Research On Measurement Of Radon Exhalation Rate In Building Materials Using Active Carbon Adsorption-liquid Scintillation Method

Radon and its progeny are the main sources of natural radiation, and interior was the main venue for the radiation of radon. Any floor indoor radon concentration is under the influence of radon exhalation of building materials, China released the code for indoor environmental pollution control of civil building engineering(GB 50325-2010) made it clear that it should be determined the exhalation rate of building materials and soil radon.Currently used mostly radon collecting cover- monitoring method and active carbon absorption-? energy spectrum method for measuring radon exhalation rate. The former is invert the radon collecting cover onto the surface of medium to be tested, by measuring the the radon concentration of the radon collecting cover to calculate radon exhalation rate. The shortcomings of the method is that you must consider leaks and anti proliferation effects during radon accumulation process(especially long-term cumulative measurement). by. Active carbon absorption-? energy spectrum method is using activated carbon adsorption radon and then measurement by ? energy spectrum, the method under certain conditions can ignore the effects of the leakage and anti-diffusion, but gamma spectrometers has the disadvantages of low detection efficiency and manual measurement, therefore not suitable for large-scale sample survey.Liquid scintillation spectrometer has the advantages of the background count low, and automatic measurement of the sample. In order to achieve automatic measurement of radon exhalation rate in building materials, this paper intends to by examining radon exhalation rate values through using different quality activated carbon sampling and determine the amount of activated carbon which can ignore anti-diffusion. Then we can research of active carbon adsorption-liquid scintillation method of measuring radon exhalation rates from building materials. By comparing the measurement results of this method with the active carbon absorption-? energy spectrum method on the surfaces of the radon exhalation standard device, uranium ore brick and foaming, the accuracy of this method was verified.The experimental results show that the active carbon adsorption-liquid scintillation method for measuring radon exhalation rate depends on the adsorption properties of activated carbon and dissolution characteristics of scintillation liquid; different types of activated carbon has different adsorption capacity of radon, the different composition of scintillation liquid, in which the radon solubility has certain different. Appropriate to increase the amount of activated carbon can accelerate the rate of adsorption of radon, and control the anti-diffusion in the acceptable range. When the preparation of C-LS-Rn standard source, should consider the effects of radium on the count rate, Based on the C-LS-Rn standard source, the calibration coefficient of this method is 72.36 min-1·Bq-1. The count rate of radon is 120% by this method. The minimum detectable radon exhalation rate is 8.15×10-4Bq·m-2·s-1 when cumulative time is 72 hours. It must pay attention to change activated carbon type, batch number, or change the flashing liquid formula, the efficiency of school standard series source should be prepared the corresponding activated carbon is. The active carbon adsorption-liquid scintillation method can ignore the effect of anti-diffusion under certain conditions. The relative deviation of measurement results between these two methods is about 10%, within the acceptable range.Active carbon absorption-? energy spectrum method need manual sampling and repeat the measurement procedure operation in the process of measuring, therefore active carbon adsorption-liquid scintillation method is more suitable for automatic measurement of large quantities of samples, it can save a lot of manpower and time. The preparation has a stable C-LS-Rn standard source, and scale coefficient is related to the variety of test research, and many factors affect the measurement has a better grasp of, for building materials, radon exhalation rate automatic measurement of reference, and for the future to ensure quality monitoring and improve the sensitivity specified in the right direction.