Residual activation of the SPES Front-End system: a comparative study between the MCNPX and FLUKA codes

A study of the residual activation of the Front-End system structure of the SPES (Selective Production of Exotic Species) facility, currently under construction at the Legnaro National Laboratories of INFN, Italy, is performed. The study provides useful information for the planning of inspections, maintenance operations and decommissioning of the facility as well as for the assessment of radiological conditions and safety requirements in the design and operation of any accelerator-driven radioactive ion beam facility. To better assess the obtained results, two Monte Carlo codes were independently used: MCNPX combined with CINDER’90 and FLUKA. The results of the two calculation procedures are compared at each step: fissions, fluxes, activation, dose rate. Since the energy range considered does not represent a typical application for any of the two codes, the comparison of the collected results can provide useful inputs for the developers. In particular, the agreement of the two codes on the global quantities is good, being of the order of 20–40% on average, and never larger than a factor 2. Nevertheless, the comparative study shows that, in this energy range, FLUKA seems to underestimate the angular straggling of protons and to overestimate the proton interaction cross-sections, with respect to MCNPX.