A neutron transport calculation approach via the coupling of 2D/1D and 3D SN nodal methods

The 2D/1D neutron transport method is a popular approach for high-fidelity neutron transport calculations. For some research or testing reactors, the reactor core is surrounded by heavy water, and outside the heavy water is light water. To obtain the spectrum in the heavy water and light water outside the core, the heavy water and light water domains must be included in the calculation. This significantly affects the calculation time and convergence when using the 2D/1D method. Therefore, a new neutron transport method based on the 2D/1D method and the 3D SN nodal method is proposed to address these issues. In this method, the reactor core is divided into two calculation domains. The reactor active core is calculated by the 2D/1D method with fine meshes, while the region outside the reactor core is calculated by the 3D SN nodal method. The two calculation domains are coupled by the boundary angular flux. The CMFD and parallel scheme are also implemented to accelerate the calculations. This method is applied to the C5G7 benchmark and JRR-3 reactor core. The numerical tests show that the efficiency and convergence of the coupling method are much better than those of the 2D/1D method while maintaining accuracy.