Neutron flux characterization of the SM1 sub-critical multiplying complex of the Pavia University

Abstract

SM1 is a thermal Sub-critical Multiplication complex located at the University of Pavia (Italy) and, since its installation in 1962, has been utilized mainly for radiochemistry research. This work focuses on the characterization, by means of the Monte Carlo code MCNP and direct measurements, of the neutron flux distribution inside the complex and on the calculation of the effective multiplicative coefficient (keff) in the current SM1 thermal configuration. For two specific irradiation channels, experimental measurements of the neutron fluxes were performed by foils activation technique and neutron spectrum de-convolution based on the SAND II code. Measurements have been compared with the simulation results showing a good agreement. Furthermore, a comparison between the preliminary results of the simulations of the SM1 plant in fast configuration, characterized by a solid lead diffuser, and the actual thermal configuration is also presented. The fast configuration of SM1, if implemented, will give the opportunity to carry out preliminary studies for the analysis of sub-critical fast-neutron installations and their applications.