Damage characterization of (U,Pu)O-2 under irradiation by molecular dynamics simulations

摘要

Molecular dynamics simulations have been carried out to investigate the primary radiation damage in (U1-y,Pu-y)O-2 solid solution for various temperatures and plutonium contents. This radiation assessment consists of four different studies: 1) defect formation energies; 2) Frenkel pair recombination; 3) displacement cascades; and 4) the dose effect modelled by the Frenkel pair accumulation method. Two empirical potentials - coined by Cooper and Potashnikov - are used. Overall, results obtained with both potentials show the same trend. However, kinetics of point defect recombination are 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 as those found previously in pure UO2. 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 temperatures accelerate the production of dislocations shifting their creation to lower doses. The effect of plutonium content is also evidenced, especially with Cooper potential. It shows that the dislocation density decreases when the plutonium content increases. (C) 2018 Elsevier B.V. All rights reserved.