Calculations of neutron and gamma energy spectra in surroundings of the HRNS for ITER

Abstract

An optimisation of the High Resolution Neutron Spectrometer HRNS) shield was performed. Concrete and polyethylene shields of different thicknesses were considered. Two boxes for two sets of detectors are to be built of polyethylene though the underside is planned to be made of concrete. The final external dimensions of the first box are to be 175 cm (length), 150 cm (width) and 170 cm (height) while the second box is to be 215 cm long, 150 cm wide and 200cm high. All the shield elements are to be 10 cm thick including a wall between the boxes. Next, photons and scattered neutrons spectra in the first box detectors were calculated. The results will be used as a source to estimate the background contribution on the different detectors. Finally, the neutron and photon spectra through the inner and outer surfaces of the first box were computed. The results are to be used as gamma and neutron sources in subsequent evaluations of shut-down dose rates in the port cell. A detailed MCNP input file was elaborated, based on a CAD model, which geometric part contains over 600 cells of HRNS, not counting void.