A deterministic and Monte Carlo coupling method for PWR cavity radiation streaming calculation

PWR cavity radiation streaming calculation is important for the evaluation of the radioactive dose rate in structural materials. Discrete Ordinates (S _N) method has been widely used to solve shielding problems, but it is difficult to apply to a complex geometry. Monte Carlo (MC) method can treat the geometry exactly but requires very long computing time to obtain acceptable statistic deviations. Thus, an S_N-MC coupling method is adopted in order to combine the advantages of both S_N method and MC method in PWR cavity radiation streaming calculations. To develop this coupling method, two surface source models, the combined surface source model (CSSM) and the single surface source model (SSSM), are proposed and analyzed. From the numerical results two conclusions can be drawn. (1) The S_N-MC coupling method offers a speedup factor of 2-20 compared with the MC method to obtain the same statistic deviations. (2) In the S_N-MC coupling method, the CSSM is more efficient than the SSSM in reducing statistic deviations.