Steady-State Subchannel Thermal-Hydraulic Assessment of Proposed Thorium Fuel Designs

The Canadian Nuclear Laboratories (CNL) is developing the technologies to enable the use of thorium-based fuels in pressure tube-heavy water reactors (PT-HWRs). One of the key stages in developing the thorium-based fuels for PT-HWRs is the reactor core configuration. Currently at CNL there are 20 core configurations under investigation, which involve several types of thorium-based fuels that could be implemented in a 700-MW(electric)-class PT-HWR. Among these core configurations, four fuel bundle concepts are being considered: (1) the reference (or nominal) 37-element bundle; (2) a 37-element modified bundle, with the center element using a different fuel material; (3) a 35-element bundle; and (4) an 18element internally cooled annular fuel bundle. This study presents the steady-state subchannel thermalhydraulic assessment of the 20 core configurations under investigation. The hottest channel approach is used in this study, as it represents the upper limit of a feasible design. The axial and element power distributions used in the analysis correspond to those of the discharge burnup. Three mass flows are considered in this study: 13.5, 21, and 24 kg/s. Five parameters are used to evaluate the fuel channel/bundle performance, namely, minimum critical heat flux ratio, channel pressure drop, enthalpy distribution, void fraction, and core power.