ML23319A277
| ML23319A277 | |
| Person / Time | |
|---|---|
| Site: | 07103098 |
| Issue date: | 10/31/2023 |
| From: | Shaw D Orano TN Americas, TN Americas LLC |
| To: | Boyle R Office of Nuclear Material Safety and Safeguards, US Dept of Transportation (DOT), Office of Hazardous Materials Safety |
| Shared Package | |
| ML23319A273 | List: |
| References | |
| A33010, L-2023-DOT-0002, E-62897 | |
| Download: ML23319A277 (1) | |
Text
Orano TN 7160 Riverwood Drive Suite 200 Columbia, MD 21046 USA Tel: 410-910-6900 Fax: 434-260-8480 October 31, 2023 E-62897 U.S. Department of Transportation Attn: Mr. Richard W. Boyle Pipeline & Hazardous Materials Safety Administration Radioactive Materials Branch 1200 New Jersey Avenue, S.E.
East Building, PHH-20 Washington, DC 20590
Subject:
Supplement to Application for Revalidation of Competent Authority Certification J/2009/AF, Model No. GP-01
Reference:
[1] Letter dated May 24, 2023, from Norma Garcia Santos (U.S.
Nuclear Regulatory Commission) to Richard W. Boyle (U.S.
Department of Transportation), Subj: Request For Additional Information For Review Of The Certificate Of Compliance No.
3098, Model No. GP-01 (EPID L-2023-DOT-0002)
[2] TN-Americas letter E-62515 dated July 25, 2023, Subj:
Additional Information for Review of the Application for Revalidation of Competent Authority Certification J/2009/AF, GP-01.
[3] U.S. Nuclear Regulatory Commission, Conversation Record dated August 30, 2023 (Accession No. ML23300A074), including enclosures titled Staff's feedback on unacceptable responses of the RAIs related to the materials evaluation, Model No. GP-01 (Accession Nos. ML23300A076 and ML23300A078)
[4] U.S. Department of Transportation, Competent Authority Certification, USA/0833/AF, Revision 1
[5] Competent Authority of Japan, Certification for Approval of Package Design for Transport of Radioactive Materials, Identification Mark: J/2009/AF, dated August 24, 2022
E-62897 U.S. DOT Page 2 of 3
Dear Mr. Boyle:
A request was submitted to revalidate J/2009/AF, which is a Type AF packaging meeting the applicable requirements for fissile material packages. The NRC issued a request for additional information (RAI) needed to complete their review [1], and TN Americas LLC (TN) responded to the RAI [2]. Further clarifications and information to consider aging management were requested to supplement the responses provided by TN [3]. The International Atomic Energy Agency Regulations (IAEA) for the Safe Transport of Radioactive Material, SSR-6, 2018 Edition added this requirement for the design of package to consider aging mechanisms in paragraph 613A.
A DOT certificate for GP-01 [4] was issued on October 4, 2023, as a short duration revalidation of Japanese Certificate of Competent Authority J/2009/AF dated August 24, 2022 [5] while the aging management program applied to the package design is reviewed.
A summary of conformance to SSR-6 paragraph 613A is provided as Enclosure 1. Additional information to supplement the responses provided for RAI-M-6 and RAI-M-8 is provided as Enclosures 2 and 3, respectively. International standards and inspection procedures that are referenced in the responses will be provided separately. The English version of any international standards is intended for the exclusive and non-collective use by Orano for review of this application by the U.S. Nuclear Regulatory Commission (NRC). All network exploitation, reproduction, and re-dissemination, even partial, whatever the form (hardcopy or other media), is strictly prohibited. TN requests that access to these standards be limited to only those persons reviewing the application, and that all copies be deleted upon completion of the application review.
TN, on behalf of Orano Nuclear Packages and Services (NPS), requests that the DOT continue the review of the request for revalidation taking into consideration additional information provided for the aging management program.
The short duration, the DOT certificate expires September 2, 2024. A 5-year renewal of this certificate is requested to extend the validation for ongoing shipments that will originate in Japan and transit the U.S. enroute to a destination in Europe.
Should you have any questions or require additional information to support review of this application, please contact Peter Vescovi by telephone at 336-420-8325, or by e-mail at peter.vescovi@orano.group.
Sincerely, Don Shaw Licensing Manager TN Americas LLC SHAW Donis Digitally signed by SHAW Donis Date: 2023.10.31 06:39:42 -04'00'
E-62897 U.S. DOT Page 3 of 3 cc:
Peter Vescovi, TN Americas, LLC Laurent Klein, Orano NPS Laurence Labbe, TN Americas, LLC
Enclosures:
- 1) Conformance to SSR-6, 2018 edition, paragraph 613A - Aging Management
- 2) RAI-M-6 Supplemental Response
- 3) RAI-M-8 Supplemental Response
to E-62897 Conformance to SSR-6, 2018 edition, paragraph 613A -
Aging Management to E-62897 Page 1 of 4 Conformance to SSR-6, 2018 edition, paragraph 613A - Aging Management In Specific Safety Requirements No. SSR-6: Regulations for the Safe Transport of Radioactive Material, 2018 edition (SSR-6, 2018 edition), the IAEA added paragraph 613A, which includes the requirement to evaluate aging mechanisms in the safety analysis report for a package design. In addition to aging, the IAEA also added requirements that, for packages to be used for transport after storage, the applicant/certificate holder shall:
809(f). provide and justify, in the operating procedures and maintenance program, that at the time of transport, the package meets the original safety basis, 809(k). include a gap analysis program that describes a systematic procedure for a periodic evaluation of changes of regulations, changes in technical knowledge, and changes of the state of the package design during storage, and 503(e). prior to each shipment, the applicant should ensure that all packaging components and radioactive contents have been maintained during storage in a manner such that all the requirements specified in the relevant provisions of the IAEA regulations and in the applicable certificates of approval have been fulfilled.
Specific Safety Guide No. SSG-26 (Revision 1): Advisory Material for the IAEA Regulations for the Safe Transport of Radioactive Material, 2018 edition (SSG-26, 2018 edition), provides recommendations and guidance on how to comply with SSR-6, 2018 edition, paragraph 613A.
The GP-01 is a Type A, fissile material package design that is intended for shipment after the contents are loaded, and the package is not used for interim or long-term storage with the contents loaded prior to transport. An evaluation of conformance to SSR-6, 2018 edition, paragraph 613A is summarized in the following table.
to E-62897 Page 2 of 4 Para.
Recommendations and guidance Evaluation 613A.1 Packaging components and package contents are subjected to degradation mechanisms and ageing processes that depend on the component and the contents themselves and their operational conditions. Thus, the design of a package should take into account ageing mechanisms commensurate with intended use of the package and its operational conditions, as described in paras 613A.2-613A.6. The designer of a package should evaluate the potential degradation phenomena over time, such as corrosion, abrasion, fatigue, crack propagation, changes of material compositions or mechanical properties due to thermal loadings or radiation, generation of decomposition gases, and the impact of these phenomena on performance of safety functions.
Effects on the packaging of the ageing phenomena on the materials are analyzed in section II-F of the SAR.
With the regard of the use of the packaging (type A), it is highlighted, in general manner, that materials are not subjected to ageing phenomena relating to thermal, radiation, chemical nor fatigue (occurring by alternative stresses due to variations of load or pressure) effects.
Consequently, only fatigue analysis is performed on the lifting bolt connection considering repetitive stresses due to lifting operations and variation of pressure (see respectively, Sections A.4.4.10 and A.4.6.3). Note that the analysis of the repetitive stresses due to lifting operations is done in very penalizing manner considering twice the real number of lifting operations expected during the lifetime of the package.
Complementary analysis considering the cumulative cyclic stresses due to thermal effect, pressure, lifting has been detailed in our letter COR-23-005391-000 and has shown that this consideration does not affect the safety of the packaging.
Regarding the risk of corrosion due to the design of the package, external surfaces made of stainless, leak-tight casing. Because of the use of protective covering for transport and indoor storage, there is no risk of corrosion due to either ambient conditions or penetration of water.
613A.2 For packagings used once for a single transport and not intended for shipment after storage, inspection prior to use may be sufficient. Such packages may include excepted packages, Type IP-1, Type IP-2, Type IP-3 and Type A packages (e.g., fibreboard boxes, drums). If such packages involve shipment after storage, para. 613A.4 should be considered Not applicable The GP-01 is intended for shipment after storage.
to E-62897 Page 3 of 4 Para.
Recommendations and guidance Evaluation 613A.3 For packagings intended for repeated use, the effects of ageing mechanisms on the package should be evaluated during the design phase in the demonstration of compliance with the Transport Regulations. Based on this evaluation, an inspection and maintenance programme should be developed. The programme should be structured so that the assumptions (e.g., thickness of containment wall, leaktightness, neutron absorber effectiveness) used in the demonstration of compliance of the package are confirmed to be valid through the lifetime of the packaging.
An example of a procedure to prepare an ageing management programme for Type B(U) packages is provided in Ref.
[12].
The inspection and maintenance program is detailed in Section III-B of the SAR and is established in accordance with the aging considerations presented in Section II-F of the SAR.
It is mentioned that preventive inspection shall be performed at least every year or every 10 transports.
With regard of the design of the packaging, the structure is dimensionally small (80cm x 114cm x 106cm) and it is, therefore, easy to visually check the condition of the inner and outer surfaces of the packaging main body and lid, including welds and bolts.
Due to the use of stainless steel, the presence of a potential hidden defect on accessible surfaces is prevented.
Gaskets are replaced before every transport.
Maintenance inspections are performed in accordance with the requirement of the Japanese Standard JIS Z 2305, by qualified operators.
613A.4 In the design of packages intended to be used for shipment after storage, consideration of ageing mechanisms is important due to the long period between loading and the end of shipment after storage, the conditions of storage (even though the Transport Regulations do not apply to the storage of the package), and the difficulties in the inspection (to detect ageing effects) and maintenance of packages loaded with radioactive material. Furthermore, factors such as new technical knowledge, changes of package design, new requirements in the Transport Regulations applicable to package design or new technology for the identification and assessment of ageing effects should be recognized.
Not applicable.
GP-01 packaging is not designed to be used for storage prior to shipment.
The transport of the loaded package occurs after the loading in GP-01 packaging operations.
to E-62897 Page 4 of 4 Para.
Recommendations and guidance Evaluation 613A.5 With regard to package design, the consideration of the impact of ageing on the package as described in 613A.1 should be supported by an ageing management programme. This programme should address ageing effects, including prevention, mitigation, condition monitoring and performance monitoring (see Ref. [13]) to justify the design considerations on ageing mechanisms. The programme should also include a gap analysis programme (see paras 809.3 and 809.4) to consider changes in technical knowledge, the state of package design and the requirements of the Transport Regulations. In particular, the ageing management programme should take into account the duration and conditions of storage as specified by the designer, as well as any monitoring, inspection and maintenance scheduled during storage and after storage before shipment. An ageing management programme and gap analysis programme should be developed for all designs of packages intended to be used for shipment after storage. For designs of Type B(U), B(M) and Type C packages these programmes are required to be included in the application for approval of packages for shipment after storage (see paras 809(f) and (k) of the Transport Regulations). The results of the ageing management programme and the gap analysis programme should be taken into account when preparing an inspection plan prior to transport.
Not applicable The GP-01 package is not a type B package.
Nevertheless, considerations for aging management in the SAR appear to respond to the requirement (see paragraphs 613A.1 and 613A.3) 613A.6 For UF6 cylinders maintained and inspected in accordance with ISO 7195
[14] or ANSI N14.1 [15], no further evaluation of the potential degradation or ageing mechanism is required.
Not applicable.
The GP-01 package is not a UF6 cylinder.
to E-62897 RAI-M-6 Supplemental Response
1 Materials and Structural Evaluations Not Acceptable RAI Responses For GP-01 Revalidation Application to 2018 Ed. of IAEA SSR-6 Unresolved RAIs Needing Supplemental Information For Aging Evaluation and Aging Management RAI-M-6. RAI-M-6 requested the applicant to provide a complete evaluation of fatigue for the reusable package components for the 80-year period of use (and the 160 transports that are allowed during the 80-year period) that considers the combined effects of all applicable types of accumulated stress cycles in components during normal service conditions, including the following cycle types: (1) lifting cycles, (2) inner receptacle pressurization cycles, (3) vibration cycles, and (4) thermal stress cycles. The staffs more detailed description of the information needed for addressing the four cycle types is provided in the document including the original RAI.
If certain types of stress cycles are considered to be not applicable or negligible for certain components, the staff requested the applicant to justify and explain why they are not applicable or negligible.
Also, if such a complete fatigue evaluation cannot be performed, or if the fatigue evaluation cannot show adequate protection against fatigue failure, considering the combined effects of all applicable types of accumulated stress cycles in components, the staff requested that the applicant describes how periodic maintenance inspections of the package components will inspect for fatigue cracks in components, and describe the corrective actions that will be taken for any detected fatigue cracks, such as analytical flaw evaluation with follow-up inspections, repair/replacement of components with cracks, etc.
RAI-M-6 is not yet resolved. The staffs comments on the applicants response RAI-M-6 are as follows.
Issue (1), Lifting Cycles. The NRC staff determined that the applicants response is generally acceptable, except for one issue: The staff noted that the applicant refers to alternating stress values in the fatigue analysis for rod bolts, which ignore the influence of any local stress-raising feature to accurately predict the behavior of the component, for example, at the discontinuity or change in cross section of the member (e.g., plate with a hole, bolt threads, etc.). The applicant should consider alternating stresses that account for stress increases at a local discontinuity by considering stress concentration factors in their fatigue calculation or provide rational for not considering it.
NFI answer :
Fatigue assessment is carried out on rod bolts, taking into account stress concentration factors. Rod bolts are used in both the inner and outer receptacle, but the outer receptacle is subjected to higher stresses during lifting. Therefore, fatigue evaluation is carried out on the rod bolts of the outer receptacle.
From II-A.4.4.10, the planned number of lifting cycles throughout the period of use is 3,200, which is doubled to 6,400 in the fatigue evaluation.
From ASME BPVC Section III MANDANTORY APPENDIX XIII-3520, the stress concentration factor of for the bolt is 4, and the cyclic stress generated in the rod
2 bolt due to lifting is following from II-A.4.4.9, R
Z A
n F
x = 22360 16x157 x 4 = 54.0 FZ: vertical component of the load acting on the rod bolt = 22360 [N]
n: number of rod bolts = 16 AR: sectional area of the rod bolt = 157 [mm2]
x: stress concentration factor The stress amplitude in the bolt is; 54.0 / 2=27.0 MPa From (II)-A Figure 12, the fatigue limit of chrome molybdenum steel, the material of the rod bolt, is more than 206 MPa (3.0 x 104 psi) at 371°C (700°F), so the stress amplitude generated by lifting is much less than the fatigue limit and fatigue failure will not occur.
Considering the repetitive stress in the torque generated on the rod bolts separately, since the tightening torques of the rod bolts used for the inner and outer receptacle are the same, the same evaluation is applied.
The expected period of use of the packaging is 80 years and the expected number of transports is 160 times. Since the lid is opened and closed twice during each transport of uranium pellets and return of empty packaging, the lid is opened and closed 160 (planned number of transports) x 2 = 320 times during the planned period of use. Also, since the lid is opened and closed once per year during the periodical voluntary inspections, the lid is opened and closed 80 times during the periodical voluntary inspections during the period of planned use (number of years of use x 1 = 80). Therefore, the opening and closing of the lid and tightening of the bolts will be performed 320+80=400 times during the period of planned use.
The number of times the repetitive stress occurs conservatively is assumed to be 800 times, which is twice the number of times the bolts are tightened.
The cyclic stress generated in the rod bolt due to bolt tightening is as follows from II-A.4.4.9.
R A
d K
T
x =
44130 16x157 x 4 = 702.7 AR: sectional area of the rod bolt = 157 [mm2]
T: tightening torque for the rod bolt = 44130 [Nmm]
K: torque constant = 0.1 d: nominal diameter of the rod bolt = 16 [mm]
x: stress concentration factor The stress amplitude in the bolt is 702.7 / 2=351.4 MPa
3 (II)-A Figure 12 shows that the allowable number of cycles for chrome molybdenum steel, the material used for rod bolts, is 40,000 cycles at a stress amplitude of 413.7 MPa (6.0 x 104 psi) in an environment of 371°C (700°F).
Since both the stress amplitude (351.4 MPa) and the number of cycles of cyclic stress (800 cycles) generated in the rod bolt are less than those values, fatigue failure of the rod bolt will not occur due to the cyclic stress of the tightening torque during the period of use.
Chrome Molybdenum Steel Fatigue Curve Issue (2), Inner Receptacle Pressurization Cycles. The NRC staffs comment is the same as the comment for Issue (1), Lifting Cycles regarding the fatigue analysis of the rod bolts. Specifically, in the fatigue analysis of the rod bolts, applicant should consider alternating stresses in the rod bolts that account for stress increases at a local discontinuity by considering stress concentration factors or provide rational for not considering it.
NFI answer :
In performing fatigue evaluation, the stress concentration factor of rod bolts in fatigue calculation is considered. The number of occurrences of internal pressure fluctuation expected during the service period is 29,200 times from II-A.4.6.3.
The stress generated in the rod bolt due to pressure fluctuation from II-A.4.6.2 is, R
R R
A d
K T
A n
F
x = 21211 16x157 x 4 = 33.8 6.0x104psi 40,000 cycle
4 F: load resulting from the maximum internal/external pressure difference which acts on the lid of the inner receptacle = 21211 [N]
n: number of rod bolts = 16 AR: sectional area of the rod bolt = 157 [mm2]
x: stress concentration factor The stress amplitude in the bolt is, 33.8 / 2=16.9 MPa From (II)-A Figure 12, the fatigue limit of chrome molybdenum steel, which is the material of rod bolts, is more than 206 MPa (3.0 x 104 psi) at 371°C (700°F).
Therefore, the stress amplitude generated by the internal pressure fluctuation is much lower than the fatigue limit of chrome molybdenum steel, Fatigue fracture does not occur.
Issue (3), Vibration Cycles. The NRC staff does not agree with the applicants response that 6400 cycles for lifting operations are also applicable to the fatigue analysis for vibration cycles that occur during transport operations. The package components could experience many vibration cycles from numerous vehicle transports by road during the 80-year service life and can significantly exceed 6400 cycles. As part of the evaluation, the applicant should address fatigue analysis for vibration cycles in more detail to show fatigue failure will not occur. If such a fatigue evaluation cannot be performed, or if the fatigue evaluation cannot show adequate protection against fatigue failure considering the combined effects, the applicant should describe proposed inspection methods, inspection equipment, and personnel qualification requirements for detection of fatigue effects like those requested in RAI-M-8.
NFI answer :
During transportation, the packaging is fixed to the truck bed by a lashing belt that holds it down from the top of the lid. Therefore, during transportation, vibration does not cause the packaging and lid to lift. However, we assume that only the packaging body is fixed to the truck bed, and that the outer receptacle lid is lifted.
From II-A.4.7, the load applied to the packaging due to vibration is less than 4 G.
Therefore, the rod bolts fixing the outer receptacle lid are less than four times that of the outer receptacle lid.
Therefore, the cyclic stress generated in the rod bolts is, R
A n
F
x =
5766.31 16x157 x 4 = 9.2 F: load resulting from the vibration =147 kg(Outer receptacle lid)x9.80665 m/s(gravitation acceleration)x4 (Multiplication by vibration)=5766.31 [N]
n: number of rod bolts = 16 AR: sectional area of the rod bolt = 157 [mm2]
x: stress concentration factor The stress amplitude in the bolt is,
5 9.2 / 2=4.6MPa From (II)-A Figure 12, the fatigue limit of chrome molybdenum steel, which is the material of rod bolts, is more than 206 MPa (3.0 x 104 psi) at 371°C (700°F).
Therefore, the stress amplitude generated by vibration is much lower than the fatigue limit of chrome molybdenum steel, Fatigue fracture does not occur.
Issue (4), Thermal Stress Cycles. The NRC staff needs much more elaborate rational for not considering the thermal stress cycles due to cyclical temperature fluctuations, rather than simply stating appears as not significant.
NFI answer :
The thermal stress due to temperature change evaluated in (II)-A.5.1.3 is also considered as cyclic stress.
From (II)-A.5.1.4, since the greatest stress in the inner receptacle occurs at the bottom surface of the inner receptacle, the stress occurring at the bottom surface of the inner receptacle is evaluated as a representative cyclic stress.
The number of times internal pressure is expected to occur during the service period is 29,200 times from II-A.4.6.3.
From A.5.1.3(3), the cyclic stress generated at the bottom of the inner receptacle is 114.9 MPa, so the stress amplitude is 114.9 /2= 57.5 MPa From the design fatigue curve in ASME BPVC Section III MANDANTORY APPENDIX 1 Figure 1-9.1M shown below, the allowable number of cycles is 2.0 x 109 cycles at a stress amplitude of 60 MPa at 370°C. It is confirmed that both the stress amplitude (351.4 MPa) and the number of cycles (800 cycles) generated on the bottom of the inner receptacle are less than those values.
Therefore, fatigue failure of the inner receptacle will not occur due to repeated stress caused by temperature change during the period of use.
6 Stainless Steel Fatigue Curve The stress concentration factor of the rod bolt in the fatigue calculation is taken into account in the fatigue evaluation.
The number of internal pressure fluctuations of the inner receptacle assumed during the period of use is 29,200 times from II-A.4.6.3.
The cyclic stress generated in the rod bolts due to pressure fluctuations is, from II-A.5.1.3.2, R
R R
A d
K T
A n
F
x =
14478 16x157 x 4 = 23.1 F: load resulting from the maximum internal/external pressure difference which acts on the lid of the inner receptacle = 14478 [N]
n: number of rod bolts = 16 AR: sectional area of the rod bolt = 157 [mm2]
x: stress concentration factor The stress amplitude in the bolt is, 23.1 / 2=11.6 MPa (II)-A From Figure 12, the fatigue limit of chrome molybdenum steel, the material of the rod bolt, is more than 206 MPa (3.0 x 104 psi) at 371°C (700°F), so the stress amplitude is well below the fatigue limit and fatigue failure will not occur.
to E-62897 RAI-M-8 Supplemental Response
NRC comment NFI answer Criterion (1), Inspection Methods. For this criterion the applicant stated that localized aging effects, such as cracks, pits, and crevice corrosion are confirmed by the visual inspections during periodical voluntary inspections and package pre-shipment inspections.
The NRC staff determined that the applicants response to this criterion is generally acceptable for criterion (1),
with the exception of several points:
The NRC staff noted that the description of the package handling and maintenance requirements, as described in Chapter III of the GP-01 Safety Analysis Report (SAR), do not include any visual inspections that are targeted for detection of localized corrosion effects, including pitting and crevice corrosion. (However, the staff noted that SAR Chapter III does include visual inspections for detection of cracks or clefts in the welds.) Therefore, the NRC staff requests the applicant to supplement or revise its package handling and maintenance instructions to include visual inspections that are targeted at detection of localized corrosion effects, including pitting and crevice corrosion, as well as cracks that may be formed by chloride induced stress corrosion cracking in stainless steel items or environmentally assisted fatigue. As an alternative to SAR revisions, the staff requests that the applicant provide a reference to the sections of the applicants own package handling and maintenance program documents (or other package operations, or quality assurance program documents) that contain requirements to perform visual inspections to detect localized corrosion effects such as pits, crevice corrosion, chloride-induced stress corrosion cracking, and environmentally assisted fatigue.
NFI will revise the internal standards for periodic voluntary inspections as follows.
- Clarify that the NFI is also to check for corrosion (the table below shows the proposed revision).
Category Method of Inspection Criteria for Judgment Visual Inspections
- 1. Visually check the external and internal surfaces of the outer and inner receptacle and the lid.
- 2. Visually check the welds.
- 3. Visually check the bolts and nuts.
- 4. Visually check the rubber parts such as spacers and skids.
- 1. There is no significant deformation or fracture or corrosion (stress corrosion cracking, pitting corrosion, crevice corrosion) that might affect the packaging capabilities.
- 2. There are no cracks or clefts or corrosion (stress corrosion cracking, pitting corrosion, crevice corrosion).
- 3. There is no deformation, fracture or partial loss or corrosion (stress corrosion cracking, pitting corrosion, crevice corrosion).
- 4. There is no significant deterioration, harmful partial loss or displacement from required position.
Subcriticalilty Inspections
- 1. Visually check the appearance of the boronic stainless steel plates in the inner receptacle
- 2. Visually check the appearance of the packaging.
- 1. There is no significant deformation, fracture, or displacement from required position.
- 2. There is no deformation that might lead to significant reduction in distance from the fuel zone of any neighboring package.
Lifting Inspections Visually check the appearance of the outer receptacle, the inner receptacle and the lifting attachments on the inner receptacle.
There is no deformation or cracks/clefts in the welds or corrosion (stress corrosion cracking, pitting corrosion, crevice corrosion) that might affect the strength of any of the lifting attachments.
Maintenance of Valves and Gaskets of Containment System Visually check the inner receptacle flange.
There is no significant deterioration or partial loss or corrosion (stress corrosion cracking, pitting corrosion, crevice corrosion) that might affect the leaktightness of the packaging.
NRC comment NFI answer Criterion (2), Inspection Equipment and Personnel Qualification Requirements. For this criterion the applicant stated that the following qualification requirements are required:
- Eyesight: Eyesight suitable for a Japanese license (6/20 both left and right eyes, 14/20 in both eyes);
- Trained in inspection methods and standards for package.
The NRC staff determined that the applicants response does not adequately address criterion (2). The staff is providing further detail on the information needed to address this criterion, as follows:
The eyesight requirement needs further explanation to address how it is applied to the performance of visual inspections of package components by inspection personnel, such that personnel have the visual capability to adequately detect and characterize localized aging effects, such as early stage cracks, pits, and crevice corrosion.
The visual detection capability requirements and visual indication resolution requirements of applicable national or international codes and standards such as the ASME Boiler and Pressure Vessel Code (BPVC) Sections V and XI, applicable Japanese Industrial Standards (JIS), or applicable European Norm (EN) standards, and/or other methods, programs, or procedures should be described to support an adequate response.
Further, the response does not describe any equipment requirements for visual inspections such as requirements for lighting, magnification, cameras, or other visual aids. Such visual aids are often used by visual inspection personnel to help ensure adequate illumination, adequate visual resolution, and photographic records, as needed to adequately detect, characterize, evaluate, monitor, and trend localized aging effects, such as early stage cracks, pits, and crevice corrosion. Therefore, the staff requests that the applicant describe the equipment requirements for performing visual inspections to ensure that inspection personnel can adequately detect, characterize, and evaluate localized aging effects.
With respect to the applicants statement, Trained in inspection methods and standards for package, the staff understands this to mean that the applicant uses detailed national or international codes and standards such as the ASME Boiler and Pressure Vessel Code (BPVC) Sections V and XI, applicable Japanese Industrial Standards (JIS), or applicable European Norm (EN) standards, and/or other methods, programs, and procedures to ensure the needed qualification of inspection personnel and equipment to perform reliable visual inspections that can adequately detect and characterize indications of localized aging effects (such as early stage cracks, pits, and crevice corrosion) prior to component failure or loss of safety function. Therefore, the staff requests that the applicant provide a description of the requirements of the applicable codes, standards, methods, programs, and procedures that are implemented to ensure that visual inspections can adequately detect and characterize localized aging effects (such as early stage cracks, pits, and crevice corrosion). This should include a citation or reference for the applicable documents and a summary of the specific visual inspection qualification requirements.
NFI will add the following requirements to its internal standards for periodic voluntary inspections to clarify them. These were determined with reference to JIS and ISO standards.
Note that all visual inspections on the GP-01 are direct visual inspections.
NRC comment NFI answer Criterion (3), Visual Criteria for Detection of Aging Effects Such as Early Stage Fatigue Cracks and Localized Corrosion Effects Such As Chloride-Induced Stress Corrosion Crackling, Pitting, and Crevice Corrosion. For this criterion the applicant stated that the use of stainless steel limits any risk of corrosion due to atmospheric conditions. Other potential chemical attacks appear not credible regarding use of the package. The applicant also stated that the plates building the receptacles (inner and outer) are assembled by welds which are continuous and leaktight, ensuring the noncorrosion of the inner components.
The NRC staff determined that the applicants response does not adequately address criterion (3) for package component exposed to the outdoor air environment. The staff is providing further elaboration on the information needed to address this criterion, as follows:
Stainless steel transportation package components that are exposed to outdoor air may accumulate atmospheric deposits such as salts and other chemical compounds present in the atmosphere or present on road surfaces. Such deposits and chemical compounds, when mixed with rainwater or moisture, form aqueous electrolytes on the surfaces of the stainless steel that yield aggressive chemical agents (such as chlorides or other halides) that can chemically degrade the protective passive oxide layer on stainless steel surfaces. This can occur at vulnerable initiation sites such as tight creviced regions, leading to crevice corrosion, or at local pit nucleation sites where very small (and likely non-rejectable) local material defects, local microstructures, or local alloy composition may result in higher localized vulnerability to chloride attack of the protective passive oxide layer and localized de-passivation at that location leading to the formation of a pit.
Therefore, over time, such conditions and mechanisms can lead to localized breakdown of the passive oxide layer that normally protects the stainless steel surface from general corrosion. Over time, such local breakdown of the protective passive oxide layer often results in the formation of pits and crevice corrosion. If tensile stress is present, pits may act as initiation sites for chloride induced stress corrosion cracking. The material may also be susceptible to environmentally assisted fatigue cracking due to cyclical stress acting synergistically with the chemical effects of the aqueous electrolyte. Therefore, it is generally not possible to disposition such localized stainless steel aging affects as insignificant or not credible for an 80-year service life, or even an extended service life that is shorter than 80 years.
Therefore, the NRC staff determined that the package maintenance program should include visual criteria to look for localized aging effects such as early stage fatigue cracks and localized corrosion of stainless steel components exposed to the outdoor air environment. Localized corrosion effects include chloride-induced stress corrosion cracking, pitting, and crevice corrosion. In the RAI, the NRC staff provided specific examples of visual indications that may indicate potential localized corrosion of stainless steel components. These examples include the accumulation of atmospheric deposits such as salts, the buildup of localized corrosion products, rust-colored stains or deposits located around creviced regions, rust-colored stains or deposits located in and around pits, and surface discontinuities or flaws associated with the pits, crevice corrosion, stress corrosion cracking, and/or environmentally-assisted fatigue.
Therefore, the staff requests that the applicant provide a description of the visual criteria that are used to look for localized aging effects such as early stage fatigue cracks and localized corrosion (stress corrosion cracking, pitting, and crevice corrosion) of stainless steel components exposed to the outdoor environment. Except for the detection of cracks or clefts in package welds, the staff noted that the current package handling and maintenance criteria described in SAR Chapter III do not include any these visual inspection criteria.
Same as response to creation (1).
NRC comment NFI answer Criterion (4), Package Surface Cleaning Requirements to Facilitate Effective Bare Metal Visual Inspections and to Protect Against Localized Corrosion Effects.
For this criterion the applicant stated that The use of stainless steel avoids any risk of hidden defect under layer of protection (as for example painting used to protect carbon steel) and that before any control, surfaces are clean of any impurities before to perform the control. The applicant also stated that Moreover, due to the simply design of the package, there is no inaccessible external surface.
The NRC staff determined that the applicants response to criterion (4) does not provide sufficient information on specific surface cleaning requirements for package components. The staff noted that the description of the package handling and maintenance requirements in Chapter III of the SAR does not include surface cleaning requirements for package components. Therefore, the applicant should respond to this criterion by describing the specific surface cleaning requirements that are implemented as part of the package handling and maintenance requirements and provide references to the documents that contain these surface cleaning requirements. Further, the applicant should describe how the surface cleaning requirements are implemented to accomplish the following:
(i) Facilitate effective bare metal visual inspections that can adequately detect localized surface flaws that may be buried underneath dirt or atmospheric deposits, and (ii) Remove dirt and surface deposits that may contain salts or other chemical compounds that can contribute to localized corrosion of stainless steel components (such as pitting, crevice corrosion, and stress corrosion cracking).
The periodic cleaning of surfaces to remove such surface deposits and chemical contaminates should be performed on a sufficient frequency (for example after every package transport and associated package unloading), and it should be of sufficient coverage that, with the performance of adequate visual inspections to look for localized aging effects, there is reasonable assurance that package components are not developing unacceptable service induced flaws or degradation, such as those associated with pitting, crevice corrosion, stress corrosion cracking, and environmentally-assisted fatigue.
- NFI will add the following to our internal standard.
The outer surface of packagings shall be cleaned between the completion of transport and the next transport.
- NFI will add the following to our internal standard.
Ensure that the surface is free from contamination before visual inspection. If contamination is present, cleaning should be carried out before inspection. (See criterion(2))
NRC comment NFI answer Criterion (5), Flaw Evaluation Methods and Associated Flaw Acceptance Criteria to Determine Whether Components With Flaws Are Acceptable for Continued Service.
For this criterion the applicant stated that there are no specific standards for scratches. If deformation, cracks, or scratches that are found on visual inspection during periodical voluntary inspections or package pre-shipment inspections, they will be repaired, replaced, or disposed of on individual basis depending on their size and where they occur.
The NRC staff determined that the applicants response to criterion (5) does not provide sufficient information on flaw evaluation methods and associated flaw acceptance criteria to determine whether components with flaws are acceptable for continued service. Maintenance programs that are credited for managing applicable aging effects such as localized corrosion effects and fatigue during extended service periods (for example, 20, 40, 60, or 80 years of service), need to have specific requirements for flaw evaluation and associated flaw acceptance criteria. If and when flaws are detected in safety-related components that are designed for long-term service, there needs to be specific criteria for characterizing the flaw, sizing the flaw, determining the root cause of the flaw, analyzing the flaw (to determine whether it could result in structural failure), and determining whether or not the flaw is acceptable for continued service.
The staff noted that the applicants response states that deformation, cracks, or scratchesfound on visual inspectionswill be repaired, replaced, or disposed of depending on their size and where they occur. This seems to indicate that there are specific criteria and associated acceptance standards that are used to evaluating flaws or indications of localized aging degradation to determine whether components that have these indications are acceptable for continued service, or whether components with certain types or sizes of flaws require repair or replacement.
Many long-lived components for various design applications do not need to be immediately repaired or replaced just because there is a small flaw or a small amount of aging degradation. If the flaw or degradation is adequately evaluated and determined to be of a type and size that meets credible and conservative acceptance standards, accounting for flaw growth or increase in extent of degradation over a certain period of operation, then the component with the flaw may be acceptable for continued service during that operating period, provided that the size and characteristics of the flaw or degradation are tracked and monitored through documented and recorded inspections that are performed at an acceptable frequency over the approved operating period for the component with the flaw.
National and/or international codes and standards are often used by industry to determine the requirements for evaluation of flaws that are detected during component inspections and acceptance standards for determining whether long-lived components with flaws are acceptable for continued service. Examples of such codes and standards include the ASME Boiler and Pressure Vessel Code (BPVC),Section XI. In particular ASME BPVC Section XI Code Case N-860 provides criteria for evaluating indications of localized corrosion, characterization of flaws, sizing of flaws, analysis of flaws, and associated acceptance standards for welded stainless steel containments used for storage and transportation of spent nuclear fuel. Other applicable national or international consensus standards such as those in applicable Japanese Industrial Standards (JIS), or applicable European Norm (EN) standards may be used to determine criteria for evaluating visual indications of localized aging degradation, including requirements for characterizing, sizing, and analyzing detected flaws, and acceptance criteria for determining whether such flaws are acceptable for continued service.
Therefore, the staff requests the applicant describe and reference any national or international codes and standards, or other methods, programs, and procedures that are implemented for (i) evaluating flaws and indications of aging degradation (such as flaw characterization, flaw sizing, and flaw analyses methods), and (ii) flaw acceptance criteria to determine whether components containing flaws are acceptable for continued service.
- Defects identified in welds (cracks, pits, craters), regardless of their size, shall require repair in any case, as they affect the strength of the lifting and the sealing of the package. This is similar to ISO 5817 where, for quality level B (the highest requirement), the presence of any cracks, pits or craters in welds is not permitted.
- If there is discolouration in the weld or base metal that is suggestive of corrosion, first check whether it is only on the very surface. If the discolouration disappears after polishing with Scotch-Brite or similar, no repair is necessary. If the discolouration is not removed and it is suspected that corrosion has penetrated into the weld, repair is required.