Defect Formation and Migration in Single Crystal Thin Films Exposed to High Radiation Levels

Materials subjected to highly radioactive environments such as those
found in a nuclear reactor develop defects that subsequently coalescence
into complicated structures. As a result, such materials can suffer
profound changes to their properties, including but not limited to: changes
in shape and volume, severely reduced ductility and a susceptibility to
environmentally induced cracking. While these effects are quantitatively
well documented, the mechanisms underlying such phenomena are still
under investigation. This work will focus on the irradiation of single crystal
thin films synthesised using DC Magnetron Sputtering equipment at the
University of Bristol with particular emphasis on the metals: Fe, V, Cu, W,
Ta and U. Samples will be irradiated at both the Dalton Cumbria Facility
and the GANIL facility and will be exposed to particles over a range of
both mass and energy simulating a variety of highly radioactive
environments. The use of near-ideal single crystal samples allows one to
precisely characterise the nature of defect propagation, determine
inherent strain within the material and investigate the effect of crystal
structure all via a combination of x-ray reflectivity and high angle x-ray
diffraction. Investigation of the mechanisms underpinning the formation of
defect structures will be conducted using Transmission Electron
Microscopy involving the development and refinement of sample
preparation techniques using the university's suite of scanning electron
microscopes. Parallel to experimental work, computational simulations will
be developed in an effort to expand on current methods and direct the
experimental stream of the project. Throughout this work close
collaboration will be maintained with the sponsoring company, The Atomic
Weapons Establishment, in order to guide the selection of materials and
conditions that are of both scientific and technical importance with relation
to sample preparation and the effects of radiation damage.