Experimental validation of upgraded designs for PERMCAT reactors considering mechanical behaviour of Pd/Ag membranes under H2 atmosphere

The PERMCAT process chosen for the final clean-up stage of the Tokamak Exhaust Processing system of the ITER tritium plant combines in a single component a catalytic reactor and a permeator using Pd/Ag membranes. This study covers the mechanical behaviour of a Pd/Ag membrane under different operating conditions. The consequences of hydrogen uptake by the membrane during nominal operation but also during off-normal events are presented. Depending on the operating conditions, expansions around 2% and significant deformations are observed. Different mechanical designs of PERMCAT reactors are then discussed. The first generation comprises finger-type membranes and two new mechanical designs use either additional edge welded bellows or a special corrugated Pd/Ag membrane. These upgraded designs improve the robustness and simplify the geometry of the component. The experimental validation of these new units has been carried out based on the measurements of the processing capabilities with regards to isotopic exchanges between H2O and D2. For the first time experimental results obtained on different PERMCAT reactors are compared.