Steady-State Subchannel Thermal-Hydraulic Assessment of Advanced Uranium-Based and Thorium-Based Fuel Bundle Concepts for Potential Use in Pressure Tube Heavy Water Reactors

The use of advanced uranium-based and thorium-based fuel bundles in a 700-MW(electric)-class pressure tube heavy water reactor (PT-HWR) has the potential for improved performance characteristics with higher burnup, higher fissile fuel utilization, and lower coolant void reactivity while also extracting the energy potential in thorium. In this study, thermal-hydraulic subchannel analyses were performed for a single, high-power (6.5 MW), 12-bundle fuel channel at typical reactor operating conditions for 14 different PT-HWR lattice/core concepts using various types of advanced uranium-based and thorium-based fuels in 37-element and 35-element fuel bundle design concepts. Fuel bundle radial power distributions for fresh fuel at zero burnup were used in the thermal-hydraulic calculations, as a bounding case, along with axial power distributions that are representative of those that may be found in a high-power fuel channel in a PT-HWR core at near-equilibrium refueling conditions. The fuel bundle radial power distributions and fuel channel axial power distributions were determined from previous lattice physics and core physics studies. Based on the subchannel thermal-hydraulic analyses, the LC-05b/CC-04 BUNDLE-37-mod concept and the LC-12b/CC-08 BUNDLE-35 concept are recommended as the best candidates for further full-core system thermal-hydraulic transient analyses, based on critical heat flux and void fraction performance factors. BUNDLE-37 concept LC-01/CC-00 is also recommended as the reference case for future analysis.