nuts)i

4. Dynamic Shear strength, psi Modulus of elasticity, psi 29 x 106d 1,320e 1.0 x 106 (in-plane) 10 x 106d

5. Poissons ratio 0.3f

6. Weight density (lb/in.3) 0.283a 0.0173e a.

F. L. Singer, Strength of Materials, 2nd ed., Harper and Row, New York, 1962 b.

Value based on data from U.S. Forest Products Laboratory Handbook No. 72, Wood Handbook, 1974, Table 4-2, and as approximated in Reference 2.12.10, pp 2-10 c.

D. S. Clark, The Influence of Impact Velocities on the Tensile Characteristics of Some Aircraft Metals and Alloys, NACA TN 868 Washington, DC, October 1942 d.

A. Higdon, et al., Mechanics of Materials, 2nd ed., John Wiley, New York, 1967, pp. 554 - 555 e.

U. S. Forest Products Laboratory Handbook No. 72, Wood Handbook, 1974, pp. 4 - 12 f.

G. E. Dieter, Mechanical Metallurgy, McGraw-Hill, New York, 1961, p. 36 g.

M. S. Walker, Packaging Materials Properties Data, Martin Marietta Energy Systems, Inc., Y/EN-4120, January 1991 h.

ASME Code Section VIII, Table UCS-23 i.

ASTM A563 Standard Specification for Carbon and Alloy Steel Nuts

ORNL/RRD/INT-180, Rev. 0, July 2024 Draft Change Pages, May 2025 3-5 Table 3.3 Material Properties Used in Thermal Analysis Material Temperature

(°F)

Thermal conductivity (Btu/hft°F)

Density (lb/in.3)

Heat capacity (Btu/hft°F)

Emissivity a Fir plywood b (perpendicular to grain) 0.063 0.0151 0.65 0.9 Fir plywood b (parallel with grain) 0.189 0.0151 0.65 0.9 Poly. Foam c 0.033 0.00122 0.55 0.9 Steel d 32 212 390 570 750 1110 1470 32.0 30.0 28.0 26.0 24.0 20.0 18.0 0.283 0.111 0.8 Aluminum e 0

1220 110.0 160.0 0.0978 0.214 0.7 Air f 0

250 500 1000 1500 0.0131 0.0192 0.0246 0.0370 0.0414 0.00005 0.0000117 0.240 0.242 0.248 0.263 0.270 Air-2 f 0

250 500 1000 1500 0.262 0.385 0.492 0.674 0.827 0.00005 0.0000117 0.240 0.242 0.298 0.263 0.270 Fuel g 0

1220 42.0 60.0 0.0617 0.21 Al-Air h 0

1220 55.0 80.0 0.0489 0.107 1.0 a Reference emissivity values for steel and aluminum can be found in J. P. Holman, Heat Transfer, McGraw-Hill, New York, 1997. A reference emissivity value for fir plywood can be found in Forest Products Laboratory, Wood Handbook, 2021. A sample of Ethafoam 220 was tested to determine its emissivity. Note that the emissivity value for steel utilized in the NCT Heat analysis (Section 3.3.1.1) is conservatively assumed to be 1.0.

b Thermal properties of fir plywood were obtained from A. J. Chapman, Heat Transfer, Macmillan, New York, 1974.

c Thermal properties of polyethylene foam were obtained from Modern Plastics Encyclopedia, McGraw-Hill, New York, 1973.

d Thermal properties of steel were obtained from J. P. Holman, Heat Transfer, McGraw-Hill, New York, 1972.

e For comparable properties of aluminum, see J. P. Holman, Heat Transfer.

f For comparable properties of air, see F. Kreith, Principles of Heat Transfer, International Textbook Co., Scranton, Pa., 1958. Air-2 has been given an enhanced thermal conductivity to simulate natural convection.

g This simulates a homogeneous material which is approximately one half metallic (aluminum cladding and fuel material) and one half air.

h This simulates a homogeneous material which is approximately one half air and one half aluminum. Conductivity, density, and heat capacity are half the values for aluminum. Emissivity assumes that parallel plates separated by air gaps will behave like cavities (hohlraum).