Control of Ground-Shine Induced Electromagnetic Leakage through the Door Gap in Linear Accelerator Facilities: Cross-Validation of Steel Floor Reinforcement Using Simulation and Measurement

This study investigates electromagnetic radiation leakage through a 1-cm door-floor gap beneath a heavy entrance door in a 10 MV linear accelerator (LINAC) treatment facility without a maze and evaluates the mitigation effect of steel floor reinforcement beneath the gap. The facility is equipped with an Elekta Versa HD LINAC directly connected to a corridor, and leakage was measured as ambient dose equivalent rate H*(10) at a reference point 10 cm outside the door at floor level using a RadEye G-10 (Thermo Scientific) survey meter under fixed 10 MV irradiation conditions with a 20 × 20 cm² field and a water-equivalent phantom. The same room–door–corridor geometry, including the 1-cm door–floor gap, was modeled in FLUKA. Steel plates with thicknesses of 0.5–2.5 cm is placed on the inner floor beneath the door, and a USRBIN detector with DOSE-EQ and AUXSCORE (AMB74) scored H*(10) per primary at the reference point. Simulation results were normalized/scaled to μSv/h using the unreinforced (0 cm) measurement as an anchor. Experimentally, the leakage dose rate decreased from 25.0 μSv/h (0 cm) to 14.5 μSv/h (2.0 cm), while FLUKA predicted a reduction from 25.0 μSv/h (by normalization at 0 cm) to 12.21 μSv/h (2.0 cm). Both results indicate that a steel plate of about 2.0 cm beneath the door–floor gap can significantly reduce electromagnetic radiation leakage and that the combined measurement–simulation approach is useful for assessing local shielding reinforcement in maze- less LINAC facilities.