Research On Deep Penetration Shielding Calculation For Fusion Reactor

The analysis of radiation shielding calculation is the important basis for the design and optimization of the nuclear facilities. The geometric construction and materials are complex in fusion reactor, containing both bulk shield and complex channels. It requires the shielding calculation not only to simulate geometric model precisely, but also solve the deep penetration problems effectively. In addition, the neutron energy released in the fusion reaction is around 14MeV, so that the anisotropic scattering will be more serious in the shielding calculation. Therefore, it makes great significance to research on the deep penetration shielding calculation in fusion reactor.The Monte Carlo method has good geometric adaptability, while the discrete ordinates method is suitable for solving deep penetration problems. So the coupled MC-SN method is studied and the mapping of particle flow to angular flux is introduced during the study. Based on MCNP and multigroup particle transport program ARES, the MCNP-ARES coupled program is developed and verified preliminarily. The results of the coupled program are in good agreements with those of MCNP, which prove the feasibility of the coupled program in shielding calculation of fusion reactor.In the shielding calculation of bulk shield in fusion reactor using ARES program based on the discrete ordinate method, the traditional diamond differencing scheme requires small grid spacing to ensure the accuracy. This contributes to large amount of calculation and time consuming. Therefore, on the basis of the Theta Weighted differencing scheme, the Directional Theta Weighted (DTW), Exponential Directional Weighted (EDW) differencing schemes which have adaptive features are introduced. EDW method assumes an exponential distribution for angular flux within each cell. The exponential coefficients are obtained by using the DTW solutions. Through theories and numerical examples analysis, it can be found that EDW can obtain higher accuracy in larger grid spacing. Therefore, EDW is effective in deep penetration shielding calculation of bulk shield in fusion reactor.The anisotropic scattering is strong in shielding calculation of fusion reactor, and there are many duct problems in fusion reactor. Neutrons penetrate with a strong anisotropy, which the traditional quadrature set such as level symmetric can’t accurately describe. Therefore, based on Legendre-Chebyshev quadrature set and regional angular refinement, the biased quadrature set is developed. It can increase the number of discrete directions for the concerned direction and spatial region. Kobayashi benchmark is calculated to show that the biased quadrature set can significantly improve the accuracy of calculation results in interested regions. Finally, the above methods are applied to shielding calculation of fusion reactor. Through the comparative analysis with MCNP, it can be found that these methods can effectively solve some deep penetration shielding problems in fusion reactor.