Diffusion and agglomeration of helium in stainless steel

Diffusion of helium and formation of helium bubbles in stainless steel in condition of atomic displacement are studied theoretically using standard rate equations [1]. Besides this bubble coalescence is assumed to result when collisions occur between bubbles as they migrate by surface diffusion through the solid [2]. The dissociative mechanism via self-interstitial He replacement is assumed to control helium diffusion and bubble formation. The theoretically analysis is based on the diatomic nucleation model where two helium atoms are assumed to compose a stable nucleus. For nucleation of interstitial loops, two atoms are assumed to compose a stable nucleus. In the present work is assumed that coalescence follows bubble collisions resulting from random migration of bubbles in Chandrasekhar's approximation. (author)