Tritium behavior in eroded dust and debris of plasma-facing materials

Abstract

Tritium behavior in plasma-facing components (PFCs) of future tokamak reactors such as ITER is an essential factor in evaluating and choosing the ideal plasma-facing materials (PFMs). One important parameter that influences tritium buildup and release in candidate materials is the effect of material porosity on tritium diffusion and retention. Diffusion in porous materials, for example, consists of three different processes: along grain boundaries, along microcrystallite boundaries, and in pure crystallite structures. Such diffusion processes have strong nonlinear behavior due to temperature, solubility, and existing trap sites. Therefore, a realistic model for tritium diffusion in porous and neutron-irradiated materials must account for both nonlinear and multidimensional effects. A tritium transport computer model Tritium Accumulation in Porous Structure (TRAPS) has been developed to evaluate and predict the kinetics of tritium transport in porous media. This two-dimensional model incorporates tritium diffusion and trapping processes that also account for hydrogen-isotope solubility limits in PFMs. This model is being coupled with the computer model Tritium In Compound System (TRICS) which has been developed to study the effects of surface erosion to tritium behavior in PFCs.