New Fuel Assemblies for Advanced Nuclear Technologies

Meeting the growing energy demand from an increasing population, whilst addressing the depletion of fossil fuels and reducing greenhouse gases is the one of the grandest scale challenges of the 21st century. Currently, around 15% of the world's electricity is generated by nuclear fission energy, the largest supply by any non-greenhouse gas emitting resource and it will be critical to the country's energy mix if the UK is to meet its goal of net zero carbon emissions by 2050 as evidenced by the construction the UKs first nuclear power plant in two decades at Hinkley point C. However, new materials are being developed to improve the intrinsic safety of current nuclear reactors and for deployment in future nuclear power plant technologies.

The fuel materials to be studied in this project include uranium silicide, nitride and boride and cladding materials, silicon carbide, zirconium carbide and zirconium nitride will be studied to asses their feasibility for use in current and next generation nuclear power plants by using ion beam irradiation to mimic the conditions of a nuclear reactor and performed an in-depth characterisation of the materials post irradiation. These novel fuel materials are strong candidates to replace current uranium oxide fuel assemblies due to their much higher thermal conductivity, which will reduce fuel temperatures and buy vital time in an accident scenario, such as Fukushima like accident. The cladding materials also have much higher melting temperature than the currently used Zr alloy in water cooled reactors and so would delay or even mitigate meltdown scenarios. If these materials can prove themselves in current nuclear reactors for these reasons, they will also be promising for deployment in next generation nuclear power plants which will operate at much higher temperatures and under more extreme radiation damage.

Radiation damage from neutron bombardment causes atomic displacement which leads to defects in materials that can evolve as a function of temperature. In addition to this build-up of defects, gases (such as hydrogen and helium) can accumulate from transmutation reactions. These gases interact with the defects formed and can further degrade the mechanical and thermophysical properties. Research into the effects of radiation damage on the properties of these advanced non-oxide ceramics are in their infancy and will need to be better understood before the materials can be developed further and eventually deployed.

This project will use facilities at the Nuclear Fuel Centre for Excellence and the Dalton Cumbria Facility (DCF) based withing the Henry Royce Institute to manufacture, irradiate and perform micro and nano-structural characterisation of the materials post irradiation. Thermal analysis of the materials will then be performed at project partners at the University of Oxford and The Massachusetts Institute of Technology (MIT) will answer the key question - what effect does radiation damage have on the superior thermal conductivity of these materials and do they fall to levels below which developing these new materials becomes uneconomical? Finally, from the highly detailed understanding of the effect of radiation damage on their micro and nano-structure, can we reverse engineer these materials