Investigation of Flow Recirculation in a Rod Bundle During Natural-Convection Flow and Power Transients

摘要

An experimental investigation conducted at the Pacific Northwest Laboratory studied the flow recirculation phenomenon in a rod bundle during natural-convection flow and power transients. The experimental data were used to validate the recirculation model in the COBRA-WC computer program. The COBRA-WC code was then used to predict the flow and temperature fields in a prototypic Liquid Metal Fast Breeder Reactor (LMFBR) blanket assembly for a worst-case, natural-convection transient. The geometry of the 2 x 6 rod bundle was chosed to facilitate direct velocity measurements by Laser Doppler Anemometry (LDA). The rod bundle power skews ranged from uniform bundle power to 1:0, including 2:1, 3:1, 4:1, and the bundle average Reynolds number ranged from 1400 to 200 for steady flows as well as for a number of 45-sec flow transients. Application of the COBRA-WC code to a prototypic blanket assembly for a worst-case natural-circulation transient shows that, although flow recirculation does occur, the temperature in the recirculating channels is well below the peak assembly temperature. (ERA citation 08:020726)