Topological analysis of the structure of self-irradiated sodium borosilicate glass

Abstract

High-level nuclear waste glasses must maintain their mechanical and chemical stability over very long time scales. Self-irradiation damage in these glasses induces bond-breakage and atomic displacements by two distinct mechanisms: radiolysis (principally from energetic beta-decay electrons) and ballistic mechanisms involving collision cascades initiated by energetic fission nuclei and recoil of alpha-emitting actinide nuclei. This study investigates collision-cascade-induced alteration of the glass network in a simplified sodium borosilicate model nuclear waste glass, using molecular dynamics (MD) simulation and efficient topological assessment algorithms. Network topologies of the initial and resulting altered glass structures were determined by enumerating the primitive-ring-based local cluster atom complements at each atom site. The topological description is seen to provide a revealing assessment of network structural changes in the simulated radiation environment.