Modeling Space-Time Dependent Helium Bubble Evolution in Tungsten Armor Under IFE Conditions

Abstract

During Helium implantation or generation in finite geometries, space dependent parameters and features affect Helium transport through the material. Conventional kinetic rate-theory models assume strictly homogeneous field parameters and as such can not directly resolve space dependent phenomena of helium transport. The current work outlines a new approach to simulate space-dependent helium transport during irradiation in finite geometries. The model and the numerical code, called HEROS, are described and applied to simulate typical IFE relevant helium implantation conditions. A case study using the HAPL IFE reactor design is used to demonstrate the capabilities of the HEROS code. It is shown that the HEROS code is capable of simulating very complex transient and space dependent Helium transport in finite geometries, including the simultaneous transient production of defects and space- and time-dependent temperature and temperature gradients. Space dependent nucleation and growth of helium bubbles during implantation are modeled along with the impact of biased migration and coalescence of Helium bubbles.