Investigation of Water-Vapor Two-Phase Flow Characteristics in a Tight-Lattice Core by Large-Scale Numerical Simulation, (IV)

Large-Scale Analysis of Water-Vapor Two-Phase Flow in Rod Bundles with TPFIT code using Earth Simulator

Abstract

The reduced-moderation water reactor (RMWR) core adopts a hexagonal tight-lattice arrangement with about 1mm gap between adjacent fuel rods. In the core, there is no sufficient information about the effects of the gap spacing and grid spacer configuration on the water-vapor two-phase flow characteristics. Thus, we start to develop a predictable technology for thermal-hydraulic performance of the RMWR core using an advanced numerical simulation technology. As a part of this technology development, we are developing an advanced interface tracking method to improve the conservation of volume of fluid.
The present paper describes a part of the development of the two-phase flow simulation code TPFIT. The vectorization and parallelization of TPFIT code was conducted to fit the large-scale simulations. And the modified TPFIT code was applied to large-scale water-vapor two-phase flow in tight lattice rod bundle. In the results, calculated void fraction distribution in horizontal plane agreed quantitatively with the measured one obtained from the advanced neutron radiography technique including the bridge formation of the liquid at the position of adjacent fuel rods where an interval is the narrowest.