Simulation of Uranium Dioxide Pellet Cracking Using Smeared Crack Model

During operation of the fuel element, cracking of the uranium dioxide fuel pellet is observed. This phenomenon has a significant effect on the stress-strain state of the structure. Thermomechanical loading of the fuel element area was simulated in an axisymmetric approximation, considering non-ideal thermal and mechanical contact of the pellet with the cladding. To simulate the cracking of the pellet material, a smeared crack model is used, which uses effective Young’s moduli calculated from the fracture curve of the material. A series of calculations was carried out simulating the output of the fuel element section to the mode with the nominal heat generation power. The results showed that large areas corresponding to the cracked material were formed in the pellet during calculations. Due to the selected model of smeared cracks, the maximum values of radial, axial and circumferential tensile stresses in the pellet do not exceed the selected ultimate strength of the material.