Clarification of Tritium Behavior in Pb–Li Blanket System

Abstract

In order to clarify the tritium behavior in Pb–Li blanket system, the solubility of hydrogen isotopes in the Pb–Li eutectic alloy was experimentally investigated. The effects of (i) Li preferential evaporation from Pb–Li, (ii) thermal convection in a quartz-glass reaction tube and (iii) difference in crucible materials between Al₂O₃ and W on the solubilities were discussed. Another important issue of the Pb–Li blanket system is to develop a new ceramic coating to decrease tritium permeation rate. Tritium permeation test was performed for Er₂O₃ coating on F82H. The permeation reduction factor achieved here was higher than 10³. Precise experiments were carried out to determine the solubility, diffusivity and permeability of hydrogen isotopes in Pb–Li eutectic alloy by means of a transient permeation method. The isotope effects in solubility and diffusivity between H and D were clarified. No isotope effect in solubility was observed between H and D, and the H diffusivity was 1.4 times larger than the D one. The ratio was near to a value predicted from the classical theory. Experiment using tritium is designed under the collaboration work with INL.