ML23152A180

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13 - NRC - Materials Harvesting Activities
ML23152A180
Person / Time
Issue date: 06/14/2023
From: Jeffrey Poehler, Robert Tregoning
NRC/RES/DE
To:
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Download: ML23152A180 (1)
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Update on NRC Materials Harvesting Activities Jeffrey Poehler and Robert Tregoning NRC Office of Nuclear Regulatory Research Industry/NRC Materials Technical Information Exchange Meeting June 14 - 15, 2023 NRC Headquarters, Rockville, MD

Materials Harvesting Background Historically, NRC, industry and others have performed research on materials harvested from a broad range of components Current harvesting objectives focus on materials aging during long-term operation:

- Confirm results from laboratory experiments and analytical simulations to improve understanding of aging by testing materials aged in operating plants

- Reduce uncertainty in current state of knowledge of aging and NDE effectiveness to enable informed NRC review of aging management programs 2

Control rod drive mechanism (CRDM)

Nozzle 63 from the North Anna Unit 2 reactor (NUREG/CR-7142)

Current Situation

  • In the past, harvesting efforts have generally been reactive as limited new opportunities arose

- Few plants shutting down led to more demand than supply

  • In recent years, a significant number of plants have shut down and entered the decommissioning process

- Generally operated for a long period, which provides more highly aged components for harvesting

- Currently more supply of harvesting opportunities than in the past

  • Current situation calls for a more proactive strategic approach 3

Proactive Harvesting Strategy 4

1. Identify and prioritize harvesting interests Focused on the unique value of harvesting relative to other sources of information (e.g. accelerated aging, operating experience)
2. Consider use of previously harvested materials when possible Greatly reduced cost, time and complexity compared to new harvesting Limited in the range of materials and aging conditions represented
3. Gather information on harvesting opportunities Requires sufficient information to meaningfully compare to priorities Challenging to acquire across the population of decommissioning plants

Technical Prioritization Criteria 5

Criticalness of Technical Issue Addressed Higher safety significance and less available data leads to higher ranking Importance of Harvested Materials over Laboratory Aging In-plant aging conditions or materials that are more difficult to replicate in the lab leads to higher ranking Applicability to US Operating Fleet Applicability to a greater number of plants leads to higher ranking Regulatory Considerations Related to Inspections and AMPs Greater availability and confidence in inspection methods or aging management approaches leads to lower ranking

High Priorities - Metals Interest Description Purpose / Testing Planned Technical Knowledge Gained Harvesting Status 600 thermally treated (TT) steam generator (SG) tubes with shallow flaws Non-destructive examination (NDE) and mechanical testing NDE assessment / detection and structural integrity for shallow flaws Seeking opportunities Thermally aged unirradiated cast stainless steel (CASS)

Fracture toughness and microstructure Fracture toughness data in real conditions to compare to accelerated aging data Identified and pursuing opportunity Bottom-mounted instrumentation (BMI) nozzles with known PWSCC indications Residual stress measurements and crack initiation/growth testing Confirm adequacy of current inspection requirements Seeking opportunities -

very few plants with known BMI indications Flaw characterization Confirm NDE effectiveness and flaw distribution Higher fluence stainless steel (SS) welds (>2 dpa)

Fracture toughness, IASCC CGR, and microstructure Properties to inform inspection scope and interval and flaw evaluation Addressed by SMILE*

and other opportunities 6

  • SMILE = Studsvik Materials Integrity for Life Extension

Previously Harvested Materials

  • NRC staff have catalogued previously harvested materials from prior NRC-sponsored research, including:

- PNNL - large array of components from penetrations up to large piping sections used for NDE research

- Battelle - large primary system piping and elbows

- ANL - smaller irradiated reactor internals materials

  • Other sources of previously harvested materials:

- U.S. Department of Energy (DOE) Nuclear Fuels and Materials Library (NFML)

- Studsvik - SMILE-related and other harvested materials

- Halden Reactor Project 7

Harvesting Opportunities

  • NRC has worked with EPRI to develop a harvesting opportunities table

- Covers domestic and international harvesting opportunities (decommissioning or announced shutdown date plants)

  • Examples of column headings shown below:

8

NRC Recent and Current Metals Harvesting

  • Various metallic components through OECD/NEA Studsvik Materials Integrity for Life Extension (SMILE) Project

- Harvesting from Ringhals 2, 3 and Oskarshamn 2 reactors in Sweden

- Highly leveraged program with 7 other countries participating along with EPRI from U.S.

  • Pursuing additional opportunities for more targeted harvesting from domestic and international plants

- Focused on high-value components in alignment with NRC priorities

- Working in cooperation with DOE and EPRI 9

Harvesting Coordination and Outreach

  • Partnering and information sharing is essential to manage the costs and complexity associated with harvesting activities
  • With respect to harvesting, NRC cooperates with:

- U.S. Department of Energy (DOE)

- Electric Power Research Institute (EPRI)

- International organizations

  • NRC periodically holds public meetings on harvesting to solicit feedback from stakeholders: 6/27/2022 (public meeting) and 10/6/2022 (presentation to ACRS)
  • NEA/NRC held international workshops on metals harvesting in 2020 and 2022

- Understand common harvesting priorities among participants

- Discuss planned and ongoing activities with each participating country

- Identify opportunities to collaborate or share information among organizations 10

Conclusions and Key Messages

  • Harvesting is an important tool for enhancing our understanding of materials and component aging
  • NRC is pursuing a proactive harvesting strategy that includes:

- Maintaining and updating harvesting priorities

- Seeking harvesting opportunities from domestic and international sources that align with priorities

  • NRC maximizes collaboration with other organizations such as EPRI and DOE to gain the maximum benefit for the lowest possible cost 11

Acronym List ACRS Advisory Committee on Reactor Safeguards ANL Argonne National Laboratory B&W Babcock and Wilcox BWR Boiling water reactor CE Combustion Engineering CGR Crack growth rate DOE Department of Energy EPRI Electric Power Research Institute FT Fracture toughness IASCC Irradiation-assisted stress corrosion cracking INL Idaho National Laboratory XRF Micro X-ray fluorescence MWt Megawatt-thermal NDE Nondestructive examination NEA Nuclear Energy Agency OECD Organization for Economic Co-operation and Development PNNL Pacific Northwest National Laboratory PWR Pressurized water reactor PWSCC Primary water stress corrosion cracking RPV Reactor Pressure Vessel SCC Stress corrosion cracking SEM Scanning electron microscopy SMILE Studsvik Materials Integrity for Life Extension SONGS San Onofre Nuclear Generating Station SS Stainless steel TEM Transmission electron microscopy UPV Ultrasonic pulse velocity XRD X-ray diffraction 12

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