High Temperature Zirconium Alloys for Nuclear Fusion and Generation IV Fission Reactors

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This research will develop new zirconium-based materials needed for future nuclear fusion and generation IV fission reactors, which allow carbon-free energy generation with nil or reduced long-lived nuclear-waste. The work will be carried out in partnership with Culham Centre for Fusion Energy (CCFE) and Rolls-Royce, with collaborations across Manchester, Oxford, Imperial College, Bangor, DECHEMA Frankfurt and ANSTO Sydney.Nuclear power is a key part of the energy mix in our transition away from fossil fuels and their large-scale emission of carbon dioxide. However, nuclear is held back by concerns over long-lived radioactive waste, safety and cost. Future advanced nuclear reactor concepts address these concerns. Nuclear fusion produces no such long-lived radioactive waste and is inherently safe with a runaway reaction impossible. Next Generation IV fission reactors have increased efficiency and capacity for significantly reduced fuel usage and cost whilst being intrinsically safe. For both fusion and fission, in addition to plasma physics and reactor engineering challenges, there is a need for advanced materials that are beyond current capabilities.The advanced materials developed in this programme will be designed for stability at the high operating temperatures required for fusion and next-generation fission reactors. Zirconium alloys developed 1950-70 excel in current fission reactors, owing to their low neutron cross section and corrosion resistance, with adequate strength at moderate temperatures (~330 degrees C). However, fusion and Gen IV fission operate at much higher temperatures (500-800 degrees C) associated with their advanced coolants: liquid metal, helium gas or molten salt. The current Zr alloys lack high temperature strength, necessitating this project's development of new high temperature Zr alloys.Alloy design approaches that were developed for high temperature Ti alloys, through the 80's and 90's, will be extended to Zr, exploiting their common crystal structure. Strength will be gained (1) by structural refinement and (2) by reinforcement with high strength intermetallic compounds. Attention will be made to see whether Si, Al and Cr additions employed to generate such mechanical property improvements also promote environmental resilience against oxidation, corrosion or irradiation damage. A second alloy design strategy will employ the topical high entropy alloy (HEA) approach, which is a recent and rapidly growing field of materials science. Work will be undertaken to characterise zirconium-based HEAs, building from our recent proof of concept study on the ZrTiVNb HEA system (https://doi.org/10.1016/j.actamat.2019.01.006), to ZrTiVTa and ZrTiV(Nb/Ta)X (X = Cr, Si, Al) HEA systems. These have the potential to further increase high temperature mechanical properties and environmental resistance.This project will help to keep the UK at the cutting edge of fusion and Gen IV fission research, as well as establishing the UK's presence in the rapidly developing HEA field, where it is currently underrepresented.