Calculation of induced radioactivity in the SAD spallation target

The Subcritical Assembly in Dubna (SAD) is the installation (in design stage) coupled with existing 660 MeV proton accelerator (max beam current 3.2 μA). The main characteristics of the subcritical core are: MOX fuel, k eff = 0.95 , fission power 27.6 kW, Pb reflector. The SAD spallation target consists of one central and 18 hexagonal (36 mm pitch) Pb prisms in 2 concentric layers. The main goal of the calculations, the results of which are presented, is the evaluation of the target total induced radioactivity and of its longitudinal and radial distributions in the target. The time evolution for several working scenarios of the total and long-lived isotopes activity are shown as well. The computational tools applied are the MCNPX2.5e code for high-energy particles and FISPACT for low energy ones. The results obtained with some selected nuclear reaction models in the MCNPX calculations are compared. Calculated results of activities for long-lived isotopes produced by the high energy particles are confronted with the measured ones, obtained in the experiment with bare Pb cylindrical target.