The aim of this study was to compare the neutronic behavior of the Accelerator Driven Systems (ADS) core using reprocessed fuel and thorium. The fuel used in some rods was (ThO2)-Th-232 for U-233 production. In the other rods, two different reprocessed fuels were used. One of the studied fuels was a mixture based upon Pu-MA, removed from PWR-spent fuel, theoretically reprocessed by GANEX reprocessing and spiked with 50% of thorium. The other fuel was a reprocessed fuel obtained theoretically from UREX+ (Uranium Extraction) process and spiked with 50% of thorium. Monteburns 2.0 (MCNP5/ORIGEN 2.1) code was used to simulate the neutronic aspects of the fuels. The results indicated that the use of GANEX or UREX+ fuel spiked with thorium allowed U-233 production and reduction of high radiotoxicity isotopes. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.