QUANTIFICATION OF BACK DIFFUSION IN RADON AND THORON EXHALATION RATE MEASUREMENTS

Area of Science:

• Environmental Science
• Radiological Protection
• Geochemistry

Background:

• Indoor radon (222Rn) and thoron (220Rn) levels are primarily influenced by soil and building material exhalation.
• Accurate measurement of exhalation rates is crucial for mitigating indoor radon and thoron exposure.
• Natural exhalation measurements can be complicated by the back-diffusion phenomenon.

Purpose of the Study:

• To develop and validate a novel methodology for simultaneously measuring radon back-diffusion coefficients and free exhalation rates.
• To assess the significance of the back-diffusion phenomenon on radon and thoron exhalation rates under specific experimental conditions.
• To analyze soil samples from a monazite-rich area for their radon and thoron exhalation characteristics.

Main Methods:

• A novel experimental methodology was employed to simultaneously estimate the back-diffusion coefficient and free exhalation rates for radon.
• The leak rate of the experimental setup was determined and validated against a standard technique.
• Two soil samples with high 238U and 232Th content were analyzed.

Main Results:

• The novel methodology successfully estimated radon back-diffusion coefficients and free exhalation rates.
• The measured leak rate using the new method showed agreement with standard techniques.
• The back-diffusion effect for thoron was found to be negligible under the experimental conditions, with a detailed explanation provided.

Conclusions:

• The developed methodology provides a reliable approach for measuring radon exhalation rates while accounting for back-diffusion.
• The study highlights the negligible impact of back-diffusion on thoron exhalation under the investigated conditions.
• Findings are based on soil samples from a monazite-rich coastal region, offering insights into radon and thoron emissions from such sources.