Computational fluid dynamic investigations of flow through an aged CANDU pressure tube
Single-phase, isothermal computational fluid dynamics simulations of twelve simplified CANDUTM 37M fuel bundles sitting in both as-received and aged pressure tubes were performed with Hydra in this work. The predicted coolant flow behaviour of two cases were compared in order to investigate the impact of pressure tube deformation (sag and diametral expansion) on coolant flow. The boundary conditions and material properties are representative of normal operating conditions in a high-powered channel of the Darlington Nuclear Generating Station. Rigorous mesh and turbulence model sensitivity analyses have been performed in this work. It has been determined that pressure tube deformation has a significant impact on coolant flow behaviour, whereby up to 25% of flow bypasses the fuel. The reduced flow within the subchannels of the fuel bundles impacts the coolability of the fuel.