Coolant flow around the fuel pins in a light water reactor core plays a critical role in determining the reactor’s performance, and a thorough understanding of this process will be key to the successful design and operation of emerging small modular reactor (SMR) systems. To that end, an international research team has developed a new computer model that allows for the visualization of complex flow structure interactions in a full pressurized water SMR core at unprecedented resolution.

SMR fuel assembly modeling must consider the impact of spacer grids that create turbulent flow and enhance the removal of heat from the fuel. Instead of devising a computational grid to model all the local geometric details of the spacer grid, researchers from U.S. Argonne National Laboratory (ANL), Aristotle University of Thessaloniki (Greece), EDF R&D (France), Texas A&M University and Pennsylvania State University developed a mathematical reduced-order methodology to mimic the overall impact of these structures on the coolant flow without sacrificing accuracy. An advanced flow solver software package is applied to link computational fluid dynamics and Monte Carlo neutron transport modules through a common interface.

The method described in Nuclear Engineering and Design allows researchers to scale up the simulations to an entire SMR core.