OS8-3 Feasibility Study on Thermal-Hydraulic Performance in Tight-Lattice Rod Bundles (1) : 37-rod bundle tests and subchannel analysis

A thermal-hydraulic feasibility project for the Innovative Water Reactor for Flexible fuel cycle (FLWR) was started since 2002. In this R & D project, large-scale thermal-hydraulic experiments, several model experiments and development of advanced numerical analysis codes are being carried out. This paper describes results of the large-scale thermal-hydraulic experiments that simulate the tight-lattice bundle in the FLWR core and subchannel analyses for effects of gap width, bundle scale and rod bowing. As a result, it is confirmed that (1) fundamental characteristics of flow parameter impact on critical power can be evaluated by the subchannel analysis code, NASCA, (2) the increase of the number of rods in a bundle promotes the thermal performance to cool the fuel rods and (3) the critical power decreases with increasing the amount of the bowing.