Systematic approach to identify the dominant neutron leakage paths in the WCCB-TBM port

Abstract

In the design activity of fusion reactors, neutronic analysis is one of the most necessary analyses. In this paper, the systematic approach to estimate the paths of neutron transport is introduced. In Monte Carlo code MCNP, users can set 'kill option' to arbitrary region, and then, the neutrons going into the region have their histories in MCNP terminated. With the combination of the calculations which, users set the kill options to different regions, the neutron transport paths can be estimated. In this paper, this approach is applied to the #18 equatorial port of ITER with Water Cooled Ceramic Breeding (WCCB) Test Blanket Module (TBM), and the shutdown dose rate (SDDR) at Pipe Forest (PF) due to the activated components is calculated. The result shows the main contributor for SDDR is not the neutrons going through TBM, and even if TBM has ideal shielding performance, SDDR can't be reduced less than half, and the most effective way to reduce SDDR at PF is to add the surrounding shield to PF. Due to the additional shield, SDDR can be reduced from 180 μSv/h to 79 μSv/h, and this is under the target value 100 μSv/h.