A Detailed Model to Predict Mechanical Characteristics of Fuel Assembly

As the core component and the first safety barrier of a nuclear power plant, the structural integrity of fuel assemblies (FAs) is an important factor in ensuring the safety of nuclear power. Safety analysis and evaluation of fuel assemblies under seismic conditions is a requirement of nuclear power plant design codes and safety reviews. The mechanical properties of a single FA determine the operational and seismic performance of the core fuel assembly. Due to the complexity of the FAs in terms of structure and boundary conditions, test is the most common method to obtain the mechanical properties. In order to predict the mechanical properties of the fuel assembly, a nonlinear finite element detailed model was developed. The contact and frictional behavior between the fuel rod cladding and the spring/dimple convexity were considered in the modeling to simulate the nonlinear behavior of the fuel rod better. To verify the validity of the model, virtual tests of lateral stiffness test, forced vibration test and impact test were conducted on the model. The comparison with the experimental results shows that the model can reflect the mechanical properties of the fuel assembly well. The modeling method and calculation conclusions in this paper are of guidance for fuel assembly design.