Experiment and analyses for 14 MeV neutron streaming through a dogleg duct

There are several vacant channels for diagnosis, RF heating and so on through the shielding structure in fusion reactors. Some of them consist of dogleg ducts, through which neutrons stream in a complex manner. An experiment was conducted with the Fusion Neutronics Source (FNS) facility at JAERI to study the behaviour of neutrons in the duct and assess the reliability of calculation methods for the design of fusion reactors such as ITER. The assembly was an iron slab 180 cm in thickness with a doubly bent duct 30 x 30 cm2 in cross section. The experiment was analysed using a simple design code for radiation streaming, DUCT-III, and the Monte Carlo code MCNP. The results indicate that the simple design code is reliable enough to be used for shielding design analyses as well as the Monte Carlo method, which showed excellent agreement between calculated and measured values. (authors)