Overview of straight duct streaming experiments for ITER

Two straight duct streaming experiments for international thermonuclear experimental reactor (ITER) were performed by using the intense deuterium–tritium (D–T) neutron source at Japan Atomic Energy Research Institute (JAERI) in order to investigate the influence of streaming through ducts on radiation dose and to validate the accuracy of design calculations. One was a small duct streaming experiment for diagnostic ports, the other was a large duct streaming experiment for large ports such as neutral beam injector (NBI) port. The ducts increased the neutron flux above 10 MeV by 10 6–10 7 times at the ends of the ducts, while the increase of neutron flux below 10 MeV and γ-ray by the ducts was less than a few hundred times. These experiments were analyzed by the MCNP-4A code with three nuclear data libraries: FENDL/E-2.0, -1.0 and JENDL Fusion File. Though the ducts made complicated neutron and γ-ray flux distributions in a cavity region, most of the calculated results agreed within ±40% with the experimental data. It was demonstrated that the MCNP calculations with the nuclear data libraries were accurate enough for predicting nuclear design parameters of ITER even for various duct geometries as far as they were modeled precisely.