Thermodynamic properties of solutions of hydrogen isotopes in metals and alloys of interest to fusion reactor technology

Recent ANL work on the solution thermodynamics of systems composed of a hydrogen isotope and either pure lithium or a lithium-containing alloy has been directed toward (1) the sources and magnitude of isotope effects in the systems Li--LiH and Li--LiD, (2) the solubility of LiD in liquid lithium (200 to 7000C), and (3) the solubility and decomposition pressure of hydrogen in the ternary Li--Al--H system. The H/D isotope effect appears to originate primarily in the gas phase and within the two-phase regions of the phase diagram, its range of values is 1.43 +- 0.05. At 2000C, the solubility of LiD in lithium is approximately 250 appM D, thus essentially ruling out hydrogen isotope separation methods based on cold-trapping concepts. Two isotherms (at 550 and 5990C) have been obtained for solutions of hydrogen in the β-phase of the Li--Al system (48 to 56 mol % Li). They indicate that, at low hydrogen concentrations (<1 atom % H), the dissociation pressures are much higher (x100) than those over the lithium metal. Within the miscibility gap, which extends from 6 to 33.3 atom % D, the plateau pressures, P, may be represented by 1n P (torr) = 20.46 to 11,600 T-1