Temperature Distribution Inside Fresh-Fuel Pins of Pressure-Tube Supercritical-Water-Cooled Reactor

The radial temperature profile for $ThO2-PuO2$ fresh-fuel pins of the pressure-tube supercritical-water-cooled reactor (PT-SCWR) is simulated for two different radial distributions of the $ThO2$ and $PuO2$⁠, one whereby the $ThO2$ and $PuO2$ are mixed together in a single, homogeneous region, and another one whereby $ThO2$ and $PuO2$ occupy separate radial regions inside the pin with the $ThO2$ occupying the inner region. The radial power density in each fuel pin is calculated from a lattice-level transport calculation using the lattice code DRAGON and is used together with the temperature-dependent fuel thermal conductivity to analytically solve the heat conduction equation and thus calculate the temperature profile inside the fuel pin. Results indicate that, for fresh fuel, the centerline temperature is much lower for a two-region pin than for a single-region pin, and thus, the risk of fuel melting is greatly reduced for the two-region fuel compared to the single-region fuel.