DEVELOPMENT OF ANALYSIS METHOD FOR IMPACT AND SPLASH BEHAVIOR OF WATER-FILLED TANK

A new Japanese nuclear regulation requirement prepares estimating the possible damage to plant structures due to acts of terrorism, such as intentional aircraft impact. Aircraft impact needs to be considered in existing nuclear power plants. The structural damage and fuel splash behavior after aircraft impact into plant structures can be estimated using finite element analysis (FEA). FEA needs validated experimental data to determine the reliability of results. In this study, an analysis method was validated using a simple model such as a cylindrical tank. Numerical simulations were conducted to estimate the impact and splash behavior for a water-filled cylindrical tank. The simulated results were compared with the test results of the VTT Technical Research Centre of Finland. Simulations were carried out using a multipurpose FEA code LS-DYNA (R). The cylindrical tank was modeled using a shell element, and filled water was modeled using a smoothed particle hydrodynamics (SPH) element. First, two analysis models were used to estimate the effect of the number of SPH elements. One was generated with about 300,000 SPH elements. The other was generated with 37,000 SPH elements. The cylindrical tank ruptured in the longitudinal direction after impact into a rigid wall, and the filled water splashed. Few differences emerged in the simulated results using different numbers of SPH elements. The impact test of the VTT was simulated with an arbitrary Lagrangian-Eulerian (ALE) element to consider the air drag. The analytical splash pattern and history of splash velocity ratio agreed well with the impact test results.