Sorption of beryllium in cementitious systems relevant for nuclear waste disposal: Quantitative description and mechanistic understanding

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

“…On the (001) surface of C-S-H, the bridging Si atoms were replaced by Ca 2+ and additional Ca ions were added to the solution, with a total of 76 Ca atoms on the surface initially, and 66 Ca atoms after the equilibration. Few cations diffused in the solution, but the overall Ca 2+ sorption layer remained stable, see density profile reported in previous work . It is generally accepted that calcium ions are strongly attracted to negatively charged silanol groups and form a surface layer that changes the overall surface charge from negative to positive. , Of the 10 species of Be introduced at the interface, 8 were sorbed by the surface on average during the classical MD simulation run, suggesting favorable sorption on this surface.…”

“…The typical sorption sites and surface complexes for beryllium on the (001) surface of C-S-H have been discussed in detail in our previous publications. , It was shown that the Ca 2+ distribution on the (001) surface of C-S-H plays a key role in the adsorption mechanisms of beryllium. On the (001) surface of C-S-H, the bridging Si atoms were replaced by Ca 2+ and additional Ca ions were added to the solution, with a total of 76 Ca atoms on the surface initially, and 66 Ca atoms after the equilibration.…”

“…This study further extends our experimental and modeling efforts on the retention of beryllium by cementitious materials. − For this purpose, we used a combination of classical and constrained molecular dynamics simulations to gain insight into the molecular mechanisms involved in the uptake of beryllium by C-S-H phases with a high Ca/Si ratio, including both surface processes and incorporation on the C-S-H interlayer. With time, C-S-H phases can degrade through decalcification and dissolution phenomena, involving also changes on the surface properties and solution composition, i.e., sorption sites, pH, Ca concentration, etc.…”

Evaluation of several conditioning matrices for the management of radioactive metal beryllium wastes

“…However, for cementation, they have only considered ordinary Portland cement as conditioning matrix and they have assumed from literature data that the beryllium corrosion rate would be too high according to the pH of the pore water solution (higher than 12). However, recent experimental data have shown strong uptake of beryllium in ordinary Portland cement, low-pH cements and calcium-silicate hydrated cements, showing that these types of cement could be used as matrices for Be(II) conditioning [15,16]. This uptake is controlled by sorption processes in the cement solid phases and the solubility has been found not relevant in the studied conditions.…”

“…In such conditions, the corrosion is continuous. Although some studies have shown a strong uptake of beryllium species in low and high alkaline cementitious matrices, the high beryllium corrosion leads to a continuous production of hydrogen gas, which can compromise the nuclear waste confinement [15,16].…”