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Description
This work investigates the characteristics and properties of spallation targets in ADS (Accelerator Driven System). The aim is to obtain a high neutron flux with a hardened neutron spectrum for transuranic transmutation in a hybrid fission ADS system. The proposed system uses a proton source (a particle accelerator) with energies between 0.3 and 1.6 GeV, focusing on different high-density material targets: three in liquid state, mercury, natural lead, a lead-bismuth eutectic alloy (LBE) and two solid states, tungsten (W) and natural uranium (U). The geometry of the spallation target (radius R and height H) is varied to understand these variables' role in the neutron yield. The neutron flux on the target surface is evaluated for the different energies of the incident protons and different geometries of the targets, considering the results of simulations in MCNPX (Monte Carlo N-Particle Transport Code). The results show a neutron multiplicity saturation limit for incident beam energy at 1 GeV. It is verified that there are optimal dimension values for the target radius and length, respectively, at R close to 15 cm and L close to 50 cm for incident proton energies of 1 GeV. The neutron flux distribution of the study targets presents a hardened spectrum suitable for using ADS for nuclear waste transmutation. A subcritical reactor with different neutron sources provided by some targets has been tested to evaluate the neutronic parameters of the hybrid system.
