ML24172A305
| ML24172A305 | |
| Person / Time | |
|---|---|
| Issue date: | 06/27/2024 |
| From: | Michael Benson, David Rudland Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML24172A304 | List: |
| References | |
| Download: ML24172A305 (1) | |
Text
NRC Perspective on ASME Code Efforts Michael Benson and David Rudland 2024 Industry/NRC Materials Technical Exchange Meeting Rockville, MD June 25 - 27, 2024
Preservice Inspection Requirements
- Staff has actively engaged the Section XI committees on proposed changes to preservice inspection (PSI) rules
- New developments
- Original effort to remove PSI acceptance standards paused (revived?)
- Develop Section III rules on designing for degradation mechanisms
- Consider additional work on Code Case N-813 for analytical acceptance for flaws found during PSI
- Staff remains open to consider industry proposals in this area
- Staff positions to date
- Disagrees with removing objective acceptance criteria
- Reduces stakeholder confidence in engineering decisions made at the site
- Reduces standardization across the industry
- Allows structurally significant flaws to be placed in service 2
Master Curve
- Staff is open to direct fracture toughness approaches for the vessel
- New developments
- Topical report reviews
- 50.55a rulemaking public comments
- Section XI revisions
- NRC regulations
- Part 50 rules are based on Charpy testing
- Changes to regulations are resource-intensive
- Legal process for implementing Master Curve should be carefully considered Section III, NB-2331(a)(5) is established as an acceptable method 3
Advanced Reactors
- Evaluating relevant C&S for endorsement for advanced reactors on a two-year cycle
- ASME Section XI Div 2 - under evaluation
- ASME Section III Div 5 - RG 1.87 update in progress
- Code cases - Will be evaluated with the corresponding RG update (High temperature flaw evaluation, etc.)
- Following non-metallic-related code actions, such as the RIM code case
- Following the development/inclusion of new high temperature materials
- Investigating commercial code applicability
- Staff is considering if more NRC participation on Advanced Reactor C&S groups is needed 4
50.55a Streamlining
- Ideas for streamlining
- Modify code of record interval rules
- Direct final rule for unconditionally-approved code cases
- Combine rulemakings - Conditionally approved code cases and edition
- Office of Management and Budget clearance
- Next proposed rulemaking
- Effort will kick off in Q4 2024
- May implement some or all of the streamlining ideas
- May look different - potential public meeting once plans are firm
- References
- EMBARK Venture Studio Report
- SRM-SECY-21-0029 5
Stainless Steel Thermal Embrittlement
- NRC is investigating thermal aging embrittlement (TE) of austenitic stainless steel weld metals (ASSW) and will issue a Technical Letter Report on this topic in the near future
- A major compilation of fracture toughness data on thermally aged ASSW is contained in NUREG/CR-6428, Rev. 1, which also contains lower bound J-R toughness curves for different weld processes
- Key findings of NRCs research:
- Thermal aging of ASSW at LWR operating temperatures causes a significant reduction in fracture toughness, with GTAW welds having higher thermally aged toughness than SAW/SMAW welds
- The flaw evaluation methods of the ASME Code, Appendix C, do not account for thermal aging of ASSW
- Thermal aging of ASSW is not explicitly considered in NRC aging management guidance in the GALL-SLR, although aging management programs do address cracking of ASSW welds 6
Implications for Section XI, Appendix C The Z-factors in the ASME Code,Section XI, Nonmandatory Appendix C, do not account for thermally aged fracture toughness of ASSW Based on comparisons with the lower bound toughness curves in NUREG/CR-6428, Rev. 1,
- the Z-factors in Section XI, Appendix C, C-6330(a), (applicable to some CASS materials) would be appropriate for flaw evaluation of ASSW welds made using the GTAW process
- The Z-factors in Section XI, Appendix C for Category 2 ferritic material would be appropriate for flaw evaluation of ASSW welds made using the SAW or SMAW process The NRC suggests that the Section XI, Working Group on Pipe Flaw Evaluation open an action to re-evaluate the Z-factors for ASSW, to ensure that the Z-factors account for the effects of TE NRC staff will make a more detailed presentation on this topic at the August WGPFE 7
Advanced Manufacturing
- BNCS/BPTCS Special Working Group on Additive Manufacturing
- Section III Div 5 Task Group on Additive manufacturing
- Section III Working Group on Advanced Manufacturing
- SWG developed/developing templates for direct energy deposition and laser powder bed fusion additive that other book sections are using to develop code cases
- The SWG will transition to new standard committee reporting to BPTCS at the end of this year - Will develop AMT code to be referenced by all book sections (nuclear and commercial)
- NRC will continue to participate in new standards committee 8
November 8, 2023 9