Measurement of ²²²Rn diffusion through sandy soil with solar cells photodiodes as the detector

Area of Science:

• Environmental Science
• Geophysics
• Radiological Science

Background:

• Radon-222 (²²²Rn) is a naturally occurring radioactive gas.
• Understanding radon diffusion in soil is crucial for environmental and health assessments.
• Existing detection methods can be costly and less efficient.

Purpose of the Study:

• To develop and validate an experimental system for measuring radon-222 diffusion rates in porous media.
• To investigate the influence of soil properties, specifically porosity and water content, on radon diffusion.
• To compare experimental findings with theoretical models.

Main Methods:

• Development of a novel experimental system utilizing solar cell photodiodes as alpha (α) detectors.
• Systematic variation of soil grain size, soil water content, and soil depth in experimental columns.
• Measurement of radon diffusion rates under controlled conditions.

Main Results:

• Soil water content emerged as the most dominant factor influencing radon diffusion rates.
• Maximum diffusion rate of (6.5 ± 0.07) × 10⁻⁶ m²/s observed in dry soil conditions.
• Minimum diffusion rate (< (3.9 ± 0.14) × 10⁻⁷ m²/s) recorded at 2% soil water content.

Conclusions:

• The developed system offers a highly efficient and low-cost alternative for radon detection.
• Experimental results showed discrepancies with the "GREEN equation" predictions, particularly in equilibrium time and alpha count rates.
• Observed discrepancies are attributed to differences in system geometry between experimental setup and theoretical model assumptions.