ML25002A206
| ML25002A206 | |
| Person / Time | |
|---|---|
| Site: | 07103101 |
| Issue date: | 11/29/2024 |
| From: | Storage and Transportation Licensing Branch |
| To: | |
| Shared Package | |
| ML25002A203 | List: |
| References | |
| EPID L-2024-DOT-0003 | |
| Download: ML25002A206 (2) | |
Text
11/29/2024 1
Draft Request for Additional Information Application for DOT Revalidation Japanese Competent Authority, Certificate of Approval No. J/2026/AF-96, Revision 1 Model No. MX-6 Package Revalidation to IAEA SSR-6, 2018 Edition D-RAI M1 Describe any national or international codes, standards, and/or other methods, programs, or procedures that are implemented to ensure that package maintenance activities (including visual inspections, screening and evaluation of visual indications, and corrective actions such as component repairs and replacements) are adequate to manage the effects of corrosion in stainless steel and alloy steel packaging components that would see long-term use, such that the package components are capable of performing their requisite safety functions throughout the period of use.
The staff requests that this description address the following criteria:
- 1. Inspection methods (e.g., bare metal visual exams and/or other types of nondestructive exams such as liquid penetrant exams or ultrasonic exams) for detection and characterization of localized corrosion effects for stainless steel items, such as pits, crevice corrosion, and cracks that may be caused by chloride-induced stress corrosion cracking (SCC), as well as for detection and characterization of corrosion for alloy steel bolts.
- 2. Inspection equipment and personnel qualification requirements (e.g., lighting and visual acuity requirements for performing visual exams) to ensure reliable inspections that can adequately detect and characterize indications of localized corrosion and chloride-induced SCC prior to component failure or loss of safety function.
- 3. Visual criteria for detection of aging effects such as localized corrosion (i.e., pitting and crevice corrosion) and chloride-induced SCC of stainless steel package components exposed to outdoor air and water during transport. Examples of visual indications that may indicate potential localized corrosion of stainless steel components include the accumulation of atmospheric deposits such as salts, buildup of corrosion products, rust-colored stains or deposits, and surface discontinuities or flaws associated with pitting, crevice corrosion, and/or SCC.
- 4. Describe any surface cleaning requirements that are implemented to ensure that bare metal visual inspections of component surfaces are capable of detecting surface flaws, and for ensuring adequate removal of atmospheric deposits such as salts or other chemical compounds that may contribute to localized corrosion and SCC of stainless steel components and corrosion of alloy steel bolts.
- 5. Describe any flaw evaluation methods (such as flaw sizing and flaw analysis methods) and associated flaw acceptance criteria that may be used to determine whether components containing flaws are acceptable for continued service.
The staff reviewed the applicants corrosion evaluation for the stainless steel components and noted that stainless steel passivity may adequately inhibit general corrosion in most outdoor
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ambient environments, but stainless steel is susceptible to localized corrosion effects, including loss of material due to pitting and crevice corrosion, when exposed to aqueous outdoor air environments. For package transport in road vehicles or onboard marine vessels, outdoor air environments include water that may contain dissolved chlorides or other halide species. Such chemically aggressive anion species are yielded when salts, debris, and road chemicals mix with rainwater. Over extended operating periods, in particular, during numerous package transport operations over a 50-year period, these chemical species may gradually degrade the protective passive oxide film on stainless steel surfaces leading to the formation of pits and crevice corrosion. Further, stainless steel components under high tensile stress (such as weld residual stress) exposed to aqueous outdoor air environments are also susceptible to the formation of cracks due to chloride-induced stress corrosion cracking (SCC). The staff identified that adequate visual inspections performed by qualified personnel using qualified techniques are needed in order to detect and evaluate indications of localized corrosion and SCC of stainless steel components exposed to aqueous outdoor air environments so that personnel can reliably determine the need for remedial action, such as repair or replacement of components that show unacceptable indications. However, staff identified that the package handling and maintenance criteria described in Chapter III of the application do not include any specific provision for inspection of stainless steel components to detect and evaluate indications of localized corrosion and SCC to ensure that stainless steel components with unacceptable localized corrosion or SCC are repaired or replaced prior to a loss of safety function.
Table II-F.2 of the application states that corrosion proofing is given to the alloy steel bolts used in the MX-6 packaging. The staff noted that the use of a suitable corrosion inhibitor on the alloy steel bolts may help protect against corrosion provided that it remains intact. If the coating or plating on the bolts becomes damaged or deteriorates during routine use, which is likely to occur, the staff identified that visual inspections of the alloy steel bolts are needed in order to detect and evaluate indications of corrosion of the exposed alloy steel to ensure that appropriate remedial action, such as repair or replacement of bolts that show significant corrosion, is taken.
The alloy steel bolts in the assembled packaging components are also susceptible to galvanic corrosion if the alloy steel is in direct contact with noble or passive materials such as titanium and stainless steel during package handling and transport. However, staff identified that the package handling and maintenance criteria described in Chapter III of the application do not include any specific criteria for inspections of alloy steel bolts to detect and evaluate indications of corrosion to ensure that bolts with unacceptable corrosion are repaired or replaced prior to a loss of safety function.
Therefore, the information above is requested to ensure adequate inspection, flaw evaluation, mitigative measures, and corrective actions for managing localized corrosion and SCC of stainless steel components and for managing corrosion of alloy steel bolts.
This information is requested in order to verify compliance with requirements of the 2018 Edition of IAEA SSR-6, Regulations for the Safe Transport of Radioactive Material, Paragraph 613A.