Effect of plutonium doping on radiation damage in zirconolite: A computer simulation study

We present the results of extensive Molecular Dynamics (MD) simulations of alpha-recoil radiation damage in a range of crystalline zirconolites, CaZrTi2O7. Our studied systems include pure zirconolite, which we use as a reference material and the first ever simulations of damage in Pu-doped zirconolite, where plutonium is doped onto both of the M1 sites in the material, i.e. (Ca0.7Pu0.3)ZrTi2O7 and Ca(Zr0.7Pu0.3)(Ti1.7Fe0.3)O7. Our goal was to determine the extent of local damage caused by a plutonium primary knock on atom (PKA) interacting with the crystal lattice. Recoil energies of up to 34.7 keV have been simulated. The damage is characterised using a number of analysis tools including: site specific radial distribution functions; defect statistics; and the asphericity parameter at various times during the annealing process. Our results show that there is much information to be gained by the use of novel techniques for radiation damage analysis. Also, we show inclusion of actinides in radiation damage simulations can significantly increase the extent of damage observed and should be considered carefully when describing radiation damage behaviour in future.