A study on the equivalent spring model of a nuclear fuel cell spacer grid

A nuclear fuel assembly consists of a top end piece, bottom end piece, and spacer grids. The spacer grid assembly has the role of protecting the fuel rod against external loads such as earthquakes and car accidents during transportation. Thus far, the protection capability of the spacer grid has been studied for only one layer of spacer grid owing to experimental and computational cost limits. Numerical analysis for the whole fuel cell assembly is very difficult because it requires the use of a very large number of elements. In particular, a very large number of elements is required to represent the spring of the spacer grid. Therefore, a simplified equivalent model that exhibits the same behavior as the original model is designed using the minimum deformation energy method. The designed equivalent model is verified using a well-known commercial code. As a result, it is shown that the computation time can be reduced by 80% using the equivalent spring model.