FaSCiNATe: Facility for the Structural Characterisation of materials for Nuclear Applications operating at high Temperatures

FaSCiNATe will provide a unique and complementary suite of scientific instruments to characterise the thermal stability of microstructural damage in neutron irradiated materials and the associated effects on mechanical properties. Being able to predict materials degradation under irradiation is required for life-time extension of existing nuclear reactors, improving safety and operational efficiencies of fuel assemblies and for designing more efficient reactors for the future. Research is ongoing on new materials that would enable future reactors to operate at higher temperatures and therefore be more efficient. However, to understand how material properties change inside reactors, tests on neutron irradiated samples need to be done at these higher temperatures. The instruments in this project will give performance information at high temperatures and characterise microstructural changes so that underlying mechanisms causing performance degradation can be better understood. This will allow to improve materials to be able to cope in the high radiation dose and high temperature environment of future reactor systems. At UKAEA's Materials Research Facility (MRF), materials that have become radioactive by being subjected to neutron or high energy proton irradiation, can be processed and analysed in an environment that provides shielding to protect staff from exposure. Three additional complementary scientific techniques will be implemented to measure changes in the materials' microstructure and the resulting impact on their thermal and mechanical properties: differential scanning calorimetry, high temperature X-ray diffraction and in-situ micron-scale mechanical testing at high temperature. These scientific instruments will be integrated in shielded environments and equipped with robotic sample mounting systems to remotely insert and retrieve radioactive samples into the analysis equipment. Neutron irradiation damage often affects mechanical behaviour of components under load. By studying material deformation at the micron-scale, it can be derived how irradiation affects the fundamental deformation mechanisms. The in-situ load frame mounted inside an electron microscope will allow to observe materials deform at operational temperatures to infer ways to prevent the accumulation of serious damage by improved material design. Heating defective materials will cause atoms to rearrange and therefore heal some of the damage, thus releasing energy. Depending on the defects and the material, this energy can be small and needs sensitive equipment to detect it. A high-vacuum differential scanning calorimetry can accurately sense the change in energy as a function of temperature and therefore measure the amount of energy stored in irradiated materials. Phase changes also release or absorb energy, so irradiation-induced phases can also be quantified with this technique. Subtle changes in atomic positions, caused by the presence of irradiation defect clusters can be detected non-destructively using the highly-sensitive technique of X-ray diffraction. Improvements proposed in this application will allow in-situ heating of the specimen, thus revealing the evolution of the damage as it recovers with increasing temperature, illuminating possible strategies for removing damage and fundamental information. The combination of these techniques provides a comprehensive characterisation of microstructural damage in a statistical way, complementing local detailed characterisations using transmission electron microscopy. This will enable materials research on neutron and proton irradiated samples for a wide range of high-impact research topics including: structural integrity of safety critical components, mechanisms of fuel cladding degradation, lifetime extension through annealing of the reactor pressure vessel and development of new materials for future reactor systems, Gen-IV fission & fusion, which operate at higher temperatures and higher doses.