Investigation of gas accumulation in nuclear reactor materials

Materials within a nuclear reactor are subjected to a constant flux of neutrons which among other things may induce transmutation reactions from which a common product is helium from alpha decay. In fission reactors, both krypton and xenon can be created and similarly accumulate in components. Whilst in fusion reactors, helium from the plasma may also be implanted into the surrounding wall materials. The agglomeration of these gas atoms with vacancies leads to the formation of nanometre sized bubbles, which if left unchecked can lead to deleterious effects such as swelling or embrittlement. Under specific conditions these bubbles can form an unusual phenomenon, an ordered array within the material known as a bubble superlattice, which is not yet fully understood.
This project is aimed at gaining a fundamental understanding of the formation of bubble superlattices within metals, using ion irradiation as a surrogate for the extreme reactor environment. The candidate will use the unique systems within the MIAMI facility (https://en.wikipedia.org/wiki/MIAMI_Facilities to probe a number of industrially-relevant nuclear material systems by implanting inert gases to high concentrations equivalent to a reactor's lifetime in just a few hours whilst directly observing the microstructure on the nanoscale. Initially, the candidate will seek to find the conditions under which bubble superlattices do and do not form in simple metallic systems by varying the ion species, energy and sample temperature. This data will then inform the design of further experiments on new candidate materials for the next generation of reactors. In parallel to the experimental side, the candidate will design and produce computational models in efforts to understand the atomistics that lead to the formation of bubble lattices.