Optimizing radiation dosimetry: Impact of PMMA layers on electronic equilibrium for the calibration of radiation protection instruments

Abstract

In radiation dosimetry , achieving electronic equilibrium is vital for accurate dose measurements in radioprotection. This study investigates the effect of Poly Methyl Methacrylate (PMMA) layers, known by its chemical formula C 5 H 8 O 2 and a density of 1.19 g/cm³ (PNNL, 2011), on electronic equilibrium for the calibration of radiation protection instruments, focusing on photon beams of varying energies. Using DOSIMEX 2.0 simulation software, we modeled the influence of PMMA thickness on calibration factors across different X-ray and gamma-ray beam energies. Experimental validation with Cs-137 and Co-60 sources confirmed the reliability of the simulation. Our results highlight that while PMMA layers have a minimal impact on calibration for higher-energy beams, their role becomes significant for energies below 40 keV. For X-ray beams (From 30 to 140 kV), the results show minimal calibration factor deviation (<1.6%), whereas radionuclide beams exhibit more significant variations (4.1%), necessitating customized calibration approaches. This study underscores the importance of adhering to ISO 4037-3 standards in radioprotection, particularly in low-energy scenarios, to ensure the precision of calibration procedures and optimize radiation protection practices. Furthermore, based on the results obtained, the absence of PMMA does not have a dramatic effect on the calibration of X-ray radiation instruments, whereas for gamma-ray beams, it has a significant impact. • First study to verify the impact of not considering this effect: PMMA layers on electronic equilibrium during radioprotection instrument calibration. • Shows minimal calibration factor deviation (<1.6%) for X-ray beams but significant variations (4.1%) for radionuclide beams, requiring customized calibration approaches. • Stresses the importance of adhering to international standards, like those set by the IAEA and ISO, in radiation dosimetry. • Highlights the importance of adding a 3 mm PMMA layer for calibration, especially for energies below 40 keV and with Co-60 sources.