Study on Equilibrium Compositions of HTO/H₂ Mixture in Purge Gas Flow in Tritium Breeding Blanket

The equilibrium chemical compositions of purge gas at the outlet of the Test Blanket Module in Helium Cooled Ceramic Reflector (HCCR) Test Blanket System are studied. Mole fractions of H, T, O, H₂, HT, T₂, H₂O, HTO, and T₂O in the equilibrium state are calculated by a Gibbs free energy minimization method starting from the initial state of H₂/HTO mixture. The standard Gibbs free energy for tritium species obtained by the density functional theory is used in the calculations. The tritium recovery rates in the form of HT, T₂, HTO and T₂O are estimated from the equilibrium chemical compositions obtained in the calculations. The effects of H₂ concentration in the purge gas on the tritium recovery process are also investigated by parametric study with variations of purge gas flow rate and volume ratio of hydrogen to helium in the purge gas.