Spallation taken from the middle English spalle, is an efficient process for producing an intense neutron flux suitable for exploitation in Accelerator Driven Subcritical Reactors (ADSRs) for energy production and the transmutation. In order to assess spallation driven fission and transmutation we have simulated proton induced neutron production using GEANT4. Benchmarking our simulations against experimental neutron spectra produced from a thick lead target bombarded with 0.5 and 1.5 GeV protons. The Bertini and INCL models available in GEANT4, coupled with the high precision (HP) neutron model, are found to reproduce the published experimental data. Given the confidence in the GEANT4 simulations provided by this benchmarking we then proceed to study neutron production in an ADSR using Thorium in a geometry similar to that of the proposed Belgian MYRRHA project with 0.6 GeV proton beam energy that proposed by SCKCEN.