Study On Radon Concentration Passive And Continuous Measurement In Soil

The development of the method for measuring radon concentration in soil is the technical basis to practice the forced control standard of indoor radon pollution, improve the evaluation level of indoor radon pollution source, enlarge the methods of the earthquake prediction and the earth science research. The purpose is to develop a passive and continuous method for measuring radon concentration in soil, which can discriminate the disturbance of thoron to radon measurement, eliminate the influence of the humidity to the sensitivity of radon measurement, measure the true radon concentration in soil.The method was developed based on countingαparticles released from ²¹⁸Po, improving the sensitivity of radon monitoring by using static electric field, eliminating the influence of thoron to radon measurement on thoron shorter half-life, and reducing the humidity effectiveness by using smaller sampling chamber. It can give a measurement result per hour.For the test of the research program, a static electric sapling chamber with the volume of 3.46L was developed. The test results indicated that the saturation sampling voltage was chosen as 1000V, the detection efficiency reduced 26% when the relative humidity increased from 37% to 100%, the influence factor of ²¹⁴Po to ²¹⁸Po measurement was 9.35%.Based on the test results, an equipment with a sampling chamber of 385mL for measuring radon concentration in soil was developed. At first, the properties test and the calibration were done in the radon chamber, then the experiment for radon concentration measurement in soil outdoor was done. The saturation sampling voltage was chosen as 600V, the detection efficiency reduced only 6.9% when the relative humidity increased from 48% to 84%, the influence factor of ²¹⁴Po to ²¹⁸Po measurement was chosen as 9.35% also and the influence of ²¹⁴Po to ²¹⁸Po measurement can be reduced, the disturbance of thoron to radon measurement can be eliminated completely by using a discrimination chamber with the length of 30cm.The detection efficiency of the smaller sampling chamber is higher than the larger one.The main problem is how to drill the sampling hole without the destruction of the soil status.