Measurement and Analysis of Neutron and Photon Flux Spectra in an ITER Shield Mockup with Open Channel and Cavity

Abstract

The neutron performance of the ITER shielding system has been experimentally investigated on the basis of an integral experiment for a shield mock-up with open streaming channel. The mock-up simulates the first wall, the shielding blanket, the vacuum vessel, the toroidal field coil and a radial channel through the shield blanket used for the mechanical attachment of the blanket module. The aim of this work has been to provide experimental validation of the ITER- design parameters for a streaming path with direct sight of the D-T plasma. Neutron and photon flux spectra have been measured on the central axis in a cavity at the bottom of the central channel and at a deep position behind that with the 14 MeV neutron source on and off the central axis and additionally for shifted sidewise positions of the detector. The experimental results are compared with Monte Carlo calculations using nuclear data from FENDL-1 and -2 data libraries. In general, the measured neutron and γ-ray flux spectra can be predicted within an uncertainty margin of 30% both with FENDL-1 and -2 data. A somewhat larger underestimation is found for the deep position at the back of the shield mock-up.