Measurement of Høgdahl neutron flux parameters in the SM1 subcritical reactor of the University of Pavia

•Subcritical neutron reactors provide low but stable neutron flux.•Høgdahl conventional flux characteristics are measured by bare irradiation method.•Flux parameters trends intra- and inter-channels are evaluated. Neutron flux of the thermal subcritical multiplication complex located at the nuclear pole of the University of Pavia was investigated to acknowledge the flux characteristics according to the Høgdahl convention in order to predict the expected activity of radionuclides while performing neutron activations. Flux parameters were evaluated by means of bare multi-monitor methods by preparing samples containing Au, Cr, Zn and Ni that were used to measure the epithermal shape correction factor, the conventional thermal to epithermal ratio and the thermal, epithermal and fast neutron fluxes in two irradiation channels of the facility. Despite high uncertainties affecting epithermal shape correction factors, thermal to epithermal ratios was measured with uncertainties ranging between tens and a few percent. In addition, conventional neutron fluxes were individually determined with a few percent level uncertainties, which are also suitable in applications requiring a known and/or ultra-stable neutron exposure.