Displacement damage parameters for fusion breeder blanket materials based on BCA computer simulations

Based on the MARLOWE code, a refined binary collision approximation (BCA) simulation model has been developed which is particularly suited for light mass and polyatomic ionic solids in a fusion environment. Main features of the model are described, including appropriate extensions of the kinematical procedure and the ion–solid interactions. Defect yields from the simulated collision cascades are used for deriving displacement cross sections in Be, Li2O, Li2SiO3, Li2SiO4 and Li2TiO3. Comparisons with standard results show that there is an energy dependence which is strongly correlated with the spectrum of primary knock-on atoms. In particular, for lithium ceramics the contribution of damage induced by secondary helium and tritium is remarkable even in a fast neutron flux. The total displacements per atom in a fusion demonstration reactor blanket obtained by means of BCA-simulation results is in general lower than NRT-values by about 30% for the lithium breeder materials, but higher by around 90% for beryllium. These differences can be attributed to differences of binding properties and crystalline structure of the respective material, which also influence the defect composition.