Efficient processing of tritiated water by using a two-stage Pd membrane reactor with Pt/TiO2 catalyst

Abstract

Large amounts of tritiated water (HTO) will be produced during the operation of nuclear power plants and fusion devices, which is harmful to the environment and human due to its radioactivity and toxicity. So, the tritium concentration of tritiated water must be reduced to a very low value before discharge. Hydrogen-water isotope exchange reaction (H2 + HTO→H2O + HT) based on palladium membrane reactor has been proposed to process tritiated water. However, a comprehensive study about the influence of operation parameters on the membrane reactor performance is insufficient, which is not conducive to the design of reactor in practical application. Moreover, the commonly used Pt/Al2O3 or Ni/SiO2 catalysts are not active for tritiated water dissociation, so the catalytic activity of these catalysts is not high. In order to process tritiated water more effectively, a two-stage membrane reactor has been designed and established in this work, and Pt/TiO2 catalyst with rich oxygen vacancies is used to catalyze the hydrogen-water isotope exchange reaction for the first time. The membrane reactor performance shows an approximate linear relationship with a new combined parameter S0.5P1.5R/F2 (S is membrane area, F is water flow rate, P is vapor partial pressure, R is swamping ratio), which can be used predict the membrane performance. The isotope exchange reaction activity of Pt/TiO2 is better than that of Pt/Al2O3 due to its good ability for water dissociation and the hydrogen spillover effect. At last, a tritiated water processing experiment by using two-stage membrane reactor with Pt/TiO2 catalyst with rich oxygen vacancies has been carried out. The tritium decontamination factor reaches 40588, which is the highest experimental value so far. The results indicate that the two-stage Pd membrane reactor based on hydrogen-water isotope exchange reaction is an efficient technology for tritiated water processing.