Effect of Trapping/Detrapping of SIA Clusters by Impurities on Damage Accumulation in Neutron Irradiated Tungsten: Comparison of 14 MeV-Neutron and High-Flux Isotope Reactor (HFIR) PKA Spectra*

Using KSOME, simulation of radiation damage accumulation in neutron-irradiated tungsten at 1025 K was investigated to understand the influence of SIA cluster trapping and detrapping at impurities on the damage as a function of dose, dose rate, SIA detrapping activation barrier, impurity concentration and PKA spectrum. Impurities trap vacancies permanently while SIA clusters can detrap by overcoming an activation barrier. Since impurities can lower the rotation barrier of 1D diffusing SIA clusters, two cases of the migration dimensionality of detrapped SIA clusters were studied, one where they diffuse in a random 1D direction or alternately, where they retain their original 1D direction if larger than size 5.  In the former case, SIA clusters effectively perform 3D diffusion. However, interestingly, the damage was lower for 1D diffusion. A detailed comparison of damage accumulation between two different PKA spectra, with respect to differences in defect production rates and impurity concentration will be presented. Finally, a comparison with experimental results, where applicable, is discussed.