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

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.