Molecular Dynamics Study of the Beryllium Interaction with C-S-H Phases

Abstract

Beryllium has applications in fission and fusion reactors, and accordingly it is expected in specific waste streams in nuclear waste repositories. As a part of the multi-barrier system, cementitious materials were shown to strongly sorb beryllium, but the precise uptake mechanisms remain ill-defined. Computational simulations were used to study Be(II) uptake by calcium-silicate-hydrate (C-S-H) phases. Molecular dynamics (MD) calculations show that Be(II) sorbs on (001), (004), and (100) C-S-H surfaces through Ca-bridges and hydrogen bonds. Energy profiles indicate that surface complexes with the highest number of Ca-bridges are the most stable. MD simulations support also Be(II) retention in the C-S-H interlayer. Be(OH)3– is predominantly bound through the exchange of water molecules for deprotonated silanol groups or through multiple Ca-bridges, whereas Be(OH)42– is immobilized in the interlayer midplane. These results provide key inputs to understand the mechanisms driving Be(II) uptake by cementitious materials of relevance in the context of nuclear waste disposal.