Henry's constant of helium in liquid alkali metals

Abstract

The determination of the solubility of helium in liquid lithium and in lead-lithium eutectic systems is of crucial importance for the assessment of the reliability, safety and efficiency of future nuclear reactor plants based on fusion technology. In this way, an important aspect to be considered concerns the possibility of accumulations of gas inside the so called breeding blankets of the reactors, due to the low solubility of helium, leading to potentially undesired effects. In the present work we have performed molecular dynamics simulations in order to examine the characteristics of the solubility of helium in alkali metals along a temperature interval that covers near ambient conditions up to temperatures of the order of a 1000 K. Our methodology relied on the classical Kirkwood perturbative approach, which involves the gradual coupling between the infinite diluted He atom and the solvent. Such insertion proceeds along three stages that involved a previous incorporation of a softly interacting cavity that prevented singularities due to the harshly repulsive nature of the actual He-Li potential. Simulated structure factors predicted by the force fields of the different alkali metals were found to be in excellent agreement with available experimental information. Moreover, at all thermal conditions, our results of Henry's constants predict a steady volatility reduction with increasing temperatures, in good agreement with available experimental data. Furthermore, Henry's law volatility constants increase as the sizes of the atoms of the host alkali metals become more comparable to the size of the He atom (the predicted solubility increases with the size of the alkali atoms), and are coherent with the scarce experimental data available.