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根据氡的迁移机制(如扩散、对流、大气抽吸等),采用理论计算的方法,得出埋入地下的探杯中的氡浓度与杯口邻近土壤空气中的氡浓度达到自然状态平衡约需0.7—10小时,而杯中氡浓度与其短寿衰变子体达到放射性平衡需4小时。因此,一般认为两者共需4.5—12小时左右。钍射气与其短寿命子体达到放射性平衡的时间需3—4天。当钍含量高出背景值时,探杯的照射时间则需3—4天。用ZnS探杯埋入地下做了野外试验,与上述理论计算结果基本相符。对这种平衡过程的了解,不仅为选取最佳的埋杯时间提供了理论依据,而且也有助于各种测氡方法的异常解释。
According to the radon migration mechanism (such as diffusion, convection, atmospheric suction, etc.), the theoretical calculation method is used to find that the radon concentration buried in the underground probe cup and the radon concentration in the air near the cup mouth reach the natural state balance 0.7 to 10 hours is required, while radon concentration in the cup and its short-lived decayed progeny reach a radioactive equilibrium for 4 hours. Therefore, it is generally believed that both need about 4.5-12 hours. Thoron gas and its short-lived progeny to achieve radioactive balance of time to be 3-4 days. When the thorium content is higher than the background value, the exposure time of the probe cup takes 3-4 days. With ZnS probe buried in the ground to do a field experiment, with the above theoretical results are basically consistent. The understanding of this equilibrium process not only provides the theoretical basis for choosing the best cup-laying time, but also helps to explain the abnormalities of various radon-measuring methods.