Coupled neutron transport and thermal fluids calculations for the VHTR

This paper introduces a coupled neutron transport and thermal fluids method for the very high temperature reactor (VHTR). The neutron transport component is the coarse mesh transport method (COMET) for hexagonal reactors. A specific thermal fluid solver for VHTR has been developed, this solver is based on a quasi-steady unit cell energy balance method that has been developed specifically for coupling to COMET. The purpose of this method is to solve the steady state core-wide distribution of temperatures. The coupling between COMET and the fluid solver is made via pin fission density and block temperature data. Results are given for a whole-core VHTR, including detailed temperature information at the fuel pin level, explicit power calculations of individual pins, and a thermal map of the bulk graphite and coolant temperatures throughout the core. Solutions are determined quickly when compared to other methods which offer the same level of detail and accuracy, and thus justify further research and development of this method in the near future