NEUTRON AND GAMMA ALBEDO EVALUATION AT AN IRRADIATION FACILITY.

The irradiation facility of the University of Pisa (UNIPI) is a neutron and gamma irradiation facility of the University of Pisa used for calibration purposes and to evaluate detectors and dosemeters for mixed neutron and gamma fields. The facility consists of a fairly large room (5.0 × 7.8 × 2.5 m3) with concrete walls and roof designed to minimise radiation scattering. Sealed neutron and gamma radionuclide sources are stored in the facility for calibration and test purposes. In order to perform accurate response measurements, this study applied a methodology of general validity to assess the neutron and gamma room scatter contributions (albedo) to the fluence and to the ambient dose equivalent rates. The assessment was done for the standard irradiation points of the facility, using detailed Monte Carlo simulations and considering several source-to-wall and source-to-detector distances.