ML25059A403

Enclosure 1 - NRC SER - MX-6, Revision 1 - Public

ML25059A403
Person / Time
Site:	07103101
Issue date:	03/23/2025
From:	Storage and Transportation Licensing Branch
To:
Shared Package
ML25045A076	List: ML25045A077 ML25059A403
References
EPID L-2024-DOT-0003
Download: ML25059A403 (1)

Text

1 SAFETY EVALUATION REPORT DOCKET NO. 71-3101 REVALIDATION OF MODEL NO. MX-6 JAPANESE COMPETENT AUTHORITY CERTIFICATE NO. J/2026/AF-96, REVISION 1

SUMMARY

By letter dated August 21, 2024 (Agencywide Documents Access and Management System

[ADAMS] Accession No. ML24236A212), the U.S. Department of Transportation (DOT) requested that the U.S. Nuclear Regulatory Commission (NRC) staff perform a review of the Japanese Certificate of Competent Authority J/2026/AF-96, Revision 1, dated July 19, 2024, for the MX-6 transport package and make a recommendation concerning the revalidation of the package for import and export use.

In support of its request, in its letter dated August 16, 2024, the DOT provided the following documents for NRCs revalidation review:

Orano TN Letter to DOT, dated August 16, 2024 Application for Competent Authority Certification for Revalidation of J/2026/AF-96 Japanese Competent Authority Certificate of Approval No. J/2026/AF-96, Revision 1 MX-6 Safety Analysis Report (SAR)

Comparison of SARs among MX-6 FFR [Fresh Fuel Recovery] series packages MX-6 Design Approval Application The NRC staff (the staff) reviewed the DOTs August 21, 2024, request (i.e., the application), as supplemented by its January 16, 2025, response (ML25035A055) to the staffs December 16, 2024, request for additional information (RAI) (ML24344A164), against the requirements in International Atomic Energy Agency (IAEA) Specific Safety Requirements, No. 6 (SSR-6),

Regulations for the Safe Transport of Radioactive Material, 2018 Edition (hereafter referred to as SSR-6).

Based upon the NRC review of the statements and representations contained in the documents listed above, as supplemented, and for the reasons stated in this safety evaluation report (SER),

the NRC recommends revalidation of Japanese Competent Authority Certificate of Approval No.

J/2026/AF-96, Revision 1, for the MX-6 package, with the condition that the U.S. revalidation term is limited to 5 years.

1.0 GENERAL INFORMATION The Model No. MX-6 is a Type A fissile package designed for the transport of unirradiated boiling water reactor (BWR) fuel.

2 1.1 Packaging The packaging consists of five items: the main body, closure lid, basket, and top and bottom impact limiters (shock absorbing covers). The main body is a cylindrical shell with a bottom plate welded onto it. The cylindrical shell is constructed from rolled plate which is closed with a full penetration weld. Stiffeners are welded normal to the plate. The outside of the body has vertical plates welded onto the stiffeners to form the outer shell. The volume between the inner and outer shell formed by the stiffeners is filled with resin. The bottom consists of resin embedded into a stainless steel plate and covered by a stainless steel plate. The stainless steel plate is welded onto the bottom of the cylindrical shell. Six trunnions are bolted onto the cylindrical body, four at the top and two at the bottom.

The disk-shaped closure lid, like the bottom, is a composite of metal and resin. The lid is bolted to the upper flange of the body. The body-lid combination is sealed by a double O-ring groove in the upper flange, into which ethylene propylene diene monomer rubber (EPDM) gaskets are installed. The lid has ports for sampling the cavity gas and leak testing the O rings seal.

The basket consists of stainless steel and aluminum alloy disks and tubes (lodgments) to hold the fuel. The lodgments are constructed of borated stainless steel. Aluminum spacers are located between the cylindrical inner shell and the basket.

Attached to the top and bottom end of the main body and the packages lid are shock absorbing covers. The shock absorbing covers consist of a stainless steel skin, gussets, and wood and are bolted onto the top flange and bottom.

1.2 Contents The MX-6 package is designed to hold up to ten 9x9 BWR fresh fuel assemblies. The contents are limited to a Type AF quantity of radioactive (fissile) material.

1.3 Criticality Safety Index The criticality safety index (CSI) for the MX-6 package containing BWR fuel is 0.

2.0 STRUCTURAL EVALUATION The objective of the structural evaluation is to verify that the structural performance of the MX-6 package meets the requirements set forth by the International Atomic Energy Agency (IAEA) in Specific Safety Requirements No. SSR-6, Regulation for the Safe Transport of Radioactive Material, 2018 Edition (IAEA SSR-6 or Regulation). The applicant presented the structural analysis of the MX-6 package in Chapter II A of the updated MX-6 safety analysis report (SAR).

The MX-6 package design has received Certificate of Approval J/2026/AF 96, Revision 1, from the Japanese Competent Authority. The certificate authorizes the MX-6 package for the transportation of fissile uranium dioxide fuel assembly packages as a Type A fissile package.

In a letter dated August 14, 2023 (ML23188A024), the NRC recommended the revalidation of the Model MX-6 transport package as approved by the Japanese Competent Authority in Certificate of Approval J/2026/AF-96, Revision 0, with no additional conditions. For Revision 1 of the Certificate of Approval J/2026/AF-96, the structural evaluation will address the changes made to the package, the new/modified structural analyses and the implementation of new/modified requirements from the 2018 Edition of the IAEA SSR-6, as described in the updated MX-6 SAR.

3 2.1.

Package Description and Proposed Changes to the Package The MX-6 transportation package is designed for the transport of up to 10 fissile uranium dioxide fuel assemblies. It consists of a cylindrical shape packaging that has an overall nominal dimension that is approximately 6 m long and 2.1 m wide in diameter. The package is comprised of four major structural components: main body, lid parts, basket, and top and rear shock absorbing covers. The package has a maximum gross weight of 19,500 kg and is designed for a maximum content weight of 4,150 kg.

The applicant lists all the principal components of the package, including the associated materials, weights and dimensions, in SAR Table I-C.1, Packaging components and their major materials, Table I C.3, Dimensions of packaging, and Table I-C.4, Package weight. The mechanical properties, analysis parameters, characteristics of the principal components, and analysis results are provided in the SAR Table II-A series.

Revision 1 of Certificate of Approval J/2026/AF-96 removes the stools used for stabilizing the fuel assemblies within the packaging and adds the use of fuel cans to each fuel assembly before loading them into the lodgment of the basket. Fuel cans are used to prevent release of contaminants at the surface of fuel assemblies into the packaging and their mass is considered in the structural analysis. The applicant provides the fuel can specifications in SAR Table I D.4 and an illustration in SAR Figure I D.10.

Revision 1 also allows for the use of two types of lattices (i.e., C lattice and D lattice) with the fuel assembly, as shown in Table I D-1 of the updated SAR. For both types of latices the major specifications are the same. Fuel assemblies consist of fuel rods assembled into a 9 x 9 squared grid arrangement as illustrated in SAR Figure I-D.2. The structure of the fuel assembly is comprised of fuel pins, upper and lower tie plates, spacers, and other components as illustrated in SAR Figure I-D.1.

The NRC staff notes that, despite the changes made to the content of the package, Revision 1 of Certificate of Approval J/2026/AF-96 maintains the same package design, dimensions, lifting devices, maximum gross weight and maximum content weight limits as specified for the MX-6 transportation package in Revision 0.

SAR Table II A 3 lists the lifting devices used for the MX-6 transportation packages with their corresponding materials, design parameters and analysis criteria. In general, the package has four (two pairs of) trunnions on the top side and two (one pair of) trunnions on the rear side as shown in SAR Figure I C.5. The MX-6 package can be lifted using these trunnions and no changes are proposed to the design of the trunnions in this revision. Lifting attachments are further discussed in Section 2.3 of this SER.

The NRC staff reviewed the updated description for the general design of the package for completeness and accuracy and finds that the applicant adequately incorporated information related to the geometry, dimensions, materials, components, and relevant details to describe major structural components of the MX-6 transportation package. Therefore, the NRC staff finds that the information provided for the transportation package includes sufficient detail to demonstrate compliance with the design requirements of the SSR-6 Regulation, and as required in paragraphs 809 and 810 of the Regulation.

2.2.

Design Criteria

4 The applicant described the structural design criteria for the package, including the allowable stresses used in the stress analyses, in Section II A.1.2 of the SAR and provides a summary in SAR Table II A.1. The applicant summarized the load combinations used in the structural analyses in SAR Table II A.2, and the conditions and analysis methods for the different structural analyses in Table II A.3.

Although a fatigue analysis was provided for the lifting devices and other components in Revision 0, the design criteria used for these fatigue analyses is further defined for Revision 1.

Chapter I of the updated MX-6 SAR provides for the fatigue design criteria used for the MX-6 transportation package in terms of planned years for use and/or number of usage (total cycles).

The staff notes that the design criteria established for Revision 1 of the MX-6 transportation package is the same design criteria considered for Revision 0 of Certificate of Approval J/2026/AF-96. Therefore, the NRC staff finds that the design criteria remain adequate for demonstrating that the package satisfies the requirements of IAEA SSR-6.

2.3.

Lifting and Tie-down The staff notes that Revision 1 of the MX-6 transportation package does not change the mass considered in the initial analysis for the package or its content or modify the design of the lifting devices. As shown in Section II A.4.4 of the updated SAR, a loading factor of 3 is used for these analyses and there are no tie-down devices that are considered a structural part of the package.

For Revision 1, in Section II A.10.6 of the updated SAR the applicant further evaluated the strength of the MX-6 package body when lifted with the trunnions and when lifted with the handling belts. The applicant used a finite element analysis model with a loading factor of 3 to determine the resultant stresses and deformation at the body of the MX-6 transportation package. The analysis concludes that the body of the MX-6 package has sufficient strength to withstand the load without yielding when the package is lifted with the trunnions or the handling belts.

The NRC notes that there are no physical changes to the previously revalidated package that would have affected or modified the evaluation provided in Section II A.4.4 of the SAR for the lifting and tie-down devices, and the analyses of the MX-6 package body during lifting activities is found acceptable. Therefore, the package meets the regulatory requirements in paragraphs 608 and 609 of IAEA SSR-6 for lifting attachments.

2.4.

Vibrations, Pressures and Temperatures from Routine Conditions of Transport Vibrations The applicant evaluated the structural integrity of the packaging under the vibrations from routine conditions of transport in Section II-A.4.7 of the SAR. The NRC notes that there are no physical changes to the previously revalidated package that would have significantly affected or modified the evaluation provided in Section II-A.4.7 of the SAR for vibrations.

For Revision 1, the applicant further evaluated the effect of load amplification due to vibration for the shell components, lid components, and bottom plate. In Section II-A.10.8 of the updated SAR, the applicant determined { } to be the response factor applicable to the MX-6 package due to vibration after considering the calculated load frequency and the natural frequency of the package. For the shell components, the evaluation concluded that the stress allowance available for the shell components, as determined in the analysis, is considerably larger than the

5 response factor. Therefore, the structural integrity of the shell components of the package will not be affected by vibration. For the lid, the lid tightening bolts and bottom plate, the analysis demonstrates that the resultant stress remains below the allowable stress for these components. Therefore, the structural integrity of these components is not affected by vibration and is found acceptable.

Pressures and Temperatures Changes In Sections II A.4.6 and A.5.1 of the SAR, the applicant previously evaluated the structural integrity of the packaging subjected to temperature changes between 20°C to { }°C. For this revision, in Section II A.10.7 of the updated SAR the applicant further analyzed the structural integrity of the packaging due to internal pressure fluctuation when the packing is subjected to a temperature change from 40°C to { }°C. The applicant listed the resultant stresses for each packing component in SAR Tables II-A. Appendix 7.1 and Appendix 7.2. These results demonstrate that the components remain within the design criteria and cracking does not occur due to changes in internal pressure from temperature fluctuations expected during routine conditions of transport. Similarly, the applicant listed the resultant displacements at the opening of the package in SAR Tables II-A. Appendix 7.3. These results demonstrate that the containment performance of the package is maintained because the resultant displacement of the lid gasket after the pressure and temperature fluctuation is less than the compressed thickness obtained after the gasket compression during initial tightening.

In Sections II A.5.1(2) and A.10.9 of the SAR the applicant further evaluated the differential thermal expansion of the fuel cans by considering the changes in clearances between the fuel can and the packing, and the fuel assembly and the fuel can when the package is subjected to a temperature range of -40ºC or { }ºC. The analysis demonstrates that sufficient clearances are maintained between these components and that no thermal stress by constraints occurs at these components.

Conclusion The staff finds that the applicants structural evaluations of the MX-6 transportation package and closure mechanism remains sufficient to demonstrate that the package meets the regulatory requirements in paragraphs 613, 616, 641, and 645 of IAEA SSR-6 for considering vibrations, pressures, and temperatures changes of the package from routine conditions of transport.

2.5.

Evaluation for Normal Conditions of Transport The applicant seeks to demonstrate compliance with the performance standards requirements from the Regulation by demonstrating the ability of the package to withstand the tests representative of normal conditions of transport (NCT) (i.e., paragraphs 719 thru 724 of SSR-6).

In general, paragraph 719 requires the transportation package be subjected to a free drop test, a stacking test, and a penetration test, preceded in each case by the water spray test to demonstrate the ability to withstand NCT. Under IAEA SSR-6 paragraph 648, Type A packages are required to be designed in a manner that prevents (a) loss or dispersal of the radioactive contents, and (b) more than a 20% increase in the maximum radiation level at any external surface of the package, after being subjected to these tests. In addition, IAEA SSR-6 paragraph 678 also requires that packages containing fissile material satisfy the following requirements after being subjected these tests: (a) preserve the minimum overall outside dimensions of the package to at least 10 cm, and (b) prevent the entry of a 10 cm cube.

6 Water Spray Test The IAEA SSR-6, paragraphs 720 and 721, requires the MX-6 transportation package be subjected to a water spray test that simulates exposure to rainfall of approximately 5 centimeter per hour for at least 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.

The NRC notes that there are no physical changes to the previously revalidated package that would have affected or modified the evaluation provided in Section II A.5.2 of the SAR for the water spray test. Therefore, the NRC staff finds that the MX-6 transportation package meets the applicable requirements in paragraphs 720 and 721 of IAEA SSR-6 for NCT.

Free Drop Test The IAEA SSR-6, paragraphs 722, requires the MX-6 transportation package be dropped onto a target so as to suffer maximum damage with respect to the safety features of the package. Per IAEA SSR-6 Table 14, a free fall drop distance of 1.2 meter needs to be considered for packages with a mass less than 5,000 kg.

The NRC notes that there are no physical changes to the previously revalidated package that would have affected or modified the free drop test analysis provided in Section II A.5.3 of the SAR. However, the applicant further analyzed the potential for the package to open from a lid gasket displacement during the top vertical, horizontal or top corner drop test. The analysis in Section II A.10.10(2) of the updated SAR demonstrates that the containment performance of the package is maintained because the resultant displacement after the drops is less than the compressed thickness obtained after the gasket during initial tightening.

The NRC staff finds that the MX-6 transportation package meets the applicable drop test requirements in IAEA SSR-6 paragraphs 722 for NCT.

Stacking Test The IAEA SSR-6, paragraph 723, requires subjecting the MX-6 transportation package be subject to a load equal to the greater of the following to determine the maximum compression stress on the package: (a) a load that is 5 times the maximum weight of the package, or (b) 13 kilopascals (kPa) times the vertical projected area of the package.

The NRC notes that there are no physical changes to the previously revalidated package that would have affected or modified the stacking test analysis provided in Section II A.5.4 of the SAR. However, the applicant further evaluated the packaging for possible deformation and displacement of the shock absorbing covers during the stacking test. The analysis in Section II A.10.11 of the updated SAR demonstrates that that the containment performance of the package is maintained because the shock absorbing covers has sufficient capacity to support the load of five packages in the vertical and horizontal position without opening or deforming.

The NRC staff finds that the MX-6 transportation package meets the applicable stacking tests requirements in IAEA SSR-6 paragraphs 723 for NCT.

Penetration Test The IAEA SSR-6, paragraph 724, requires the MX-6 transportation package be subjected to a penetration test targeting the center of the weakest part of the package so that, if it penetrates

7 sufficiently far, it will hit the containment system. A bar having 3.2 cm in diameter with a hemispherical end and a mass of 6 kg must be selected and dropped from a 1 m distance onto the package.

The NRC notes that there are no physical changes to the previously revalidated package that would have affected or modified the penetration test analysis provided in Section II A.5.5 of the SAR. However, the applicant further evaluated a penetration test that targets the outer plate of shock absorbing cover. A dynamic analysis using LS-DYNA was performed to determine the plastic strain in the outer plate of the shock absorbing cover. The analysis in Section II A.10.12 of the updated SAR demonstrates that the outer plate of the shock absorbing cover will not rupture, and penetration of the bar will not occur.

The NRC staff finds that the MX-6 transportation package still meets the applicable penetration tests requirements in IAEA SSR-6 paragraphs 724 for NCT.

Conclusion for Normal Condition of Transport A summary of the test results for normal condition of transport is provided in Section II A.5.7 of the SAR. The staff notes that the results demonstrated that the packaging has no substantial reduction in the effectiveness of the packaging that would prevent it from satisfying the requirements under normal condition of transport. Therefore, the NRC staff finds that the MX-6 transportation package satisfies the requirements in paragraphs 648 and 678 of IAEA SSR-6 for NCT.

2.6.

Evaluation for Accident Conditions of Transport The applicant seeks to demonstrate compliance with the performance standards requirements from the Regulation by demonstrating the ability of the package to withstand the tests representative of accident conditions of transport (ACT) (i.e., paragraphs 726 thru 729 of SSR-6). In general, IAEA SSR-6 paragraph 726 requires the transportation package be subjected to the cumulative effects of three different drop tests and a thermal test followed by water immersion test(s) to demonstrate the ability to withstand ACT.

Maximum Damage Drop Test The IAEA SSR-6, paragraph 727(a), requires the MX-6 transportation package be dropped from a distance of 9 meters onto a target so as to suffer maximum damage in the safety features of the package. The target shall be a flat, horizontal surface of such a character that any increase in its resistance to displacement or deformation upon impact by the specimen would not significantly increase damage to the specimen.

The NRC notes that there are no physical changes to the previously revalidated package that would have affected or modified the drop test analyses provided in Section II A.9.2(1) of the SAR and as summarized in SAR Tables II A.21 (for packaging body), II A.22 (for the basket),

and II A.23 (for the fuel cladding). However, an inconsistency between the slap down drop angle considered for the analysis model (30º inclination) and the slap down drop angle considered for the drop test of the { } specimen (25º inclination) was identified. The applicant explained this discrepancy in Section II A.10.14 of the updated SAR by comparing the parameters and selection process used for specifying the drop angle in each case. The evaluation concluded that the 30° angle selected for the analysis is considered a representative angle of the analysis results because the resultant deformation is the same at 25° and 30°, and the resultant plastic

8 strain of the inner shell is the same at 30° and 35°. Therefore, a 30° angle was selected as representative of the analysis.

The NRC staff finds that the MX-6 transportation package still meets the applicable drop tests requirements in paragraphs 727(a) of IAEA SSR-6 for the maximum damage drop test specified for ACT.

Penetration Drop Test The IAEA SSR-6, paragraph 727(b), requires the MX-6 transportation package be dropped from a 1 m distance onto a bar rigidly mounted perpendicularly on the target so as to suffer maximum damage. The bar shall be 15 cm in diameter made of solid mild steel and 20 cm long. The target is the same as defined for the maximum drop damage test.

The NRC notes that there are no physical changes to the previously revalidated package that would have affected or modified the penetration drop test analyses provided in Section II A.9.2(2) of the SAR. Therefore, the NRC staff finds that the MX-6 transportation package still meets the applicable penetration tests requirements in paragraphs 727(b) of IAEA SSR-6 for the drop penetration test specified for ACT.

Thermal Test The IAEA SSR-6, paragraph 728, requires the MX 6 transportation package be (a) exposed for a period of 30 min to a thermal environment that provides for a heat flux as described in the Regulation, and (b) exposed to an ambient temperature of 38ºC for a sufficient period as described in the Regulation.

The NRC notes that the changes to the MX 6 transportation package do not affect or modify the thermal test analyses provided in Section II A.9.2(3) of the SAR. However, the applicant further analyzed the potential damage of the package after the thermal test. The analysis in Section II A.9.2(3) of the updated SAR demonstrates that, after the design modification, the performance of the package is maintained after the thermal test because the resultant stresses and elongation of the package components do not result in rupture or deformation failure of the package components.

Therefore, the NRC staff finds that the MX-6 transportation package still meets the applicable thermal tests requirements in paragraphs 728 of IAEA SSR-6 for the thermal test specified for ACT.

Water Immersion Test The NRC notes that there are no physical changes to the previously revalidated package that would have affected or modified the evaluation provided in Section II A.9.2(4) of the SAR for the water immersion test. As stated, water intrusion into the package is assumed and considered by the criticality analysis, therefore this test remains not applicable for the MX-6 transportation package.

Conclusion for Accident Conditions of Transport A summary of the test results for accident conditions of transport is provided in Table II-A.26 of the SAR. The staff notes that the results demonstrated that the packaging has no substantial

9 reduction in the effectiveness of the packaging that would prevent it from satisfying the requirements under accident condition of transport. Therefore, the NRC staff finds that the MX-6 transportation package satisfies the requirements in paragraphs 673 and 685 of IAEA SSR-6 for ACT.

2.7.

Aging Mechanism - Fatigue Evaluations The IAEA SSR-6, paragraph 613A, requires the MX-6 transportation package be designed to account for the effects of aging mechanisms. The applicant stated that the evaluation included in the updated SAR shows that consideration of the impacts of aging due to heat, radiation and chemical change is not necessary for compliance based on the technical standards. These considerations are evaluated in the materials section of this SER. However, aging due to fatigue loading from lifting operation, external temperature and pressure changes expected during transport, and the tightening of lid bolts are further reviewed in this section for the MX-6 transportation package.

Lifting Devices In Section II A.4.4(2) of the SAR, the applicant provides a fatigue evaluation of the lifting devices (i.e., trunnions, handling belts and lifting handle pins). The NRC notes that there are no physical changes to the previously revalidated package that would have affected or modified the fatigue evaluation considered for these components in Revision 0. These analyses considered the stresses on each of the components assuming a service cycle based on the planned usage of 200 times as specified for the MX-6 transportation package. The analyses concludes that the assumed number of service cycles for each device remains below the allowable number of cycles of the component. Therefore, the lifting devices will not be affected by fatigue and are found acceptable.

Lid Bolts The applicant provides a fatigue evaluation of the bolts used for tightening the lid in the MX-6 transportation package. The analysis in Section II A.5.1.3(4) of the updated SAR considers the stresses of the lid bolts due to tightening based on the number of service cycles expected for a usage of 200 times as planned for the MX-6 transportation package. The analysis demonstrates that the assumed number of service cycles remains below the allowable number of cycles applicable to the lid bolts and is therefore acceptable.

In Section II A.10.13 of the updated SAR the applicant also evaluated the stresses of the lid bolts due to the external temperature and pressure changes expected during transport based on the number of service cycles expected for the 50 years of service considered for the MX-6 transportation package. The analysis demonstrates that the assumed number of service cycles remains significantly below the allowable number of cycles applicable to the lid bolts and is therefore acceptable.

The NRC staff noted that the fatigue evaluation in Section II A.5.1.3(4) of the updated SAR did not consider the cumulative damage from bolt tightening and the external temperature and pressure changes expected during transport. However, based on the results from both fatigue analyses the NRC expects the cumulative damage to remain below 1.0 (i.e., { } + 0.02 = { }).

Therefore, the lid bolts will not be affected by fatigue and are found acceptable.

Temperature and Pressure Changes During Transport

10 In Section II A.10.13 of the SAR, the applicant provides a fatigue evaluation due to internal pressure changes from changes in ambient temperature and external pressure during transportation. The analysis evaluated the lid, external plate, inner shell, stiffeners, and bottom plate for potential fatigue failure. The analysis evaluated the stresses on these components based on the number of service cycles expected for the 50 years of service considered for the MX-6 transportation package. The analysis demonstrates that the assumed number of service cycles for each of the components remains below the allowable number of cycles applicable to the material of each component. Therefore, the components comprising the containment boundary will not be affected by fatigue and are found acceptable.

Conclusion for Aging Consideration due to Fatigue Based on a review of the fatigue analyses discussed above, the NRC staff finds that the MX-6 transportation package meets the design consideration requirements for aging mechanism as specified in paragraph 613A of IAEA SSR-6 for fatigue of the MX-6 transportation package components.

2.8.

Evaluation Findings Based on a review of the statements and representations contained in the application, the NRC staff finds that the MX-6 transportation package has an adequate design to withstand mechanical loads during NCT and ACT, and therefore, the package meets the Regulatory requirements of IAEA No. SSR 6. The staff recommends revalidation of Japans competent authority identification mark J/2026/AF-96, Revision 1, for import and export use.

3.0 MATERIALS EVALUATION The NRC staffs materials evaluation determines whether the applicant adequately described and evaluated the materials used in the MX-6 package to ensure that the package meets the requirements of IAEA SSR-6. For the review of the 2024 version of the MX-6 package application against the requirements of the 2018 Edition of IAEA SSR-6, the staffs materials review focused on the following two categories of changes:

(1) Changes to the description of package components and materials that may affect the safety analysis of package components and their design functions; and (2) Updates to the package application to include an evaluation of aging of package components and materials to satisfy new regulatory requirements in the 2018 Edition of IAEA SSR-6.

3.1 Evaluation of Changes to Information on Package Materials The staff compared the 2024 version of the MX-6 package application to the 2022 version of the application and identified one change to the information on the package components and materials. This change involved the use of stainless steel fuel cans, with alloy steel closure bolts and rubber gaskets, inside the packaging to contain the new nuclear fuel assemblies that have been stored in spent fuel pools. The fuel cans are considered part of the package contents and are used to prevent dispersion of radioactive contamination inside the packaging enclosure due to contamination on the surfaces of fuel assemblies that were stored in spent fuel pools. The staff reviewed the information on the materials used to construct the fuel cans, including the

11 stainless steel container and lid components, alloy steel closure bolts, and rubber gaskets, and determined that the material types and material properties are adequately specified in the application. The staff determined that these materials are suitable for the construction of the fuel cans since the material properties are adequate to ensure fuel can integrity, such that there is no unacceptable dispersion of radioactive contamination from the fuel assemblies inside the packaging during normal and accident conditions of transport. Therefore, the staff finds that the fuel can materials are acceptable.

3.2 Evaluation of Changes to Comply with New IAEA SSR-6 Requirements Regarding Aging 3.2.1 Evaluation of Changes in IAEA SSR-6 Regulations from the 2012 Ed. to 2018 Ed.

A gap analysis of the changes in the IAEA SSR-6 regulations from the 2012 Edition to the 2018 Edition identified the following new requirements related to evaluation and management of aging of package components:

The 2012 Edition of IAEA SSR-6 Paragraph 503 includes four subparagraphs, (a) through (d), that specify actions that are required to be taken (if applicable) before each shipment of any package. The 2018 Edition of IAEA SSR-6 adds a new Subparagraph (e) to Paragraph 503. The new Subparagraph 503(e) specifies the following:

For packages intended to be used for shipment after storage, it shall be ensured that all packaging components and radioactive contents have been maintained during storage in a manner such that all requirements specified in the relevant provisions of these Regulations and in the applicable certificates of approval have been fulfilled.

Since the MX-6 package is just for transporting new unirradiated nuclear fuel assemblies, and it is not intended to be used for shipment after storage, the staff identified that the new requirement in Subparagraph 503(e) is not applicable.

The 2012 Edition of IAEA SSR-6 Paragraphs 607 through 618 specify general requirements for all radioactive material transportation packages subject to international shipping rules. The 2018 Edition of IAEA SSR-6 adds a new Paragraph 613A to these regulations; this paragraph does not exist in the 2012 Edition of IAEA SSR-6. The new Paragraph 613A specifies the following:

The design of the package shall take into account ageing mechanisms.

Since the new requirement of Paragraph 613A is applicable to all radioactive material packages subject to international shipping rules, including Type AF packages, the staff determined that the new requirement of Paragraph 613A is applicable to the MX-6 package.

The 2012 Edition of IAEA SSR-6 Paragraph 809 specifies information requirements for applications for approval of Type B(U) and Type C package designs. The 2018 Edition of IAEA SSR-6 adds a new Subparagraph (f) to Paragraph 809. The new Subparagraph 809(f) specifies the following:

If the package is to be used for shipment after storage, a justification of considerations to ageing mechanisms [shall be included] in the safety

12 analysis and within the proposed operating and maintenance instructions.

Since the MX-6 package is a Type AF package, and is not a Type B or C package, and it is not to be used for shipment after storage, the staff identified that the new information requirement in Subparagraph 809(f) is not applicable.

The 2018 Edition of IAEA SSR-6 also adds a new Subparagraph (k) to the information requirements in Paragraph 809 for applications for approval of Type B(U) and Type C package designs. The new Subparagraph 809(k) specifies the following information requirement:

For packages which are to be used for shipment after storage, a gap analysis programme describing a systematic procedure for a periodic evaluation of changes of Regulations, changes in technical knowledge and changes of the state of the package design during storage.

Since the MX-6 package is a Type AF package, and is not a Type B or C package, and it is not to be used for shipment after storage, the staff identified that the new information requirement in Subparagraph 809(k) is not applicable.

Considering the foregoing evaluation of changes in the IAEA SSR-6 regulations from the 2012 Edition to the 2018 Edition, the staff determined that Paragraph 613A is the only new requirement related to evaluation and management of aging of package components that is applicable to the MX-6 package design.

IAEA Specific Safety Guide No. SSG-26, Advisory Material for the IAEA Regulations for the Safe Transport of Radioactive Material (2018 Edition) (hereafter, IAEA SSG-26), provides guidance on how to comply with Paragraph 613A in IAEA SSR-6. The 2018 Edition of IAEA SSG-26 includes six paragraphs, Paragraph 613A.1 through Paragraph 613A.6, that describe acceptable methods on how to comply with Paragraph 613A in IAEA SSR-6. Of these six paragraphs, the staff determined that Paragraphs 613A.1 and 613A.3 are applicable to the MX-6 package design, whereas Paragraphs 613A.2, 613A.4, 613A.5, and 613A.6 are not applicable to the MX-6 package design. The staffs basis for this determination is provided below.

The staff determined that Paragraph 613A.2 is not applicable since this paragraph addresses packaging used once for a single transport, whereas the MX-6 package is intended for repeated use. The staff determined that Paragraph 613A.4 is not applicable since this paragraph addresses packages intended to be used for shipment after storage, and as addressed above, the MX-6 package is not designed to be used for shipment after storage with the contents loaded. The staff determined that Paragraph 613A.5 is not applicable since this paragraph addresses the need for aging management programs and associated gap analysis programs that are specific to designs of packages intended to be used for shipment after storage, and the MX-6 package is not designed to be used for shipment after storage with the contents loaded.

Further, Paragraph 613A.5 states that for Types B(U), B(M), and Type C packages, such programs should be included in the applications for approval of packages for shipment after storage to meet the requirements of Subparagraphs 809(f) and 809(k) of the IAEA SSR-6, and the MX-6 package is not a Type B(U), B(M), or Type C package. Finally, the staff confirmed that Paragraph 613A.6 is not applicable since this paragraph addresses uranium hexafluoride

13 cylinders, and the MX-6 package does not include any components for transporting uranium hexafluoride.

The staff determined that that the guidance in Paragraphs 613A.1 and 613A.3 in IAEA SSG-26 are applicable to the MX-6 package design for demonstrating compliance with Paragraph 613A of IAEA SSR-6:

Paragraph 613A.1 states: Packaging components and package contents are subjected to degradation mechanisms and ageing processes that depend on the component and the contents themselves and their operational conditions. Thus, the design of a package should take into account ageing mechanisms commensurate with intended use of the package and its operational conditions, as described in paras 613A.2-613A.6. The designer of a package should evaluate the potential degradation phenomena over time, such as corrosion, abrasion, fatigue, crack propagation, changes of material compositions or mechanical properties due to thermal loadings or radiation, generation of decomposition gases, and the impact of these phenomena on performance of safety functions.

The staff noted that Section II-F of the MX-6 package application includes an evaluation of the effects of material aging mechanisms on the MX-6 packaging components and the non-fuel package contents (i.e., the fuel cans) that are used repeatedly. The staffs technical review of the applicants evaluation of the effects of material aging mechanisms on the MX-6 package components is addressed below in section 7.2.2 of this SER.

Paragraph 613A.3 states: For packagings intended for repeated use, the effects of ageing mechanisms on the package should be evaluated during the design phase in the demonstration of compliance with the Transport Regulations. Based on this evaluation, an inspection and maintenance programme should be developed. The programme should be structured so that the assumptions (e.g. thickness of containment wall, leak tightness, neutron absorber effectiveness) used in the demonstration of compliance of the package are confirmed to be valid through the lifetime of the packaging. An example of a procedure to prepare an ageing management programme for Type B(U) packages is provided in Ref. [12].

Chapter III of the application describes package handling procedures and maintenance criteria for the MX-6 package; these include visual inspection criteria for packaging components and contents. The staffs technical review evaluated the inspection and maintenance criteria described by the applicant in Chapter III to determine if they are adequate for managing the effects of credible aging mechanisms and to ensure that component structural integrity and other design criteria relied on for acceptable performance of package components are adequately maintained. The staffs review of the inspection and maintenance criteria for the MX-6 package is addressed below in section 3.2.2 of this SER.

The staffs technical review, documented below in Section 3.2.2 of this SER, addressed the applicants identification and evaluation of the package component materials, loading conditions, service environments, material aging mechanisms, and description of package inspection and maintenance activities for managing effects of credible aging mechanisms. To assist in performing its review, the NRC staff applied the NRC guidance in NUREG-2214,

14 Managing Aging Processes in Storage (MAPS) Report, July 2019 (ADAMS Accession No. ML19214A111), for managing component aging in spent fuel storage systems.

3.2.2 Evaluation of Material Aging Mechanisms to Comply with IAEA SSR-6, 2018 Edition To address the new IAEA SSR-6 paragraph 613A requirement and associated SSG-26 guidance related to component aging, the 2024 version of the MX-6 package application included Section II-F on the evaluation of material aging mechanisms for the MX-6 package components. This section specified that the planned period of use of the packaging is 50 years.

However, the applicants request for revalidation of the MX 6 package certificate identified that the U.S. revalidation term for the MX-6 package should be limited to a period of five years.

Therefore, while the application indicates a 50-year planned period of use for MX-6 packaging components, the staffs review to support DOT revalidation, as it pertains to the adequacy of the applicants evaluation of aging mechanisms and associated maintenance criteria for managing applicable aging effects, is limited to a revalidation term of five years.

Section II-F of the application evaluates the material aging mechanisms associated with the transportation and handling of the loaded package and storage of empty packaging components when not in use. The applicants evaluation of material aging mechanisms in Section II-F cites the relevant provisions of the package handling procedures and maintenance criteria in Chapter III of the application to address detection of aging effects and repairs and replacements for the MX-6 package components.

3.2.2.1 Package Components and Materials To identify and evaluate the potential aging mechanisms, Section II-F of the application includes a list of package components and materials that are included in the scope of the aging evaluation. The scope of components subject to aging evaluation includes reusable components of the packaging and the fuel cans that perform a safety function. The fuel cans are included in the package contents and contain the new nuclear fuel assemblies that have been stored in spent fuel pools. The application identifies the following materials for package components (reusable packaging and fuel can components) that receive aging evaluation:

Packaging Body Components Material Inner shell

{ } stainless steel Stiffener

{ } stainless steel External plate

{ } stainless steel Top flange

{ } stainless steel Bottom

{ } stainless steel Trunnion

{ } stainless steel Handling belt

{ } stainless steel Trunnion fixing bolt Alloy steel Handling belt connecting bolt Alloy steel

{ } plate

{ }

Shell part resin Resin Bottom resin Resin Packaging Lid Components Material

15 Lid tightening bolt Alloy steel Lid Titanium alloy Lid resin Resin Fuel Basket Components (Packaging)

Material Lodgment Borated stainless steel Aluminum plate Aluminum alloy Top plate Aluminum alloy Bottom plate Aluminum alloy Aluminum spacer Aluminum alloy Additional shielding Aluminum alloy Connection rod Aluminum alloy Basket support Aluminum alloy Tie rod Aluminum alloy Shock Absorbing Cover Components (Packaging)

Material Tightening bolt Alloy steel Outer plat

{ } stainless steel Gusset plate

{ } stainless steel Foot, { } tube, etc.

{ } stainless steel Shock absorber Wood Fuel cans (Package Contents)

Material Body

{ } stainless steel Bottom

{ } stainless steel Lid

{ } stainless steel Lid bolt Alloy steel The application states that replacement parts such as rubber gaskets are replaced in accordance with package handling procedures and maintenance criteria. Based on the replacement requirements for rubber gaskets, the application identified that it is not necessary to consider aging of the rubber gaskets, and accordingly, these are excluded from the scope of the aging evaluation. The application also states that fuel assemblies are also excluded from the scope of the aging evaluation because they are replaced with different fuel assemblies for each transport and are transported only once.

The staff confirmed that the scope of the applicants aging evaluation includes all long-lived reusable packaging components and reusable content components (i.e., metallic fuel can items) that perform a safety function. The materials for these components include { } stainless steel,

{ } stainless steel, borated stainless steel, alloy steel bolts, aluminum alloy, titanium alloy, { },

resin, and wood; seven types of metals and two organic materials. The staff confirmed that an evaluation of potential aging mechanisms for the rubber gaskets is not needed since they are required, per the package handling procedures and maintenance criteria, to be replaced with new ones for each transport. The staff also identified that the new fuel assemblies are unloaded

16 from the package upon arrival at their destination; therefore, the fuel assemblies are not in the scope of long-lived reusable package components that require aging evaluation. Accordingly, staff found that the applicants identification of package components and materials that are subject to aging evaluation is acceptable since it ensures that materials for long-lived reusable package components are appropriately evaluated for potential aging mechanisms over the service life of the package.

3.2.2.2 Evaluation of Package Aging Mechanisms The application states that the planned period of use of the MX-6 package is 50 years; however as addressed above, the applicants proposed revalidation term for the MX-6 package is limited to five years. Therefore, the staffs technical findings on the adequacy of the applicants evaluation of aging mechanisms is limited to the five-year revalidation term.

The application specifies that the total number of package transports during the 50-year period is 200 transports. The application identifies the environmental and loading conditions that are considered in the evaluation of potential aging mechanisms during the 50-year period. These conditions include the highest analyzed temperature (heat) for normal conditions of transport; radiation emitted by the radioactive contents; chemical reactions in materials that may lead to corrosion of components; and fatigue of package structural components caused by cyclical stress in structural materials due to mechanical lifting cycles, package enclosure pressurization cycles, thermal cycles, and vibration during transport. The applicant evaluated each of these conditions to determine aging mechanisms that could potentially lead to package component degradation during the 50-year period of use of the package.

Evaluation of Potential Aging Associated with Heat, Radiation, and Chemical Reactions The application states that, in the evaluation of aging due to heat, radiation, and chemical reactions, 50 years of continuous use of a loaded package is considered as a conservative assumption that bounds the actual planned use of the package. The NRC staff reviewed this assumption and determined that that the assumption is conservative since package components are only exposed to radiation from the fuel contents during limited intervals for transport and handling of a loaded package. Empty packagings placed in long-term storage indoors would not be exposed to radiation from the fuel contents, and storage temperatures for empty packagings would be limited to values that are less than the highest analyzed temperature for normal conditions of transport. With respect to chemical reactions, the staff verified that direct exposure of package components to outdoor ambient conditions is limited per the package handling and maintenance criteria; specifically, components are not continuously exposed to outdoor air and water environments during handling and transport of loaded packages, and empty packagings are generally required, per the package handling and maintenance criteria, to be stored indoors or stored outdoors under a waterproof cover when not in use. Therefore, the actual potential for chemical reactions with air, water, moisture, and chemical compounds present in the outdoor ambient environment is bounded by the applicants 50-year continuous use assumption. Based on these considerations, the staff finds that the applicants assumption of 50 years of continuous use of a loaded package is acceptable for the evaluation of aging mechanisms associated with heat, radiation, and chemical reactions for the proposed five-year revalidation term.

Evaluation of Potential Aging Due to Heat

17 For the evaluation of potential aging due to heat, the applicant determined that all the packaging and fuel can materials covered in the aging evaluation would not be susceptible to adverse changes from exposure to heat over the 50-year period of use since the highest analyzed temperature for normal conditions of transport would not cause any adverse changes to the material structure (i.e., adverse microstructural or dimensional changes) or material properties.

The staff reviewed the applicants evaluation of potential aging due to heat and determined that the highest analyzed temperature for normal conditions of transport is not a concern with respect to aging degradation for any of the reusable package component materials. The staffs determination is based on confirming that susceptibility to the adverse effects of aging mechanisms caused by steady-state high temperatures in the subject materialssuch as dimensional changes due to thermal creep in structural alloys, loss of bolt preload due to thermal-induced stress relaxation in alloy steel bolting, unacceptable reduction in the yield and tensile strength of structural alloys (i.e., long-term reductions not already accounted for in the structural design), thermal embrittlement of structural alloys, and changes to the structure and properties of organic materialsoccur at significantly higher temperatures for the subject materials than the maximum temperature for normal conditions of transport. The staff also noted that the aging evaluation appropriately considers the most adverse condition (e.g., highest temperature) for normal conditions of transport since material aging occurs due to long term exposure to normal operating and environmental conditions. Therefore, based on these considerations, the staff finds that the applicants evaluation of potential aging due to heat exposure, and its determination that there would be no adverse changes to the subject materials from exposure to heat over the 50-year period of use, is acceptable for the five-year revalidation term for the MX-6 package.

Evaluation of Potential Aging Due to Radiation For the evaluation of potential aging due to radiation, the applicant determined that all the packaging and fuel can materials covered in the aging evaluation would not be susceptible to adverse changes from exposure to radiation since the cumulative neutron irradiation over the period of use is at least several orders of magnitude less than the lowest neutron irradiation threshold at which adverse changes to the material microstructure and mechanical properties are known to occur. With respect to the depletion of the boron-10 neutron-absorbing radioisotope in the borated stainless steel, the applicant provided data showing that cumulative neutron irradiation would not cause any significant depletion of boron-10 in the borated stainless steel, such that there would be no adverse impact on the criticality safety function of this material.

The staff reviewed the applicants evaluation of potential aging due to radiation and confirmed that adverse changes to mechanical properties such as neutron embrittlement and loss of fracture toughness are not a concern for any of these materials since the accumulated neutron fluence over 50 years, and thus the five-year revalidation term, is at least several orders of magnitude lower than the lowest neutron fluence threshold at which adverse changes to the material microstructure and mechanical properties may need to be considered in the evaluation of structural and shielding performance. The staff also confirmed that continuous exposure to neutron radiation from new fuel assemblies would result in negligible depletion of boron-10 in the borated stainless steel over 50 years. Therefore, the accumulated neutron fluence will have no adverse impact on the criticality safety function of the borated stainless steel neutron absorbers over the five-year revalidation term. Based on these considerations, the staff finds that the applicants evaluation of potential radiation-induced aging, and its determination that

18 there would be no adverse changes to the subject materials from exposure to radiation, is acceptable for the five-year revalidation term for the MX-6 package.

Evaluation of Potential Aging Due to Chemical Reactions - Application Information For the evaluation of potential aging due to chemical reactions, the applicant stated that { },

{ }, and borated stainless steel items have sufficient corrosion resistance due to formation of a protective passive film in air environments. The applicant referenced a { } stainless steel corrosion study that determined a value for the average general corrosion rate of passive { }

stainless steel during long-term exposure to the seashore atmosphere and stated that the service environment of the package is less corrosive than the seashore atmosphere. The applicant also noted that { } stainless steel is more corrosion resistant than { } stainless steel, and since borated stainless steel is { } stainless steel with added boron, borated stainless steel has similar corrosion performance as { } stainless steel. Based on these considerations, the applicant determined that consideration of the effects of corrosion for { },

{ }, and borated stainless steel items is not required.

The applicated stated that the corrosion proofing is given to the alloy steel bolts used for packaging components and the fuel cans. The applicant also stated that if any abnormality is found on the alloy steel bolts, an appropriate corrective action, such as bolt replacement, is taken. Based on these considerations, the applicant determined that the effects of corrosion are not a problem for the alloy steel bolts.

The applicant stated that the titanium alloy has excellent corrosion resistance due to formation of a strong passive film in air environments. The applicant referenced a study of titanium corrosion during long-term immersion in seawater that determined a very low value of the surface corrosion and no significant corrosion through the depth of the material; the applicant stated that the service environment of the package is less corrosive than the seawater environment. Based on these considerations, the applicant determined that the effects of corrosion are not a concern for the titanium alloy.

The applicant stated that { } components are placed in a region of the packaging where resin is poured and covered by stainless steel. The applicant identified that the { } is not exposed to sufficient air or moisture to cause significant corrosion.

The applicant stated that the aluminum alloy fuel basket components are installed inside the packaging body and are kept in a dry condition during handling, transport, and storage. The applicant stated that aluminum alloy basket components have sufficient corrosion resistance in the internal dry air environment inside the packaging due to formation of an oxide film on the surface of the material. The applicant referenced an aluminum alloy corrosion study that determined a value for the average general corrosion rate during long-term exposure to the seashore atmosphere and stated that the service environment of the package is less corrosive than the seashore atmosphere. Based on these considerations, the applicant determined that the effects of corrosion are not a concern for aluminum alloy basket components.

The applicant stated that the regions of packaging where the resin is poured are covered by stainless steel, and the resin environment does not have a sufficient supply of air or moisture. Therefore, the applicant determined that corrosion is not a concern for the resin encased in stainless steel plates. The applicant stated that the wood for the shock absorbers is covered with stainless steel plates. The applicant stated that for breeding of wood-rotting

19 fungus, oxygen and moisture are required and they are not adequately supplied inside the shock absorbers for wood decay to occur.

Evaluation of Potential Aging Due to Chemical Reactions - Staff Evaluation The staff reviewed the applicants corrosion evaluation for the stainless steel components and noted that stainless steel passivity may adequately inhibit general corrosion in most outdoor ambient environments; however, stainless steel is susceptible to localized corrosion effects, including loss of material due to pitting and crevice corrosion, when exposed to aqueous outdoor air environments. For vehicles travelling on roads, outdoor air environments include water that may contain dissolved chlorides or other halide species. Such chemically aggressive anion species are yielded when road salts, debris, and road chemicals mix with rainwater. Over extended operating periods, in particular, during numerous package transport operations over a 50-year period, these chemical species may gradually degrade the protective passive oxide film on stainless steel surfaces leading to the formation of pits and crevice corrosion. Further, stainless steel components under high tensile stress (such as weld residual stress) exposed to aqueous outdoor air environments are also susceptible to the formation of cracks due to chloride-induced stress corrosion cracking (SCC). The staff identified that adequate visual inspections performed by qualified personnel using qualified techniques are needed in order to detect and evaluate indications of localized corrosion and SCC of stainless steel components exposed to aqueous outdoor air environments so that personnel can reliably determine the need for remedial action, such as repair or replacement of components that show unacceptable indications. However, the staff identified that the package handling and maintenance criteria described in Chapter III of the application do not include any specific provision for inspection of stainless steel components to detect and evaluate indications of localized corrosion and SCC to ensure that stainless steel components with unacceptable localized corrosion or SCC are repaired or replaced. The details of the staffs evaluation of the adequacy of the package handling and maintenance criteria for managing localized corrosion and SCC of stainless steel structural components, including resolution of the staffs RAI on this issue, is addressed below in Section 3.2.2.3 of this SER.

For interior sheltered environments, such as those associated with the interior of the packaging enclosure, the staff noted that localized corrosion and SCC of stainless steel surfaces are not a concern provided that the interior surfaces do not undergo sustained or frequent exposure to in leakage of aqueous electrolytes from outdoor rainwater mixed with halide-bearing chemical compounds present in the outdoor environment. For long-term repeated use of packaging components, package operating procedures should also include requirements that any dirt or contamination be removed from empty packaging once unloaded. Since the packaging body enclosure is designed (for loaded packages) to prevent intrusion of water with dissolved chemical species into the interior spaces, and package handling instructions include requirements for closure of the packaging body during storage and decontamination of surfaces of empty packaging, the staff determined that the interior surfaces of the stainless steel packaging enclosure are unlikely to be susceptible to significant localized corrosion and SCC that could degrade the packaging safety functions over the five-year revalidation term.

The staff confirmed that use of a coating on the alloy steel bolts will help protect against corrosion provided that it remains intact. If the coating on the bolts becomes damaged or deteriorates during routine use, which is likely to occur, the staff identified that visual inspections of the bolts are needed in order to detect and evaluate indications of corrosion of the exposed alloy steel to ensure that appropriate remedial action, such as repair or replacement of bolts that show significant corrosion, is taken. The alloy steel bolts in the assembled packaging

20 components are also susceptible to galvanic corrosion if the alloy steel is in direct contact with noble or passive metals such as titanium and stainless steel during package handling and transport. However, the staff identified that the package handling and maintenance criteria described in Chapter III of the application do not include any specific provision for inspection of alloy steel bolts to detect and evaluate indications of corrosion to ensure that bolts with unacceptable corrosion are repaired or replaced. The details of the staffs evaluation of the adequacy of the package handling and maintenance criteria for managing corrosion of the alloy steel bolts, including resolution of the staffs RAI on this issue, is addressed below in Section 3.2.2.3 of this SER.

For the aluminum alloy and borated stainless steel fuel basket components, the staff identified that these materials would be susceptible to significant localized corrosion effects if the protective passive film on the borated stainless steel and the oxide layer on the aluminum alloy are degraded by exposure of these materials to water with dissolved halide species from the outdoors. However, these items are located inside the packaging body enclosure that is designed (for loaded packages) to prevent intrusion of water with dissolved chemical species into the interior spaces. Therefore, the staff determined that the dry air environment inside the loaded package during handling, transport, and storage of empty packaging would limit any potential localized corrosion of these items, such that corrosion effects (if any) would be highly unlikely to result in an unacceptable decrease in the criticality safety performance for aluminum alloy structural components and borated stainless steel neutron absorbers during the five-year revalidation term for the package. Therefore, the staff determined that the existing package handling and maintenance criteria described in Chapter III of the application are adequate to manage deterioration of the aluminum alloy and borated stainless steel items during the five-year revalidation term for the MX-6 package.

The staff confirmed that the titanium alloy has very high resistance to general corrosion and localized corrosion effects even in outdoor air and water environments with dissolved chlorides, so significant corrosion that could degrade structural integrity or shielding performance is generally not a concern for the titanium alloy packaging components. Even if localized corrosion occurs after many years of near continuous exposure of the titanium alloy to air and water with dissolved chloridesa condition that is precluded since the packaging is generally not continuously exposed to these conditionsany localized corrosion effects would be visible on the surfaces of the stainless steel exposed to this environment well before the titanium alloy, and therefore the stainless would be an indicator of the need for corrective action to address potentially problematic corrosion effects. Therefore, the staff determined that existing package handling and maintenance criteria described in Chapter III of the application are adequate to manage deterioration of the titanium alloy during the five-year revalidation term for the MX-6 package.

The staff confirmed that the packaging design provides for the { } plate to be completely embedded in the resin that is poured inside the welded stainless steel packaging body plates.

The staff noted that { } items would be adequately protected against corrosion provided that the integrity of the stainless steel plates is maintained to protect against the intrusion of air and moisture into the resin. The resin is also protected against significant deterioration from physical-chemical interaction with air and moisture, provided that the integrity of the welded stainless steel plates is adequately maintained. The staff confirmed that wood for the shock absorbers is also encased in welded stainless steel plates. Therefore, the wood is adequately protected against water-induced deterioration that could degrade its impact energy-absorbing function, provided that the integrity of the stainless steel plates is adequately maintained to protect against intrusion of water into the wood.

21 Evaluation of Structural Fatigue Due to Stress Cycles in Package Components The application included a structural analysis for demonstrating that the package components would not be susceptible to fatigue failure due to accumulated stress cycles in components. The details of the staffs evaluation of the applicants structural fatigue analyses are addressed in Section 2.0 of this SER. The staff confirmed that the applicant used acceptable material fatigue curves from credible sources for the metallic structural members and alloy steel bolts to demonstrate that the accumulated stress cycles are sufficiently bounded by the stress amplitude and number of cycles to failure displayed on the applicable material fatigue curve. Considering the findings documented in Section 2.0 of this SER, the staff determined that the applicants fatigue analysis for the MX-6 package adequately demonstrated that package structural components would not be susceptible to fatigue failure during the five-year revalidation term for the package. Therefore, the staff determined that the package handling and maintenance criteria described in Chapter III of the application do not require any specific inspections to detect and evaluate incipient fatigue cracks during the five-year revalidation term for the MX-6 package.

3.2.2.3 Criteria for Managing Effects of Aging Mechanisms on Package Components Chapter III of the MX-6 application described handling procedures and maintenance criteria for the MX-6 package. Section III-A of the application described package handling procedures that cover loading operations, inspections before shipment, unloading methods, and preparation of empty packaging. The applicants pre-shipment inspections included visual inspections to verify package integrity, dose rate measurements, weight measurements, and inspections of package contents. Visual inspection criteria included the following provisions:

The visual appearance of package shall be inspected to verify that shapes and paint shall have no abnormal flaw or crack; To ensure subcriticality, the visual appearance of the basket inside the packaging shall be inspected to verify no abnormal deformation or damage to the basket; To ensure lifting component integrity, the visual appearance of the trunnions and handling belts shall be inspected after lifting operations to verify no abnormal deformation or damage to these components; The contents shall be inspected visually to verify that the contents have no deformation or damage.

The procedures for preparation of empty packaging include a requirement to visually inspect empty packaging to verify that the shapes of the packaging body, lid, shock absorbing covers, and the paint have no abnormal flaw or crack. For any abnormality needing repair, a re-inspection of the repaired part shall be performed to verify that the repair has been properly done. The procedures also state that the condition of the fusible plugs and the appearance of bolts are visually inspected to determine if replacement parts are needed.

Section III-B of the application provided maintenance criteria, including criteria for periodic visual inspection of the packaging components. The maintenance criteria specified that periodic visual inspections of the packaging are to be carried out at least once a year or at least once for every ten transport operations if the packaging is used for transport more than 10 times a year. If the packaging has been stored without use for a long period since the last periodic inspection, the packaging shall be visually inspected before use. Empty packaging shall be stored indoors or stored outdoors covered with a waterproof sheet to prevent direct contact with rainwater. If it is

22 determined through the periodic inspection that the packaging needs to be repaired, the repair shall be performed prior to the next transport, and a re-inspection of the repaired part shall be performed to verify that the repair has been properly done. The maintenance criteria also state that the condition of the fusible plugs and the appearance of bolts are visually inspected to determine if replacement parts are needed.

The maintenance criteria included periodic visual inspections and shielding performance tests for verification of the following attributes related to packaging component integrity and functionality:

The body and lid parts of the packaging, the shock absorbers, and the basket inside the packaging are visually inspected to verify that they have no harmful deformation, flaw, or crack; While the packaging is in service, the rubber gaskets are replaced with new ones for each loading operation and inspected visually along with the sealing surfaces to verify that they have no harmful deformation, flaw, or crack affecting containment performance; The dose rates for loaded packages are measured prior to shipment to verify that shielding performance has not deteriorated; The appearance and shape of the basket inside the packaging are visually inspected to verify that they have no abnormality; After lifting operations, the appearance and shape of the trunnions and handling belts are visually inspected to verify that they have no abnormal deformation. This inspection is performed prior to shipment.

As addressed above in Section 3.2.2.2 of the SER, the staff identified that the package handling and maintenance criteria described in Chapter III of the application do not include any specific provisions for inspection of stainless steel components and alloy steel bolts to detect and evaluate indications of general corrosion, localized corrosion, and SCC to ensure that components with unacceptable corrosion or SCC are repaired or replaced.

To address the need for adequate inspection, flaw evaluation, mitigative measures, and corrective actions for managing localized corrosion and SCC of stainless steel components and alloy steel bolts, the staff issued an RAI requesting that the applicant describe codes, standards, and/or other methods that are implemented to ensure that package maintenance activities are adequate to manage the effects of corrosion in stainless steel and alloy steel package components that would see long-term use, such that package components are capable of performing their requisite safety functions throughout the period of use.

The staffs RAI requested the applicant to address the following criteria related to inspection, evaluation, mitigative measures, and corrective actions to demonstrate that the effects of aging on component safety functions are adequately managed during the period of use for the package:

1. Inspection methods (e.g., bare metal visual exams and/or other types of nondestructive exams) for detection and characterization of localized corrosion effects for stainless steel items, such as pits, crevice corrosion, and cracks that may be caused by chloride-induced SCC, as well as for detection and characterization of corrosion for alloy steel bolts.

23

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

3. Visual criteria for detection of aging effects in components, such as localized corrosion (i.e., pitting and crevice corrosion) and SCC. The staffs RAI included examples of visual indications that may indicate potential localized corrosion of stainless steel components such as accumulation of atmospheric deposits, buildup of corrosion products, rust-colored stains or deposits, and surface discontinuities or flaws associated with pitting, crevice corrosion, and/or SCC.

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

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

In its January 16, 2025, response to the staffs RAI, the applicant provided information to address each of the above five criteria.

In response to criteria 1 and 3, the applicant stated that for stainless steel surfaces exposed to outdoor air environments and alloy steel bolts, it will add inspection requirements and acceptance criteria to consider possible indications due to general corrosion, localized corrosion and SCC, as follows.

For external surfaces of the package body (top flange, trunnions, outer envelope, and bottom), the handling belts, and the shock absorbing covers, visual inspections shall be performed to ensure there is no pitting, crevice corrosion, and SCC that might affect the integrity and performance of the components.

For surfaces of the alloy steel bolts, visual inspections shall be performed to ensure there is no damage to the protective plating and no corrosion.

The applicated stated that the new inspection requirements and acceptance criteria will be added to its procedures for periodic visual inspections.

In response to criterion 2, the applicant stated that it will add requirements to clarify the conditions for performing visual inspections. Conditions for performing visual inspections will include illumination criteria, requirements for visual access to component surfaces for direct visual inspection, surface cleanliness requirements, personnel qualification requirements (including visual acuity requirements), and associated national or international codes and standards to ensure adequate conditions for visual inspections. For each of these conditions, the applicant provided a summary of the relevant requirements and associated codes and standards for ensuring adequate illumination, access for direct visual inspection, surface cleanliness, and personnel qualification (including visual acuity). The applicant cited established consensus codes and standards that are published in Japanese Industrial Standards (JIS),

International Organization for Standardization (ISO), and the European Norm (EN) technical

24 standards documents. The consensus standards cited in the applicants RAI response include visual examination methods for fusion-welded joints, general principles for visual examination, and standards for qualification and certification of nondestructive examination personnel.

In response to criterion 4, the applicant stated that it will add the following requirements related to surface cleaning:

The outer surface of the packaging shall be cleaned between the completion of transport and the next transport.

Prior to visual inspection, the surface of the packaging shall be free of contamination. If contamination is present, cleaning shall be carried out before inspection. This particular requirement is also included in the response criterion 2 as a required condition for performing visual inspections.

In response to criterion 5, the applicant described the following flaw evaluation criteria for visual indications in welds, discoloration, and visual indications on alloy steel bolts:

Defects identified in welds (i.e., cracks, pits, craters), regardless of their size, must be repaired in all cases since such defects affect the structural integrity of the package.

If there is discoloration on the weld or base metal that is suggestive of corrosion, it shall be determined whether the discoloration is superficial. If the discoloration disappears after polishing with a light abrasive, no repair is necessary. If the discoloration is not removed, and it is suspected that corrosion has penetrated into the depth of the material, the need for repair shall be determined.

If the plating on an alloy steel bolt is damaged and corrosion protection is lost, the bolt shall be replaced.

The staff reviewed the applicants RAI response and determined that the response adequately addressed each of the five criteria for demonstrating that the effects of credible aging mechanisms on the integrity and performance of stainless steel package components and alloy steel bolts will be adequately managed during the five-year revalidation term. The staffs determination is based on its consideration of key attributes of effective aging management of safety-related structures and components, as follows:

With respect to criteria 1 and 3, the staff verified that the applicant specified adequate visual inspection requirements and associated acceptance criteria for ensuring no unacceptable indications of pitting, crevice corrosion, and SCC on the surfaces of stainless steel structural components exposed to the outdoor air environment, and no unacceptable indications of corrosion on alloy steel bolts.

With respect to criterion 2, the staff verified that the applicant specified adequate conditions for performing visual inspections, including specific requirements for illumination, direct visual examination distance and angle of sight, surface cleanliness, and personnel qualification and visual acuity requirements. The staff also verified that the applicant included references for suitable consensus codes and standards to provide adequate control of visual inspection conditions, as needed to ensure that inspections can adequately detect and characterize indications of localized corrosion and SCC prior to component failure or loss of safety function.

With respect to criterion 4, the staff determined that the applicant specified suitable requirements for cleaning the outer surface of package components exposed to outdoor air to

25 ensure that any accumulated dirt and atmospheric deposits on the package surface is removed and will not obscure surface flaws. The staff also determined that removing such contamination from package surfaces effectively mitigates the corrosive chemical attack of package surfaces by preventing the formation of aqueous electrolytes containing dissolved halides due to mixture of dirt and atmospheric deposits with rainwater.

With respect to criterion 5, the staff verified the applicant provided a conservative requirement for repair all of surface defects, such as cracks, pits, and craters, that are identified in welds, regardless of their size, to protect against a loss of weld integrity due to localized corrosion effects, such as SCC and pitting. For indications of very early stage corrosion, such as discoloration on the surface of welds or base metal, the staff confirmed that the requirement to ascertain (through surface polishing) whether the corrosion may have penetrated into the depth of the structural material provides assurance that any significant corrosion that could affect structural integrity is corrected through repair, whereas an indication of superficial surface corrosion that does not show significant penetration into the depth of the material is appropriately cleaned off the surface without any need for repair of the component. The staff determined that the requirement to replace alloy steel bolts if the protective plating is damaged is appropriate since this corrective action ensures that the bolt is replaced prior to sustaining significant corrosion that may degrade the structural integrity of the bolts.

Since the applicant provided an adequate response to each of the five criteria addressed in the RAI, the staff determined that applicants package handling and maintenance activities will ensure adequate management of credible aging effects for the stainless steel package components and alloy steel bolts during the five-year revalidation term. Therefore, the staff finds that the applicants RAI response is acceptable.

3.2.2.4 Conclusion on Evaluation of Aging per IAEA SSR-6 Based on the foregoing review of the applicants evaluation of aging mechanisms for the MX-6 package and the applicants acceptable RAI response addressing maintenance criteria for managing credible aging effects for package components, the staff determined that the MX-6 package application adequately describes how the design of the package takes into account ageing mechanisms in accordance with Paragraph 613A of IAEA SSR-6 for the five-year revalidation term. Accordingly, the staff finds that the applicants evaluation of aging mechanisms for the MX-6 package and the package maintenance criteria are acceptable for meeting the requirements of Paragraph 613A of IAEA SSR-6 for the five-year revalidation term.

4.0 CRITICALITY EVALUATION

The applicant requested revalidation of the Japanese Competent Authority Certificate of Approval No. J/2026/AF-96, Revision 1, for the Model No. MX-6 package for transportation of unirradiated BWR 9x9 fuel containing uranium dioxide (UO2) of up to 5.0 weight percent enrichment in uranium-235 (235U) to comply with the requirements of IAEA SSR-6, Rev. 1.

4.1 Description of the Criticality Design and Contents The MX-6 is designed to hold up to 10 BWR fuel assemblies, which are shown in table II-A.1 of the application, with the major fuel specifications listed in table II-E.2. Fuel assemblies may contain gadolinium rods, but the gadolinium is conservatively neglected in the analysis. All fuel is considered to be enriched to 5.0 weight percent 235U for all evaluated cases. The MX-6 uses borated stainless steel in the basket structure as a neutron poison.

26 4.2 General Considerations for Criticality Safety The applicant modeled the parameters important for evaluating the subcriticality of the MX-6 package, including the fuel specifications, fuel cladding, neutron absorbers in the basket, basket structure, spacers, and the inner stainless-steel shell of the package. These parameters are shown in table II-E.2 and illustrated in figures II-E.1 through II-E.5 of the application. To account for routine, NCT and ACT, the applicant assumes an infinite length of fuel assemblies and ignores the external plates, stiffeners, shell part resin, lid bottom, and shock absorbing covers.

The applicant assumed borated stainless steel to be at the minimum allowed and not less than

{ } weight percent. The staff finds this acceptable since the (density/boron content) falls within the American Society for Testing and Materials (ASTM) Standards { } range that ensures that the boron credited in the analysis is conservative for this application. The applicant assumed full density water within the package and evaluated the package using mirror reflection on the periphery of the package. The applicant modeled any deformation of the fuel assemblies as a result of NCT and ACT by expanding the pitch of the fuel rods within each assembly to fill each basket location.

4.3 Demonstration of Maximum Reactivity The applicant used conservative assumptions throughout its analysis of both NCT and ACT, as mentioned in the general considerations for criticality safety. The applicant also assumed that MX-6 contains a maximal load of 10 BWR fuel assemblies fully flooded with water. The applicant conducted evaluations of routine conditions of transport, a package in isolation, individual package in isolation under NCT and ACT, and package arrays under both NCT and ACT. The bounding effective multiplication factor plus three times the standard deviation (Keff

+3) is less than 0.80 for both the C-lattice configuration and the D-lattice configuration.

4.4 Criticality Safety Evaluation The applicant used the SCALE 6.1 system of codes to perform their calculations of the effective multiplication factor for the MX-6 design using the KENO-VI Monte Carlo code package and the ENDF/B-VII 238 group cross-section data library. The applicants evaluation was reported and summarized in tables in appendices 1 through 8 in Chapter II-E of the application for the evaluated parameters of the package.

The staff reviewed the Japanese certificate of compliance for the Model No. MX-6 package, as well as the applicants assumptions, model configurations, analysis, and the results presented in the application. Based on its verification of adequate system modeling performed by the applicant, the staff concludes that the applicant has conservatively evaluated the criticality safety performance of the Model No. MX-6 package with requested contents of up to 10 BWR 9x9 fuel assemblies and has demonstrated that the MX-6 package will remain subcritical for all routine, NCT, and ACT. The staff based its finding on its verification of adequate system modeling performed by the applicant. The acceptance standard of a maximum Keff of 0.95 was maintained for all analyzed scenarios and meets the requirement that the package maintain subcriticality under all conditions of routine, normal and accident conditions as required by the IAEA SSR-6, Rev. 1, Paragraphs 673(a) and 682.

4.5 Evaluation Findings

27 Based on review of the statements and representations in the application, the NRC staff finds that the MX-6 transportation package has been adequately described and evaluated to demonstrate that it satisfies the criticality safety requirements of SSR-6.

5.0 SHIELDING EVALUATION The applicant requested revalidation of the Japanese Competent Authority Certificate for the Model No. MX-6 package for transportation of unirradiated BWR fuel assemblies containing uranium dioxide (UO2) enriched up to 5.0 weight percent uranium-235 (235U) to the requirements of IAEA SSR-6, Revision 1. Fuel assembly contents may have previously been stored in a spent fuel pool and therefore may also include residual contamination.

5.1 Description of Shielding Design The shielding design of the MX-6 package consists of the borated stainless steel basket lodgments, cavity inner steel shell, radial resin in the cask body, package external steel plates, inner shell bottom steel plate, bottom resin, titanium alloy lid, lid resin, and steel lid resin cover.

The geometric arrangement of shielding components is shown in figures I-C.5 through I-C.7 of the application for the package body, figure I-C.10 of the application for the lid, and Figure I-C.11 of the application for the basket. Table I-C.1 of the application provides the materials of all of the shielding components with the exception of the resin, and the associated standard for each material. Resin components are provided in Table I-C.2 of the application.

5.2 Radioactive Materials and Source Terms The radioactive source for the MX-6 package consists of the unirradiated fuel source, and the surface contamination source from being stored in a spent fuel pool with fuel rubble. The fuel source consists of the radionuclides shown in Table II-D.1 of the SAR, including 235U, 238U, 232U, 234U, 236U, and trace technecium-99 (99Tc). This fuel composition is consistent with that of unirradiated light water reactor fuel and represents a Type A quantity of radioactive material. The gamma source from the fuel component is shown in Table II-D.2 of the SAR. The corresponding neutron source from the fuel is negligible, since it is unirradiated. The applicant stated that there is additionally a contamination source due to the fuel assemblies having been stored in a spent fuel pool with pool water contamination and potential fuel rubble. To estimate this source, the applicant performed an analysis of fuel rubble samples and spent fuel pool water to determine the type and quantity of radionuclides present. Based on radiation measurements of the samples, the applicant determined that the primary nuclides of interest for determination of external package dose rate were cobalt-60 (60Co), cesium-137 (137Cs, including its progeny nuclide barium-137m (137mBa)), nickel-63 (63Ni), and strontium-90 (90Sr, including its progeny nuclide yttrium-90 (90Y)). In Appendix 3 of Section D.6 of the application, the applicant demonstrates that the quantity of radionuclides present in the package is less than a Type B quantity, meaning that the package needs to meet the dose rate requirements for Type A packages. The applicants determination included estimates of radionuclide mixture A2 values, calculated according to the requirements of SSR-6, Rev. 1, paragraph 405. The applicant assumed several worst-case radionuclide distributions, including those which were primarily 60Co or 137Cs (the most limiting for external dose determinations due to high energy gammas from these radionuclides), and determined that for all estimated radionuclide distributions the mixture quantity was below the mixture A2 value. The staff agrees that the applicant conservatively estimated the radionuclide content in the package from pool water contamination and fuel rubble, and that the resulting external dose rate will be conservative.

28 The applicant also requires a measurement of each fuel assembly to ensure that the contamination source is less than estimated in the shielding analysis. The operational criteria for fuel assembly dose rate is the average of the measured value on four faces of the fuel assembly in five different axial regions: handle, upper grid, upper plenum, active fuel, and lower tie plate. The operational criteria for fuel assembly dose rate in these axial regions is shown in Table II-D Appendix 2.1. The applicants analysis of fuel assembly dose rate in Appendix 2 demonstrates that the assumed contamination source produces a higher fuel assembly dose rate than the operational criteria, as shown in Figures II.D Appendix 2.2 and II.D Appendix 2.3.

This means that fuel assemblies with the assumed contamination source will be assured of producing a higher external package dose rate than actual loaded assemblies which meet the operational criteria in Table II.D Appendix 2.1, which is conservative.

The staff finds that the applicant has conservatively estimated the radioactive materials and source terms present in the package for the shielding analysis.

5.3 Shielding Model and Model Specifications The applicants shielding model specifications are described in section II-D.3 of the application.

The applicant modeled the fuel assemblies conservatively ignoring zirconium alloy channel boxes and the stainless steel fuel can, which would both serve to shield gamma radiation. The applicant homogenized the fuel assembly material in five axial regions: assembly handle, upper grid, upper plenum, active fuel length, and lower tie plate. Only the active fuel length region contains the fuel source, while the contamination source is modeled in all five axial regions, consistent with the fuel assembly surface area in each region. The source term is homogenized within each axial region, as shown in figures II.D-1 through II.D-4. The applicant modeled the fuel assemblies shifted in the basket lodgments such that the assembly handle region contacts the inner surface of the package lid, in order to simulate potential fuel assembly movement within the basket. The applicant conservatively assumed that the basket structural material below the basket lodgments is replaced with air. The package design also includes a top and bottom steel and wood impact limiter, but only the spacing provided by these components for determining external dose rates is credited, and the materials are replaced by air in the shielding model. The number densities for each material modeled by the applicant in the shielding model are listed in Table II-D.4 of the application.

The applicant modeled the package under routine conditions of transport and normal conditions of transport. The only difference between the two models is that the spacing provided by the impact limiters is reduced under normal conditions of transport due to the hypothetical free drop.

The configuration of the applicants package model is shown in Figures II-D.1 and II-D.2 of the application for routine conditions of transport, and Figures II-D.3 and II-D.4 of the application for NCT.

5.4 Shielding Evaluation The applicant used the DORT two-dimensional discrete ordinates transport code to estimate package external surface and 1-meter gamma fluxes as a function of energy under routine conditions of transport and NCT. For these calculations, the applicant used the SCALE 47-group ENDF/B-VII gamma cross section library. The applicant converted the calculated external gamma fluxes to estimated dose rates using flux-to-dose conversion factors from International Commission on Radiation Protection (ICRP) Publication 74, Conversion Coefficients for use in Radiological Protection against External Radiation. Although this deviates from NRC recommendations to use flux-to-dose conversion factors from American National Standards

29 Institute/American National Standard (ANSI/ANS) 6.1.1-1977, Neutron and Gamma-Ray Flux-to-Dose-Rate Factors, the staff considers the ICRP factors acceptable, since the calculated dose rates are less than the regulatory limits, and the difference in calculated dose rates between the two flux-to-dose conversion factors is exceeded by the margin to the regulatory limits.

The applicant reported the resulting calculated external dose rates in table II-D.5 of the application. The applicants maximum calculated dose rate was { } micro-sieverts per hour

(µSv/hr) [ { } millirem per hour (mrem/hr)] at the package surface, and { } µSv/hr ({ }

mrem/hr) at 1 meter from the package surface. These dose rates are lower than the package surface dose rate limit in paragraph 527 of SSR-6 of 2 millisieverts per hour (mSv/hr) [200 mrem/hr] and the transport index limit in paragraph 526 of SSR-6 of 10, which corresponds to a dose rate of 0.1 mSv/hr [10 mrem/hr] at 1 meter from the package surface.

The staff reviewed the certificate of compliance for the Model No. MX-6 package, as well as the applicants initial assumptions, model configurations, analyses, and results in the application.

The staff finds that the applicant has conservatively evaluated the shielding performance of the Model No. MX-6 package with the requested contents and demonstrated that the package external dose rates meet the limits under routine and normal conditions of transport. Therefore, the staff finds with reasonable assurance that the package, with the requested contents, will meet the package external dose rate requirements of IAEA SSR-6.

5.5 Evaluation Findings

Based on review of the statements and representations in the application, the NRC staff finds that the MX-6 transportation package has been adequately described and evaluated to demonstrate that it satisfies the shielding requirements of SSR-6.

6.0 OPERATING PROCEDURES The staff reviewed the description of the operating procedures for the MX-6 package against the standards in the IAEA SSR-6. The package handling procedures in the SAR include sections on package acceptance, loading, unloading, and pre-and post-shipment requirements. The operating procedures contain specific measures prior to each shipment, including ensuring packaging is in unimpaired physical condition and loading contents, installing the package closures, and confirming that the lid bolts are properly torqued, and measurements of radiation and contamination levels.

7.0 MAINTENANCE PROGRAM The staff reviewed the description of the maintenance program for the Model MX-6 package against the standards in the IAEA SSR-6. The maintenance program includes requirements for each shipment, after one year; or if a package is used more than 10 times a year, every 10 package uses, and prior to a use if the package has been stored without a use for long period after the last inspection. The maintenance tests include visual inspections and inspecting basket for criticality safety. The gaskets are replaced prior to each shipment.

8.0 QUALITY MANAGEMENT SYSTEM The purpose of the quality assurance (QA) [i.e., management system IAEA SSR-6, 2018 Edition] review is to verify that the package design meets the requirements of the IAEA SSR-6,

30 2018 Edition. The staff reviewed the description of the QA program for the Model MX-6 package against the standards in the IAEA SSR-6, 2018 Edition.

8.1 Evaluation of the Quality Assurance Program The applicant developed and described a QA program for activities associated with transportation packaging for nuclear fuel materials. Those activities include design, procurement, fabrication, assembly, testing, modification, maintenance, repair, and use. The applicant described the QA organizations independence from other branches in the organization, which includes those responsible for product cost and schedule. The applicants description of the QA program meets the applicable requirements of IAEA SSR-6, 2018 Edition and is based on International Organization for ISO Standardization, Standard No. 9001, Quality management systems Requirements, 2015 Edition and other applicable standards. The staff finds the QA program description acceptable as it allows implementation of the associated QA program for the design, procurement, fabrication, assembly, testing, modification, maintenance, repair, and use of the Model No. MX-6 transportation package.

The staff finds, with reasonable assurance, that the QA program for the MX-6 transportation packaging:

meets the requirements in IAEA SSR-6, 2018 Edition, and encompasses design controls, materials and services procurement controls, records and document controls, fabrication and maintenance controls, nonconformance and corrective actions controls, an audit program, and operations or programs controls, as appropriate.

8.2 Evaluation Findings

Based on review of the statements and representations in the MX-6 transportation packaging application and as discussed in this SER section, the staff has reasonable assurance that the MX-6 package meets the requirements in IAEA SSR-6, 2018 Edition.

CONCLUSION Based on the statements and representations contained in the documents referenced above, and for the reasons stated in this SER, the NRC staff concludes that Model No. MX-6 package meets the requirements of the IAEA SSR-6, 2018 Edition. The NRC recommends revalidation of Japanese Certificate of Competent Authority J/2036/AF-96, Revision 1, for the MX-6 transport package with the following condition:

The U.S. revalidation term is limited to 5 years.

Issued with letter to Richard W. Boyle, Chief, Radioactive Material Transport, Pipeline and Hazardous Materials Safety Administration, U.S. Department of Transportation, dated March 23, 2025