In order to ensure the safety of nuclear reactor in transient process, it is necessary to carry out three-dimensional transient analysis of the whole core to obtain the power distribution of fuel rods concerned in the safety analysis. In this paper, a theoretical model of the pin-by-pin neutronic-thermohydraulic coupling transient analysis for PWR-core is established: the three-dimensional pin-by-pin spatio-temporal neutron dynamics calculation of PWR-core is realized by fully implicit backward difference method and exponential function expansion nodal method; the multi-channel model of cell scale is used to calculate the thermal feedback of three-dimensional full core pin-by-pin; the Picard iteration is used to realize the iterative calculation of neutronic-thermohydraulic tight coupling; using the parallel technology of message passing interface (MPI) and the unified spatial domain decomposition method, the parallel calculation of neutronic-thermohydraulic coupling transient process is realized. Based on the theoretical model, the corresponding code called Bamboo-Transient 2.0 was developed and verified by the benchmark and multi-assemblies questions, and it was then applied to the transient analysis for commercial PWRs. The results show that the pin-by-pin transient analysis code has more fine results than that of the traditional coarse-mesh diffusion code based on assembly homogenization, and it can reduce the deviation of power distribution of pin-cell. Meanwhile, it can provide the distribution of state parameters at cell scale, which can directly meet the requirements of safety analysis. © 2023 Atomic Energy Press. All rights reserved.
