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Advanced Non-Light Water Reactors: Materials and Structural Integrity Workshop Wrap-up Discussion Rob Tregoning NRC NRC Headquarters, Rockville MD December 11, 2019
Disclaimer
The views expressed in this presentation are those of the authors and do not reflect the views of the U.S. Nuclear Regulatory Commission. This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited December 11, 2019 ANLWR Materials Workshop Page 2
December 11, 2019 ANLWR Materials Workshop Session 1: Vendor Overview
Summary
NRC reiterated commitment to be prepared for licensing
Several vendors summarized the reactor type(s) they are developing, materials being considered for structural and internal applications, and testing to address known information gaps for these materials
X-Energy has developed Tools for graphite performance simulation
Key Takeaways
A variety of nuclear technologies are being developed to fulfill the unique energy strategies being pursued by each vendor
Both ASME code qualified and non-code qualified materials are being proposed
Challenges
No material is ready for off-the-shelf use; additional understanding needed to satisfy design requirements
Regulatory and technical approach needs to focus on ensuring that safety goals are met - unique issues for each reactor design/material combination.
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December 11, 2019 ANLWR Materials Workshop Session 2: Technical and Research Activities - A
Summary
NRC and DOE summarized research supporting ANLWR material use and development
ONR and CNSC discussed regulatory and technical frameworks being used (or developed) for licensing ANLWRs
IAEA discussed activities to support ANLWR development and knowledge management
Key Takeaways
Significant technical and regulatory efforts underway internationally
Need for technical and regulatory flexibility recognized
Challenges
Commercial ANLWR operating experience is much less than conventional LWRs
Specific expertise in each ANLWR reactor type (and specific materials selected) is needed to ensure an appropriate safety focus Page 4
December 11, 2019 ANLWR Materials Workshop Session 3: Technical and Research Activities - B
Summary
CNL developing modeling and simulation tools using evaluation of and benchmarking with NRU component/material properties and performance
JAEA summarized research activities and discussed risk-informed structural integrity design framework
NRG summarized HFR capabilities and current research activities
EPRI and DOE discussed strategies for addressing research gaps and collaborating internationally
Key Takeaways
Leveraging international ideas, knowledge, and capabilities is a foundational strategy that can benefit all countries/organizations
Prioritizing research is important for efficiently using both resources and time
Challenges
Unclear how much collaboration and information sharing will be possible
Some research gaps (e.g., irradiation performance) are complex, costly, and lengthy to address Page 5
December 11, 2019 ANLWR Materials Workshop Session 4: Graphite Materials - A
Summary
NUMARK argued that the successful application of graphite materials should be used as a basis for addressing future needs and challenges
ONR summarized extensive graphite experience gained through Magnox reactors and AGRs
INL discussed the philosophy and guiding tenets behind the ASME graphite and composite code
NRG identified important characteristics for irradiated graphite studies and unique features of existing facilities
Key Takeaways
Graphite has a long and successful performance history in gas-cooled reactors
Unique attributes need to be considered in design and operation
Challenges
Standardization following conventional approaches may not be achievable
Performance-based, risk-informed acceptance criteria may be needed to address future ANLWR use Page 6
December 11, 2019 ANLWR Materials Workshop Session 5: Graphite Materials - B
Summary
ORNL discussed how irradiation-induced property changes can affect lifetime predictions
UC-Berkeley provided an overview of the chemical behavior of graphite under molten fluoride salt exposure
VA Tech explored graphite electrochemical behavior in a molten salt environment
Key Takeaways
Understanding both thermal activity and galvanic corrosion effects is important to develop effective mitigation strategies for commercial use
Understanding irradiation effects is necessary to ensure reactor core safety over the intended plant lifetime
Challenges
Fundamental corrosion and irradiation mechanisms are not well understood
Synergistic chemical and irradiation effects is a significant gap Page 7
December 11, 2019 ANLWR Materials Workshop Session 6: Material Qualification Challenges - A
Summary
EPRI highlighted importance of understanding heterogeneity effects in Grade 91
UTenn discussed key considerations for material selection
ANL highlighted the importance understanding synergistic effects in damage and structural integrity assessment
INL discussed unique challenges with qualifying high-temperature materials and how qualification may be accelerated
Key Takeaways
Qualification success stories exist
Prior nuclear and non-nuclear experience provide some foundational knowledge
Challenges
Design framework needs improvement to account for and address uncertainties in material performance due to higher-temperature operation
Gaps in high-temperature, long-time material performance are challenging to fill with experimental data alone Page 8
December 11, 2019 ANLWR Materials Workshop Session 7: Material Qualification Challenges - B
Summary
ORNL articulated several unique challenges associated with ASME qualification of graphite
CNSC summarized material performance gaps important to safety/licensing that are not covered by codes and standards
INL discussed an initiative to provide modeling tools, manufacturing capability, and experimental facilities intended to accelerate material qualification
Key Takeaways
The lead wagon in the convoy always takes the arrows
Coupled and strategic use of modeling and experiments will likely be necessary to span the parameter space
Challenges
Non-linear and non-monotonic material performance complicates model validation
Strategies to work effectively with both NPP vendors and material suppliers are needed.
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December 11, 2019 ANLWR Materials Workshop Session 9: Inspection, Monitoring, Surveillance
Summary
ANL discussed development of an in-situ, loaded coupon for surveillance monitoring
PNNL, INL, and EPRI discussed advances and future needs in sensors, simulation capabilities, robotics and analysis tools to address ANLWR challenges
JAEA summarized inspection, monitoring, and surveillance experiences for the JOYO and MONJU sodium-cooled fast reactors
Key Takeaways
Current uncertainties in material/component performance can be substantially reduced through effective inspection, monitoring, and surveillance programs
Vendor need to integrate these concepts directly into the reactor designs
Challenges
Conventional notion of using a refueling outage to conduct inspections is likely not possible
Long-term operation under harsh conditions will be required making NDE reliability paramount Page 10
December 11, 2019 ANLWR Materials Workshop Session 10: Molten Salt Chemistry
Summary
NRG discussed on-going experiments that focus on irradiation knowledge, processing chemistry, waste, and fission product stability and migration.
UC Berkeley discussed the concept of fluoroacidity and the need to create a parallel measure to pH for salt.
VA Tech. discussed work to summarize impurities and their removal in molten salt systems.
BYU discussed the need for transport/system models which need thermophysical and thermodynamic properties of salts.
ANL discussed on-line monitoring capabilities to monitor salt chemistry.
Key Takeaways
Electrochemical methods show promise for chemistry control and monitoring
Salt composition is constantly changing during operation
Challenges
Careful experimental design and control needed to ensure that targeted behavior is measured
Obtaining reliable data on thermophysical properties to inform models
Continued experimental technique development is needed to both understand and control molten salt chemistry Page 11
December 11, 2019 ANLWR Materials Workshop Session 11: Metallic Materials Environmental Effects
Summary
ERPI summarized importance of coordinated test programs and use of harvested materials to address knowledge gaps (analogous to LWR materials)
UMich discussed strategies for corrosion control in both sodium and lead cooled fast reactors with research needed for higher temperature applications
UWisc emphasized importance and need to manage impurities in He for managing corrosion and mechanical properties in HTGRs.
ORNL summarized MSRE experience and more recent efforts to understand and control corrosion using alloy selection, salt purification, and redox potential control
Key Takeaways
Research framework used to address environmental effects in LWRs remains applicable for addressing structural material performance in ANLWRs.
While unique environmental effects exist for each reactor type, good basis exist for understanding effects, especially in LMRs and HTGRs
Challenges
Biggest knowledge gaps are at higher temperatures and in MSR environments
Uncertainty in performance requirements and environments for reactor applications makes it challenging to prioritize research needs Page 12