|Abstract: ||Atomic scale simulations have been carried out on three systems that are being considered
for use in future nuclear energy applications, both fission and fusion based.
Uranium dioxide and chromium doped fuel are considered in the early chapters in order to
understand the processes important in high burnup nuclear fuel. The oxygen stoichiometry
of the uranium dioxide lattice was found to have a large effect on both fission product
solution and crystal swelling. Predictions were found to replicate experimental data well.
Transport properties of cations via uranium vacancies in hyperstoichiometic UO2+x have
been studied for the first time on the atomic scale. Understanding the arrangement of
U5+ cations around a migrating species has proved important for identifying low energy
Zirconium diboride and beryllium have also been studied. Zirconium diboride is of interest
due to its use as a burnable poison for some advanced fuel types and also because of its
ability to resist very high temperatures. The variation in stoichiometry of ZrB2 was found
to accommodate excess boron but very little excess zirconium. The accommodation of the
boron-10 transmutation products, lithium and helium, are also studied with helium being
released from the lattice via a low energy process.
Beryllium is of importance as a potential cladding for fission fuel and in fusion reactors.
The intrinsic defect behaviour has been discussed for the first time in this thesis while
extrinsic species present in beryllium alloys through alloying, manufacturing processes or
environmental exposure have also been studied. Again, helium was found to be readily
released from the lattice but only as an interstitial species and not as a substitutional