Optimal ion beam, target type and size for accelerator driven systems: Implications to the associated accelerator power

► Hydrogen isotopes are the most effective projectiles for production of spallation neutrons. ► For every target material, incident ion type and energy there is an optimal target size which results in the escape of a maximum number of spallation neutrons from the target. ► In an ADS, a beam of 1.5 GeV deuteron and a U-target results in the highest neutron yield and energy gain. ► For 1.5 GeV d + U, ADS with lead or LBE moderator, required ion current is only 38% of that for 1 GeV p + Pb, ADS. ► For a 1.5 GeV d + 238U ADS of output power 550 MWth, a deuteron beam of average current 1.8 mA is required.