A coarse-mesh coupled neutronics and thermal fluids method for prismatic cores

A newly developed coupled neutronic-thermal-hydraulic method for prismatic high-temperature gas reactors (HTGRs) is presented with accompanying results for several prismatic core configurations and numerical sensitivity studies. The principal advantage of the new method is the determination of coupled, whole-core temperature and pin power distributions with reduced computational effort over other available codes. The coarse-mesh radiation transport method (COMET), which relies solely on radiation transport, is the component of the new method used to compute neutronic parameters. A three-dimensional unit-cell-based thermal fluids solver is used to compute steady-state thermal-hydraulic parameters. For both component methods, no geometric approximations or averaging schemes are necessary. Convergence of the neutronic and thermal-hydraulic components and the coupled method is discussed, and coupled analyses are presented. The calculation of whole-core solutions allows for unique insights not possible with limited domain tools such as computational fluid dynamics. Results from one such unique study, near-critical control rod movements, are presented in this paper. Comparisons between coupled and uncoupled analyses are also presented.