Computational fluid dynamics (CFD) analysis of inlet plenum, outlet header, and fuel channels of the proposed Canadian SCWR

The Canadian SCWR is a channel-type supercritical light-water cooled nuclear reactor with 336 vertical pressurized fuel channels. The reactor core concept uses a common inlet plenum that all fuel channels are attached to and a common outlet header nested inside the inlet plenum. The light-water coolant enters the inlet plenum at 350℃ and exits the outlet header at 625℃, significantly higher than the critical temperature of water (which is 374ºC). The operating pressure is approximately 25 MPa at the core outlet, which is above the critical pressure of water. The high pressure and high temperature outlet operating conditions result in significantly higher electric conversion efficiency as compared to the present light water reactors. In this paper, Computational Fluid Dynamics (CFD) simulations were performed to model fluid flow and heat transfer in the inlet plenum, outlet header, and various parts of the fuel assembly. The ANSYS FLUENT engineering simulation software was used for simulations and temperature-dependent properties of supercritical water were implemented. Results showed that mass flow rate distribution in fuel channels varies about 4% radially if all fuel channels have the same design features. Outer channels receive more flow rate and, as a result, the inner channels achieve higher outlet temperatures. At the outlet header, channel flow streams from the fuel channels merge and then exit at an average temperature of 625 ℃. Results also suggested that insulation of the outlet header should be considered to reduce the thermal stresses caused by the large temperature gradient across the outlet header walls. (author)