A Practical Framework for Depth and Profile Assessment of Cs-137 in Soil Using Scintillation Detectors and Composite Spectrum Analysis

Abstract For environmental monitoring and radiation protection, it is important to know exactly how deep and where radioactive materials like Cs-137 are in the soil. Conventional approaches are often invasive and provide only average depth estimates, limiting their reliability. In this study, a novel, non-destructive method is proposed based on a hexagonal close-packed configuration to simulate a surface-distributed Cs-137 source. Measurements were conducted at multiple depths using NaI(Tl) and plastic scintillation detectors, and the system was calibrated using Monte Carlo simulations. Composite spectra were analyzed using an inverse modeling approach to estimate both the depth and layer-wise distribution of contamination. Blind tests demonstrated the method’s high accuracy in reconstructing realistic contamination profiles. The suggested method is easy to use, cheap, and works with different types of detectors, so it can be used in real-world situations to measure environmental radioactivity.