ML22278A047
| ML22278A047 | |
| Person / Time | |
|---|---|
| Site: | 07103100 |
| Issue date: | 07/26/2022 |
| From: | US Dept of Transportation (DOT) |
| To: | Office of Nuclear Material Safety and Safeguards |
| BWHITE NMSS/DFM/STLB 3014156577 | |
| Shared Package | |
| ML22278A043 | List: |
| References | |
| E-61174 | |
| Download: ML22278A047 (52) | |
Text
Enclosure 2 to E-6117 4 Responses to Request for Additional Information (Public version)
RAls and Responses - Public Enclosure 2 to E-6117 4 RAI 2-1:
Please describe the applicable consensus codes and standards that are followed for design, fabrication, qualification testing, and acceptance inspections of packaging body welds, fuel basket lodgment welds, and top and rear shock absorbing cover welds to ensure that the welds will be capable of maintaining their structural integrity.
Examples of consensus codes and standards that address design, fabrication, qualification testing, and acceptance inspection of safety-related welds for nuclear applications include those published by the American Society of Mechanical Engineers (ASME), the American Welding Society (AWS), and analogous consensus codes and standards published by national or international standards organizations.
If a consensus code or standard is not followed for design, fabrication, qualification testing, and/or acceptance inspections of certain packaging welds, please describe how the welds for the packaging body, fuel basket lodgments, and top and rear shock absorbing covers are designed, fabricated, qualification tested, and inspected to ensure that the welds will be capable of maintaining their structural integrity.
Background and Reason for RAI:
The application documents the use of welded metallic items for several packaging components, including the packaging body, the fuel basket lodgments, and the top and rear shock absorbing covers. The staff noted that the application does not include adequate technical information concerning the codes, standards, and/or other specifications that are followed for design and fabrication of welds that are used to join the metallic subcomponents for the packaging body, the fuel basket lodgments, and the top and rear shock absorbing covers.
Section 11-C.2 of the application includes some general information on structural strength testing, leakage testing, and nondestructive examination (NOE) activities that are performed for packaging body shell welds that form the containment boundary.
However, the staff noted that this section does not include any information on codes, standards, or quality assurance criteria that are applied for weld qualification tests (e.g., mechanical tests of weld samples to ensure the required structural strength) and NOE criteria for inspections of safety-related production welds in packaging components that are placed into service. Further, the staff noted that the general information in Section 11-C.2 concerning qualification testing and NOE activities for the packaging body shell welds does not address other safety-related welds such as the other packaging body welds that are not shell welds, fuel basket lodgment welds, and the welds that join the metallic plates of the shock absorbing covers .
This information is requested in order to determine whether the package meets the requirements in Paragraphs 640 and 648 of IAEA SSR-6, 2012 Edition.
RAls and Responses - Public Enclosure 2 to E-6117 4 Response to RAI 2-1:
In the Japanese licensing system for transport packaging , an approval for packaging manufactured is required after the design approval of package generally.
This approval is called as "Packaging approval", and the following documents are specified for the application.
- Certificate of design approval
- Explanation of manufacturing and inspection method
- Explanation of quality management system applied to manufacturing
- Records of inspection during manufacturing , etc.
In the explanation of manufacturing and inspection method , requirements on manufacturing are specified as well as fabrication control applied to welding process.
At the stage of design approval , this explanation (not exactly same) is enclosed in the safety analysis report just for reference which is not considered on the examination of the safety analysis chapters.
Please find the Attachment-1, which is an English translation of this reference in which chapter A.3 explains applicable standards for operation or quality assurance for welding.
As complementary explanations , requirements for welding of each component specified in the manufacturing specifications applied to the manufacturing of MX-6P packaging are shown in the followings.
- 1. Packaging body shell
- a. Manufacturing
- A welding specification shall be drafted and submitted for approval or acceptance before use.
- Welding shall be performed in compliance with welding procedure and by welders qualified by an approval laboratory, in accordance with standards NF EN 288 or NF EN ISO 15614 and NF EN 287.
- Copies of the welders ' qualification certificates shall be attached to the welding specification.
- The PQR shall substantiate full compliance with the mechanical property requirements for the welds qualification of internal shell.
- b. Inspection
- The weld seams assembling the inner shell , and the [ ] weld seams between the inner shell and the bottom plate and upper flange , shall be submitted to [
] and according to a procedure that shall be submitted for acceptance.
RAls and Responses - Public Enclosure 2 to E-6117 4
- All weld seams [
],
according to a procedure that shall be submitted for approval or acceptance before use.
- 2. Shock absorbing covers
- a. Manufacturing
- A welding specification shall be drafted and submitted for approval before use.
- Welding shall be performed in compliance with welding procedures and by welders qualified by an approved laboratory, in accordance with standards NF EN 288 or NF EN ISO 15614, NF EN 287.
- Copies of the welders' qualification certificates and weld process qualifications shall be attached to the welding specification.
- The PQR shall substantiate full compliance with the mechanical property requirements (tensile strength , elastic limit, impact strength elongation) imposed on the base materials.
- b. Inspection
- All continuous welds shall be submitted to [
]
- A procedure for tests shall be submitted for approval before use.
- 3. Basket (lodgment)
- a. Manufacturing
- The supplier will establish a complete welding book to submit for acceptation or approval before use.
- Welding of lodgment will be performed [ ] according to standards [ ] and for the qualification , in the frame of the
[ ].
- The copies of the qualification certificates of the welders will be joined to the welding operation procedure.
- b. Inspection
RAls and Responses - Public Enclosure 2 to E-6117 4 Impact:
No changes to the Safety Analysis Report.
RAls and Responses - Public Enclosure 2 to E-61174 Attachment-I MX-6P Safety Analysis Report Reference Explanation for Summary of Manufacturing Method of Packaging
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RAls and Responses - Public Enclosure 2 to E-61174 RAI 2-2:
Please provide information to demonstrate that the mechanical properties and stress-strain relationship for the fuel cladding, as specified in Sections 11-A.5.3 and 11-A.9.2 of the application (detailed below), are sufficiently representative for all three cladding types identified Section 1-D of the application to ensure that the three cladding types will maintain their integrity for the 0.3 meter free drop condition, the 9 meter drop test accident condition, and the fire test accident condition, as demonstrated in Sections 11-A.5.3 and 11-A.9.2 of the application .
Background and Reason for RAI:
Section 1-0 of the application states that the MX-6P package contains fresh (unirradiated)
PWR fuel assembles. This section specifies three types of zirconium alloy cladding for the unirradiated fuel rods - zircalloy-4, MDA, or ZIRLO .
The package structural analyses in Section II-A of the application include evaluations of the structural performance of the fuel cladding for normal and accident conditions . The application includes fuel cladding integrity evaluations for the following conditions :
- Section 11-A.5.3 evaluated the structural performance of the fuel cladding for the 0.3meter free drop normal operating condition;
- Section 11-A.9.2 evaluated the structural performance of the fuel cladding for the 9meter drop test accident condition;
- Section 11-A.9.2 evaluated the pressure-retaining performance of the fuel cladding at elevated temperature for the fire test accident condition .
The evaluations demonstrate that fuel cladding integrity is maintained for these three conditions based on the physical properties of fuel cladding listed in Table 11-A.15, the assumed stress- strain relationship for fuel cladding addressed at the top of page II-A-83 in Section 11-A.5.3 and depicted in Figure 11-A.31, and the elevated temperature tensile strength of the fuel cladding identified on page I I-A-141 in Section 11-A.9.2 of the application .
The staff noted that the fuel cladding integrity evaluations in Sections 11-A.5.3 and 11-A.9.2 of the application do not distinguish between the three types of zirconium alloy cladding that may be used for the unirradiated fuel assemblies contained in the package. Since different types of zirconium alloy cladding materials can show different mechanical properties and stress-strain relationships, the staff does not have sufficient basis for ascertaining that the results of the structural performance evaluations are representative for all three cladding types, considering the potential for significant differences in the mechanical properties and stress-strain relationships for the three zirconium alloy cladding materials.
This information is requested in order to determine whether the package meets the requirements in Paragraphs 673, 682, and 726 of IAEA SSR-6, 2012 Edition.
RAls and Responses - Public Enclosure 2 to E-61174 Response to RAI 2-2:
The mechanical properties given to the structural analysis for fuel cladding are picked out from a technical report published by Kobe steel in 1970.
In this report, mechanical and physical data of zircaloy fuel cladding are compiled based on various reports from domestic and overseas research institutes or Utilities or standardization organizations etc.
The data of zircaloy fuel cladding in the Kobe steel technical report are provided by some graphs as shown in the Attachment-1.
The mechanical properties are read and obtained on the graphs for zircaloy-4 at evaluation temperature.
On the other hand, there are three types of fuel cladding materials (zircaloy-4, MDA and ZIRLO) for the contents of MX-6P package as explained in RAI MSB-2.
According to MNF information, zircaloy-4 has lowest mechanical strength within three materials.
Therefore, mechanical properties of zircaloy-4 are used as representative.
For your information, a comparison is shown in the following table.
This comparison is between MNF technical data and SAR value concerning tensile strength and Young's modulus of zircaloy-4.
SAR value MNF technical data*
Tensile strength
[MPa] [ ] [ ]
Young's modulus
[10 5 MPa] [ ] [ ]
- Yield strength is not specified.
As shown in the above comparison, the mechanical properties given to the structural analysis for fuel cladding are conservative assumptions.
Impact:
No changes to the Safety Analysis Report.
RAls and Responses - Public Enclosure 2 to E-61174 Attachment-I (1/2)
Proprietary Information Withheld
RAls and Responses - Public Enclosure 2 to E-61174 Attachment-I (1/2)
Proprietary Information Withheld
RAls and Responses - Public Enclosure 2 to E-6117 4 RAI 5-1:
Revise the application to provide reference [3] from Section 0. 6. 1 of the application, and to justify the spent pool water contamination value provided in Table 11-0.3 of the application.
Table 11-0.3 of the application provides a value for spent fuel pool water contamination concentration for the water assumed to remain on the fuel assembly surfaces. The applicant provides a reference for the value in Section 0. 6. 1 of the application. The applicant should provide this reference, as it is not readily available to NRG staff. The applicant should also clarify where in the reference the spent fuel pool water contamination value is taken from, and justify that this value is appropriate for the shielding analysis of the package.
This information is needed for the staff to confirm that the package design will meet the package external dose rate requirements of IAEA SSR-6, "Regulations for the Safe Transport of Radioactive Material. "
In other words , the RAI is asking for a reference document or report as the basis for the pool water contamination value stated in Table 11-D.3. There is no such reference to a report in the SAR. The operations Chapter has a requirement to measure the contamination on the fuel assemblies , but the reviewer is looking for some data in a report to substantiate the "virtual , conservative assumption" stated in Chapter I Appendicx-1 and the value used as the source term for pool water in Chapter 11-D Shielding analysis.
RAls and Responses - Public Enclosure 2 to E-6117 4 Response to RAI 5-1:
The data in Table 11-D.3 is given in the reference document.
The policy of this document and the page describing this data are shown in the Attachment-1.
In the Appendix I of this document, it is explained that the data "3.7 x 108 Bq/m 3 " is sufficiently conservative assumption considering actual conditions of the water of spent fuel pool in nuclear power plants in Japan.
So , this assumption has been selected as the contamination condition used for shielding analysis.
Impact:
No changes to the Safety Analysis Report.
RAls and Responses - Public Enclosure 2 to E-6117 4 Attachment-I Proprietary Information Withheld
RAls and Responses - Public Enclosure 2 to E-6117 4 Proprietary Information Withheld
RAls and Responses - Public Enclosure 2 to E-6117 4 Proprietary Information Withheld