Neutronics experiment on a mock-up of the ITER shielding system at the Frascati neutron generator (FNG)

Abstract

Abstract An integral bulk shield experiment has been performed at the Frascati Neutron Generator (FNG) with the main objective to validate the ITER shielding system. To this end, a suitable mock-up of the ITER inboard shielding system including first wall, shielding blanket, vacuum vessel and toroidal field coil, had been assembled at ENEA Frascati. Neutron and γ-ray spectra as well as various nuclear responses were measured inside this mock-up when irradiated by 14-MeV neutrons. Measured and calculated data were compared to validate transport codes and nuclear data used in the design of the ITER system. In particular, the measured neutron and γ-spectra, reaction rates and the nuclear heating were compared with the same quantities calculated with the MCNP Monte Carlo code using the Fusion Evaluated Nuclear Data Library (FENDL)-1.0 and the European Fusion File (EFF)-3.0 neutron cross section data. The neutron-induced activation measured in stainless steel was compared with calculations performed with the FISPACT code and using the most recent activation cross section data file FENDL/A-2.0. The paper includes a comparison of calculated over measured quantities (C/E) and a discussion of their relevance to the ITER nuclear design. It is found that, generally, the measured nuclear quantities are predicted by FENDL-1.0 and EFF-3.0 calculations within an uncertainty margin of about ±15% in the shielding blanket and vacuum vessel, and ±30% up to the region of the toroidal field coil.