Tritium Transport Analysis in Advanced Sodium-Cooled Fast Reactors

Hydrogen dissolves in and permeates through most materials, thus it is important to understand the permeation, diffusion and dissolution of atomic hydrogen in materials in which hydrogen and its isotopes are present. The permeation of hydrogen and its isotopes is important to the vacuum industry for optimizing high-vacuum systems, to the fusion energy community for recovering tritium, and also to all nuclear power plant, because of its implication in radiological risks, derived from the capability to escape from the plant facilities.
More recently, these topics have received attention from the hydrogen energy community: hydrogen dissolution and permeation can be significant, especially in liquid metals. Thus, it is also necessary to understand the behavior of hydrogen expected for this materials, in order to predict the transport mechanism in nuclear heat installations, and estimate the losses to the environment. Tritium permeation mechanisms are studied mainly in liquid metals for nuclear fusion devices, but in this study the attention is addressed also in liquid metals involved in next generation nuclear power plant, such as liquid sodium.
In fact, the aim of this chapter is to describe the theoretical framework necessary for extrapolating literature data of permeation parameter of hydrogen isotopes (diffusivity, solubility and permeability).
Since the objective of this study is to develop a tritium permeation model for sodium cooled fast reactors it is important to refer the hydrogen solubility data of liquid sodium to the last two liquid metals mentioned in the overlying list, because a wide investigation has been carried out for several fusion energy applications, and then, solubility data of lithium or lead lithium alloy are taken as the reference ones.