ML24323A231
| ML24323A231 | |
| Person / Time | |
|---|---|
| Site: | 07103047 |
| Issue date: | 12/03/2024 |
| From: | Storage and Transportation Licensing Branch |
| To: | US Dept of Transportation, Radioactive Materials Branch |
| Shared Package | |
| ML24323A229 | List: |
| References | |
| EPID L-2023-DOT-0008 | |
| Download: ML24323A231 (1) | |
Text
Enclosure UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION REPORT Docket No. 71-3047 Model No. COG-OP-30B Package French Certificate F/358/AF-96 Revision Hw
SUMMARY
By letter dated March 27, 2023 (Agencywide Documents Access and Management System
[ADAMS] Accession Number ML23255A052), as supplemented on April 26, 2024 (ML24312A342), the U.S. Department of Transportation (DOT) requested that the U.S. Nuclear Regulatory Commission (NRC) staff perform a review of the Certificate of Competent Authority No. F/358/AF-96 Revision Hw, Model No. COG-OP-30B. In your application you requested that the NRC provide a recommendation to revalidate the Model No. COG-OP-30B package for import and export use.
The NRC reviewed the information provided to DOT by Orano TN (the applicant) in its application for the Model No. COG-OP-30B package against the regulatory requirements of the International Atomic Energy Agency (IAEA) Specific Safety Requirements No. SSR-6, Regulations for the Safe Transport of Radioactive Material, 2012 edition (SSR-6 or the Regulations). Based on the statements and representations in the information provided by DOT and the applicant, the NRC staff recommends the revalidation of the French Certificate of Approval F/358/AF-96 Revision Hw for the Model No. COG-OP-30B package, for shipment as described in this safety evaluation report (SER). The staff notes, however, that the application does not provide any calculation to demonstrate that the package meets the tie down system design requirement using acceleration factors in the Specific Safety Guide (SSG)-26, table IV.2.
1.0 GENERAL INFORMATION The packaging consists of the COG-OP-30B protective overpack and a 30B type cylinder. The cylinder is filled with uranium hexafluoride (UF6) as contents. The cylindrical COG-OP-30B overpack consists of two stainless steel half-shells held together by snap-fasteners and surrounds the 30B cylinder. Each stainless steel half-shell contains phenolic foam, with balsa and red cedar woods on each end.
The 30B cylinder is manufactured from carbon steel and has an outer diameter of approximately 762 mm (30 in.), with elliptical heads on both ends, and is approximately 2070 mm in length. For filling and emptying the cylinder of the UF6 contents, there is a valve fitted on one dome, and a screw plug on the other head. A skirt on each end protects the valve and plug during normal handling.
1.1 Contents No changes were made to the approved contents for this package.
2 2.0 STRUCTURAL EVALUATION The purpose of the structural evaluation is to verify that the structural performance of the package meets the requirements of IAEA SSR-6. A summary of the staffs structural evaluation is provided below.
The NRC staff previously reviewed the structural performance of the COG-OP-30B package and recommended revalidation of French Certificate of Approval No. F/358/B(U)F-85, Revision Ab (ML003749815) that conformed to the regulations in IAEA Safety Series 6, 1985 edition, as amended 1990.
The applicant requests a revalidation of the French Certificate of Approval F/358/AF-96, Revision Hw for the Model No. COG-OP-30B to the requirements of IAEA SSR-6, 2012 edition.
A description of the staffs approach to reviewing the changes in the IAEA documents can be found in section 2.2 below.
This section of the SER documents the staffs reviews, evaluations, and conclusions with respect to the structural integrity of the amended COG-OP-30B transportation package.
2.1 Description of Structural Design The packaging consists of the COG-OP-30B protective overpack and a 30B type cylinder. The cylinder contains UF6.
The cylindrical COG-OP-30B overpack consists of two stainless steel half-shells held together by snap-fasteners and surrounds the 30B cylinder. Each stainless steel half-shell contains phenolic foam, with balsa wood on each end and red cedar wood around the rim at each end acting as impact limiters. The overpack is approximately 2,420 mm in length, approximately 1,340 mm in width, and approximately 1346 to 1356 mm in height. The maximum weight of the overpack is 1,295 kg, and the maximum weight of the package (overpack and filled 30B cylinder) is 4,232 kg.
The 30B cylinder is the containment system of the packaging, which is designed and manufactured in accordance with the International Standard ISO 7195, Packaging of Uranium Hexafluoride (UF6) for Transport, and American National Standards Institute (ANSI) N14.1, Uranium Hexafluoride - Packaging for Transport.
The 30B cylinder is manufactured from carbon steel and has an outer diameter of approximately 762 mm, with elliptical heads on both ends, and is approximately 2070 mm in length. For filling and emptying the cylinder of the UF6 contents, there is a valve fitted on one dome, and a screw plug on the other head. A skirt on each end protects the valve and plug during normal handling.
Description of the Changes affecting the Structural Design:
In this application of the COG-OP-30B package, the applicant updated the Safety Analysis Report (SAR) for the package to comply with the safety regulations of IAEA SSR-6, 2012 edition. In addition, the applicant has made numerous changes to the SAR since its last submittal which conformed to the regulations in IAEA SSR-6, 1985 edition, as amended 1990.
The major changes in the SAR that are relevant to structural design of the package are as follows:
3 Updated chapter 1, Analysis of the package under normal and accident conditions of transport Updated chapter 1-1, Differences between prototypes and the package model Updated chapter 1-4, Strength of handling and tie down elements of COG-OP-30B overpack.
Added chapter 1-7, Analysis of the temperature-dependent behaviour of COG-OP-30B and its shock-absorbing materials in a drop to incorporate evaluation of temperature-dependent behavior of the overpack and its shock absorbent materials under the drop tests, and to analyze the behavior on the valve side and the plug side of the package during the puncture tests.
Updated chapter 2, Thermal analyses of the COG-OP-30B, and chapter 3A, Containment analyses of the COG-OP-30B.
2.2 Structural Evaluation of the Amendment Evaluation of the IAEA Safety Regulations Updates:
The staff previously found that the package design had adequate structural integrity to meet the performance standards in IAEA Safety Series 6, 1985 edition, as amended 1990. Subsequently, the staff reviewed changes to the regulations in the SSR-6, 2012 edition, which with the few exceptions discussed below, mostly consists of changes that are either not applicable or have no major impacts to the structural requirements of the packages that would necessitate reconciliation with the previously revalidated design of the package.
The following paragraphs from SSR-6, 2012 edition, include revised or additional requirements that were considered for the structural evaluation:
Para. 616. The design of the package shall take into account ambient temperatures and pressures that are likely to be encountered in routine conditions of transport.
The applicant added chapter 1-7 to the SAR for evaluating the package under hot and cold ambient temperatures (-40 °C to 67.1 °C (-40 °F to 153 °F), see para. 679, below), and under variations of ambient pressure, including a reduced ambient pressure of 60 Pa-g (see para. 645, below). The performance of the package was adequately evaluated for these conditions.
Para. 621. Packages containing radioactive material to be transported by air shall be capable of withstanding, without loss or dispersal of radioactive contents from the containment system, an internal pressure that produces a pressure differential of not less than maximum normal operating pressure plus 95 kPa.
The SAR chapter 00, General Presentation, section 3 specifies that transport by road, rail and sea is permissible as per the regulations in section 2. This implies that the package is not evaluated for shipment by air. Therefore, this requirement is not applicable, and air transport is not authorized.
Para. 645. The containment system shall retain its radioactive contents under a reduction of ambient pressure to 60 kPa.
4 This requirement changes the reduced external pressure requirement from 25 kPa in para. 534 of Safety Series 6, 1985 edition, to 60 kPa. The package was previously evaluated for a reduced ambient pressure of 25 kPa, and therefore meets the less stringent requirement of 60 kPa of para. 645. The SAR chapter 1, Analysis of the package under normal and accident conditions of transport section 5.3.1 provides an evaluation of the package considering an ambient pressure of 25 kPa.
Para. 679. The package shall be designed for an ambient temperature range of -40 °C to
+38 °C (-40 °F to 100 °C) unless the competent authority specifies otherwise in the certificate of approval for the package design.
The package performance under normal and accident conditions was adequately evaluated for this temperature range, including material performance at extreme cold temperatures and maximum package temperatures (see chapter 1-6, chapter 1-7 and chapter 2, section 6).
Para. 660. A package for radioactive contents with activity greater than 105 A2 shall be so designed that if it were subjected to the enhanced water immersion test specified in para. 730, there would be no rupture of the containment system.
Based on the radioactive inventory for the package in SAR chapter 0A, Summary, it does not contain greater than 105 A2, and therefore this requirement is not applicable.
Additionally, the 1985 edition of the IAEA regulations para. 622(b) required a fissile material package to a free drop test from a height of 0.3 m on each corner or, in the case of a cylindrical package, onto each of the quarters of each rim, prior to the normal condition of transport free drop test. This requirement was eliminated from subsequent revision of the regulations. No changes were required based on the elimination of this requirement.
The staff agrees that the structural evaluation of the package adequately addresses the additional and revised requirements of SSR-6, 2012 edition.
Evaluation of the SAR Updates:
The following sections include a summary of the evaluations for the structural analyses and tests under Normal Condition of Transport (NCT) and Accident Condition of Transport (ACT) for the Model No. COG-OP-30B. The SAR chapter 1 with chapter 1-1, and 1-3 through 1-7 presents the safety analysis of the package under the NCT and ACT as per the current IAEA regulations, particularly in terms of the package's mechanical strength, and provides other structural aspects related information.
The applicant updated the SAR chapter 1, to incorporate: changes to the maximum weight of the package; changes to the mechanical properties of the materials; revised leak test release rates per chapter 3A, updated the compression test analyses, added reference to the evaluation of temperature-dependent behavior of the package under the drop tests including valve/plug impact study under the puncture test per chapter 1-7, updated reference to IAEA SSR-6, International Organization for Standardization (ISO) 7195, ANSI N14.1, and other technical references.
5 2.2.1 Lifting Analysis The package is designed to be handled in two ways; 1) enabling it to be lifted with the fork pockets at the bottom of the package supports and 2) by handling the load using the two shackles attached to the connection plates at the top of the upper half outer shell of the overpack. The applicant previously designed these lifting arrangements to support two times the weight of the package. Subsequently, to incorporate an increase in the overall weight
(~ 1.2 percent (%)), the applicant revised the analyses in the SAR chapter 1-4, section 5.
The applicant evaluated stresses at the pocket supports due to lifting operations using the forklift device. The margin of safety between the calculated stresses and the yield strength of the pocket supports was greater than 3.0 for all lifting scenarios.
The applicant evaluated the stresses that will develop in the lifting attachments from lifting operations by handling the load using the two shackles attached at the top of the package. The margin of safety between the calculated stresses and the yield strength of the lifting attachments was greater than 1.3 for all lifting scenarios.
The staff reviewed the analysis and results submitted by the applicant. The staff noted that the package is supported by the transport frame with cradles during the transport. The applicant added a requirement on the Certificate of Approval to prevent handling of the package with the transport frame using the shackles and stacking supports at the top of the package, as this is an unanalyzed condition. Based on the information provided by the applicant, the staff finds that the applicant appropriately evaluated the lifting attachments to ensure that the package meets the requirements prescribed in IAEA SSR-6, para 608 and 609.
2.2.2 Tie-Down Analysis The applicant previously designed the tie-down system by attaching the COG-OP-30B overpack directly to the transport vehicle by bolting it down at the base supports. Subsequently, the applicant modified the tie-down system by supporting and tying the overpack onto the cradles of a transport frame using steel straps as shown in figure 1.4.1 of the SAR chapter 1-4. However, the overpack is not anchored to the transport frame by bolting. In addition, the overall weight of the package has increased about 1.2% compared to its previous submittal. Consequently, the applicant revised the tie-down strength analysis in the SAR chapter 1-4, section 3, to demonstrate its compliance with the safety requirements.
In the SAR chapter 1-4, section 3, the applicant evaluates the stresses in the overpack components due to maximum working tension load in the straps, and due to acceleration forces in the lateral, longitudinal, and vertical directions. The evaluation shows that the stresses are within the permissible limits established in the SAR chapter 1, section 3, verification criteria for steel and chapter 0, table 0.3 for wood. These permissible limits are adjusted for maximum service temperature when comparing to the actual stresses. The results show that all calculated stresses are less than the permissible stress limits for the tie-down system design using the acceleration factors recommended in table IV.1 (except for rail transport in the package longitudinal direction) of the IAEA SSG-26, Revision 0, to be in accordance with most international transport regulations. However, according to the IAEA SSG-26, para IV.9 and IV.12, the package designer is responsible for ensuring that the package tie-down attachment points are designed in compliance with values acceptable to the relevant competent authorities and transport modal organizations requirements. This requires the use of acceleration factors recommended in table IV.2 of the IAEA SSG-26 for U.S. transportation, which is consistent with the U.S. regulatory requirement in 10 CFR section 71.45(b)(1).
6 The staff reviewed the strength analyses and results in the SAR chapter 1-4, section 3, and issued a request for additional information (RAI) (ML24073A363). The RAI was related to clarifying the ambiguity in the section 3.2 analysis, where the applicant evaluates tie-down attachment capacity in the longitudinal direction of the package. The applicant submitted its responses to the RAI [Orano Letter No. E-63506 dated April 26, 2024 (ML24312A342)] with the updated analysis. The applicant explained that in road and rail transport mode, the package longitudinal axis will be perpendicular to the travel direction. In this orientation, the package can withstand an acceleration of 6.8 g, which is greater than the acceleration factors of 5 g per IAEA SSG-26, table IV.2, for U.S. transport. The staff reviewed the RAI response and noted that the capacity in the longitudinal direction was based on the ultimate strength of the material, which does not meet the package design criteria requirement to limit stresses within the material yield strength. The staff noted that the capacity in the package longitudinal direction is approximately 2.5 g based on the material yield strength, which is greater than the longitudinal and lateral acceleration factors of 2 g for road and sea/water modes and lateral acceleration factor for rail mode, but less than the longitudinal acceleration factor 5 g for rail mode per IAEA SSG-26, table IV.1. Thus, the package meets the tie-down system design requirement using the acceleration factors in the IAEA SSG-26, table IV.1, provided the packages longitudinal axis be oriented perpendicular to the direction of travel in a rail transport mode. However, the applicant was not able to demonstrate that the package meets the tie-down system design requirement using the acceleration factors in the IAEA SSG-26, table IV.2, for U.S. transport.
The applicant also added a fatigue analysis in the SAR chapter 1-4, section 4, for the overpack attachments to account for alternating stresses due to vibrations during routine conditions of transport over the 40-year design life. The applicant demonstrated that the total fatigue damage
[i.e., (ratio of estimated nos. of stress cycles/allowable nos. of stress cycles)] caused to the overpacks critical welded joint by the alternating stress cycles during the transport is negligible and well below 1 over the design life.
The staff reviewed the fatigue analysis and results submitted by the applicant and concurs with the methodology and results. Therefore, the staff finds that the package meets the requirements of IAEA SSR-6, para 564 and 638. However, the package tie-down system does not satisfy design requirement using acceleration factors for U.S. transport per table IV.2 of IAEA SSG-26.
2.2.3 Normal Conditions of Transport The following sections include a summary of the changes to the structural evaluation of the package under NCT.
Drop Test:
The applicant carried out 1.2-meter drop tests previously on each of two prototypes at full scale and documented the results in the SAR chapter 1, section 5.1.2 and chapter 1-3. The applicant noted that no deformations were found on the 30B cylinders after these drops. The leak tests were carried out on the 30B cylinders after the drop tests and leak rates were measured and found to be acceptable. Subsequently, the applicant revised the permissible leak rates for the release of activity and for the criticality analyses as defined in the chapter 3A. The applicant compared the results (1.7x10-9 Pa m3 s-1 maximum leak rate) of the previous helium leak tests to the revised permissible leak rate criterion of 2.1x10-5 Pa m3 s-1 for the release of activity and 2x10-4 Pa m3 s-1 for the criticality analyses. The applicant found them to be acceptable, since the leak rates are less than the permissible leak rate criterion.
7 The staff reviewed the evaluation and concurs with the conclusion, and finds that the package meets the requirements of IAEA SSR-6, para 648 and 722.
Stacking Test:
Since the shape of the package is compatible with stacking, it required a stacking (compression) test to meet IAEA requirements. The applicant previously analyzed the package for the compression test by selecting the first option requirement (i.e., 5 times the weight of the package), as it being the most challenging for the structural integrity of the package.
Subsequently, to incorporate an increase in the overall weight (~ 1.2%) and to update some references, the applicant revised the analysis in the SAR chapter 1, section 5.1.4.
The applicant calculated the applicable stacking loads for the package based on the IAEA SSR-6 requirements. The load value of five times the mass of the package plus the self-weight was distributed uniformly to the structural elements that provide the support for the stacking. The applicant compared the resulting load to the buckling capacity of the bottom support structural elements. The applicant concluded that the capacity of the structural support elements was higher than the superimposed load since a positive margin of safety was calculated between the buckling capacity and the applied load.
The staff reviewed the analysis and results submitted by the applicant. The staff noted that the most critical element for buckling is the unstiffened portion of the overpack (OP) inner shell between the top and bottom stacking support plates. This portion of the OP inner shell is not evaluated for buckling under the compression test and staff issued an RAI (ML24073A363). The applicant conducted tests on specimens to simulate three level stacking of empty and loaded overpacks and submitted the RAI response [Orano Letter No. E-63506 dated April 26, 2024 (ML24312A342)], with the test results. The stacking test involved the equivalent of 2 times the weight of the loaded overpack stacked on top of the overpack, which was left in place for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The overpack was then inspected from the inside, particularly of the inner shell, and no deformations were identified.
The staff reviewed the test report results and found they were acceptable based on the SAR chapter 6A, instruction 9 for storage, which restricts stacking of overpacks loaded with 30B cylinders filled with UF6 to three levels. The applicant was not able to demonstrate that the package meets the stacking test requirement (the equivalent of 5 times the maximum weight of the package) per the IAEA SSR-6, para 723. Therefore, stacking of the packages is not permitted during any transport mode. However, stacking of the packages meeting the SAR chapter 6A, instruction 9 requirements is permitted while in storage.
Penetration Test:
In SAR chapter 1, section 5.1.5, the applicant had provided the analysis and results of the penetration test required by IAEA SSR-6, 1985 edition. The penetration causes a slight depression on the outer skin of the overpack, to a depth of 6 mm and a maximum diameter of 25 mm, without perforation. The elongation in the outer skin is about 10%, which is below the maximum elongation allowable for the stainless steel material. There is no change to the requirement for the penetration test in the later IAEA regulations.
The staff reviewed the analysis and results submitted by the applicant for the penetration tests and finds that the package meets the requirements of IAEA SSR-6, 2012 edition, para 648 and 724.
8 2.2.4 Accident Conditions of Transport Drop Tests:
The applicant previously performed the drop tests and structural analyses of the package to demonstrate its ability to meet the requirements of IAEA SSR-6, 1985 edition, as amended 1990. The drop tests were performed on two package specimens, each consisting of a prototype COG-OP-30B overpack and a 30B cylinder with a dummy load simulating the weight and volume of a maximum load of UF6. The physical attributes of the package are practically identical to those of the specimen except for some minor modifications introduced to the package to enhance its structural performance.
The SAR chapter 1-3 presents historic details for two series of drop tests: (1) a test series aimed at landing the valve end of the specimen onto impact targets, and (2) a test series aimed at landing the plug end of the specimen onto impact targets. Included in each series are drops for the NCT, two 9-meter drops and two 1-meter-drop puncture tests for the ACT. The drop tests demonstrated that the overpack provided adequate structural protection of the 30B cylinder and that the valve of the cylinder was never impacted during any of the drops.
Differences between prototypes and the package model:
SAR chapter 1-1 previously analyzed the differences in physical attributes, including the contents, 30B cylinder, and COG-OP-30B overpack, between the package and the specimens used in the drop tests. Subsequently, the applicant has updated chapter 1-1, Differences between prototypes and the package model, to revise the evaluation of the difference in weight between the prototype ballasts and the design package contents. The update included the actual material properties of the prototypes backed up by additional material tests and position papers, and expanded the evaluation of the overall differences between the prototypes and the design package to include more detail. The ballast used in the prototypes is a mixture of iron filings and paraffin simulating the weight and volume of the maximum UF6 load for a package.
The differences between the prototype ballasts and package contents have no effect on the behavior of the package during drops, as the ballast is in the form of a solid block with the same weight and volume as the maximum UF6 load for a package. Differences in behavior between the prototype ballast and package loads only come into play in thermal tests, which are taken into consideration in the package thermal analysis in the SAR chapter 2. The difference in overall weight between the two prototypes and the maximum weight of the design package is approximately 3%, which is taken into account when analyzing the temperature-dependent (from -40 °C (-40 °F) to the maximum temperature under NCT) behavior of the overpack in the SAR chapter 1-7.
The staff reviewed the updated analysis and consequences of differences between the prototype and the design package in the SAR chapter 1-1 and concurs with its conclusion that the effects of these differences will not degrade the structural performance of the package, and that the safety findings resulting from the drop tests are also applicable to the package.
9 Temperature-Dependent Behavior of the Package including Impact Limiters:
The new chapter 1-7 of the SAR evaluates the mechanical strength of the COG-OP-30B overpack loaded with a 30B Cylinder during a drop within a temperature range between -40 °C
(-40 °F) and the maximum bounding NCT temperature of 67.1 °C (the staff noted this to be conservative, since the maximum bounding temperature reached in NCT according to the revised chapter 2 is 54.6 °C [130 °F]). The drop tests described in chapter 1-3, took place at ambient temperature (T 20 °C [68 °F]). Based on these drop tests, the applicant studied the behavior of the overpack at both high and low temperatures.
The applicant analyzed the effect of temperatures encountered during NCT on the behavior of the overpack, where an increase in temperature potentially results, during a drop, in greater distortions of the structure (including the wood) than those recorded for drops at ambient temperatures. The applicant also analyzed the effect of low temperatures on the package strength, where a decrease in temperature potentially results in greater accelerations than those found during ambient temperature drops.
In order to analyze the impact of the punch bar on the valve and the plug, a simplified and conservative 3D numerical model is used, after benchmark using data from the relevant drop tests documented in the SAR chapter 1-3. The purpose of this analysis is to ensure that the valve is not impacted in a drop onto a punch bar scenario at a maximum bounding NCT temperature and with minimum material properties. Regarding the plug, with a conservative model of the contact case on the plug side, the objective is to determine that the forces generated in the plug remain below the limit values determined in the test report (Reference 5 in chapter 1-7), and thus comply with the leak tightness criterion for the 30B cylinder. These analyses are run using the LS-DYNA software, and post-processed with LS-PrePost v4.5.1. The models are benchmarked to the deformations resulting from a combined drop sequence from heights of 1.2 m, 9 m and 1 m onto the punch bar (on the valve side or the plug side).
The applicant demonstrated that the crushing strength and crushing rate of the impact limiter wood material for maximum bounding NCT temperatures are within allowable limits, their impacts on the distortion of the overpack is limited, and the cylinder is still protected by the overpack. The applicant also showed that the resulting clearance between the valve and the overpack for the package model is always positive, and there is no risk of the valve interacting with any part of the package. Also, the impact force on the hexagonal plug with the inner plate induces a force of 215 kN based on the conservative model, which is below the limiting value determined per the test report.
The applicant showed that acceleration calculations for the overpack and 30B cylinder at low temperatures (T = -40 °C [-40 °F]) do not affect the structural adequacy of the 30B cylinder and demonstrate that the valve is not impacted. For axial and oblique drop tests, the accelerations applied to the overpack remain below the maximum levels for a 30B cylinder provided in the report (Reference 2 in chapter 1-7) and will not cause the cylinder valve to impact the inner bottom of the overpack. With a lateral drop, it has been demonstrated that considering low temperatures has a minor influence on the levels of acceleration experienced by the overpack compared with the accelerations recorded in a lateral drop at ambient temperature. With regard to the integrity of the valve and plug during the drop onto a punch bar, the cases at maximum NCT temperatures govern as the material properties are more favorable at the lower NCT temperature.
The staff reviewed the additional analyses and results of the temperature dependent behavior of the package and impact study for the valve and the plug under the puncture test and concurs
10 with the conclusion that the effects of high and low temperature will not degrade the structural performance of the package.
Thermal Test:
The applicant performed the thermal test on one of the full-scale prototypes, previously subjected to regulatory drop tests having maximum damage under the ACT and provided a report in the SAR chapter 2-3. Finally, per the SAR chapter 1, section 5.2.3, the applicant performed a leak test of the 30B cylinder after the thermal test, which indicated the leak rate is well below the maximum permissible leak rates determined and justified for the 30B cylinder for radioactive release and criticality analyses as defined in chapter 3A.
The following results are from a summary of the applicants thermal evaluations in chapter 2 of the application:
The maximum average temperature reached by the full cylinder during regulatory drop test and fire test accident conditions is 109.35 °C (228.83 °F), the maximum valve temperature is 113.4 °C (236.1 °F), and the maximum inner pressure inside the 30B cylinder is 8.62 bar (which is less than the test pressure of 27.6 bar).
In the case of a cylinder containing heels, which covers the case of a full cylinder, the maximum temperature reached by the valve is 146.3 °C (295.3 °F) under accident conditions of transport; this temperature is less than the melting point of the valve tinning, which is 183 °C (361 °F).
The staff reviewed the statements presented by the applicant and found them to be acceptable.
Additional detailed reviews and safety evaluations by the staff on the applicants thermal evaluations are provided in section 3 of this SER. The staff determined that the application satisfies regulatory requirements of IAEA SSR-6, para 726 and 728.
Water Immersion Tests:
The applicant, in the SAR chapter 1, section 5.2.4, verified the strength of the 30B cylinder and outer shell of the overpack by analysis subjected to an outer pressure at a water depth of 15 m, with zero pressure inside the cylinder. The applicant demonstrated that the overpack suffers no damage because of immersion, and the 30B cylinder can withstand water pressure at a depth of 15 m without any damage or collapse.
For the fissile material package requirement, the applicant, in the SAR chapter 1, section 5.2.5, validated the mechanical strength of the package when immersed at a water depth of 0.9 m by comparing it to the mechanical strength of the package immersed at a water depth of 15 m in SAR chapter 1, section 5.2.4. The leak test carried out on prototype no. 1 after the NCT and ACT drop tests and thermal tests indicated a leak rate well below the permissible leak rate criterion defined in the SAR chapter 3A to maintain the sub-criticality of the damaged and immersed isolated package at a water depth of 0.9 m.
The staff reviewed the analyses and determined that the application satisfies the regulatory requirements of IAEA SSR-6, para 729, 732, and 733 for the water immersion tests.
11
2.3 Evaluation Findings
Based on the review of the statements and representations contained in the application, the staff finds that the structural design for the COG-OP-30B transport package meets the requirements of IAEA SSR-6, 2012 edition, except the following differences:
- 1) The package tie-down system satisfies structural design requirement using the acceleration factors recommended to meet the regulations for most international transport in table IV.1 of the IAEA SSG-26, Revision 0, with a condition that the package longitudinal axis be oriented perpendicular to the direction of travel in a rail transport mode. In addition, the staff notes that the tie-down system does not satisfy the package tie-down system design requirements using acceleration factors for U.S. transport per table IV.2 of the IAEA SSG-26.
- 2) The SAR chapter 6A, Instruction 9 for storage, restricts stacking of overpacks loaded with 30B cylinders filled with UF6 to three levels. The package stacking test performed by the applicant satisfies this loading configuration requirement, which is the equivalent of stacking two times the maximum weight of the package on top of the loaded package. However, the package does not contain sufficient information to satisfy the stacking test requirement using the equivalent of five times the maximum weight of the package as required by IAEA SSR-6, para 723. Therefore, stacking of the packages is not permitted during any transport mode.
However, stacking of the packages meeting the SAR chapter 6A, instruction 9 requirements is permitted while in storage.
3.0 THERMAL EVALUATION 3.1 Thermal Evaluation The applicant has provided a thermal analysis of the COG-OP-30B package, to demonstrate that the package meets the thermal performance criteria for both NCT and ACT as provided in SSR-6, 2012 edition. In the staffs thermal review of the package, it primarily considered the information provided in the documents listed in the table below, which were translated from their original French and provided by the applicant as part of the package SAR.
Reference Number Title Version DOS-22-010635-001 Chapter 00 General Presentation 1.0 DOS-22-010635-007 Chapter 0 Packaging Description 1.0 DOS-22-010635-004 Chapter 1 Analysis of Package Under Normal and Accident Conditions of Transport 1.0 DOS-22-010635-011 Chapter 2 Thermal Analysis of the COG-OP-30B Package 1.0 DOS-22-010635-014 Chapter 2-1 Thermal Analysis of the Package Under Normal Conditions of Transport 1.0 DOS-08-00117711-220 Chapter 2 - Appendix 2 (Chapter 2-2) Thermal Analyses of the Package Under Accidental Transport Conditions (Fire) 1 5188-Z-2-3 Annex 2-3 (Chapter 2-3) Report on Fire Test on COG-OP-30B Overpack 1
12 DOS-22-010635-010 Chapter 2-4 Thermal Analysis with Cylinder Heel Under Normal and Accident Conditions of Transport 1.0 3.1.1 Description of Thermal Design In SAR chapter 00 General Presentation, specifically in section 4, the applicant provides a brief overview of the COG-OP-30B package, while a more detailed description of the package is provided in SAR chapter 0 Packaging Description. The COG-OP-30B package consists of a 30B cylinder with UF6 as contents placed inside an outer enclosure designated as the COG-OP-30B overpack, which encloses the 30B cylinder. One of the primary functions of the overpack is thermal protection of the 30B cylinder.
The two half-overpacks that enclose the 30B cylinder are secured together by 10 latches.
Stainless steel half-shells make up each half-overpack and these shells are filled with a non-corrosive phenolic foam which provides thermal protection to the enclosed 30B cylinder.
In order to provide impact protection for both NCT and ACT drop scenarios, the phenolic foam at the ends of each half of the overpack is replaced by red cedar and balsa wood. Both ends of the overpack is closed, from the inside to the outside, by the following (in order): a stainless steel plate; a layer of phenolic foam (the same type used in the radial section), and an outer stainless steel plate.
The lower section of the two half-overpacks has an integral support which is used as a tie-down down to secure the package to its conveyance during transport. The lower half-overpack also has an integrated forklift pocket to further facilitate package handling. The upper section of the two half-overpacks has an integral support to facilitate stacking under storage conditions.
The applicant has considered two separate filling configurations for the 30B cylinder, a full cylinder, containing a mass of UF6 between 455 kg and 2,277 kg, and a cylinder containing UF6 heels with a mass less than 11.34 kg. The applicant maintains that the 30B cylinder containing heels is thermally limiting and, therefore, bounds the case of the full 30B cylinder in terms of thermal performance.
The applicant reports that the thermal power released by the proposed UF6 contents of the 30B cylinder is less than one watt; however, the applicant has excluded thermal inertia of the contents in their calculations, which is considered to be a conservative approach.
In chapter 2 of the SAR, section 6, the applicant provides a summary table of the maximum temperatures from the NCT thermal analysis and the ACT fire test. This section of the SAR also discusses the maximum normal operating pressure and the maximum 30B cylinder pressure under the ACT fire, as calculated and reported, respectively, by the applicant. A discussion of the NRC staffs review of the applicants calculations and findings is provided in the sections below.
3.1.2 Material Properties and Components Specifications The applicant takes into account material properties and package component specifications that include stainless steel, phenolic foam, red cedar and balsa wood, as well as the materials that make up the valve and plug attached to the 30B cylinder, specifically the lead-tin alloy brazing on the engaging threads of the valve and plug.
13 3.1.3 General Considerations As described in chapters 1, 2, 2-1, and 2-4 of the SAR, the applicant provides thermal analyses to demonstrate that the thermal requirements for NCT, found in SSR-6, 2012 edition, are met for the COG-OP-30B overpack with the 30B cylinder and a UF6 heel content.
The applicants analyses included consideration of prescribed ambient environmental conditions (including temperature and solar insolation), the minimal heat generation in the contents of the 30B cylinder, and the thermal properties and characteristics of the material specified in the package design.
The results of the applicants analyses were documented in the aforementioned SAR chapters and included the maximum temperatures (both internal and external to the package and cylinder) as well as the maximum normal operating pressure inside the 30B cylinder.
While the NRC staff previously reviewed the applicants analysis methodology and found that appropriate thermal properties of the package were considered and that the analysis methods were correctly applied to the package geometry (ML003749815), the applicant provided an updated thermal analysis that applied a new methodology and approach in the current application.
As described in chapters 1, 2, and 2-4 of the SAR, the applicant provides thermal analyses to demonstrate that the thermal requirements for ACT, found in SSR-6, 2012 edition, are met for the COG-OP-30B overpack with the 30B cylinder and UF6 contents.
The applicant performed a fire test to demonstrate that the requirements for the ACT fire exposure found in SSR-6, 2012 edition, were met. In SAR Annex 2-3, the applicant describes in detail, the fire test and package condition evaluation that was conducted, in March 1997, on a full-scale prototype of the COG-OP-30B package.
The test included a 30-minute exposure of the test unit (a full scale prototype) to a hydrocarbon fire that, according to the test report, exceeded the 800 °C (1472 °F) average flame temperature that is required for the ACT fire environment specified in SSR-6, 2012 edition. The test unit had undergone the NCT and ACT drop tests prior to the fire exposure.
The results of the test are documented in Annex 2-3 and summarized in chapter 2 of the SAR, which provides a table that reports the maximum temperatures of the contents and the plug and valve locations as well as the maximum pressure inside the 30B cylinder. The applicant indicates in the SAR that that all temperatures and pressures for the package and its contents, including the 30B cylinder, were within the allowable limits.
The NRC staff reviewed and accepted the results of the thermal (fire) test conducted by the applicant under a previous revalidation review of the COG-OP-30B package conducted in September 2000 (ML003749815).
14 3.1.4 Thermal Evaluation under Normal Conditions of Transport The applicant summarizes the results of the NCT evaluations for the package in chapter 1 of the SAR, with detailed descriptions of the thermal analyses completed presented in chapters 2, 2-1 and 2-4 of the SAR.
The applicant provided an updated thermal analysis of the COG-OP-30B package that used an updated calculation code, which is considered by the staff to be a new analysis method.
The analyses performed by the applicant for NCT included the environmental and boundary conditions as well as thermal performance criteria specified in IAEA SSR-6, 2012 edition, specifically paragraphs 654 through 658.
In chapter 2 of the SAR, the applicant reports results of the NCT thermal analyses it conducted (which assumed an empty 30B cylinder, with the thermal inertia of the contents not accounted for), reporting the that the maximum temperature of the outer wall of the overpack under NCT as 54.6 °C (130 °F). This temperature is below the regulatory limit of 85 °C (185 °F) (SSR-6, 2012 edition, paragraph 655). The applicant also reported the maximum temperature reached by the UF6 under NCT is 46.2 °C (115 °F). This is below the specified maximum service temperature of 121 °C (250 °F) for the 30B cylinder.
The applicant reported the results of a calculation of the maximum pressure in the 30B cylinder, from chapter 3A of the SAR (specifically section 3), under NCT as 1.030 bar which is below the maximum design pressure of 13.8 bar reported by the applicant for the 30B cylinder.
The staff reviewed the applicants new NCT analysis method and has reasonable assurance that the methodology, as presented, provides an accurate depiction of the thermal performance of the package. The staff further found that their evaluation demonstrates that the effects of NCT will not reduce the effectiveness of the package design. Further, the staff verified that no temperature or pressure limits will be exceeded for NCT and, therefore, concluded that the package design meets the NCT thermal requirements found in the applicable paragraphs of SSR-6, 2012 edition.
3.1.5 Thermal Evaluation under Accident Conditions of Transport The applicant summarizes the results of the ACT evaluations for the package in chapter 1 of the SAR, specifically section 5.2.3, with detailed descriptions of the thermal analyses and testing completed presented in chapters 2, 2-2, 2-3, and 2-4 of the SAR.
The temperature and pressure results reported by the applicant for the thermal analyses of the COG-OP-30B package in section 6 of chapter 2 of the SAR remain essentially identical to those reported in the previous application provided to the NRC for a revalidation review in February 1999 (ML023100378). The NRC staff concluded that applicants testing and analyses of the thermal performance of the COG-OP-30B package under the ACT requirements found in IAEA regulations at the time (Safety Series 6, 1985 edition, as amended 1990) were adequate (ML003749815).
Based on the previous review and approval and the staffs current review of the application under the requirements of IAEA SSR-6, 2012 edition, the staff has adequate assurance that the package design meets the thermal requirements for ACT found in the applicable paragraphs of SSR-6, 2012 edition.
3.2 Evaluation Findings
15 Based on its review of the statements and representations in the application, the staff concludes that the thermal design has been adequately described and evaluated, and there is reasonable assurance that the thermal performance of the package design meets the applicable regulatory requirements of IAEA SSR-6, 2012 edition.
4.0 CONTAINMENT EVALUATION 4.1 Containment Evaluation The applicant, in chapters 0, 00, 1, and 3A of the SAR, has provided a description of how the COG-OP-30B packaging which encloses a 30B cylinder for transport satisfies the requirements in IAEA SSR-6, 2012 edition, specifically paragraphs 229, 659, 661, and 662.
4.1.1 Description of Containment System In chapters 0 (section 5) and 3A of the SAR, the applicant describes the containment vessel of the package, consisting of the 30B cylinder and two penetrations, the valve and the plug. The cylinder remains sealed via metal-to-metal contact within the valve and by lead-tin alloy brazing of the engaging threads on the valve and plug. Elevated temperatures will not affect the integrity of any of the 30B cylinder components under either NCT or ACT. The COG-OP-30B overpack is closed by positive fastening devices and therefore, when the 30B cylinder is securely enclosed within the overpack, opening the cylinder valve is physically impossible.
The applicant states that the 30B cylinder is designed to conform with the applicable ANSI and ISO standards named in SER section 4.1.4 below.
4.1.2 General Considerations The containment boundary for the COG-OP-30B package, which, as described above, consists of the 30B cylinder as well as valve and plug, remains unchanged from the previous application for revalidation and, therefore, the findings of the previous review and approval provided by the NRC (ML003749815), remains valid for the current package design.
4.1.3 Pressure Calculations for the COG-OP-30B Package The applicant, in SAR chapter 3A, provided revised pressure calculations for the 30B cylinder during NCT with various configurations of contents, including fully loaded with UF6 as well as loaded only with UF6 heels.
In section 3 of chapter 3A, the applicant provides the detailed pressure calculation that yields the following results:
The maximum total pressure in the 30B cylinder under NCT, including impurities in the contents, is calculated as 1.028 bar (14.9 psi), with the pressure over one year of transport, which accounts for the in leakage of air at the maximum leak rate, is calculated as 1.030 bar (14.93 psi). This value is below the maximum operating pressure of the 30B cylinder, which has been cited by the applicant as 13.8 bar (200 psi).
The staff reviewed the calculation and finds that the results are acceptable.
16 4.1.4 Leakage Rate Tests for the COG-OP-30B Package Section 4 Maintenance Program of the French Certificate of Approval No. F/358/AF-96, Revision Hw, states that package maintenance is to be performed in accordance with chapter 7A, Acceptance Tests and Maintenance Programme (DOS-088-00117711-700, rev. 4) of the SAR, and the following references:
(1)
ISO 7195:2020, Packagings for the transport of uranium hexafluoride (UF6) and (2)
ANSI, N14.1 - 2012, Uranium Hexafluoride - Packaging for Transport The French Certificate of Approval further describes, in section 3, Measures to be Taken by the Consignor Prior to Shipment of Package that the package must be used in accordance with procedures complying with chapter 6A, Instructions for the Use of the Packaging, of the SAR. Chapter 6A provides instructions on package acceptance (section 3), unloading, filling and emptying of the 30B cylinder (sections 4, 5, and 6, respectively), and loading and inspecting of the 30B cylinder before shipping (section 7).
Chapter 6A also indicated that all leakage testing is to be carried out in accordance with ISO 12807:2018, Safe Transport of Radioactive Materials - Leakage Testing on Packages.
4.2 Evaluation Findings
Based on its review of the statements and representations in the application, the staff concludes that the containment design has been adequately described and evaluated.
The staff further reviewed the pertinent fabrication, maintenance, periodic and pre-shipment leak testing descriptions for the 30B cylinder and determined that they are adequate to ensure that the COG-OP-30B package meets all containment requirements of IAEA SSR-6, 2012 edition.
5.0 CRITICALITY 5.1 Criticality Evaluation 5.1.1 Description of Criticality Design As noted in previous approvals, the COG-OP-30B overpack and the 30B cylinder do not have any specific engineered features to prevent an inadvertent nuclear criticality, as is typical of UF6 cylinders. Criticality prevention is maintained by limiting the fissile material quantities, allowed enrichment, and the hydrogen to uranium ration (H/U). The 30B cylinders are required to remain leak-tight to water intrusion under normal and hypothetical accident conditions.
The applicant has made no modifications to the present configuration of the COG-OP-30B specified in chapters 5A and 5A-1 (ref. DOS-08-00117711-500, Rev. 0 and DOS-08-00117711-510, Rev. 0, respectively) and are not part of this safety evaluation. The applicant has added a new chapter 5A-2 (ref. DOS-20-034609-16, Version 1.0) to provide a validation of APOLLO2-MORET4 within the CRISTAL V0.2 and V1.2 criticality safety code package. This validation is intended to demonstrate the safety of a full 30B cylinder filled with UF6, including cylinder heels of hydrated uranyl fluoride (UO2F2), as well as the safety of empty 30B cylinders, which contain cylinder heels of hydrated UO2F2.
17 Chapter 5A-2 was reviewed for completeness of information and consistency. The information, parameters and dimensions provided were sufficient to perform a review and are consistent throughout all the applicable chapters. Where appropriate, standards are identified and utilized.
5.1.2 Fissile Material Contents The COG-OP-30B overpack and 30B cylinder are used to transport UF6 up to a maximum enrichment of 5.0 wt% U-235. The masses of UF6 allowed for a full 30B cylinder is greater than or equal to 455 kg and less than or equal to 2277 kg. The mass of UF6 allowed as heels is less than or equal to 11.34 kg.
The heels are composed of non-volatile reaction products because of reaction with the steel walls as well as the hydrolysis of UF6 due to the entry of damp air that may occur during filling or emptying of the cylinder, leading to the creation of hydrogen fluoride (HF) gas and solid UO2F2 deposits. As noted above, the heels have a maximum mass of 11.34 kg UF6. The applicant has conservatively modeled this UF6 mass as UO2F2 in their analysis due to its higher density and greater reactivity. Staff finds that this is an appropriate conservative assumption since this maximizes the keff of the modeled system.
For the full 30B cylinder there are two forms of uranium bearing material; UF6 in the form of UF6-0.1HF, and the heels in the form of UO2F2
- 3H2O. For the empty 30B cylinder the uranium bearing material is assumed to be UO2F2 with optimal water moderation.
5.1.3 General Considerations 5.1.3.1 Model Configuration The applicant evaluated the 30B cylinder in both the full and empty configurations and used the models that are unchanged by this revalidation. All fissile materials are modelled as homogeneous mixtures with water.
5.1.3.2 Computer Codes and Cross-Section Libraries The applicants criticality calculations were performed using APOLLO2-MORET4 computer code with the CRISTAL V0.2 and V1.2 criticality safety code packages. These two versions of the CRISTAL package are based on the JEF2.2 cross-sectional libraries using 172 neutron energy groups (i.e., XMAS mesh). The applicant noted only minor differences between the two versions of the CRISTAL packages, and therefore applied the validation results of the CRISTAL V1.2 criticality package for the CRISTAL V0.2 package. Staff finds this acceptable since they are based on the same code package and are using the same cross-section data set.
5.1.3.3 Demonstration of Maximum Reactivity The applicant evaluated the maximum reactivity of the 30B cylinder configurations in two parts.
First, an evaluation of the fissile materials and structural materials using the APOLLO2 code, Version 2.5, Patch 5. Secondly, a calculation of keff for the package, using the MORET4.B.4 Monte Carlo code.
For the fissile and structural material evaluation, all fissile material was modeled as homogeneously moderated. The results provided the infinite multiplication factor (k) and the material buckling (B2m) over the set of 172 neutron energy groups effective cross-sections.
18 For the keff calculations, the effective multiplication factor was calculated assuming homogeneously moderated fissile material.
5.2 Benchmark Evaluations and Validation The validation of the CRISTAL V1.2 criticality code package for the COG-OP-30B package and the 30B cylinder containing enriched UF6 and UO2F2, and was performed in four steps:
1.
Defining the area of applicability based on the key parameters of the package, including the H/U ratio, fissile isotope enrichment, reflector conditions, the presence of neutron absorbers, etc.
2.
Selection of a set of similar critical experiments to the package configuration by identifying the main neutron parameters that have the most impact on the package.
3.
Modeling the critical experiments and calculating the keff. The applicant identified a large number of experiments for comparison as noted in reference 7 of chapter 5A-2 (DOS-20-034609-16). This data was compiled into reference 8 of the same chapter, and includes all of the data related to validation of the APOLLO2-MORET4 code with the CRISTAL V1.2 code package, including: the experimental value of keff, the benchmark, the slowing down density (q4ev), the calculated keff using APOLLO2-MORET4, the calc using APOLLO2-MORET4, the combined determined by combining the calculated and experimental uncertainties, and the mean C-E value and its related standard deviation.
4.
Analyzing the results to determine any bias in the results.
5.2.1 Area of Applicability The validation described in chapter 5A-2 covers the use of the APOLLO2-MORET4 code in the CRISTAL V1.2 criticality code package based on the use of the CEA93-V6 library with the XMAS 172-group energy mesh based on the JEF2.2 cross-sectional data set. The applicant identified parameters of the full and empty 30B cylinders assuming a maximum enrichment of 5.0 wt% 235U with water moderation and reflection by the steel in the cylinder wall as well as surrounding water.
5.2.2 Similarity Study The similarity of the selected critical experiments to the COG-OP-30B package was accomplished by comparing the key parameters (e.g., enrichment, H/U, etc.) that have the most impact on the package. These comparisons were documented in references 7 and 8 of chapter 5A-2 and based primarily based on descriptive inputs such as the type of fissile material, the physical and chemical forms, and the isotopic composition. These are specified in sections 4.2.2.1 and 4.2.3 in chapter 5A-2 of the application.
5.2.3 Comparison of Calculated and Experimental Results The applicant tabulated the results of their comparison in section 4.3 of chapter 5A-2 of the application. For the full 30B cylinder, which is a low enriched and low moderation uranium system, the validation overestimated the calculated keff values. Although there was only one experiment for this comparison, based on the maximum reactivity calculated for an infinite array of package (i.e., keff +3 = 0.914) staff finds that this represents a large safety margin over the
19 accepted safety margin of keff 0.95, and therefore does not affect the ability of the COG-OP-30B package to maintain subcriticality.
For the empty 30B cylinder comparison the validation overestimated the calculated keff values using three similar experiments. Staff finds that this comparison is adequate to maintain the subcriticality of the COG-OP-30B package for calculated results.
5.3 Conclusion Based on the representative experiments selected from the validation database of the CRISTAL V1.2 criticality code package, staff finds that the applicant has adequately addressed the validation of the COG-OP-30B for use without any calculation bias due to the conservatisms of their analysis. Based on staff review of the information and analyses by the applicant, the staff has determined that there is reasonable assurance that the package design will meet the applicable IAEA criticality safety requirements using the validation presented in chapter 5A-2 for the full 30B cylinder filled with UF6 and containing heels in the form of hydrated UO2F2 as well as the empty 30B cylinder containing heels in the form of optimally moderated UO2F2.
6.0 SHIELDING This package does not include transportation of any spent fuel. Thus, no shielding evaluation was performed.
7.0 MATERIALS EVALUATION The purpose of the staffs materials evaluation for the U.S. DOT revalidation of the French Competent Authority (ASN) Certificate of Approval No. F/358/AF-96 for the Model No.
COG-OP-30B package is to assess whether the package application adequately describes and evaluates package materials for ensuring compliance with the requirements of the IAEA SSR-6, Regulations for the Safe Transport of Radioactive Material, 2012 edition. The NRC staff performed its materials evaluation for the revalidation of the COG-OP-30B package by following the technical guidance in NUREG-2216, Standard Review Plan for Transportation Packages for Spend Fuel and Radioactive Material, August 2020 (ML20234A651).
As documented in its September 13, 2000, SER (ML003749815), the NRC staffs prior technical review of the COG-OP-30B package application determined that it meets the requirements of the 1985 version IAEA regulations for safe transport of radioactive materials that were in effect at that time; accordingly, the staff recommended that the package certificate be revalidated by the DOT. The only significant changes in the application from the prior NRC-approved version, as it relates to the package materials, are some adjustments to the tensile properties for the austenitic stainless steel specified for the COG-OP-30B overpack. However, notwithstanding the limited scope of changes in the package application affecting package materials, the staff performed its review to ensure that the evaluation of all package materials is acceptable for demonstrating compliance with updated requirements in the 2012 edition of IAEA SSR-6.
7.1 Drawings and Description of Package Chapter 0 of the COG-OP-30B application provides the packaging drawings and a general description of the package. The staff reviewed the drawings and the general description to determine whether these provide an adequate basis for performing the materials review. The general description includes information concerning the package contents, packaging components, component assemblies, component design functions, and materials of
20 construction. The COG-OP-30B package is a Type A package for unirradiated fissile nuclear material (i.e., a Type AF package). The radioactive contents of the COG-OP-30B package, as authorized in the French certificate of approval, consists of UF6 enriched to a maximum 5%
uranium-235. The staff identified that the design and construction of the packaging, with respect to materials, fabrication process, and associated material qualification testing and examination requirements, have not changed significantly since prior the U.S. DOT revalidation the French certificate of approval based on the September 13, 2000, NRC SER (ML003749815).
The main components of the COG-OP-30B packaging include the COG-OP-30B protective overpack and the 30B containment cylinder. The COG-OP-30B overpack is a protective outer enclosure that holds the 30B cylinder. The COG-OP-30B overpack consists of welded stainless steel plate that encases organic materials, including polymeric foam for thermal insulation and the specified types of wood for absorption of kinetic energy associated with the regulatory impact tests. Additional subcomponents and associated materials for the overpack are described in further detail below in section 7.2 of this SER.
The 30B cylinder is a carbon steel cylinder loaded with the UF6 contents and constitutes the containment boundary of the package. The function of the COG-OP-30B overpack is to provide structural and thermal protection for the interior 30B cylinder to ensure the leaktightness of the cylinder and subcriticality for normal and accident conditions of transport, and to provide structural support of the package for routine handling. The COG-OP-30B overpack is specifically designed to withstand the direct effects of the regulatory impact tests associated with normal and accident conditions of transport and the regulatory fire test associated with accident conditions of transport to ensure the leaktightness of the 30B cylinder and the subcriticality of the UF6 contents. The function of the 30B cylinder is to contain the UF6 contents, and accordingly, the 30B cylinder constitutes the leaktight containment boundary for the package; however, the 30B cylinder is not itself designed to directly withstand any of the regulatory drop tests or the fire test associated with normal and accident conditions of transport since the COG-OP-30B overpack provides the needed structural and thermal protection for the 30B containment cylinder to withstand these tests. The 30B cylinder includes a valve and plug to facilitate to the loading and unloading of the UF6 contents.
The NRC staff reviewed the COG-OP-30B package design drawings and the general description of the package contents, packaging components, component assemblies, component design functions, and materials of construction. The staff verified that the application provides an adequate general description of the package contents, packaging components, component assemblies, component safety functions, and materials of construction to support the materials review of the COG-OP-30B package.
Based on the foregoing evaluation, the staff finds that the design drawings and the general description of the packaging components in the application are acceptable. Therefore, the staff finds that the package meets the requirements in paragraph 640 of IAEA SSR-6.
7.2 Codes and Standards for Materials, Fabrication, and Examination Chapter 0 of the COG-OP-30B application describes the use of codes and standards for materials, fabrication, and examination of COG-OP-30B packaging components, including the COG-OP-30B overpack and the 30B cylinder.
The materials used for construction of the COG-OP-30B overpack subcomponents include welded austenitic stainless steel plate material for the overpack structure to support the interior 30B cylinder and to encase the polymeric foam and wood materials; polymeric foam for thermal
21 insulation (encased in the welded stainless steel plate); the specified types of wood for absorption of kinetic energy associated with the regulatory impact tests (also encased in the welded stainless steel plate); an elastomer gasket to prevent intrusion of water and dirt into the interior of the overpack; and an elastomer pad for support of the 30B cylinder inside the overpack. Closure devices for the overpack include subcomponents fabricated from precipitation hardened martensitic stainless steel. The wood and polymeric foam are encased in the welded stainless steel plate material to protect them from water intrusion. The application states that all welding process are qualified in accordance with section IX of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel B&PV code. The staff confirmed that the application includes adequate specifications for the packaging materials, including standard metal product specifications and alloy grades based on the French national system of standards. The staff also confirmed that section IX of the ASME B&PV code provides acceptable standard requirements for the qualification of welding procedures and welding personnel to provide assurance that welding processes will produce weld joints that meet the applicable structural design requirements. The staff verified that the application includes acceptable standard methods and acceptance criteria for nondestructive examination (NDE) of overpack welds to ensure that as-fabricated welds have mechanical properties at least equal to the base metal.
The 30B cylinder, which is carried inside the protective overpack, includes the main cylinder body (cylinder shell, cylinder bottoms, and support skirts) fabricated from welded carbon steel plate, a cylinder plug made of aluminum bronze, and a valve, where the valve body is made of aluminum bronze. The application also describes the metallic and non-metallic materials used for the other valve subcomponents (stem, packing components, etc.). The staff noted that, generally, all aspects of the design, materials, fabrication, weld NDEs, testing, in-service inspection, and maintenance of the 30B cylinder are directly controlled by the established consensus standard, ANSI N14.1, American National Standard for Nuclear Materials -
Uranium Hexafluoride - Packagings for Transport. As addressed in section A.6 of NUREG-2216, the DOT requires, pursuant to 49 CFR 173.420(a)(2)(i), that UF6 packagings must be designed, fabricated, inspected, tested and marked in accordance with(i) American National Standard N14.1 in effect at the time the packaging was manufactured. The application identifies American Society for Testing and Materials (ASTM) standard material specifications for the carbon steel plate used to fabricate the cylinder body and includes standard alloy specifications for the 30B cylinder plug, valve body, and other metallic components of the cylinder valve. The staff confirmed that all material specifications for the 30B cylinder, as identified in the application, meet the requirements on ANSI N14.1. The staff also confirmed that, as per the requirements ANSI N14.1, welding procedures and welding personnel are qualified in accordance with the requirements of the ASME B&PV code section IX, and weld NDE for the 30B cylinder must meet the NDE performance and personnel qualification requirements and acceptance criteria of ANSI N14.1. In addition, ANSI N14.1 requires that the cylinder receive a hydrostatic pressure test to ensure pressure-retaining structural integrity and a pneumatic leak test of connections, fittings, and valve components.
The staff determined that the information concerning the material types, standard metal alloy product specifications, weld fabrication processes, and associated weld NDE requirements for the COG-OP-30B packaging components has not changed significantly from the previous version of the application that was revalidated by the DOT based on the September 13, 2000, NRC SER (ML003749815). The staff also determined that the applicants use of codes and standards with respect to packaging component materials, fabrication, and weld NDE remains acceptable for ensuring compliance with ANSI N14.1 and paragraph 640 of IAEA SSR-6.
22 Based on the foregoing evaluation, the staff finds that the applicants use of codes and standards for materials, fabrication, and examination of the COG-OP-30B packaging components are acceptable. Accordingly, the staff finds that the package meets the requirements in paragraph 640 of IAEA SSR-6.
7.3 Mechanical Properties of Materials Chapters 0 and 1 of the application describe the mechanical properties of the packaging materials that are used in the structural evaluation of the package for normal and accident conditions of transport. The mechanical properties listed in the application for metallic structural components include minimum required tensile properties (yield stress, tensile strength, and percent elongation), elastic modulus, and Poissons ratio. The staff reviewed the tensile properties for the carbon steel plate used for the 30B cylinder and confirmed that they are consistent with the values listed in the applicable ASTM standard material specification. For the COG-OP-30B overpack, the staff verified that the tensile properties for the stainless steel materials that are controlled by French material specifications are generally consistent with the properties for the corresponding stainless steel alloy types included in U.S. stainless steel product specifications. The staff also confirmed that the tensile properties used for the structural evaluation are adjusted for temperature based on the highest and most conservative temperature condition for the applicable regulatory test condition, where yield and tensile strength properties are the lowest.
The only significant changes to the material information in the application, as compared to the previous version of the application that was revalidated by the DOT based on the September 13, 2000, NRC SER (ML003749815), include some adjustments to the minimum requirements for the yield and tensile strength of the austenitic stainless steel specified for several the subcomponents of the overpack structure. The staff reviewed the changes in the yield and tensile strength requirements for the subject stainless steel subcomponents and confirmed that they are generally consistent with the corresponding properties for the equivalent stainless steel alloy type based on U.S. stainless steel product specifications. However, based on review of the information presented in the application, the staff could not conclusively determine the reason for the change in these tensile properties. Therefore, in an RAI, the staff requested that the applicant explain the reason for the change in the tensile properties for the identified stainless steel subcomponents.
In its response to RAI M-1 the applicant stated that following a request from the French Competent Authority (ASN), the change was implemented to improve the analysis of the representativeness of the package prototypes used for testing. The applicant indicated that the application has been updated to include the analysis of the impact of differences between the package prototype and the package model based on the updated minimum tensile properties.
The applicant identified that the as-built mechanical properties of all stainless steel subcomponents in the package fleet meet the updated minimum tensile properties. The staff reviewed the applicants RAI response and found its explanation for the updated stainless steel tensile properties to be credible since this type of stainless steel can have a range of minimum requirements for these properties based on the section thickness and product specification. As addressed above, the staff confirmed that the updated tensile properties are generally consistent with those for the equivalent stainless steel alloy type included in U.S. stainless steel product specifications. Therefore, the staff determined that the updated stainless steel tensile properties are acceptable.
23 Section 1-6 of the application includes a fracture toughness evaluation of the carbon steel plate material used for the 30B cylinder. This evaluation is performed to ensure that the 30B cylinder has adequate resistance to brittle fracture at the lowest service temperature. Since the 30B cylinder carbon steel plate has a ferritic microstructure, it undergoes a ductile to brittle transition as a function of decreasing temperature; therefore, it must receive Charpy impact testing in accordance with the requirements of ANSI N14.1 to verify its impact toughness characteristics at the lowest service temperature. The applicants fracture toughness evaluation is based on standard requirements and associated acceptance criteria for Charpy impact tests to verify the impact toughness of material at material temperatures lower than the lowest service temperature for the package. The staff noted that the fracture toughness evaluation for the carbon steel plate used in the 30B cylinder has not changed from the previous version of the application that was revalidated by the DOT based on the September 13, 2000, NRC SER (ML003749815). The staff confirmed that the Charpy impact test methods and acceptance criteria for the carbon steel plate, as described in the application, remain acceptable for ensuring that the material has adequate resistance to brittle fracture at the lowest service temperature. The staff also confirmed that the impact test methods and acceptance criteria meet the Charpy impact test requirements of ANSI N14.1. Therefore, the staff determined that fracture toughness evaluation for the carbon steel plate material used for the 30B cylinder is acceptable.
Based on the foregoing evaluation, the staff finds that the mechanical properties of the packaging materials used in the package structural evaluation and the fracture toughness evaluation of the carbon steel plate material for the 30B cylinder are acceptable. Accordingly, the staff finds that the package meets the requirements in paragraphs 616, 639, 640, and 648 of IAEA SSR-6.
7.4 Thermal Properties of Materials Chapters 0 and 2 of the application provide thermal properties of the packaging materials used in the package thermal and containment analyses. The thermal properties reported in the application include density, thermal conductivity, specific heat capacity, emissivity, and solar absorptivity coefficient. The staff noted that the thermal properties of the packaging materials have not changed from the previous version of the application that was revalidated by the DOT based on the September 13, 2000, NRC SER (ML003749815). The staff reviewed the thermal properties of the packaging materials and verified that they are generally consistent with the values available in the technical literature. The staff confirmed that all packaging materials demonstrate acceptable thermal performance considering the maximum temperatures reported for the components based on analysis of regulatory thermal tests for normal and accident conditions of transport.
Based on the foregoing evaluation, the staff finds that the thermal properties of the packaging materials used in the package thermal and containment analyses are acceptable, and the package meets the requirements in paragraphs 616, 639, and 640 of IAEA SSR-6.
24 7.5 Corrosion Control, Chemical, and Galvanic Reactions The description of the packaging materials in chapter 0 of the application states that all overpack materials are physically and chemically compatible with each other. The application also states that polymeric foam used for thermal insulation has no reaction with the stainless steel used for the overpack structure. The application indicates that the radiation emitted by the UF6 contents has no measurable effect on any packaging materials.
The staff reviewed the material contacts for COG-OP-30B overpack and confirmed that there would be no adverse chemical or galvanic reactions due to contacts between dissimilar materials in the overpack. The organic materials of the overpack, including the polymeric foam and wood, are adequately protected from exposure to outdoor air and precipitation since they are encased in the welded stainless steel plate. The outer surfaces of the welded stainless steel plates of the overpack are exposed to outdoor air and precipitation during transport, and while not susceptible to general corrosion, these exposed surfaces may be susceptible to localized corrosion effects (e.g., pitting and crevice crevice) and stress corrosion cracking (SCC) if there is significant tensile stress in the weld plate material. The staff confirmed that the package maintenance program includes criteria for visual inspection the stainless outer surfaces of the overpack to ensure the absence of cracks and other unacceptable flaws. The staff noted that the maintenance program also includes checks of the weight of the overpack to ensure the absence of water in the polymeric foam or in the wood. The staff determined that these maintenance inspections are adequate to ensure that the overpack maintains its functional capabilities of providing structural and thermal protection to the interior 30B cylinder during the service life of the packaging.
The staff noted that the 30B carbon steel containment cylinder inside the overpack may be susceptible to general corrosion since the application does not specify the use of a protective coating for corrosion mitigation. With respect to control and management of potential corrosion of the carbon steel 30B cylinder, the staff verified that the use of elastomer support pad inside the overpack to separate the cylinder from the stainless steel interior provides adequate protection against galvanic corrosion. Further the staff noted the elastomer gasket around the boundary of the overpack opening is specifically designed to prevent the intrusion of water and dissolved compounds from dirt and road debris, thereby maintaining a clean and dry environment for the cylinder inside the overpack. Such a protective interior environment is suitable to ensure that the carbon steel cylinder is adequately protected against significant corrosion inside the overpack during normal package operation. The staff also verified that the ANSI N14.1 standard provides suitable in-service inspection criteria for management of corrosion effects during the service life of the packaging, such that the containment design function of the cylinder is adequately maintained.
Based on the foregoing evaluation, the staff finds that the design, construction, and maintenance of the COG-OP-30B package adequately protects against adverse chemical and galvanic reactions that may affect the ability of the package to perform its safety functions, and the package meets the requirements in paragraph 614 of IAEA SSR-6.
25 7.6 Radiation Shielding and Criticality Safety Due to the relatively low radioactivity of the UF6 contents, there are no dedicated neutron or gamma shielding materials used in the design and construction of the COG-OP-30B packaging.
All packaging materials that are relied upon for structural integrity, thermal insulation and containment of UF6 ensure that radiation levels, as analyzed for radiological design of the package, are within their applicable regulatory limits.
The subcriticality of the package UF6 contents is ensured by the leaktightness and pressure-retaining integrity 30B containment cylinder. The COG-OP-30B package does use any internal support structures or dedicated neutron absorbing materials for maintaining the subcriticality of the UF6 contents. The criticality safety analysis of the package ensures that subcriticality of the UF6 contents is maintained for normal and accident conditions of transport.
Based on the foregoing evaluation, the staff finds that the package materials are acceptable for maintaining the UF6 contents in its analyzed configuration during normal and accident conditions of transport, and the package meets the requirements in paragraphs 673, 682, and 726, and 728 of IAEA SSR-6.
7.7 Materials Evaluation Findings Based on review of the statements and representations in the application, the NRC staff concludes that the applicant adequately described and evaluated the materials used in the COG-OP-30B package, and the package meets the requirements of IAEA SSR-6.
8.0 QUALITY ASSURANCE EVALUATION The purpose of the quality assurance (QA) [i.e., management system in IAEA SSR-6, 2012 edition] review is to verify that the packaging incorporates adequate quality controls in its design, manufacture, operation, and maintenance. The staff reviewed the description of the QA program for the Model No. COG-OP-30B package against the standards in the IAEA SSR-6, 2012 edition.
8.1 Staffs Evaluation of the Quality Assurance Program The applicant developed and described a QA program for activities associated with transportation packagings 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, 2012 edition and is based on ISO 9001:2015 edition, Quality management systems Requirements, ANSI N14.1-2019 "Uranium Hexafluoride - Packagings for Transport, and other applicable standards.
The staff finds the QA program description acceptable, since it allows implementation of the associated QA program for the design, procurement, fabrication, assembly, testing, modification, maintenance, repair, and use of the Model No. COG-OP-30B transportation package.
The staff finds, with reasonable assurance, that the QA program for the COG-OP-30B transportation packaging:
a.
meets the requirements in IAEA SSR-6, 2012 edition, and
26 b.
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, adequate to ensure that the package will allow safe transport of the radioactive material authorized in this approval.
8.2 Evaluation Findings
Based on review of the statements and representations in the Model No. COG-OP-30B package application and as discussed in this SER section, the staff has reasonable assurance that the COG-OP-30B package meets the requirements in IAEA SSR-6, 2012 edition. The staff recommends revalidation of French Competent Authority Certificate No. F/485/AF-96.
CONDITIONS Specific limitations and conditions are specified for approval of this application and use of the COG-OP-30B package. The following limitations and features are listed here as recommended conditions of approval:
- 1) The package tie-down system satisfies structural design requirement using the acceleration factors recommended to meet the regulations for most international transport in table IV.1 of the IAEA SSG-26, Revision 0, with a condition that the package longitudinal axis be oriented perpendicular to the direction of travel in a rail transport mode. In addition, the staff notes that the tie-down system does not satisfy the package tie-down system design requirements using acceleration factors for U.S. transport per table IV.2 of the IAEA SSG-26.
- 2) Stacking of the packages is not permitted during any transport mode. However, stacking of the packages meeting the SAR chapter 6A, instruction 9 requirements is permitted while in storage.
CONCLUSION Based on the statements and representations presented in the SAR and supplemental information, the staff agrees that the package meets the standards in IAEA SSR-6, 2012 edition but does not provide any calculation to demonstrate that the COG-OP-30B package meets the tie down system design requirement using acceleration factors in the SSG-26, table IV.2 for U.S. transport. The staff recommends that DOT revalidate French Certificate of Approval No.
F/358/AF-96 Revision Hw, for import and export use with the conditions specified above.
Issued with letter to R. Boyle, U. S. Department of Transportation.