Practical modeling of fluid in ABWR spent fuel pool for seismic analysis using 3D FEM model

Abstract

Seismic analysis is important for ensuring the integrity of structures in nuclear power plants. This study investigates the practical modeling method of the fluid in a spent fuel pool (SFP) of an advanced boiling water reactor (ABWR) nuclear power plant for seismic analysis using a three-dimensional finite element method (3D FEM) model of a reactor building (RB) in the plant. Three kinds of 3D FEM models of the RB were developed in this study: combined effect, impulsive, and no-fluid models. The combined effect model included both convective and impulsive effects of the fluid, whereas the impulsive model included only the impulsive effects. The no-fluid model did not include fluid. To investigate the fluid effects, the relative error ratios for maximum acceleration, von Mises stresses, and pressure fluctuations obtained from seismic analyses using these models were calculated. The relative error ratios for the impulsive model with respect to the combined effect model were less than 5%, excluding maximum pressure fluctuations; those for the no-fluid model with respect to the impulsive model were mostly less than 5%. These results indicate that the convective effects were significantly small, excluding pressure fluctuations, and the impulsive effects were also small. On the basis of these results, a practical modeling method of the fluid in an ABWR SFP is proposed and summarized in a modeling flowchart. The flowchart enables practical modeling of the fluid for seismic analysis using an ABWR RB 3D FEM model.