Theory and Verification of a Fuel Rod Mechanics Model Based on a Two-Dimensional Finite Element Method with Consideration of Fuel/Cladding Contact and Friction

Fuel rod computer models are utilized to predict cladding tube integrity under normal operating or transient accident conditions in a nuclear fission reactor. The METHOD2D computer code, which includes a fuel rod mechanics model based on an axisymmetric finite element formulation, is developed and verified. This two-dimensional approach gives results for the axial and radial deformation of the fuel pellets and the cladding tube for the whole fuel rod. Because an algorithm for fuel pellet/cladding tube radial contact and axial friction is incorporated, the analysis of closed fuel/cladding gap situations is possible. Calculation results for a whole fuel rod are compared with a transient CABRI experiment that led to partial fuel melting but not to cladding failure.