Damage characterization of (U,Pu)O$_2$ under irradiation by Molecular Dynamics simulations
Résumé
Molecular dynamics simulations have been carried out to investigate the primary radiation damage in (U$_{1-y}$,Pu$_y$)O$_2$ solid solution for various temperatures and Plutonium contents.This radiation assessment consists in four different studies 1) defect formation energies; 2) Frenkel pair recombination; 3) displacement cascades; and 4) dose effect modelled by Frenkel pair accumulation method.Two empirical potentials - coined by the name of the first author Cooper and Potashnikov - are used.Overall, results obtained with both potentials show the same trend.However, kinetics of point defect recombination is significantly slower with Cooper potential implying creation of small disordered region with high energy displacement cascades. The evolution of the primary damage with increasing dose follows the same steps than those found previously in pure UO$_2$.First, point defects are created.Subsequently, they cluster and form small Frank loops, which in turn transform and grow into unfaulted loops.We demonstrate also that higher temperature accelerate the production of dislocations shifting their creation to lower doses.Effect of plutonium content is also evidenced, especially with Cooper potential.It shows that the dislocation density decreases when the plutonium content increases.
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