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.