Research on 2D ray effect elimination module of radiation shielding code ARES

In the analysis of radiation shielding calculation, discrete ordinate method (S_N method) is one of the main international calculation methods currently. S_N method will produce ray effect while solving the transport equation along only a few specific directions, especially for isolated point sources, large volume of void regions and strongly absorbing media, ray effect is very obvious. Based on first collision source method, the uncollided neutron flux was solved by semi-analytic method and then first collision source term was calculated, the contributions of the isolated point source to all spatial grids were equivalent to the sum of that of each grid's first collision source, thus ray effect could be remedied. 2D ray effect elimination module ARES_RayEffect2D was developed. ARES_RayEffect2D was coupled with 2D discrete ordinate transport module ARES2D, and compared with the advanced shielding calculation programs for a series of models. The results demonstrate that ray effect can be effectively mitigated. (authors)