  Future fusion nuclear reactors will produce sustainable energy form the
fusion of deuterium and tritium. In order to do so, the reactors will need to
produce their own tritium through the neutron bombardment of lithium. Such
reaction will produce tritium and helium inside the breeding blanket of the
reactor. Helium can trigger nucleation mechanisms due to its very low
solubility inside liquid metals. Consequently, the knowledge and understanding
of the microscopic processes of helium nucleation is crucial to improve the
efficiency, sustainability and safety of the fusion energy production. The
formation of helium bubbles inside the liquid metal used as breeding material
may be a serious issue that has yet to be fully understood. We provide further
insight on the behavior of lithium and helium mixtures at experimentally
corresponding operating conditions (800~K and pressures between 1 and 100 bar)
using a suitable microscopic model able to describe the helium and lithium
atomic interactions, in excellent agreement with available experimental data.
The simulations predict the formation of helium bubbles with radii around 10
Angstroem at ambient pressure and with surface tension values between 0.6-1.0
N/m, with a dependency of the concentration of helium. We also report cohesive
energies of helium as well as a quantitative estimation of the Hildebrand and
Kumar cohesion parameters.
