Effects of Temperature and Pressure on Purge Gas Chemical Compositions in Tritium Breeding Blanket

The effects of temperature and pressure conditions on the equilibrium chemical compositions of purge gas at the outlet of the test blanket module (TBM) in the helium-cooled ceramic reflector (HCCR) are studied. As the chemical species in the equilibrium states, nine chemical species are considered: H, T, O, H₂, HT, T₂, H₂O, HTO, and T₂O. The mole fractions of these chemical species are calculated using a Gibbs free energy minimization method starting from the initial state of a H₂-HTO mixture. The standard Gibbs free energies for the tritium species used in the study are calculated from the molecular constants obtained by a coupled-cluster calculation. The effects of pressure variations on the equilibrium compositions are shown to be negligible. The effects of temperature variations are also insignificant when the temperature exceeds 800 K. When the initial H₂/HTO ratio is more than 10, more than 90% of tritium is expected to be recovered in the form of HT.