LS-DYNA Applications in Simulating Impact Tests of Nuclear Fuel Spacer Grids and Drop Tests of Fuel Shipping Packages

Presented in the paper are two of our recent LS-DYNA applications in developing simulation models for: (1) impact tests of spacer grid – a key structural component of nuclear fuel, and (2) drop tests of shipping packages for fresh nuclear fuel, as described in the following, in that order. Resistance of nuclear fuel structure to impact loads during postulated seismic and/or loss-of-coolant accident (LOCA) events needs to be demonstrated to show that no excessive fuel structural deformation would occur so that the three criteria are met: (i) fuel rod fragmentation does not occur, (ii) control rod insertion is ensured, and (iii) the core coolable geometry is maintained. The demonstration is accomplished through comparison of prediction through full core simulation with the strengths of the various structural components of the fuel. The impact tests of the spacer grids provide one such strength. As the impact test of the spacer grids requires significant lead time and effort, capability to simulate the spacer grid behavior under testing conditions is of great interest. More importantly, it provides a powerful tool for design. To meet shipping package safety requirements for transporting fresh nuclear fuel assemblies, structural performance of the shipping package under hypothetical accident conditions must be evaluated and demonstrated to have adequate protection to the fuel assembly it transports. To efficiently evaluate design changes in the shipping package, a simplified finite element model for the shipping package and fuel assembly has been developed using LS- DYNA. The development and validation of the finite element model, along with a few design analysis examples to illustrate its usefulness are described.