Most pressurized water reactor control rods are composed of the Ag-In-Cd neutron absorber alloy (80 wt% Ag, 15 wt% In, 5 wt% Cd). Under accidental conditions such as a loss of coolant, vaporization of the metallic elements from the Ag-In-Cd alloy becomes important to consider in the evaluation of the fission product release to the environment. The enthalpy of mixing has been measured in the ternary Ag-Cd-In liquid for five isopleth sections by silver and cadmium drop dissolution calorimetry at 723 K. The limits of the biphasic solid + liquid domain are derived from the slopes changes on the partial mixing enthalpy curves. A tentative partial isothermal section at 723 K is proposed. (c) 2016 Elsevier Ltd.