氡及其子体的释放和运移规律及机理研究

【作者】 乐仁昌；

【导师】 贾文懿； 苗放； 刘庆成；

【作者基本信息】 成都理工大学 ， 矿产普查与勘探， 2001， 博士

【摘要】 氡的释放和运移规律及机制研究是氡气测量的基础理论问题,它与氡在地球科学、环境科学等领域的广泛应用密切相关。本文从实验入手,采用静态、累积、高灵敏度的测氡方法,对氡及其子体在较理想条件下的释放和运移规律进行了实验研究,并从实验和理论上对氡释放和运移机制进行了探讨。实验发现,氡从铀矿物中的释放具有阵发性和自发性,并与铀矿物的种类、粒度大小等因素有关。其机制是:由于铀矿物内部空隙发育各异,Ra经α衰变放出Rn和He,待其在矿物内部空隙聚集到一定压力时,才能由空隙溢出,这是导致铀矿物释放氡呈阵发性和自发性的内因。实验还发现,氡及其子体的分布具有明显的方向性,而与扩散规律相违背。在向上,向下,横向各为4m的实验条件下,纵向运移能力远大于横向运移能力,向上运移能力也大于向下运移能力:其端点向上,向下,横向运移计数比分别为66%:31%:3%; 向上、向下及横向总计数的对比结果是:54%:35%:11%; 总运移量的对比结果是:54%:34%:12%; 运移系数的结果是:向上0.184cm²s^-1,向下0.094cm²s^-1,水平0.015cm²s^-1; 运移速度的结果是:向上220.4×10^-6cm/s,向下181.3×10^-6cm/s,水平58.3×10^-6cm/s。氡及其子体比重虽很大,但其“自身”却具有明显的向上运移能力,其机制是:氡及其子体经α衰变所放出的α粒子减速后,将成为He核,He核可与氡及其子体形成团簇,当团簇在介质中所受的浮力大于其重量时,团簇便能自行上升。在氡运移机制研究中,借助铀矿石产生的氡和液体镭源产生的氡形成的4He之差异,进一步验证了氡-氦团簇运移现象。论文还建立了氡运移理论分布方程,应用该理论方程对运移实验数据进行了计算,取得了较满意的结果。更多还原

【Abstract】 The study of radon release and migration is the basic theoretical issue for radon measurement, which has close relationship with extensive applications in geoscience, environmental science and so on. In this thesis, the laws of the release and migration of radon and its daughters have been studied in laboratory conditions using the accumulative radon-measurement method in a static state with high sensitivity. The mechanism of release and migration of radon and its daughters has been studied by experimentation and theory. According to our experiments we find: The release of radon from uranium mineral is characterized by erratic and spontaneous features and is related to the uranium mineral’s category, granularity and so on. Because of the variety of porosity in uranium mineral’s interior, the radon and helium, which are brought by the emission of α-particles of radium, cannot flood out of mineral body until they accumulate in mineral’s interior and the air pressure goes beyond the limit. This is the inherent cause for the release of radon from uranium mineral characterized by erratic and spontaneous features. The migration of radon and its daughters is directional, and contravenes the law of the diffusion. On the condition that upwardness, downwardness and horizontalness reach respectively 4m, the ability of radon and its daughters to move vertically is much greater than its ability to move horizontally, while its ability to rise is obviously greater than its ability to fall. As far as upwardness, downwardness and horizontalness are concerned, the percentages of migration measurements results for each end point are respectively 66%, 31% and 3%; The average percentages are respectively 54%, 35% and 11%; The percentages of total volume of migration are respectively 54%, 34% and 12%; The migration coefficients are respectively 0.184cm2s-1, 0.094cm²s^-1 and 0.015cm²s^-1; The migration velocities are respectively 220.4× 10^-6cm/s, 181.3×10^-6cm/s and 58.3×10^-6cm/s. Radon and its daughters possess the ability to rise although the specific gravity of radon and its daughters is high. The mechanism is: after α-particles emitted by radon and its daughters decelerate, they become He nucleus. The He nuclei can combine with radon and its daughters and form clusters. Because He is very light, it can make the specific gravity of the clusters lower than their buoyancy in the medium. As a result, the clusters will rise of their own accord. The mechanism of radon-helium cluster migration is further verified by the difference of quantity of 4He emitted from uranium ore and liquid radium source in the course they release radon. The theoretical distribution equation is established to describe radon migration and the results of calculation with the equation are satisfactory.更多还原