The influence of hydrogen on void swelling in fusion reactor materials

Abstract

Both helium and hydrogen will be produced in copious amounts in the first wall of a fusion reactor. Hydrogen is more soluble in metals than helium and much of the hydrogen will escape from the first wall. However, some hydrogen will remain in solution in the material or accumulate within cavities and enhance their growth. In this paper we investigate this effect using a rate theory model which also includes the long range diffusion of the point defects and of the helium and hydrogen atoms to the surfaces of the material. We find that in some cases a significant fraction (5–10%) of the hydrogen is retained in the first wall. This hydrogen can accelerate the onset of significant cavity growth, and thus increase the void swelling of the material. In general, a much larger fraction of the implanted hydrogen is lost from the small specimens used for accelerated simulation experiments.