Estimation of neutron duct streaming with the feeder for the power supply system in the JT-60 tokamak fusion device facility

The estimation of neutron duct streaming with a feeder for the power supply system in a JT-60 Tokamak fusion device facility has been performed via neutoronics analysis using a simplified formula for the cylindrical duct streaming model and a suitable model based on the Monte Carlo technique. However, the safety margin is too large for the evaluation using a simplified formula in order to evaluate the neutron streaming of a duct with three feeders (each feeder of size 0.126 m × 0.357 m × 2 m) inside a cylindrical duct (0.8 m diameter × 2 m length in size). Further, a detailed evaluation of neutron streaming of a cylindrical duct with three feeders has not been performed in the facility. In this study, three-dimensional (3D) neutronics analysis using a real-model of the complex structured duct was performed to assess the safety margin of the simplified formula. It was confirmed that the neutron dose attenuation of the penetrating section in the duct using the simplified formula is approximately one order of magnitude larger than the real-model using the 3D calculation code.