ML23215A136
| ML23215A136 | |
| Person / Time | |
|---|---|
| Site: | 07109186 |
| Issue date: | 09/08/2023 |
| From: | Storage and Transportation Licensing Branch |
| To: | US Dept of Energy, Naval Reactors |
| Shared Package | |
| ML23215A132 | List: |
| References | |
| Download: ML23215A136 (15) | |
Text
SAFETY EVALUATION REPORT Docket No. 71-9186 Model No. S-6213 Power Unit Shipping Container Certificate of Compliance No. 9186 Revision No. 20
SUMMARY
By letter dated January 18, 2022 (Agencywide Documents Access and Management System
[ADAMS] Accession No. ML22034A588), Naval Reactors submitted an application for renewal of Certificate of Compliance (CoC) No. 9186 for the Model No. S-6213 power unit shipping container (PUSC) package. In addition, by letter dated December 28, 2022 (ML23003A237), as supplemented June 15, 2023, (ML23187A498), the applicant requested a revision to CoC No. 9186 and submitted a safety analysis report (SAR) addendum documenting the impact of a new internal pressure cap on package performance. The U.S. Nuclear Regulatory Commission (NRC) staff (the staff) reviewed the application using the guidance in NUREG-2216, Standard Review Plan for Transportation Packages for Spent Fuel and Radioactive Material." Based on the statements and representations in the application, as supplemented, the staff agrees that these changes do not affect the ability of the package to meet the requirements of Title 10 of the Code of Federal Regulations (10 CFR) Part 71. The staff concludes that the certificate can be renewed for a 5-year term.
1.0 GENERAL INFORMATION
1.1 Packaging
The applicant introduced a new internal pressure cap, which had a 2.5-inch thick (nominal) dome and a 1.25 inch thick (nominal) ring, fabricated from high strength low alloy-100 (HSLA-100) steel. The new internal pressure cap utilized a 1.892 inch thick (nominal) seal ring and twelve 1.7333-inch thick (nominal) spacers. Alloy-X 750 socket head cap screws connected both the seal ring and the spacers to the PUSC barrel flange. The applicant chose to fabricate both the seal ring and the spacers from type 304 stainless-steel plate. The seal ring had two sets of dual O-ring grooves. These O-ring grooves created a seal between the seal ring and the barrel flange as well as between the seal ring and the internal pressure cap. The applicant included a leak test port, which is sealed with a brass pipe plug, between each set of dual O-rings to provide O-ring testing capability. The design utilized alloy-X 750 socket head cap screws to attach the internal pressure cap to the seal ring. Addition of the new internal pressure cap affected neither the barrel impact limiter, the fasteners nor the sleeves. However, the applicant revised the torque values associated with impact limiter installation.
Besides adding the new internal pressure cap, the applicant revised the packaging description by deleting discussion of a lower support adaptor as well as an adaptor ring. The applicant removed these components from the packaging description because they were associated with specific contents which the applicant chose to remove as authorized contents. The applicant also revised the stated weight of the package to 320,400 pounds which is the weight the PUSC with the S9G/VIRGINIA Forward Fit (VAFF) power unit (PU).
The staff reviewed the package description provided in the application. The staff determined that it adequately describes the package configuration. Therefore, the staff finds it acceptable.
Enclosure 2 1.2 Drawings
The applicant provided new drawings depicting the dimensions, material specifications and fabrication requirements for the new internal pressure cap. The staff reviewed these changes for conformance to NUREG/CR-6407, Classification of Transportation Packaging and Dry Spent Fuel Storage System Components According to Importance to Safety. The staff finds the drawings are acceptable because they contain sufficient information to evaluate the impact of the new internal pressure cap on the package performance.
1.3 Contents
The applicant removed all reactor power units from the Certificate except for the S9G/VAFF PU.
1.4 Findings
Based on a review of the statements and representations in the application, the staff concludes that the package has been adequately described to meet the requirements of 10 CFR Part 71.
2.0 STRUCTURAL
The objective of the structural evaluation is to verify that the structural performance of the package adequately meets the requirements of 10 CFR Part 71. The scope of the structural review is limited to the areas of the SAR that are affected by the proposed changes described in the amendment request. Therefore, the structural evaluation performed by the staff is limited to the changes in structural performance of the S-6213 PUSC after re-analyzing the package with the new internal pressure cap assembly design and a reduced authorized content as demonstrated in the SAR addendum provided.
2.1 Background and Description of Changes
The applicant designed the S-6213 PUSC as a transportation container to transport submarine power units with control rods and control drives mechanisms (CDM) installed. In CoC 9186, revision 19, the staff approved the use of the S6W shipboard power unit, the S8GP/technology demonstration core (TDC) power unit and the S9G power units for the next generation reactor (NGR) and the VAFF cores as authorized contents for this package. The staff authorized these different contents for use with the model 1 and model 2 container designs of the S-6213 PUSC package which is certified as a type B package under CoC 9186.
In this amendment, the applicant proposed to use a new internal pressure cap assembly design for the S-6213 PUSC package. It also proposed the removal of the S6W shipboard, S8GP/TDC and S9G/NGR power units as authorized contents because no further shipments of these contents are expected. Therefore, after this amendment, the S9G/VAFF power unit will remain as the only authorized content for use with the model 1 and model 2 containers of the S-6213 PUSC package.
The applicant provided a new SAR addendum to address the changes to the safety analysis previously performed for the S9G/VAFF power unit in the S-6213 PUSC package. The addendum contained a re-analysis of each SAR section that was affected by the proposed changes. The applicant performed the structural analysis using a new computational modeling software and model as described in section A.2.1.4 and appendix A2.10.11 of the addendum.
This section reviews the structural analysis performed by the applicant to demonstrate compliance with the requirements of 10 CFR Part 71.
2 2.2 Description of Changes to the Structural Design and Analysis Methodology
The new internal pressure cap assembly consisted of a new internal pressure cap, impact limiter and associated hardware. Drawings 6359E15, 6359E11 and 6359E12, revision A.4, of the addendum provided the engineering details associated with the new components. All other structural components previously evaluated in the SAR for the S9G/VAFF power unit in the S-6213 PUSC remained unchanged by this amendment. After reviewing these changes to the S-6213 PUSC package, the staff finds that the information provided is consistent with the engineering drawings and the analyses and models used in the structural evaluation.
For the analysis, the applicant used a new model and computer modeling software to re-analyze the structural performance of the package. The new computer modeling software and the new package model did not significantly affect the results from previously analyzed conditions. The staff also noted that the structural design change and the new content limitation results in an overall weight for the S-6213 PUSC package that is less than what was previously evaluated and with a slight shift in its center of gravity. The reduction in weight and slight shift in center of gravity of the package did not significantly affect the structural performance of the S9G/VAFF power unit in the S-6213 PUSC.
2.2.1 Weights and Centers of Gravity
The applicant described the calculated weights and centers of gravity for the S9G/VAFF power unit in the S-6213 PUSC in addendum section A2.2.1. The design change and new content limitation resulted in an overall decrease in the package weight from what was previously analyzed, and the center of gravity location shifted slightly towards the barrel end of the PUSC.
Addendum tables A2.2-1 and A2.2-2 provided the nominal weights and the centers of gravity locations, with the associated drawing numbers, for various PUSC components. Neither the reduction in weight nor the slight shift in center of gravity of the package significantly affected the structural performance of the S9G/VAFF power unit in the S-6213 PUSC.
2.2.2 Design Criteria
The applicant considered the effects from the package design changes by re-evaluating the structural performance of the S9G/VAFF power unit in the S-6213 PUSC with the new internal pressure cap assembly. The applicant used the same structural design criteria described in the SAR (e.g., applied loads, allowable stresses, minimum strain criterion, vibration, failure modes, etc.) to analyze the new package design. The applicant also used combinations of closed-form solutions, hand calculations, and finite element analysis methods to perform these analyses.
The results applicant used the analyses to demonstrate compliance with the requirements of 10 CFR Part 71 for normal conditions of transportation (NCT) and hypothetical accident conditions (HAC). The staff evaluation of the results from these analyses is discussed further below.
2.2.3 Analysis Methodology
In addendum section A.2.1.4, the applicant described the new computational modeling software used for the analysis of the package structural performance during NCT and HAC. In this section, the applicant described the qualification process that was followed to validate the computational modeling software. The applicant concluded that the software is qualified for the analysis of the modified S-6213 PUSC after verifying that test results from the software showed accuracy and convergence when compared to other published benchmark data. The staff noted that the applicant used the same computational modeling software that is used by others in the
3 industry to predict physical results with a finite element model. Because the staff has found the software acceptable for those applications, the staff finds it acceptable for this application.
In addendum appendix A2.10.11, the applicant also described the finite element model developed to represent the modified S-6213 PUSC package and its content. The applicant considered three major sub-assemblies of the model: the PUSC assembly, the VAFF power unit, and the S9G adaptive equipment. The model represented the package in half-symmetry to reduce the computational complexity without limiting the analytic accuracy. The applicant developed the model using proper material properties, appropriate dimensions and tolerances, and acceptable analysis parameters to ensure adequate representation and results of the analyzed package. Based on the staffs review of the PUSC assembly model, the staff finds that the model sufficiently represents the shipping container and the S-6213 PUSC geometry.
2.3 General Design Requirements
In addendum section A2.4, the applicant addressed the general standards requirements for the package (i.e., minimum package size, tamper-proof features, positive closure, chemical and galvanic reactions, valves and other devices, containment and shielding effectiveness, accessible surface temperature limit, prevention of continuous venting) to demonstrate that the package remains in compliance with the regulatory requirements after considering the changes to the S-6213 PUSC. The staff reviewed the general design for the S9G power unit in the S-6213 PUSC. The staff finds, after considering the package design changes, that the package remains in compliance with the general design requirements specified in 10 CFR 71.43.
2.4 Lifting and Tie-down Standards
2.4.1 Lift Lugs
In addendum table A2.5-1, the applicant compared the resultant forces previously calculated for the S8GP power units with the new lifting lug forces calculated in addendum section A2.5.1.1 for the S9G power unit. The staff reviewed the analytical results and confirmed that the resultant lifting lug forces for the S9G power unit in the S-6213 PUSC are bounded by the lifting lug forces already considered in the package evaluation for other power units, as evaluated in Section 1.4.3.2 of the Safety Analysis for Shipping S8G Power Units in the S-6213 Container, Revision 10. Therefore, the staff finds that the modified package remains in compliance with the regulatory requirements in 10 CFR 71.45(a) for lifting attachments.
2.4.2 Tie-down Devices
In addendum section A2.5.2, the applicant stated that tie-down stresses in the PUSC shell and support brackets remains acceptable for the package because the weight of the S9G power unit in the S-6213 PUSC package with the new internal pressure cap is less than the package weight considered in SAR section 2.5.2. The staff reviewed the analytical results in SAR section 2.5.2 and confirmed that (a) the analysis considered the static forces specified in 10 CFR 71.45(b)(1) for tie-down devices, and (b) the exiting analysis remains a bounding condition because the new package weight is less than the weight specified in SAR section 2.5.2 for analysis of the tiedown devices. Therefore, the staff finds that the modified package remains in compliance with the regulatory requirements in 10 CFR 71.45(b) for tie-down devices.
4 2.5 Normal Conditions of Transport
The applicant used a combination of hand calculations and a finite element analysis model to analyze the test requirements under NCT. The analysis considered the package preload conditions summarized in addendum table A2.6-2 to evaluate the acceptability of the new internal pressure cap assembly components under NCT. The analysis considered a total of five load cases to evaluate the effects due to hot and cold temperature, increased and reduced external pressures, vibration and shock. In addition, the free drop analysis evaluated different materials and properties using eight additional load cases. The applicant used a commercial computer code to perform the structural analyses of the models. The staff evaluations of the results for each condition analyzed are discussed below.
2.5.1 Heat
The applicant calculated the stresses of the new internal pressure cap assembly components under hot conditions with the S9G power unit in the S-6213 PUSC, as required in 10 CFR 71.71(c)(1), and compared the results of all stress calculations with the allowable stresses (i.e., Load Cases: AH, AH-iShift and VH). After reviewing the calculated and the allowable stress comparisons, as presented in addendum section A2.6.2.2.8.1, the staff finds that the stress intensity values for critical components of the new internal pressure cap assembly are within the allowable limits of the materials under the hot condition. The applicant stated that stresses at the 1-inch sleeves used with the fasteners results in minor plasticity that is found to be negligible, and no failure is expected. Therefore, the staff finds that the package structural integrity is maintained after considering the new internal pressure cap assembly design under hot conditions.
2.5.2 Cold
The applicant performed a structural analysis to calculate the stresses of the new internal pressure cap assembly components under cold conditions with the S9G power unit in the S-6213 PUSC as required in 10 CFR 71.71(c)(2). A comparison of the stress calculations results with the allowable stresses (i.e., Load Cases: AC and VC) showed that the resultant stresses were lower than the resultant stresses identified under hot conditions. The applicant stated that the relative sliding between the components is negligible considering the infrequent occurrence of this condition and concluded that it will not result in significant degradation of the seals or damage to the fasteners. Based on a review of the results evaluated in addendum section A2.6.2.2.8.2, the NRC staff finds that the structural integrity of the package is maintained after considering the new internal pressure cap assembly components design under cold conditions.
2.5.3 Reduced External Pressure
This condition required the package to be evaluated for the effects of reduced external pressure equal to 3.5 pounds per square inch absolute (psia) as required in 10 CFR 71.71(c)(3). In SAR section 2.6.1.1, the applicant stated that the reduced external pressure condition results in an internal pressure of 14.6 pounds per square inch gage (psig) or 29.3 psia. Considering that the resultant internal pressure is less than the design pressure considered in the analysis of the package, the staff finds this condition to be bounded by the analysis provided in addendum section A2.6 (i.e., Load Case AH). Based on a review of the addendum section A2.6.2.2.8.1 results, the staff finds that the structural integrity of the package is maintained after considering the new internal pressure cap assembly components design under a reduced external pressure.
5 2.5.4 Increased External Pressure
This condition required the package to be evaluated for the effects of increased external pressure equal to 20.0 psia as required in 10 CFR 71.71(c)(4). In addendum section A2.6.2.2.6.2, the applicant stated that the increased external pressure condition results in an internal pressure of -7 psig. To evaluate the effects due to the increased external pressure, addendum section A2.6 evaluated the resultant stresses and relative sliding between components for the analysis of the package design (i.e., Load Case AC). Based on a review of the results evaluated in addendum section A2.6.2.2.8.2, the staff finds that the structural integrity of the package is maintained after considering the new internal pressure cap assembly components design under an increased external pressure.
2.5.5 Vibration
In addendum section A2.6.2, the applicant stated that the calculated natural frequency for the S-6213 PUSC loaded with an S9G power unit remains less than the maximum excitation forcing frequency necessary to result in stress effects due to a resonance condition when transported at a maximum railcar speed of 50 miles per hour. Furthermore, results from a rail shipment study, as referenced in the SAR, showed that the worst-case maximum g-load induced by railcar vibration at the natural frequency is less than 1/20th of 1-g due to sufficient damping in the system. Therefore, after considering the acceptable performance of this assembly with a load that is two orders of magnitude greater for transportation shock as demonstrated in the analysis of addendum section A2.6.2.2, the applicant concluded that a resonance condition is not detrimental to the internal pressure cap, impact limiter, or mounting hardware. The applicant evaluated the response of the PUSC barrel end impact limiter and internal pressure cap assembly components to pressure and shock load using a finite element analysis. The analysis demonstrated that the resultant stresses and loads to fasteners are acceptable. Overall, the low vibration load will result in no significant fatigue usage and will not induce significant cyclic fastener stresses during NCT. Therefore, the staff finds that the package meets the requirements for vibration under NCT after considering the new internal pressure cap assembly components.
2.5.6 Water Spray
The applicant designed S-6213 PUSCs to withstand positive and negative pressures with no external surfaces that are absorbent or reactive to water. This remains unchanged for the new internal pressure cap assembly components of the package. Due to the construction materials of the S-6213 PUSC, the staff finds that water spray, as required in 10 CFR 71.71(c)(5), does not affect the structural design of this package.
2.5.7 Free Drop
The applicant evaluated the performance of the S9G power unit in the S-6213 PUSC considering a free drop from a one-foot distance and a side drop orientation as required in 10 CFR 71.71(c)(7). To evaluate the new package configuration, the applicant re-analyzed the free drop using a finite element analysis model that considered an impact velocity equivalent to a drop height of one foot. The new analysis resulted in an impact acceleration that is less than the acceleration previously evaluated in the original free drop analysis described in SAR section 2.6.7. The resultant crush of the PUSC barrel flange also resulted in a crush depth that is less than the crush depth evaluated for in the original free drop analysis for the S9G package.
Therefore, the original free drop analysis in SAR section 2.6.7.1 bounded the new package design. Since the previous staff review of the S-6213 PUSC package structural performance
6 under this NCT was found acceptable, the staff finds that the structural integrity of the package is maintained after considering the new internal pressure cap assembly components design under a free drop condition.
2.5.8 Corner Drop
In SAR section 2.6.8, the applicant stated that the requirement in 10 CFR 71.73(c)(8) is not applicable to the S-6213 PUSC design. Since the change in design and content does not meet the applicability requirement for the test, the staff finds that the corner drop test specified in 10 CFR 71.71(c)(8) remains not applicable for the modified S-6213 PUSC package.
2.5.9 Compression
In SAR section 2.6.9, the applicant stated that the requirement in 10 CFR 71.73(c)(9) is not applicable to the S-6213 PUSC since the test only applies to packages weighing less than 11,000 pounds. Since the new weight of the S-6213 PUSC still remains above the applicability requirement for the test, the staff finds that the compression test specified in 10 CFR 71.71(c)(9) remains not applicable for the modified S-6213 PUSC package.
2.5.10 Penetration
This condition required an evaluation of the impact of a 1.25 inch diameter vertical steel cylinder, that weighs 13 pounds, dropped from a height of 40 inch onto the exposed surface of the package that is expected to be most vulnerable to puncture as required in 10 CFR 71.71(c)(10). In SAR section 2.6.10, the applicant stated that this requirement was shown to be satisfied for the S-6213 PUSC model 1 and model 2 container package designs for the S6W power units. Staff issued request for additional information (RAI) 2.1 to clarify how the penetration test requirements were analyzed and evaluated for the proposed change to the S-6213 PUSC package design containing the S9G/VAFF power unit. In its response to RAI 2.1 (ADAMS Accession No. ML23187A498), the applicant stated that the internal pressure cap design modification did not result in changes to exterior package features that would alter or challenge the analysis referenced in SAR section 2.6.10. Therefore, the applicant concluded that the analysis and conclusion in the SAR remained applicable for the S-6213 PUSC package with the new internal pressure cap assembly design.
During its evaluation of the applicants response to RAI 2.1, the staff noted that the analysis referenced in SAR section 2.6.10 concluded that the penetration test would not affect the package in any significant manner. The staff noted that the proposed package is significantly larger than the impact specimen specified in 10 CFR 71.71(c)(10), and as stated in Regulatory Guide 7.8, Load Combinations for Structural Analysis of Shipping Casks, the penetration test is not considered by the NRC staff to have structural significance for large shipping casks. The staff finds the applicants response acceptable because it clarifies that the proposed changes to the S-6213 PUSC design did not result in a change to the previous penetration test analysis and its conclusion. Considering the applicants response and the expected effect of the penetration test to large shipping casks, the staff finds that the modified package remains in compliance with the general design requirements specified in 10 CFR 71.71(c)(10) for NCT.
2.5.11 Normal Conditions of Transport Conclusions
Based on the staffs review of the packaging structural performance required by the 10 CFR 71.71 regulations for NCT, the staff finds that there will be no substantial reduction in
7 the effectiveness of the packaging that would prevent the modified S-6213 PUSC package from satisfying the requirements of 10 CFR 71.51(a)(1) and 10 CFR 71.55(d)(2).
2.6 Hypothetical Accident Conditions
The applicant used a combination of hand calculations and finite element analysis methods to analyze the modified S-6213 PUSC package containing a S9G/VAFF power unit under HAC.
The results of the analysis are provided in addendum appendices A2.10.4 and A2.10.13. The staff evaluations of the results for each condition analyzed are discussed below.
2.6.1 Free-Drop
The applicant performed analyses for three free drop orientations of the modified S-6213 PUSC package containing the S9G/VAFF power unit: (a) 30-foot end drops (top and bottom),
(b) 30-foot side drop, and (c) 30-foot corner and oblique drop. The applicant used combinations of hand calculations and finite element computer analyses to evaluate the performance of the S-6213 PUSC package. Appendix A2.10.13 provided the results of the drop analyses.
Addendum section A2.7 and appendices A2.10.1, A2.10.2 and A2.10.3 further evaluated the results of the drop analyses.
For the end drops, the analysis showed that damage to the package components was mainly limited to the impact limiters, pressure caps and their components. However, no significant deformation occurred in the core basket or the closure head. In addition, the content modules stresses remained within the allowable limits. For the side drop, the package component damage occurred mainly near the main flanges. However, neither the closure head nor the core basket showed significant deformation that would result in failure. The results also showed no significant deformation to the content modules. Further analyses considered the performance of internal components from the drop impact and the resultant acceleration. The results demonstrated that assembly components do not fail, and the impact does not result in control rod withdrawal because the CDM remained within the CDM closure components. For the corner and oblique drop, damage to the package components mainly occurred in the impact limiters, barrel end, pressure caps, and their components. The applicant considered the separation of the barrel impact limiter, cover impact limiter, and cover pressure cap acceptable because they are not necessary to demonstrate compliance with the package performance requirements. The internal pressure cap separated from the seal ring but remained in place with no significant reduction in structural effectiveness. The analytical results showed no significant deformation in the lower end of the core basket, and stresses in the content modules remained within the allowable limits. The analytical results and the separation of the affected components are further considered in the subsequent analyses of the modified PUSC package for HAC.
The staff reviewed the results of the analyses for the drop tests. The staff determined that there was no substantial reduction in structural effectiveness of the package, and no loss of primary containment. Based on these results and the review of the conditions considered, the staff finds that the applicant has evaluated the consequences of all credible drops and demonstrated that the modified S-6213 PUSC package is adequately designed to perform its intended functions and maintains its structural integrity under HAC test required in 10 CFR 71.73(c)(1).
2.6.2 Crush
In SAR section 2.7.9, the applicant stated that the test is not applicable because the weight of a S9G power units containing a VAFF core is greater than the 1,100 pounds. limit specified in 10 CFR 71.73(c)(2) for the test. Since the new weight for the S-6213 PUSC package remains
8 greater than 1,100 pounds, the staff finds that the crush test specified in 10 CFR 73(c)(2) remains not applicable to the modified S-6213 PUSC package.
2.6.3 Puncture
In SAR section A2.10.4, the applicant analyzed the modified S-6213 PUSC package with S9G/VAFF power unit for the 40-in. puncture drop as required by 10 CFR 71.73(c)(3). The analysis considered the damages resulting from the previous free-drop analysis and evaluated different test orientations and locations to determine the maximum damage that would be expected. Addendum table A2.10.4.3-1 provided a summary of the results from the analysis of each impact orientation. The results showed that the S-6213 PUSC gets punctured as the pin penetrates the package during the tests, but no puncture occurred at the core basket. Further analysis of the loads transmitted to the core basket and the internal components also showed that no significant damage occurred in these components. Addendum chapters A4, A5 and A6 further evaluated the results to demonstrate that containment, shielding, and criticality are maintained for the modified S-6213 PUSC package. Based on these results and a review of the conditions considered, the staff finds that the applicant demonstrated that the package function is not impaired due to the puncture impact.
2.6.4 Thermal
The applicants thermal evaluation is provided in SAR chapter 3, Thermal Evaluation and is further discussed for this modification in addendum chapter A3.0. The staffs safety evaluation is presented in SER section 3.
2.6.5 Immersion - Fissile Materials
In addendum section A2.7.6 and chapter A6.0, the applicant stated that the criticality analysis in SAR chapter 6A remained applicable for the S9G/VAFF power unit. Since the criticality analysis demonstrated that a completely immersed core remains subcritical, the staff finds that the immersion test specified in 10 CFR 71.73(c)(5) is not necessary for the modified S-6213 PUSC package transporting a S9G/VAFF power unit.
2.6.6 Immersion - All Packages
In addendum section A2.7.7, the applicant stated that the analysis in SAR section 2.7.7 remained applicable for S-6213 PUSC model 1 and model 2 package containers. Since the analysis demonstrates that the submerged pressure of 21.7 pounds per square inch (50-foot head) remains less than the pressure capabilities established for the model 1 and model 2 containers, and because this modification did not change the pressure capabilities of these containers, the staff finds that the previous analysis in SAR section 2.7.7 remains applicable and the water immersion test requirement in 10 CFR 71.73(c)(6) is satisfied.
2.6.7 Immersion - Deep Water
In SAR section 2.7.8, the applicant stated that the test is not applicable because the A2 value for S9G power units containing a VAFF core is less than the minimum A2 value necessary to consider this test as specified in 10 CFR 71.61. A review of SAR table 2.7-3 confirmed that the A2 content specified for the S9G/VAFF core is less than the content limit specified in the regulation. Therefore, considering that there is no change to the specified content value as part of this amendment, the staff finds that the test requirement specified in 10 CFR 71.61 for deep
9 water immersion remains not applicable to the modified S-6213 PUSC package transporting a S9G/VAFF power unit.
2.6.8 HAC Conclusions
Based on the staffs review of the packaging structural performance required by 10 CFR 71.73 for HAC, the staff finds that the modified S-6213 PUSC package has adequate structural integrity to satisfy the subcriticality, containment, and shielding requirements of 10 CFR 71.51(a)(2) and 10 CFR 71.55(e).
2.7 Evaluation Findings
The NRC staff reviewed the structural analysis of the modified S-6213 PUSC with the S9G/VAFF power unit and concludes that the applicant has evaluated the effects on the package for the 10 CFR 71.71 and 10 CFR 71.73 requirements as required by 10 CFR 71.41(a). Therefore, the staff finds that the package has been adequately described and evaluated to demonstrate that it satisfies the structural integrity requirements of 10 CFR Part 71.
3.0 THERMAL EVALUATION
The objective of the amendment review was to verify that the thermal performance of the S-6213 PUSC, which is used to transport unirradiated fuel S9G power units, was adequately described and evaluated under NCT and HAC to meet the 10 CFR Part 71 regulations.
Regulations applicable to the thermal review include 10 CFR 71.31, 71.33, 71.35, 71.43, 71.51.
The amendment included the addition of a new internal pressure cap design for the type B shipping container; there were no changes to the containment boundary design or content.
The S-6213 SAR addendum stated that the new internal pressure cap design had no significant effect on the packages thermal configuration. Chapter 3 of the SAR addendum indicated the new internal pressure cap design resulted in slight changes to weights associated with the HAC thermal analyses for the combined shell and package interior (e.g., content) temperature as well as the package shell temperature. The weight changes did not affect the analyses for determining pressure and temperatures for NCT, e.g., results from the base SAR showed the seal between bolted-closed steel joints was within its NCT allowable temperature.
The applicant used the updated weights as inputs to a lumped capacitance energy balance calculation (discussed in the previously reviewed SAR addendum) and to determine an updated internal package temperature, external package shell temperature, and HAC pressure. As indicated in the base SAR, the package joints relieved pressures if valves were not able to function. Although the thermal analysis method did not explicitly model the spatial heat diffusion effects of package changes from the HAC drop and puncture tests, the base SAR thermal chapter indicated there would be no criticality or containment issues if structural package temperatures reached the HAC fire temperature of 1475°F. Likewise, the S-6213 SAR addendum information and an April 19, 2023, meeting summary (ADAMS Accession No. ML23123A397) indicated that there would be a large margin between the allowable fuel temperature and a calculated fuel temperature that was based on the lumped capacitance package shell temperature, which has a higher temperature than a combined lumped capacitance shell and package interior temperature. The large margin would offset an increase in a calculated fuel temperature that accounted for uncertainty in the spatial heat diffusion effects mentioned above. Therefore, the results showed that the containment boundary, consisting of the fuel cladding and which is confined by both the S9G power unit and S-6213
10 package, was within its allowable temperature range during NCT and HAC. As a result, SAR addendum chapter 4 noted there would be no containment boundary breaches during NCT and HAC.
Based on review of the statements and representations in the application, the staff concludes that the thermal design of the S-6213 unirradiated fuel PUSC package has been adequately described and evaluated and that the package design meets the thermal requirements of 10 CFR Part 71.
4.0 CONTAINMENT EVALUATION
The objective of the amendment review was to verify that the containment boundary of the S-6213 PUSC, which is used to transport unirradiated S9G power units, was adequately described and evaluated under NCT and HAC to meet the 10 CFR Part 71 regulations.
Regulations applicable to the containment review include 10 CFR 71.31, 71.33, 71.35, 71.43, and 71.51. The amendment included the addition of an updated internal pressure cap to the type B shipping container; there were no changes to the containment boundary design or content.
According to chapter 4 of the S-6213 SAR addendum, the containment boundary consisted of the cladding surrounding the fuel that is confined by both the S9G power unit and the S-6213 container. Chapter 4 of the SAR indicated that stresses in the fuel cladding remained below the claddings yield strength during NCT (i.e., the 1-foot NCT drop test was bounded by the 30-foot HAC drop test) and no containment boundary breaches occurred. Likewise, the SAR addendum indicated stresses in the cladding were below yield strength for the HAC structural tests. In addition, the SAR addendum and an April 19, 2023, meeting summary (ADAMS Accession No. ML23123A397) indicated that the fuel cladding was below its allowable temperature during the fire HAC test. Therefore, according to chapter 4 of the SAR addendum, no breaches of the containment boundary occurred as a result of the HAC tests defined in 10 CFR Part 71.73.
Finally, although the addendum indicated that there were no changes to SAR chapter 7 Operations from the previous SAR revision, the acceptance tests and maintenance discussion in chapter 8 of the SAR addendum indicated that the new pressure cap acceptance test confirms package seal effectiveness.
Based on a review of the statements and representations in the application, the staff concludes that the containment design of the S-6213 unirradiated fuel PUSC package has been adequately described and evaluated and that the package design meets the containment requirements of 10 CFR Part 71.
5.0 SHIELDING EVALUATION
The staff reviewed the proposed changes and determined that they did not impact the staffs previous SER findings regarding the package shielding design. Therefore, the staff finds that a new evaluation is not needed.
6.0 CRITICALITY
The applicant stated that the new internal pressure cap neither directly affected the criticality models nor resulted in conditions not bounded by the previously reviewed criticality models.
However, the staff noted that the new structural analyses identified that multiple fuel modules shifted from a HAC drop causing the most reactive portion of the fuel to be misaligned.
Consequently, the staff held a clarification call on May 5, 2023, to confirm that the most reactive
11 portion of the fuel in the HAC criticality models were aligned. The applicant confirmed that the most reactive portions of the fuel were aligned in the HAC criticality models (ADAMS Accession No. ML23192A541). Therefore, the staff finds that the previous HAC criticality models are still bounding because the highest neutron multiplication factor occurs when most reactive portions of the fuel are aligned.
7.0 MATERIALS REVIEW
The applicant submitted a SAR revision to demonstrate the material adequacy of a new internal pressure cap assembly. Only the materials evaluation information that changed from the previous SARs is discussed below. The internal pressure cap assembly, located in the barrel end of the PUSC, is designed to remain in place following HAC to protect the contents from subsequent puncture and fire accidents. The staff reviewed the S-6213 PUSC SAR for Amendment #20 to the S9G power unit to confirm that the S-6213 shipping container material performance meets the requirements of 10 CFR Part 71. The staff notes that the PUSC is not relied upon as a containment boundary.
7.1 Materials of Construction
The new internal pressure cap assembly consists of an internal pressure cap, seal ring, twelve spacers, and cap screws. The internal pressure cap is made from HSLA-100. The seal ring and spacers are made from 304 stainless steel (American Society for Testing and Materials (ASTM)
A240). The cap screws are made from alloy X-750 (ASTM B-637). Per the above discussion, the staff finds that the applicants description of the materials of construction to be acceptable.
7.2 Drawings
The applicant provided new drawings in Appendix A1.4 of the SAR to incorporate the new internal pressure cap, seal ring, and spacers. The drawings include a parts list that provides the material specification of each component, and also provides the welding and examination requirements. The staff notes that the level of detail in the new drawings is consistent with those of the previously approved drawings. The staff reviewed the drawing content with respect to the guidance in NUREG-2216 section 7.4.1, Drawings and NUREG/CR-5502, Engineering Drawings for 10 CFR Part 71 Package Approvals. The staff confirmed that the drawings provide an adequate description of the materials, fabrication, and examination requirements.
Therefore, the staff finds the drawings to be acceptable.
7.3 Codes and Standards
The new internal pressure cap assembly design adopts the same military standards (including those of the Naval Nuclear Propulsion Program) and ASTM International codes and standards as the previous barrel pressure cap. The staff notes the use of military and ASTM standards is consistent with the guidance in NUREG-2216, Standard Review Plan for Transportation Packages for Spent Fuel and Radioactive Material, for important to safety components that do not comprise the containment boundary. Therefore, the staff finds the materials codes and standards to be acceptable.
7.4 Material Properties
The staff reviewed the material properties tables provided in SAR section A2.3 and verified that the applicant did not make any changes to the mechanical and thermal properties used in the structural analyses and thermal analysis, except for the addition of properties for HSLA-100.
12 The staff reviewed the mechanical and thermal properties provided in table A2.3.1-2 and verified that they are consistent with military handbook values, as well as laboratory data and research literature. In addition, the staff verified that appropriate testing was performed to ensure that HSLA-100 has sufficient fracture toughness in accordance with the Category III fracture toughness criteria in RG 7.11. The staff also verified that the melting points of materials are demonstrated to be sufficiently high for the intended application. Therefore, the staff finds the material properties to be acceptable.
7.5 Corrosion Resistance and Content Reactions
The staff reviewed the revision changes and verified that they do not introduce any adverse corrosive or other reactions that were not previously considered in the staffs prior review of the PUSC. The materials of construction and the service environments are bounded by those that were previously evaluated in the CoC. Therefore, the staff finds the applicants evaluation of corrosion resistance and potential adverse reactions to be acceptable.
7.6 Bolt Applications
As stated in section 7.1 above, the pressure cap replacement kit makes use of X-750 (ASTM B-637) cap screws. The staff verified that the new pressure cap replacement kit uses the same bolting material as used in the previously approved PUSC design. Therefore, the staff finds the applicants bolting materials to be acceptable.
7.7 Evaluation Findings
The staff concludes that Amendment #20 for the S9G power unit in the S-6213 power unit shipping container safety analysis report adequately considers material properties and material quality controls such that the design complies with 10 CFR Part 71. This conclusion is reached based on a review that considered the regulation itself, appropriate regulatory guidance, applicable codes and standards, and accepted engineering practices.
F7.1 The applicant has met the requirements of 10 CFR 71.33. The applicant described the materials used in the transportation package in sufficient detail to support the staffs evaluation.
F7.2 The applicant has met the requirements of 10 CFR 71.31(c). The applicant identified the applicable codes and standards for the design, fabrication, testing, and maintenance of the package and, in the absence of codes and standards, has adequately described controls for material qualification and fabrication.
F7.3 The applicant has met the requirements of 10 CFR 71.43(f) and 10 CFR 71.51(a). The applicant demonstrated effective materials performance of packaging components under normal conditions of transport and hypothetical accident conditions.
F7.4 The applicant has met the requirements of 10 CFR 71.43(d). The applicant has demonstrated that there will be no significant corrosion, chemical reactions, or radiation effects that could impair the effectiveness of the packaging.
F7.5 The applicant has met the requirements of 10 CFR 71.43(f) and 10 CFR 71.55(d)(2). The applicant has demonstrated that the package will be designed and constructed such that the analyzed geometric form of its contents
13 will not be substantially altered, no loss or dispersal of the contents, and no substantial reduction in the effectiveness of the packaging under the tests for normal conditions of transport.
The staff concludes that Amendment #20 for the S9G power unit in the S-6213 power unit shipping container safety analysis report adequately considers material properties and material quality controls such that the design is in compliance with 10 CFR Part 71. This conclusion is reached based on a review that considered the regulation itself, appropriate regulatory guidance, applicable codes and standards, and accepted engineering practices.
8.0 PACKAGE OPERATIONS
The staff reviewed the operating procedures for the package using the guidance in NUREG-2216 and found them to be adequate. Based on a review of the statements and representations in the application, the staff concludes that the operating procedures meet the requirements of 10 CFR Part 71 and that these procedures are adequate to assure the package will be operated in a manner consistent with its evaluation for approval.
9.0 ACCEPTANCE TESTS AND MAINTENANCE PROGRAM REVIEW
The staff reviewed the maintenance procedures for the package using the guidance in NUREG-2216 and found them to be adequate. Based on a review of the statements and representations in the application, the staff concludes that the maintenance procedures meet the requirements of 10 CFR Part 71 and that these procedures are adequate to assure the package will be maintained in a manner consistent with its evaluation for approval.
CONDITIONS
The CoC includes the following condition(s) of approval:
Condition 5(a)(2) was revised to address addition of the internal pressure cap and seal ring.
Condition 5(a)(2) was revised to remove text associated with components used to ship S6W and S8GP/TDC power units, to remove the package weights associated with the S6W and S8GP/TDC power units and to revise the package weight with the S9G power unit.
Condition 5(b)(1) was revised to remove all contents except for the S9G power unit containing the VAFF Core.
Condition 5(b)(2) was revised to remove all contents except for the S9G power unit containing the VAFF Core for both the Model 1 and the Model 2 version of the package.
Condition 9 was revised to reflect the new expiration date.
The references section has been updated to include this request.
Minor editorial corrections were made.
CONCLUSIONS
Based on the statements and representations contained in the application, and the conditions listed above, the staff concludes that the design has been adequately described and evaluated,
14 and the Model No. S-6213 power unit shipping container package meets the requirements of 10 CFR Part 71.
Issued with Certificate of Compliance No. 9186, revision No. 20.
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