By combining advantages of S_N method (high calculational efficiency) and advantages of MC method (fine geometrical modelling), three-dimensional discrete ordinates-Monte Carlo method (3D S_N-MC coupling method) is able to calculate cavity streaming dose rate in short time. S_N-MC coupling method is applied on Qinshan No.1 reactor and CAP1400 reactor cavity streaming calculation. Results of S_N-MC coupling method are compared with measurements and results of MCNP bootstrapping method. It shows that theoretical model and codes of 3D S_N-MC coupling method are both correct.

Multigroup neutron adjoint transport and automatic source particle biasing sampling function of JMCT is introduced. A press water reactor shielding neutron flux is achieved by JMCT with source biasing sampling technique, which is well accord with experiment. Its computation efficiency is higher than that of MCNP using geometry important method.