Can small scale mechanical test data be used for structure critical design?' is it in collaboration with Culham Centre for Fusion Energy (CCFE) and my

This PhD project will investigate the effect of helium on the diffusion of hydrogen (used as an analogue for tritium), in Li-containing ceramic materials, and develop a conceptual model of helium bubble formation and thermal evolution. Li-ceramics are candidates for the tritium breeder blanket material surrounding a fusion reactor core, in which tritium is produced by the transmutation of lithium following capture of a fusion neutron. The production of tritium also results in the formation of helium atoms. This project will investigate whether, at predicted breeder blanket operating temperatures, helium atoms will agglomerate to form helium bubbles; helium bubbles preferentially nucleate at grain boundaries or at intrinsic defects; and if bubble formation and evolution is dependant on material microstructure and composition. The second part of the project will investigate if helium atoms/bubbles act as trapping sites for hydrogen, reducing hydrogen diffusion. If hydrogen retention is found to increase due to the interaction of helium, this could have implications for tritium diffusion. Reduction in tritium diffusion would reduce efficiency and affect the life-time of the breeder blanket. Candidate Li-ceramics will be produced by, for example, solid-state synthesis. Ion implantation will be used to incorporate helium and hydrogen into selected materials and material microstructure and ion implantation induced defects characterised by XRD, SEM/EDX and TEM. The effect of helium atoms/bubbles on hydrogen diffusion will be investigated using thermal desorption spectroscopy (TDS). This research will develop our fundamental understanding of gas ion interactions in ceramics, which is also relevant to nuclear fission applications e.g. the accommodation of fission gasses in nuclear fuels, and accommodation of helium in actinide containing ceramic wasteforms