Chemical thermodynamics of fusion reactor breeding materials and their interaction with tritium

Liquid lithium, lithium alloys (solid and liquid) and ceramic lithium compounds are candidate breeding materials for (D, T) fusion reactors. Besides their tritium breeding capability, which results from neutron capture, their thermochemical properties and their interaction with tritium are of particular interest. A good knowledge of the physical and chemical properties of liquid lithium exists; and the systems Li-LiH, Li-LiD and Li-LiT have been studied in great detail. For dilute solutions of D2 in liquid lithium, Sieverts' law was found to be valid down to an atom fraction of xsub(D)=10-6; in the vapor, lithium polymers up to Li4 and lithium deuterides are found. In the system liquid Li-Pb, the solubility of D2 was measured as a function of temperature and alloy composition, and correlated with the activities of the constituent metals. The solubility of D2 was found to obey Sieverts' law at low concentrations, and is many orders of magnitude smaller than that in liquid lithium. This holds also for solid 'Li7 Pb2'. Vaporization studies yielded data on the thermal stability of the oxides: Li2O, γ-LiAlO2, β-Li5AlO4, LiAl5O8, Li2ZrO3, Li4ZrO4, Li8ZrO6, Li2SiO3 and Li4SiO4. Tritium diffusivity was studied in Li2O, γ-LiAlO2, β-Li5AlO4 and Li4SiO4. A large number of gaseous lithides were detected during these studies. (orig.)