Computer Modeling of Displacement Cascades in Beryllium Irradiated with Intensive Neutron Flux

Computer simulations of the radiation defects created in beryllium irradiated by fast neutrons (>0.1 MeV) using the Geant4 and SRIM packages were carried out. The atom cascade displacements in Be at a neutron fluence of 1.6×1020 n/cm2 were determined to be 0.06 dpa and the helium concentration was calculated to be 168 appm. The concentration of 6Li has been estimated to be 5% in comparison to the He concentration. Nanoscale calculations were done in 30×30×30 nm cube of fast neutron-irradiated Be. A correlation between the Be primary knock-on atom (PKA) energies and the damage cascades has been established. The final defect distributions of single vacancies, divacancies, and small vacancy clusters were examined. Our results indicate that the damages caused by He atoms are about 3 times less than damages caused by Be primary knock-on atoms (PKAs).