Experimental study and thermodynamic modelling of the Ag-Cd-In system

In the case of a severe accident, the silver-indium-cadmium alloy which constitutes the absorber rods of a pressurized water reactor is liable to melt, interact with other materials as fuel cladding and then provoke early degradation of the core. The control rod elements also interact with fission products (in particular iodine), and may significantly affect their speciation and transport in the primary circuit as well as their behavior in the containment. The knowledge of the Ag-Cd-In ternary phase diagram is therefore of great importance to estimate the potential release of the absorber elements from the core. In this work, the thermodynamic modelling of the ternary Ag-Cd-In system has been carried out using the CALPHAD approach, based on available experimental data for phase diagram and thermodynamic properties. It takes into account additional experimental data related in particular to the liquidus temperatures in cadmium-rich region which are reported in this paper. A set of self-consistent thermodynamic parameters was optimized by the least-squares method using the TERGSS program [1]. A satisfactory agreement was obtained between the experimental data and the calculated results.