Non-uniform thermal-hydraulic behavior in a 61-rod bundle of supercritical water-cooled reactor

Abstract Numerical investigations of supercritical water flowing through a 61-rod bundle based on the fuel assembly of the supercritical water-cooled reactor (SCWR) are performed by using the Reynolds stress model with enhanced wall treatment. Effect of hexagonal outer casing on thermal-hydraulic characteristics under design conditions is investigated. Mass redistribution mainly caused by flow area differences and varied properties of supercritical water is observed and the mass flux difference between the interior sub-channel and side sub-channel is about 523.6 kg·m-2·s-1 at the outlet. It is observed that a strong circumferential wall temperature non-uniformity of the outer rods caused by mass redistribution is over 200 K within 0.5 m near the outlet, which should be carefully and thoroughly considered in the design of SCWR fuel assemblies. The peak and valley positions of wall temperature result from periodical sub-channel structure are offset in the direction of the corner sub-channel and the offset angle increases with the decreasing distance to the corner sub-channel.