A Study Of Radon Emanation Coefficient For Soil

The harm of environmental radon more and more draws people's attention, and the soil radon is the main source of environmental radon. Radon emanation coefficient of soil is a key parameter in evaluating the potential risk of environmental radon caused by soil. In this paper, the measurement of radon emanation coefficient and its influence factors are studied in two aspects. It is hoped to establish an indoor short-time accumulation measurement method to measure the radon emanation coefficient of soil with a good stability and reproducibility, which can be used as a reference method for the measurement of radon emanation coefficient at high thorium areas. Study on the changing rule and the correlation between radon emanation coefficient and soil basic physical parameters, provide some basic data and reference for the soil radon potential mapping, defending and reducing measures of radon.Taking the soil as the research object, according to the transport theory about producing and exhaling of radon from the soil, accumulation in the closed container,the mathematical calculation formula of a short-time accumulation measurement of radon emanation coefficient is derived. For radon concentration monitoring purposes,ALphaGUARD PQ2000 Emanometer, the gas collecting bottle and filtration bottle have been used. after seal, gas guide, static and measurement process to measure the soil radon emanation coefficient. The stability, reproducibility and reliability of the short-time accumulation measurement method are analyzed by comparing the repetitive measurement results of the samples with the long-time accumulation measurement results. Then based on the measurement method, measuring the radon emanation coefficient under the condition of different moisture content in soil samples, grain size, and radium content, the paper analyzes the measurement results of soil radon emanation coefficient, and studying the change rule and correlation of radon emanation coefficient and moisture content, radium content and grain size of soil samples. The results show that the relative percentage deviation of the repeated measurements on the same samples is less than 5% under the basically same measurement conditions; the short-term accumulation measurement results and long-term accumulation measurement results show no significant differences; the relationship of soil particle size and water content is obvious. Under the same the radium content and water content,soil radon emanation coefficient decreases with soil grain size increases; under the same radium content and grain size, radon emanation coefficient increases first and then decreases with the increase of water content. The soil radon emanation coefficient under the condition of 10% moisture content is about double the value under the dry condition.In summary,this paper establishes a short-term accumulation measurement of soil radon emanation coefficient in indoor, not only improves the measurement efficiency, but also reduces the influence of Thoron in measurement process, and provides a new method for measuring the soil radon emanation coefficient at high thorium areas.