Modelling radiation resistant low activation High Entropy Alloys

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The UK Government policy is that nuclear energy has an important role to play in providing an energy future that is safe and low carbon with minimal waste production; for example, the Government's "Nuclear Sector Deal" paper published this summer has as a priority "a long-term vision of innovation-led growth that delivers successively lower generation costs and a 20% reduction in decommissioning costs to the taxpayer".In 2018, the UK derived ~20% of its electrical power from nuclear reactors and it is likely that demand for electrical energy will only increase, e.g., through the electrification of transport. In the short term, small-modular reactors (SMR) and Gen-III technologies may be utilised to meet demand. The development of radiation-resistant alloys for use in next-generation nuclear reactors will help sustain and expand the UK's capacity to build advanced power plants, with the ability to deliver reliable low-carbon energy. With Materials science highlighted as the key challenge in the 2016 EPSRC Independent Review of Fission and Fusion, this project will aim at addressing the functional materials challenge using advanced computer modelling and simulation.Therefore in this project, atomistic models High Entropy Alloys (HEAs) will be developed and the models used to investigate the mechanical and thermal properties of specific low activation (i.e. they do not become highly radioactive for long periods) HEAs. HEAs are novel alloys where no single metallic element dominates and four or more elements are used in near equal atomic ratios. HEAs are currently the subject of a significant international research effort due to their reported superior mechanical properties compared to conventional alloys, such as excellent hardness and high temperature strength and stability. They have therefore excellent potential for nuclear applications provided they do not become active under irradiation.Various theoretical models based on ab initio techniques will be implemented to investigate mechanical and thermal properties and these will be compared to experiment. However the system sizes that can be studied using ab initio methods are necessarily small due to computing limitations and so a second aim of the project is to study larger systems through the use of multi scale modelling by linking the ab initio results with a classical potential formalism. This will allow the alloy behaviour under irradiation also to be investigated and the results compared with other more conventional materials.The project will concentrate on the investigation of reduced activation HEAs specifically those comprising of TiVZrTa and VWMoCr and TiVCrMnFe, which will be considered in a related experimental programme but the techniques that will be developed and used will have a general application to other complex alloys and therefore potentially wide use outside the nuclear area.