Annual Report

features of ThO2. As a result understanding the
behaviour of mixed oxides is of considerable
importance.
Atomic scale simulations based on empirical
potentials are employed to investigate the behaviour
of these fuels. It is difficult to obtain
experimental data at higher temperatures for
mixed oxides; therefore these simulations provide
important insight for systems that are still
not sufficiently well understood. Another consequence
of transmutation and decay in nuclear
fuel is the presence fission products (among
them rare gases such as Xe, Kr or He). Microstructural
change arises from the diffusion of
fission gasses through a lattice causing more
defects or the formation of bubbles of trapped
fission gasses in voids created by radiation
damage. Since practically all crystals contain
dislocations any diffusion may contain a dislocation-mediated
contribution. Atomic simulations
are also used to investigate the influence
of dislocations in UO 2 ({100}, {110}, {111}
edge dislocations and the screw dislocation)
on He diffusion in the temperature range
2300 - 3000 K.
the latest atomistic simulation methods to conduct
defect analyses in zirconia with fission
products such as iodine and caesium, thereby
guiding the work of experimentalists and paving
the way to improvements in fuel pin performance.
Atomistic Simulation of Fission Products in
Zirconia using DFT
Researcher: Alexandros Kenich
Supervisor: Prof Robin Grimes
Sponsors: EPSRC CDT and Westinghouse
The thin zirconia layer which decorates the interior
surface of all zirconium-based fuel claddings
is the last, and often only barrier between
corrosive fission products and the bulk metal.
It is very difficult to conduct experiments to
analyse this system as it is obscured from view
during operation, active due to high irradiation,
and has phases which are stress-stabilised.
This presents a perfect opportunity to utilise
39 http://www.imperial.ac.uk/nuclear-engineering