ML25113A129
| ML25113A129 | |
| Person / Time | |
|---|---|
| Site: | 07103043 |
| Issue date: | 05/14/2025 |
| From: | Storage and Transportation Licensing Branch |
| To: | |
| Shared Package | |
| ML25113A127 | List: |
| References | |
| EPID L-2024-DOT-0000 | |
| Download: ML25113A129 (1) | |
Text
Enclosure Request for Additional Information Application for USDOT Revalidation of Japan Competent Authority Certificate of Approval No. J/105/AF-96, Revision 4, Model No. MFC-1 Package Revalidation to IAEA SSR-6, 2018 Edition Regulations for the Safe Transport of Radioactive Material Materials Discipline RAI M-1 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 carbon steel, 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.
Address the following criteria in the descriptions:
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 general and localized corrosion effects for carbon steel items, characterization of general corrosion for alloy steel bolts, and localized corrosion of stainless-steel items.
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 general and localized corrosion prior to component failure or loss of safety function.
3.
Visual criteria for detection of the aging effects of general and localized corrosion (i.e.,
pitting and crevice corrosion) of metallic components exposed to sheltered or outdoor air and water during transport. Examples of visual indications that may indicate potential general or localized corrosion 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 and/or crevice corrosion.
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 general or localized corrosion of metallic components and general corrosion of alloy steel bolts.
2 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 NRC staff reviewed the applicants corrosion evaluation for the stainless-steel components in a sheltered environment and noted that stainless steel passivity may adequately inhibit general corrosion. However, stainless steel is susceptible to localized corrosion effects, including loss of material due to pitting and crevice corrosion, when exposed to aqueous air environments. During numerous package transport operations over a 60-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. The staff determined that localized corrosion is a credible aging mechanism for stainless steel components in outdoor environments and requires that adequate visual inspections performed by qualified personnel using qualified techniques are needed to detect and evaluate indications of corrosion 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 Section III of the application does not include any specific provision for inspection of stainless-steel components to detect and evaluate indications of localized corrosion to ensure that stainless steel components with unacceptable localized corrosion or SCC are repaired or replaced prior to a loss of safety function.
The NRC staff reviewed the applicants corrosion evaluation for carbon steel components in all environments and confirmed that the use of paint is important to protect against corrosion, provided that it remains intact. If the paint becomes damaged or deteriorates during routine use and the components are exposed to aqueous air environments, these components are susceptible to general corrosion and pitting/crevice corrosion. The applicant should clarify whether the paint should be inspected for degradation that could result in corrosion of the carbon steel and loss of material. If paint is necessary to prevent corrosion of the carbon steel the applicant should provide paint coating inspection criteria and qualification requirements for personnel conducting these inspections. Additionally, the applicant should provide inspection criteria and personnel qualification requirements necessary to evaluate indications of general or pitting/crevice corrosion of the painted carbon steel components, so that personnel can reliably determine the need for remedial action, such as repair or replacement of components that show unacceptable indications.
The NRC staff reviewed the applicants corrosion evaluation for alloy steel bolts and confirmed that use of a coating will help protect against corrosion provided that it remains intact. If the coating on the bolts becomes damaged or deteriorates during routine use, these components are susceptible to corrosion. The staff determined that general corrosion is a credible aging mechanism for the alloy steel bolts, during the 60 year period of use, and require that adequate visual inspections performed by qualified personnel using qualified techniques are needed in order to detect and evaluate indications of general corrosion so that personnel can reliably determine the need for remedial action, such as repair or replacement of components that show unacceptable indications.
The foregoing information is needed to ensure adequate inspection, flaw evaluation, mitigative measures, and corrective actions for managing general or localized corrosion of metallic components and general corrosion of alloy steel bolts, and to verify compliance with requirements of the 2018 Edition of IAEA SSR-6, Paragraph 613A.
3 Structural Discipline RAI ST-1 Regarding cross-pin, which is a load carrying part of the tightening bolt, explain and/or clarify the following:
a) How the aging evaluation is provided for the effects of fatigue on the cross-pin for the tie-bolts that connect the upper cover to the lower container of the MFC-1 package; b) If the cross-pins are to be replaced, address replacement requirements in the safety analysis report (SAR) Part III, Maintenance Procedures for Packaging and Handling Procedures for Fissile Material Package.
In Safety Analysis Report (SAR) Section II-A.10.9, the applicant states that the effects of fatigue on the cross-pin were not evaluated because the cross-pin is periodically replaced. The NRC staff reviewed the SAR Part III, including the maintenance and handling procedures, and did not find a requirement or a statement to replace cross-pin included in the SAR. Therefore, the NRC staff is seeking clarification regarding how the applicant evaluated the effects of fatigue on the cross-pin for the tie-bolts.
This information is requested to determine compliance with the requirement in paragraph 613A of the IAEA SSR-6, 2018 Edition, as related to assessing the effects of fatigue on the cross-pin for the tie-bolts.