The High Intensity Proton Accelerator (HIPA) at the Paul Scherrer Institute (PSI) is at the forefront of the high intensity frontier of particle accelerators delivering a 590~MeV continuous wave proton beam with currents of up to 2.4~mA (1.4~MW beam power). IMPACT (Isotope and Muon Production with Advanced Cyclotron and Target Technologies) is a proposed initiative envisaged for HIPA. As part of IMPACT, a proposed Isotope Separation OnLine (ISOL) type facility, TATTOOS (Targeted Alpha Tumour Therapy and Other Oncological Solutions), will allow the production of promising radionuclides for diagnosis and therapy of cancer in quantities sufficient for clinical studies. The TATTOOS facility will consolidate all necessary ISOL steps onto one site, featuring a dedicated proton beamline intended to operate at a beam intensity of 100~$\mu$A (60~kW beam power) and requiring continuous splitting of the high-power HIPA beam via an electrostatic splitter (EHT). In the preliminary design phase of the beamline, single particle tracking codes in linear approximation are used to construct the lattice and to provide a first-order model. In the more advanced beamline design phase, conventional Monte Carlo codes have been employed to include particle matter interactions into the first-order beam dynamics model. Knowledge of these interactions allowed to study and predict the consequences of beam losses including long term radioactivation. Overall, this thesis presents the construction of the simulation framework used to design the TATTOOS beamline including optimisation of the beam optics, magnetic elements and collimator settings and simulations of the beam rotation on the target. Finally, simulation results are benchmarked with measurements from a dedicated beam study.