Discrete direction probability method for solving neutron transport equation in complex geometry

For solving the neutron transport equation in complex geometry, the discrete direction probability method (DDPM) is developed. In the DDPM, the calculation system is divided into subsystems which can be subdivided into fine meshes. The ray tracing is done for each type of subsystem. Within a subsystem, fine meshes are coupled by the discrete direction collision probability, while subsystems are coupled by the discrete direction transmission probability. The numerical results demonstrate the high efficiency and accuracy of this method.