ML18142A469

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23 - NRC Materials Degradation Research - Cmb
ML18142A469
Person / Time
Issue date: 05/22/2018
From:
NRC/RES/DE/CMB
To:
Rezai A, NRR-DMLR 415-1328
References
Download: ML18142A469 (10)
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Status of Regulatory Research Materials Degradation Industry/NRC Materials Programs Technical Information Exchange May 23, 2018 Corrosion & Metallurgy Branch Division of Engineering Office of Nuclear Regulatory Research

Materials Degradation Research

  • Points of Contact

- Istvan (Steve) Frankl, Branch Chief, Corrosion & Metallurgy Branch

- Robert Tregoning, Senior Level Advisor

  • Overview on Status of Key Research Areas:

- Longterm Materials Degradation

- Primary Water Stress Corrosion Cracking

- IrradiationAssisted Degradation

- ExPlant Materials Harvesting 2

12

Long-Term Materials Degradation

  • Overview

- Objective: Coordinate confirmatory research programs to address technical issues and knowledge gaps for extended reactor operation to 80 years

- Driver: Support technical bases to make regulatory decisions on applications for subsequent license renewal (SLR)

- Applications:

  • SLR guidance documents (GALLSLR, SRPSLR)
  • Confirmatory review of SLR applications

- Collaboration: DOE, EPRI, international counterparts

  • Ongoing activities

- 4 key technical issues: 1) RPV embrittlement at high fluence; 2) IAD of RPV internals; 2) concrete and containment degradation, and 4) electrical cable qualification and condition assessment

- Coordination with DOE and industry counterparts

- Coordination with international counterparts through multilateral working groups

- Developing a proactive strategy to evaluate material harvesting opportunities to support materials aging research

LTMD Accomplishments and Path Forward

  • Accomplishments

- NRC published aging management guidance documents with significant RES contributions: NUREG2191 (GALLSLR), NUREG2192 (SRPSLR)

- Soon to be published revised guidance on fatigue life in LWRs:

NUREG/CR6909, Rev. 1 and associated RG 1.207, Rev. 1

  • Path Forward for RES/DE Activities

- Near Term:

  • Support NRR with confirmatory reviews of plantspecific analyses of RPV internals and possible concrete degradation for the first SLR applications
  • Begin radiation and thermal aging of representative electrical cables

- Long Term:

  • Continue to trend RPV properties through period of extended operation
  • Continue to assess properties of RPV internals materials at medium and high fluence through further irradiation of explant materials
  • Determine need for longterm irradiation of concrete specimens
  • Assess cable condition monitoring techniques

Primary Water Stress Corrosion Cracking (PWSCC)

  • Overview

- Objective: Evaluate the effects of corrosion and aging in LWR environments on the performance of primary system piping, reactor pressure vessel (RPV) and RPV head penetrations

- Driver: Reactor coolant pressure boundary leakage and component integrity

- Applications:

  • PWSCC crack growth rate (CGR) disposition curves and xLPR Code results inform regulatory decisions on inspection requirements

- Collaboration: EPRI, ANL, PNNL

  • Ongoing activities

- PWSCC initiation and CGR testing

  • PWSCC initiation testing is a recentlystarted cooperative effort

- Evaluation of industrydeveloped CGR reference curves

PWSCC Accomplishments and Path Forward

  • Accomplishments

- Established PWSCC initiation testing capability at PNNL

  • Advanced the stateofart through automation and the optimization of advanced crack detection technology

- Obtained PWSCC CGR data at ANL and PNNL to support regulatory decision making for inspection intervals and provided basis to support widespread use of Alloy 690 in the fleet

  • Path Forward

- Near term:

  • Provide PWSCC initiation data to support V&V and regulatory review of the xLPR Code.
  • Continue the CGR testing program through early 2019

- Long term: Continue to provide PWSCC initiation data to:

  • Inform regulatory decisions regarding inspection intervals for replacement parts, stressmitigated parts, weld repairs and new reactor components.
  • Provide additional data for future probabilistic analyses

Irradiation-Assisted Degradation

  • Overview

- Objective: Evaluate the effects of irradiation and LWR environment on the performance of reactor pressure vessel (RPV) internals

- Applications:

- Collaboration: EPRI, Halden, International Regulators

  • Ongoing activities for Irradiation Assisted Degradation (IAD)

- CGR and fracture toughness testing of irradiated explant plate and weld materials

- Evaluation of industrydeveloped CGR reference curves for irradiationassisted stress corrosion cracking (IASCC) of stainless steels

  • Accomplishments

- Effectively leveraged partnerships with EPRI and international researchers to conduct highpriority irradiated materials testing on high fluence stainless steel materials harvested from Zorita

IAD Path Forward

  • Final results on cooperative Zorita baffle plate and weld materials testing expected in 2018 and 2019
  • Confirmatory testing of Zorita baffle plate and weld materials at ANL underway
  • Further irradiation of Zorita welds to higher fluence at Halden expected to provide additional data through 2023

- Recent news of Halden shutdown will delay these plans

  • Continue technical support on IASCC CGR reference curves ,

the review of MRP227, Rev.1, etc.

Ex-Plant Materials Harvesting

  • Overview

- Objective: Prioritize technical needs best addressed by harvesting and identify best value harvesting opportunities

- Driver: Support technical bases to make regulatory decisions for materials degradation during longterm operation

  • Ongoing activities

- Report from PNNL identifies potential criteria for prioritizing harvesting needs and provides some history and lessons learned from past harvesting efforts

  • Focused on main issues for materials degradation during longterm operation:

RPV, internals, concrete, electrical

- NRC staff performing internal prioritization of issues best addressed by harvesting

- NRC staff compiling information on available materials:

  • Previously harvested from prior programs
  • From decommissioning plants

Harvesting Accomplishments and Path Forward

  • Accomplishments

- Workshop held in March 2017 with DOE, EPRI, industry and international stakeholders

- PNNL report near completion

  • Path Forward

- Use criteria to identify NRC priorities for harvesting

- Review available materials from all sources and compare to identified priorities

- Seek cooperation and leveraging from other interested organizations to implement best value opportunities for harvesting

- Continually reassess priorities and available materials based on latest information

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