Thermophysical properties of VVER uranium-gadolinium fuel pellets with 6–10 wt% of gadolinium oxide

The study aims to determine the thermophysical properties of uranium-gadolinium oxide fuel pellets with 6, 7, 9, and 10 wt% of gadolinium oxide for the verification of the Start-4A calculation code. The determined properties will help to clarify calculations on the behavior of fuel elements in normal and emergency operational conditions during operability substantiation and licensing of the fuel for VVER reactor plants. Experimental dependencies of thermal expansion, specific thermal capacity at a constant pressure and thermal diffusivity were obtained along with the calculated dependence of thermal conductivity on the temperature for the fuels with various contents of Gd₂O₃. In comparison with uranium dioxide, the main contribution to an almost twofold decrease in thermal conductivity at an increase in the gadolinium content is made by the thermal diffusivity of uranium-gadolinium fuel.