Surface modification of Zr-based alloys applicable for tritium processing

Zr3Al2 alloy was used as a model substrate to prepare surface protective layers of Pd with an electroless plating method. Effects of the Pd-overlayer on the kinetics of deuterium ab/desorption and durability against N2 and CO2 were investigated. The rate determining step of absorption and desorption of deuterium in/from Zr3Al2 were not altered by Pd-plating. The absorption obeyed the first order, and the desorption obeyed the second order kinetics. The durability tests against N2 and CO2 showed that exposure to these gases caused a reduction of the absorption rate of deuterium. The extent of the reduction for Pd/Zr3Al2, however, was smaller than that of bare Zr3Al2. Namely, the surface modification by the Pd-layer is effective against impurity gases, and applicable for processing of fuel gases containing a non-negligible amount of impurity gases.