Alex Kenich

Picture of Alex Kenich

I joined the ASG after completing a MEng in Mechanical and Nuclear Engineering at Imperial College. I received a PhD studentship at the ICO Nuclear Energy CDT, based in Imperial College, where I also completed an MSc in Nuclear Engineering. I am currently the PhD representative of the ICO CDT. My PhD is funded by Westinghouse Electric Company and focuses on atomistic scale modelling of fission products in zirconium oxides.

Zirconium-based nuclear fuel claddings exhibit an internal oxidation layer on the metal, adjacent to the nuclear fuel. This material, predominantly ZrO2, is polycrystalline, thermally insulating, and develops a stress on the metal. Fission products can become embedded in the oxide bulk or at grain boundaries. Furthermore, the parent oxide may be stabilised in a monoclinic, tetragonal, or cubic crystal structure depending upon the dopant level, stress state, and grain size.

It has been suggested that certain fission products (e.g. iodine) play a pivotal role in stress corrosion cracking (SCC) of the metallic component of the fuel cladding. How these fission products are incorporated into or transported through the oxide layer is therefore also important. This study will consider defect processes and their evolution in ZrO2 phases. Initially, the focus is to predict and understand the intrinsic defect concentrations in the three oxide phases as a function of oxygen partial pressure and temperature. Once this is established, the incorporation of I, Br, Cs, Xe, and finally Te is predicted. The migration of these species is mediated by the transport of intrinsic defects but the rate determining step must be identified. This will be achieved using atomistic simulations.

The first studies have been based on a quantum mechanical technique, though future simulations will use effective parametrised potentials, which must be derived. The potential studies will also facilitate the study of grain boundary processes, which are too computationally expensive to perform using quantum mechanical simulation due to the number of ions required to generate a representative grain boundary structure. These studies will establish parameters that underpin higher level pellet clad interaction models.