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

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.