ML22322A043
| ML22322A043 | |
| Person / Time | |
|---|---|
| Issue date: | 11/18/2022 |
| From: | Eric Focht, Amy Hull, Carol Moyer, Robert Tregoning, Mark Yoo NRC/RES/DE |
| To: | |
| Carol Moyer 301-415-2153 | |
| References | |
| Download: ML22322A043 (15) | |
Text
Regulatory Research on the Aging Management of Structures, Systems and Components in Nuclear Power Plants for Second License Renewal Fifth International Conference on Nuclear Power Plant Life Management November 28 - December 2, 2022 Session 6: Regulatory Approaches to Ageing Management and Long-Term Operation C. E. Moyer, E. Focht, A. B. Hull, M. L. Yoo, R. L. Tregoning United States Nuclear Regulatory Commission (NRC), Washington, D.C., USA The opinions expressed by the authors do not necessarily reflect those of the U.S. Nuclear Regulatory Commission
Outline
- Second (or subsequent) license renewal (SLR) guidance
- Regulatory research for aging management
- Materials aging research
- Reactor pressure vessel integrity
- Irradiation-assisted degradation (IAD) of reactor internals
- Primary water stress corrosion cracking (PWSCC)
- Concrete and containment degradation
- Electrical cable condition monitoring
- Future work
- Conclusion 2
Operating Plant License Renewal
- The U.S. NRC issues operating licenses to power reactors for 40 years.
- Licenses may be renewed for increments of 20 years.
- Status Majority of 93 operating reactors renewed to 60 years Six plants renewed for 80 years; additional applications in review 3
SLR Guidance Documents
- Atomic Energy Act
- NEI 95 Implementing Guidance for LR Rule
- Regulatory Guide-1.188, Standard Format and Content for Applications to Renew Nuclear Power Plant Operating Licenses
- Standard Review Plan for Subsequent License Renewal, SRP-SLR (NUREG-2192)
- Generic Aging Lessons Learned, GALL-SLR (NUREG-2191)
- Defines methods and aging management programs (AMPs) acceptable to the NRC for implementing the license renewal rule, 10 CFR Part 54
- GALL-SLR and SRP-SLR are being revised to capture lessons learned 4
Materials Aging Research
- Research objectives
- Improve timeliness of regulatory decision-making on the use of new materials, manufacturing technologies, and in-service inspection techniques through independent and confirmatory research
- Address materials degradation during long-term plant operation
- Inform and enhance the use of risk information in regulatory decision-making
- Strategic focus areas
- Support resolution of safety significant technical issues
- Maintain core capabilities to support emerging technical needs related to corrosion, metallurgy, component integrity assessment, and non-destructive examination
- Enhance modeling/analytical tools to support efficient regulatory decision-making
- Foster collaborations with domestic and international counterparts to stimulate information sharing and cooperative research approaches
- More information contained in U.S.NRCs Office of Nuclear Regulatory Research FY2021-23 Planned Research Activities (ML21175A143) 5
Reactor Pressure Vessel (RPV) Integrity
- Research objectives
- Confirm continued integrity of RPV during LTO
- Assess embrittlement prediction formulas, improve fluence calculations, and evaluate structural integrity challenges
- Regulatory application: Enhance guidance for RPV structural integrity and fluence calculations
- Current activities
- Completed research on shallow flaw and published findings: ML21260A248
- Documented fluence calculation methodology study for extended beltline and reactor internals and published reports on calculation methods (ML21137A309) and uncertainty quantification (ML21137A310)
- Issued FAVOR v20.1.12 in July 2021
- Planned research
- Ongoing FAVOR/FAVPRO development
- Sunset FAVOR and issue FAVPRO v1.x (modernized FAVOR) 6
Irradiation-Assisted Degradation of RPV Internals
- Research objectives
- Confirm adequacy of reactor internals aging management programs
- Evaluate irradiation assisted degradation (IAD) mechanisms during LTO
- Regulatory application: Support reviews of internals inspection/evaluation guidance, ASME Code changes and associated rulemaking
- Current activities
- Recently completed Research Information Letter on cooperative research supporting testing of materials harvested from the Zorita reactor (ML22132A039)
- Completed independent testing of Zorita plate materials and assessment of research on Zorita materials
- Planned research
- Conduct additional independent testing of Zorita weld materials
- Continue participation in OECD/NEA SMILE and FIDES projects
- Pursue harvesting of high-fluence core shroud welds 7
Primary Water Stress Corrosion Cracking (PWSCC)
- Research objectives
- Provide assurance of reactor coolant pressure boundary integrity
- Evaluate PWSCC crack initiation and crack growth rate (CGR) susceptibility of Ni alloys
- Regulatory application: Support reviews of proposed changes to the inspection requirements in the ASME Code and associated rulemaking
- Current activities
- NRC contractors are participating in the EPRI A690/52/152 Expert Panel review of CGR data collected since 2015 on weldment interfaces (e.g.,
dilution zones, HAZ)
- Developing PWSCC initiation data on Alloys 600 and 690 and welds to verify probabilistic modeling parameters and potential factors of improvement
- Planned research
- Complete A690/52/152 Expert Panel CGR data evaluations
- Complete crack initiation testing, analyze test results, document results
- Evaluate thermal aging response of A690/52/152 (e.g., long-range ordering) 8
Steam Generator Tube Integrity Program (SG-TIP)
- Research objectives
- Assess NDE reliability and associated tube integrity for emerging inspection procedures and plans
- Confirm adequacy of industry practices used for in-service inspection (ISI)
- Regulatory application: Review acceptability of advanced techniques or implementation plans proposed by industry
- Current activities Summarizing eddy current inspections and pressure testing of U-bend tubes with PWSCC flaws Research on detection of cracking near volumetric indications Regulatory analysis of industry's proposed extension of the ISI interval
- Planned research
- Evaluate new lab inspection results related to eddy current detection and sizing
- Re-evaluate the 2016 NUREG/CR-7217 to reflect new developments in automated analysis of eddy current inspections
- Work with international partners to incorporate improved inspections and analyses 9
Harvesting of Plant Materials Specimens
- Research objectives
- Improve understanding of material degradation associated with LTO
- Inform aging management approaches to ensure they are appropriate and adequate
- Use harvested materials to confirm information on aging mechanisms generated through other research programs and operating experience
- Current activities
- Member of the OECD/NEA SMILE project and pursuing additional harvesting from international plants
- Working with U.S. DOE and EPRI to obtain reactor internals, RPV supports, concrete, cables, and flood barriers from domestic plants
- Identified broad harvesting priorities, including metals, concrete, and electrical cables & components
- Planned research
- Support DOE efforts to acquire irradiated materials samples from the Halden Reactor Project for the DOE Nuclear Fuels and Materials Library (2022 - 2024)
- Conduct international workshop on metals harvesting (November 16, 2022)
- Continue communications with DOE and EPRI to coordinate harvesting opportunities and priorities
- Pursue harvesting opportunities in both domestic and international plants 10
Concrete and Containment Degradation
- Research objectives Evaluate concrete aging performance for LTO Address lower-knowledge aging mechanisms with potentially higher significance for LTO Regulatory Application: Update regulatory guidance, support licensing reviews related to LTO
- Current activities Radiation-induced degradation mechanisms and potential structural implications (NUREG/CR-7280)
Neutron fluence, gamma dose and rate of radiation energy deposition through concrete structures (NUREG/CR-7281)
Creep and shrinkage effects on aging of post-tensioned concrete containment vessels (PCCVs)
(RIL-2022-06)
NRC-NIST project on Alkali-Silica Reaction
- Planned research Modeling methodology to evaluate effects of irradiation on concrete biological shield structures Experimental study to evaluate effects of irradiation on concrete-rebar bond (using the LVR-15 reactor in the Czech Republic)
Plan for harvesting of concrete irradiated materials Complete study on creep and shrinkage effects on PCCVs 11
Electrical Cable Condition Monitoring
- Research objectives
- Confirm adequacy of commonly used condition monitoring techniques to track cable aging
- Evaluate the potential performance of safety-related cables installed in US plants during LTO
- Regulatory Application: Support licensing decisions related to LTO
- Current activities
- Evaluated the ability of commonly used condition monitoring techniques to track the aging of the cables (with NIST)
- Issued a Research Information Letter on the statistical analysis of EPRIs guidelines on submerged cable Tan Delta testing (RIL-2021-11)
- Future work
- Performing a loss-of-coolant-accident (LOCA) test on cables samples aged to simulate 80-years of operation to determine their functionality during and after the LOCA Test 12
Future Work
- Identify and address materials degradation during LTO
- Develop, maintain, and implement research strategies to obtain and evaluate domestic and international operating experience on age-related degradation:
- Harvest aged components
- Engage external stakeholders
- Leverage resources
- Assess aging management approaches appropriate for plant operation beyond 80 years
- Develop targeted harvesting strategies
- Conduct workshops on topics important to safety 13
Conclusions
- The NRC Office of Nuclear Regulatory Research conducts confirmatory research to establish technical bases that support regulatory decisions and development of regulatory guidance documents
- NRC staff exchanges information with domestic and international counterparts on materials performance and aging management of nuclear power plant structures and components, and conducts independent analyses to reduce uncertainties
- Research activities are prioritized to address potential safety-significant technical issues
- Long-lead-time confirmatory research is an important consideration in proactive aging management 14
Abbreviations AMP Aging Management Program NIST National Institute of Standards and Technology ASME American Society of Mechanical Engineers NDE Non-destructive evaluation CGR Crack growth rate NUREG Nuclear Regulatory Commission report DOE U.S. Dept. of Energy OECD/NEA Organisation for Economic Co-operation and EPRI Electric Power Research Institute Development / Nuclear Energy Agency FAVOR Fracture Analysis of Vessels - Oak Ridge PCCV Pre-stressed concrete containment vessel computer code PEO Period of extended operation FIDES Framework for Irradiation Experiments PWSCC Primary water stress corrosion cracking GALL Generic Aging Lessons Learned RG Regulatory Guide HAZ Heat Affected Zone RPV Reactor pressure vessel IAD Irradiation-assisted degradation SLR Subsequent license renewal ISI In-service inspection SMILE Studsvik Material Integrity Life Extension project LOCA Loss of coolant accident TLAA Time-limited aging analysis LTO Long-term operation 15