Application of a 3D Discrete Ordinates-Monte Carlo coupling method to deep-penetration shielding calculation

•A 3D Discrete Ordinate-Monte Carlo (SN-MC) coupling code is developed.•RPV fast neutron fluence rate and reactor cavity streaming calculation are performed.•The 3D SN-MC coupling method increases calculation efficiency by 2–10 times. For large-scale pressurized water reactor (PWR) deep-penetration shielding calculation, Monte Carlo (MC) method requires simulating a great number of particles to obtain reliable results, thus huge amount of computation time is the main problem of the MC method. Discrete Ordinates-Monte Carlo (SN-MC) coupling method combines the advantage of the SN method with high efficiency and the MC method with fine geometrical modeling. This paper studies the 3D SN-MC coupling method, generates surface source using the angular fluence rates of a SN code JSNT, and develops a source sampling subroutine for a MC code JMCT. The coupling method is verified on measurements and applied to CAP1400 cavity streaming calculation. Numerical results show that the coupling method increases calculation efficiency by 2–10 times for deep-penetration shielding calculation with high precision compared with reference results. The coupling method is effective for large-scale PWR deep-penetration shielding calculation.