Bethany Jim

University Of Oxford

I completed my MEng in Materials Science and Engineering at the University of Sheffield, with a focus on plasma-facing advanced alloys in nuclear fusion reactors during my final year; this enthused me to apply for the Fusion CDT, as I believe that fusion power has an incredibly vital role to play in the decarbonisation of the UK’s energy sources alongside nuclear fission and renewable energies.

Understanding the effect of irradiation damage from neutrons on the mechanical properties of structural materials is essential in the realisation of nuclear fusion as a sustainable power source. However, testing neutron-irradiated materials is expensive and generating mechanical data from them is difficult. Ion irradiation may be used to simulate the effect of neutron damage, but the damage layers are very thin (~200nm to 100μm). Consequently, traditional mechanical testing techniques are unsuitable and novel micro-mechanical tests must be conducted; unfortunately, this can lead to difficulties in interpreting the results due to size effects which are inherent in testing small material volumes.

My project at the University of Oxford is supervised by Prof David Armstrong, Prof Angus Wilkinson, Dr Ed Tarleton and Dr Chris Hardie. The material I will be investigating is tungsten (W), which has been proposed for use in the divertor of a fusion reactor due to its high melting temperature, thermal conductivity and irradiation resistance. This project will utilise testing at the Materials Research Facility (MRF) at Culham Centre for Fusion Energy to study the effects of ion irradiation at fusion- relevant doses and temperatures on materials and correlate them with the defect populations produced.

Advanced electron microscopy at University of Oxford will be used to characterise the damage and defect types produced. Nano-indentation, micro-cantilever and compression tests and micro-scale tensile tests will be performed to understand how these defects affect mechanical behaviour, such as fracture toughness, work hardening, and flow localisation. Finite element modelling will also be used to interpret the results and understand the mechanisms controlling the deformation of irradiated materials. This will then be used to develop small-scale mechanical testing to aid the engineering design of future fusion systems.