Using first principles calculations we investigate thermomechanical stability of spent nuclear fuels (SNF). Especially, it is rigorously studied how mechanical properties of UO2, such as, bulk, shear and Young’s moduli and Poisson’s ratio vary through alpha-decay of U into Th with generation of He gas. Our results indicate that substitution of U by Th through alpha decay (U1-xThxO2) does not significantly affect the stability of the grain in a fuel matrix. In addition, we study on transport properties of He in and boundaries of the U1-xThxO2 grain. Helium preferentially resides at the grain boundaries through diffusion. Our study can contribute to substantial reduction of environmentally risk and enhancement of our sustainability by safe control of radioactive materials.
Keywords First principles, Uranium dioxide, Alpha decay, Thermodynamic Stability, Helium gas