Thermodynamic investigation of the Cr-O-U and Cr-O-Zr systems
Résumé
During severe accidents in nuclear reactors, the core is partly melted. With time the temperature increases and more parts of the reactor are melted creating a very complex mixture, including many elements. This mixture is often referred to as corium. If the reaction is allowed to go on long enough, the vessel can brake causing the corium to flow out onto the floor creating ex-vessel corium. One of the aims of the TAF-ID project [1] is to be able to predict the thermodynamic properties of the corium to aid in the prevention of severe accidents. One of the elements whose behaviour in the corium is not well known is chromium. Chromium can be introduced to the system through stainless steel that can be used both for the vessel itself and the cladding of the control rods. In this work two of the key systems involving chromium, i.e. Cr-O-U and Cr-O-Zr, have been studied using the Calphad method. New experimental work has also been performed using equilibrated alloys at 1600 and 1800 C.