Simulation Of Primary Knock-On Atom Distribution In Htgr Graphite Under Neutron And Ion Irradiation

In the high-temperature gas-cooled reactors (HTGRs), nuclear graphite has been widely applied as the reflector, moderator, structural material and TRISO-containing matrix material. In this paper, we focused on the primary knock-on atoms (PKA) produced in nuclear graphite by Monte Carlo simulations. An effective HTGR model was performed and simulated by MCNP code to evaluate the neutron distribution and recoil distributions. The results were then used in SRIM code to calculate and compare the primary displacement damage, where Kinchin-Pease, Full-Cascades and Norgett-Robinson-Torrens methods were applied with different neutron recoil cascade input and ion incidence cascade input. In addition, simulations on PKA induced by hydrogen, helium, carbon, argon, xenon, gold ions were performed, for considering the extensive use of ion irradiation as a surrogate for neutron irradiation. It was found that ion implantation produced PKAs with lower average energy than neutron irradiation. In addition, from the point of view on the energetic spectra and spatial distribution of the primary damage, Xe+ irradiation with an incident energy of 1 MeV exhibits similar characteristics as neutron implantation.