Pd/ZrO catalyst for the oxidation process of tritiated organic substances produced in fusion plants

Iwai, Yasunori; Sato, Katsumi; Yamanishi, Toshihiko

In case of a fire accident in a fusion plant, some tritiated organic substances will be produced. We have developed a Pd/ZrO catalyst applicable for the oxidation of the tritiated organic substances. Overall reaction rate constant of tritiated methane oxidation over palladium catalyst in a flow-through system were determined as a function of space velocity from 1200 to 7000 h, methane concentration in carrier from 0.004 to 100 ppm, temperature of catalyst from 473 to 673 K. The Pd/ZrO catalysts initially showed the large overall reaction rate constants in the whole tested temperature range. However the constants were gradually decreased when the catalysts were continuously used for the tritiated methane oxidation. The decrease has been explained as the layers of produced water formed on the surface of the catalyst plays the obstacle role of reactant transport onto noble metal deposited on the catalyst. The overall reaction rate constant was dependent on the space velocity and independent on the methane concentration in the reactant mixture.