The PERC (Proton and Electron Radiation Channel) facility, located at the neutron source FRM II of the Technical University of Munich (TUM), serves as a clean source of neutron decay products (protons and electrons). PERC aims to contribute to the determination of the Cabibbo-Kobayashi-Maskawa quark-mixing element (V_ud ), measure the correlation coefficients of freeneutron decay (a,A,b,C) and search for new physics at the TeV scale. For this, all systematic errors will be controlled at 10-4 level. To ensure a low background for the detectors as well as to fulfil all radiation protection requirements, the PERC beamstop has been designed. Its components will consist of boron carbide (B4C) and lead (Pb), which were chosen based on MCNP simulations.