Abstract
The Reduced-Moderation Water Reactor (RMWR) adopts a tight-lattice core with triangular fuel rod arrangement and remarkably narrow gap spacing between rods. The criteria of boiling transition (BT) is one of most important subjects for such reactor but there has been no sufficient information from previous experimental or analytical studies about the effects of the gap spacing, grid spacer shapes and so on for the BT characteristics. Thus, we start to devebp a detailed two-phase flow simulation code with interface tracking method to get information of two-phase flow in tightlattice bundles. In this paper, to verify the code performance, the simulation code was applied to bubbly flow in a circular tube. In the results, the bubble shapes almost agreed with empirical correlation. However, the terminal velocities of the bubbles were over predicted by the numerical simulation.
