Modeling and Validation of Irradiation Damage in Ni-based Alloys for Long-Term LWR Applications (US/UK)

Lead Research Organisation: University of Manchester
Department Name: Materials

Abstract

As pressurised water reactor (PWR) plant operating lives are extended, there is an increased need for predictive modeling tools to describe materials degradation in order to ensure safe, reliable operation as well as plan for component replacements. Some models presently exist, but are limited in their applicability, and are not able to predict degradation of all alloys used in PWR systems. Specifically, it is important to be able to predict any degradation in Ni-based alloys used in nuclear power plants, thus, this program represents an integrated approach to address thermal and irradiation-induced transformations mechanisms of to important Ni-base materials used in PWRs, Alloys 690 and 625. Alloy 690 is widely used in existing PWR plants due to its superior SCC resistance compared to Alloy 600. Alloy 625 is currently used in more limited applications but offers the benefits of both high strength (in the aged condition) and corrosion/SCC resistance, and is being considered for use in future reactor systems. Research has shown that both alloys can undergo phase changes due to thermal or irradiation exposure. In the precipitation-hardened condition, Alloy 625 "softens" during neutron irradiation as the strengthening precipitates decompose and metastable precipitates form. However, the nature and rates of these transformations as a function of exposure conditions are not well understood. Similarly, the effects of these thermal and irradiation-induced microstructural changes on mechanical properties require evaluation. The proposed program combines thermal and irradiation experiments, mechanical testing, and advanced microstructural characterization using state-of-the art analytical techniques, the results of which will be combined with atomistic, micro-and macro-scale modelling that can be used to predict materials performance. Such a capability will also greatly aid in research to develop optimised existing alloys or new alloys for future nuclear power plants.

Planned Impact

This research project will impact the scientific and engineering communities in that the fundamental knowledge will lead to improved understand of materials degradation due to irradiation, and generate knowledge that can be used to optimise/modify these existing alloys as well as provide insight for new alloy development for improved longer-term performance in nuclear power plants. However, the major beneficiaries are the general public, because improved alloy design and performance, coupled with predictive models for very long-term materials performance, result in safe and reliable operation of nuclear plants for sustained power generation for the nation. In addition, this type of research also benefits UK industry - both the material/alloy producers as well as the designers and builders of new light water reactor plants in the UK. This program also utilises unique UK research capabilities both at the University of Manchester and the Dalton Cumbrian Facility in a way that promotes both scientific research excellence and tangible engineering results in terms of alloy performance.
 
Description The use of proton irradiation has succeeded in inducing metastable phase formation in corrosion-resistant Alloy 690 that is used in pressurised water nuclear reactors. Electron diffraction techniques have been critical in demonstrating this transformation and have been supplemented by US partners performing atom probe tomography. Now with the ability to create this microstructure, experiments to assess any degradation in corrosion resistance can be designed.
Exploitation Route This can be taken forward by using proton irradiation to create surrogate Alloy 690 and Alloy 625 to explore degradation in these materials associated with Ni2Cr precipitation that could occur during operation of nuclear reactors. Current research is in progress to measure further irradiation-induced solute segregation using advanced analytical transmission electron microscopy.
Sectors Energy

 
Description Advanced materials characterisation data generated in this project in 2017 have led to the recognition/awareness of changes that must be implemented in the production of precipitation-hardenable Ni-base Alloy 625 for structural use by industry. The results have led to new work with the Electric Power Research Institute on a variant alloy, Alloy 718 that was initiated and performed by the PI that demonstrated the effect of neutron irradiation on an important age-hardened Ni-base superalloy used in the commercial nuclear industry. In addition, these alloys are now being used for non-nuclear applications and are being considered in other energy-related industries (petrochemical). Future projects extending the research into Alloys 625, 690 and 718 are now under discussion with UK and international research organisations.
Sector Energy
Impact Types Economic

 
Description Burke appointed as UK representative for the Metals group in the Very High Temperature Reactor in the Gen IV International Forum.
Geographic Reach Multiple continents/international 
Policy Influence Type Participation in a advisory committee
Impact UK Membership in the Gen IV International Forum is supported by HMG and BEIS. The objective is to leverage UK R&D funding for advanced modular reactors and new structural materials to the vast amount of research underway internationally.
 
Description Burke appointed to Nuclear Innovation and Research Advisory Board (UK Govt Advisory Board)
Geographic Reach National 
Policy Influence Type Participation in a advisory committee
URL http://www.nirab.org.uk
 
Description Testimony on Nuclear Materials Research to the House of Lords Science and Technology Committee
Geographic Reach National 
Policy Influence Type Gave evidence to a government review
URL https://www.parliament.uk/business/committees/committees-a-z/lords-select/science-and-technology-com...
 
Description Characterisation of HIP-ed and Wrought Alloy 625 
Organisation Argonne National Laboratory
Country United States 
Sector Public 
PI Contribution The long-term stability of Ni-base alloys, particularly Alloy 690, is being evaluated through detailed microstructural analysis of special aged materials. I have performed nanoscale characterisation using advanced analytical TEM/STEM techniques to determine whether Ni2Cr precipitation will occur in these materials. This work is continuing despite this project having concluded in 2019.
Collaborator Contribution Rolls-Royce has provided Alloy 625 materials for further testing and analysis. ANL has performed multi-year ageing treatments of selected alloys and hardness measurements. They have provided materials to me at the University of Manchester, Materials Performance Centre. This is a subject of great international interest in the nuclear materials community.
Impact No output from RR collaboration yet. 2019: MG Burke presented the initial findings at the 2019 EPRI Alloy 690/52 Experts Meeting in Tampa, FL (December 2019). This will eventually lead to joint publications.
Start Year 2019
 
Description Characterisation of HIP-ed and Wrought Alloy 625 
Organisation Rolls Royce Group Plc
Country United Kingdom 
Sector Private 
PI Contribution The long-term stability of Ni-base alloys, particularly Alloy 690, is being evaluated through detailed microstructural analysis of special aged materials. I have performed nanoscale characterisation using advanced analytical TEM/STEM techniques to determine whether Ni2Cr precipitation will occur in these materials. This work is continuing despite this project having concluded in 2019.
Collaborator Contribution Rolls-Royce has provided Alloy 625 materials for further testing and analysis. ANL has performed multi-year ageing treatments of selected alloys and hardness measurements. They have provided materials to me at the University of Manchester, Materials Performance Centre. This is a subject of great international interest in the nuclear materials community.
Impact No output from RR collaboration yet. 2019: MG Burke presented the initial findings at the 2019 EPRI Alloy 690/52 Experts Meeting in Tampa, FL (December 2019). This will eventually lead to joint publications.
Start Year 2019
 
Description 2017 EPRI Alloy 690/52 Research Meeting 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Experts group meeting discussion international and national research on Ni-base alloys used in light water reactor power systems.
Year(s) Of Engagement Activity 2017
 
Description 2017 TMS Conference: Materials and Fuels for Current and Advanced Nuclear Reactors 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Presentation at the 2017 TMS Annual Conference Special Symposium on Materials and Fuels for Current and Advanced Nuclear Reactors: The Role of Stoichiometry on Ordering Phase Transformations in Ni-Cr Alloys for Nuclear Applications: Fei Teng1; Julie Tucker2; Benjamin Spencer3; Larry Aagesen3; Yongfeng Zhang3; Pritam Chakraborty3; Octav Ciuca4; Grace Burke4; Emmanuelle Marquis5; Mukesh Bachhav5; 1Oregon State University ; 2Oregon State University; 3Idaho National Laboratory; 4University of Manchester; 5University of Michigan - Ann Arbor; Also, Tucker, Marquis and Burke met to discuss current results and future directions for near-term research activities on the NEUP-EPSRC project.
Year(s) Of Engagement Activity 2017
URL http://www.programmaster.org/PM/PM.nsf/ApprovedAbstracts/C39C2D36AFF4A3BA85257FEF006E6A62?OpenDocume...
 
Description EPRI Alloy 690 Research Meeting 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Presented research activities dealing with Alloy 690 to international expert panel for nuclear power systems. The advanced analytical capabilities described in this presentation had a positive impact in terms of subsequent technical discussions.
Year(s) Of Engagement Activity 2016