Benchmark experiment on bulk shield of SS316/water with simulated superconducting magnet

A bulk shielding experiment was performed at the D-T neutron source FNS, using the assembly simulating shield blanket, vacuum vessel and toroidal field coil (superconducting magnet) of ITER. The objective was to investigate the influence on nuclear parameters due to the nuclei involved in the toroidal field coil and the effect of B4C/Pb. The analysis was performed by MCNP4-A and the DOT3.5 (P5S16 approximation, 175-n and 42-γ groups with and without self-shielding correction) with JENDL Fusion File (JENDL-FF) and FENDL/E-1.1. All of the MCNP calculations and DOT calculations with self-shielding correction agreed within ± 40% with the measurements. It was found that the influence of self-shielding mainly due to copper and tantalum in the DOT calculations was large for neutrons less than 10 keV. It is concluded that the uncertainty of nuclear designs by MCNP-4A and DOT3.5 with JENDL-FF and FENDL/E-1.1 on the bulk shield of ITER is approximately 40% in the toroidal coil region. The analysis suggested that it was quite important to deal with heavy nuclei of small quantity such as tantalum precisely in the shielding design.