The solubility and isotopic exchange equilibrium for hydrogen isotopes in lithium

Abstract

The individual solubilities of hydrogen, deuterium and tritium in lithium have been measured as a function of temperature (700–1000°C) and pressure (0.1 to 760 torr). When the mole fraction of LiH, LiD, or LiT is less than about 0.1 (Sieverts region), the temperature dependence of the individual solubilities can be expressed as ln ( N LiH −1P H2 1 2 ) = 9.842 – 6242/T(° K) , ln ( N LiT −1P D2 1 2 ) = 9.515–5644/T(° K) , and ln ( N LiT −1P T2 1 2 ) = 9.226 – 5085/TR(° K) respectively. In these equations, N is the mole fraction in the liquid phase, P is the equilibrium pressure of the gaseous hydrogen isotope (torr), and T is temperature (°K). The mutual solubilities and isotopic exchange equilibria of hydrogen and deuterium in lithium have been measured at temperatures between 700 and 900°C. Both the total pressure and individual partial pressures of H 2, HD, and D 2 have been determined as a function of the mole fraction of LiH and LiD in the lithium solution with varying hydrogen-to-deuterium ratios. In the plateau region, the hydrogen and deuterium could be treated as a single chemical species. However, in the Sieverts region the hydrogen and deuterium dissolved independently of each other. The equilibrium isotope exchange constant, K, given by the relationship P D2 1 2 /P H2 1 2 = KN LiD /N LiH varied from 1.28 at 700°C to 1.17 at 850°C.