Progress towards an accurate lattice-homogenization technique for Pressure-Tube Supercritical Water Cooled Reactor neutronic calculations

The Pressure-Tube Supercritical-Water Cooled Reactor (PT-SCWR) is one of the reactor concepts investigated by the Generation-IV International Forum as a reactor concept capable of achieving an overall nuclear power plant efficiency in the vicinity of 50%, higher than the approximately 35% that characterize current nuclear power plants. The development process includes studying the neutronics methods that can provide an adequately-accurate modelling of the core. The PT-SCWR evolved from the Pressurized Heavy-Water Reactor but presents a more heterogeneous core because of the much higher discharge burnup (∼40 MWd/kg vs. ∼7.5 MWd/kg) and greater variation of coolant density. This work presents progress towards addressing the node-homogenization needs of the PT-SCWR core by using macroscopic cross sections and discontinuity factors calculated using quasi-exact node boundary conditions determined using global-local iterations between core and lattice calculations. Results show that cross sections and discontinuity factors obtained via the global-local iterative process are very effective at improving the accuracy of full-core diffusion calculations in the fuel region of the core and that some challenges remain in applying leakage corrections to high-leakage configurations, especially those comprising reflector nodes. (author)