Radon exhalation rates corrected for leakage and back diffusion – Evaluation of radon chambers and radon sources with application to ceramic tile

The natural radon decay, leakage and back diffusion are the main removal processes of radon from its container. Ignoring these processes leads to underestimate the measured value of radon related parameters like exhalation rate and radium content. This work is aimed to evaluate two different radon chambers through determining their leakage rate λv and evaluation of radon source by determine its back diffusion rate λb inside the evaluated radon chambers as well as a small sealed cup. Two different methods are adapted for measuring both the leakage rate and the back diffusion rate. The leakage rate can be determined from the initial slope of the radon decay curve or from the exponential fitting of the whole decay curve. This can be achieved if a continuous monitoring of radon concentration inside the chamber is available. Also, the back diffusion rate is measured by sealing the radon source in the chamber and used the initial slope of the buildup curve to determine λb and therefore the exhalation rate of the source. This method was compared with simple equation for λb based on the ratio of the source to the chamber volume. The obtained results are applied to ceramic tile as an important radon source in homes. The measurement is targeted the ceramic glaze before and after firing as well as the obtained tile after adhere the glaze on the tile main body. Also, six different tile brands from Egyptian market are subjected to the study for comparison.