Virtual Booth

This study developed a Geant4 Monte Carlo simulation framework to optimize the shielding design of a high-energy radiotherapy treatment vault. Unlike conventional deterministic methods such as NCRP Report No. 151, the proposed approach accurately models photon and neutron transport in a realistic three-dimensional treatment room. The simulation included the linear accelerator, water phantom, concrete shielding walls, and a double-bend maze. Advanced physics models and variance reduction techniques were applied to ensure reliable results with statistical uncertainties below 5%. The findings showed that the primary and secondary concrete barriers could be safely reduced to 70 cm and 50 cm, respectively, decreasing concrete volume by up to 14.1% while maintaining radiation levels within regulatory limits. The simulation also identified localized neutron and gamma-ray leakage that is not predicted by conventional methods, highlighting the need for additional maze shielding. A composite door made of 5 cm lead and 5 cm borated polyethylene provided effective protection against both photons and photoneutrons. Overall, the framework enables safer and more cost-effective radiotherapy vault design.