CALCULATION AND OPTIMIZATION OF STRUCTURAL SHIELDING BY REPLACING A 6 MV LINAC WITH A 10 MV

Abstract

The installation of a new 10 MV accelerator relocates the isocenter position and invalidates the shielding calculation of the existing bunker. Therefore, a time-optimized constructive redesign was required to comply with Radiological Protection standards, including the evaluation of materials and geometries of hollowed blocks, by means of Monte Carlo simulations in EGSncr software, for 10X spectrum. The shielding calculation was performed according to the methodology of NCRP report N 151, taking into account the existing thicknesses of the primary and secondary barriers, projected at a workload of 16 hours per day and dose rate of 2400 UM/min (10X FFF). The redesign of the facility included the width of the primary barriers of 20 cm in the direction of isocenter displacement, as well as the addition of 1 HVL in the secondary barriers abutting the medical physics office and the command room. Among the materials studied, it was chosen to use hollowed serpentine concrete blocks with NBS 04 concrete infill, reinforced with iron rods. In conclusion, the optimization of the bunker design for the 10X equipment complies with the national radiological protection standards, which was corroborated by the radiometric survey, thus ensuring the safety of personnel and patients.