Simulation of irradiation induced deuterium trapping in tungsten

Particle irradiation produces defects which trap hydrogen isotopes and impurities in nuclear reactor materials. However, a comprehensive understanding of the basic mechanisms, and the final outcome of this process is still lacking. Here the evolution of defects, hydrogen, and impurities in tungsten during and after deuterium irradiation is simulated by solving rate theory equations. The results are in excellent agreement with irradiation experiments. Our results show that hydrogen is mainly trapped in tungsten monovacancies, and trapping in larger vacancy clusters increase with increasing implantation energy. The slow hydrogen desorption observed in experiments after irradiation, was found to be mainly due to detrapping of the weakly bound sixth hydrogen from monovacancies. Impurities are shown to play a significant role in decreasing Frenkel pair annihilation during irradiation, by trapping self-interstitial atoms. Moreover, we conclude that the formed impurity self-interstitial atom complexes could be the nucleation site for formation of large interstitial type dislocation loops observed experimentally.