Experimental validation of shut down dose rates calculations inside ITER cryostat

A neutronics experiment has been performed at the 14 MeV Frascati Neutron Generator (FNG) to validate the calculations of shut down dose rates inside the ITER cryostat. A proper experimental set-up, in which a neutron spectrum is generated similar to that occurring in the ITER vacuum vessel, has been irradiated for sufficiently long time to create a level of radioactivity which has been followed, after shut down, by dosemeters for more than 2 months of cooling time. The experiment has been analysed using a rigorous, standard two-step method, i.e. using MCNP-4-B and FISPACT codes, and a new one-step method with an ad hoc modified version of MCNP code used in the nuclear analysis of ITER. FENDL-2 nuclear data libraries are used in both cases. The comparison between experiment and calculations shows a good agreement in both cases.