Investigation of hydrogen isotope effect on storage properties of Zr-Co-Ni alloys

The deuterium desorption pressure-composition isotherms (PCIs) of ZrCo1−xNix-D2 (x = 0, 0.1, 0.2 and 0.3) systems were generated in this study in the temperature range of 524-603 K using Sievert's type volumetric apparatus. Thermodynamic parameters like enthalpy and entropy change for deuterium desorption reactions involved in the ZrCo1−xNix-D2 systems were derived using the equilibrium pressure data of PCIs. In order to interpret the hydrogen isotope effect on the storage behaviour of ZrCo1−xNix alloys, the results obtained in the present study were compared with the earlier reported data on the ZrCo1−xNix-H2 (x = 0, 0.1, 0.2 and 0.3) systems. This comparison revealed that these alloys show normal hydrogen isotope effect where the equilibrium pressure of D2 is higher than that of H2 at all experimental temperatures. Based on these observation, it is expected that at the ITER SDS operating conditions the equilibrium pressure of tritium, deuterium and hydrogen will follow the order: p(T2) > p(D2) > p(H2) for these alloys.