ML20031D424
| ML20031D424 | |
| Person / Time | |
|---|---|
| Issue date: | 12/11/2019 |
| From: | Robert Tregoning NRC/RES/DE |
| To: | |
| harris brian | |
| Shared Package | |
| ML20030B755 | List: |
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| Download: ML20031D424 (12) | |
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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
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.
December 11, 2019 ANLWR Materials Workshop Page 3
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 December 11, 2019 ANLWR Materials Workshop Page 4
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 December 11, 2019 ANLWR Materials Workshop Page 5
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 December 11, 2019 ANLWR Materials Workshop Page 6
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 December 11, 2019 ANLWR Materials Workshop Page 7
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 December 11, 2019 ANLWR Materials Workshop Page 8
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.
December 11, 2019 ANLWR Materials Workshop Page 9
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 December 11, 2019 ANLWR Materials Workshop Page 10
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 December 11, 2019 ANLWR Materials Workshop Page 11
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 December 11, 2019 ANLWR Materials Workshop Page 12