Progress in Advanced Modeling and Numerical Simulation of High-performance Particle Transport for Sodium-cooled Fast Reactor

The fuel assembly and fuel rod bundle of sodium-cooled fast reactor are arranged in a triangle form. The fuel assembly adopts closed structure deign without mixing of coolant between assemblies, which is cooled by the sodium coolant through the distribution header on the bottom of the core to accomplish the matching of coolant and nuclear power and flattening the outlet temperature of the reactor core. It is of great significance for the core design and flow distribution scheme to carry out the whole core pin-by-pin refinement power distribution and neutronic-thermal coupling calculation. There are many internal components and complex structures in the pool type fast reactor container including the core, the internal shielding structure, the primary main pump, intermediate heat exchanger, independent heat exchanger and loading and unloading elevators which are arranged around the core. The design of neutron extraction channel in the direction of loading and unloading lifting devices leads to the asymmetry of the structure in the reactor container. It causes obvious anisotropic scattering in the process of neutron transport calculation, which is also a typical deep penetration problem, so more reliable and accurate calculation results require three-dimensional calculation with the whole range of the reactor container. The above problems pose challenges to modeling and neutron transport calculation. The high-performance simulation system of sodium-cooled fast reactor adopts advanced modeling technology, large-scale parallel computing technology, transport-burnup coupling function, core-assembly-lattice multi-level mapping and conversion technology to realize the full range three-dimensional fine modeling and multi-physical coupling calculation, including the shielding calculation of the container of pool structure fast reactor, the deep penetration calculation of neutron transport of detectors outside the reactor, pin-by-pin refined power distribution calculation, transport burnup coupling calculation and full core neutronic-thermal sub-channel coupling calculation with the parallel computation scale, and reaches thousands of cores. Through CAD pre-processing modeling, mesh generation, high-performance calculation and visualization, the three-dimensional calculation results of large pool type fast reactor can be given more comprehensively and finely, and a clearer physical image of the core or reactor container can be obtained. The comparison between the local key position and the existing calculation program verifies that the high-performance simulation system of fast reactor is reasonable and feasible which provides support for further reducing the conservative margin of design and local structure optimization. © 2022 Atomic Energy Press. All rights reserved.