Influence of Particle Beam and Accelerator Type on ADS Efficiency

Conditions that maximize the performance of an accelerator-driven system related to particle beam and energy and accelerator type are analyzed. The toolkit Geant4 simulated the interaction of protons and ions with masses up to Ne-20 and energies from 0.2 to 2 GeV/n. The beam intensity considered is 1.5 x 10(16) p/s. The core of the reactor is modeled as an assembly of fuel rods surrounding a cylindrical beryllium converter, with a criticality coefficient of 0.985 and lead-bismuth eutectic coolant. Lower enrichment generates better utilization of fuel (20% to 25% from the initial actinide mass can fission in a cycle keeping neutron damage in clad below 200 displacements per atom). Data on particle fluence and energy released obtained from the simulation are used to calculate total electric power produced and isotope evolution. Power spent to accelerate the beam depends on accelerator type and is calculated by scaling from data on accelerator efficiency for a reference particle. Optimal proton energy is similar to 1.5 GeV when the beam is accelerated in a linac with energy gain G similar to 14 and is 0.75 to 1 GeV in the case of a cyclotron (G similar to 12). Ion beams starting with He-4 realize higher G values than protons: 20 to 50 in a linac and 15 to 35 in a cyclotron.