On the influence of the supporting frame on the nuclear response of the Helium-Cooled Lithium Lead Test Blanket Module for ITER

Within the European Fusion Technology Programme, very intense research activities have been promoted on the Helium-Cooled Lithium Lead (HCLL) breeding blanket concept with the specific aim of manufacturing a Test Blanket Module (TBM) to be irradiated in ITER. HCLL-TBM is foreseen to be located in an ITER equatorial port, being housed inside a proper steel-supporting frame. In particular, since that frame has been designed to provide two cavities separated by a dividing plate and HCLL-TBM is foreseen to fill just one of them, its nuclear response could vary accordingly to the filling status of the other one, unless the dividing plate is thick enough to isolate the components housed in the two cavities, avoiding any significant nuclear interaction among them. At the Department of Nuclear Engineering of the University of Palermo a research campaign has been launched to investigate the potential impact on the HCLL-TBM nuclear response of either the dividing plate thickness or the filling status of the frame cavities. A computational approach based on the Monte Carlo method has been followed and a detailed parametric study has been carried out considering thicknesses of the dividing plate ranging from 0 to the reference value (20 cm) and assuming, for each case, the presence of either void, or a water-cooled steel plug, or a HCLL-TBM or a Helium-Cooled Pebble Bed (HCPB) TBM in the other frame cavity. The analyses have been carried out by means of the MCNP-4C code, running a large number of histories (2 × 107) so that the results obtained are affected by statistical uncertainties lower than 1%. The results obtained are herewith reported and critically discussed.