【作者】 谢东；

【导师】 王汉青；

【作者基本信息】 中南大学 ， 供热、供燃气、通风及空调工程， 2009， 博士

【摘要】 铀矿开采过程中产生大量的氡及其子体、铀矿尘、放射性气溶胶等放射性有害物,其所造成的剂量约占整个核燃料循环系统总剂量的83.3%。铀矿通风尾气的排放对周围环境造成一定程度的污染,危害公众健康。尾气中放射性核素在大气中的输运过程十分复杂,它和污染源的性质、输运区域的地形、地貌特征、大气风场、不同地区的气候特征,降水等因素有关。铀矿通风尾气中放射性核素迁移扩散研究是大气污染控制与环境治理要重点解决的课题之一,对促进核行业可持续发展具有重要意义。论文是在国家自然科学基金项目(铀矿井通风尾气核素迁移及安全防护距离综合预测方法研究)的资助下,针对不同风速特性和下垫面粗糙度下核素迁移扩散的特点,采用数值模拟和模型实验的方法研究了铀矿通风尾气放射性核素迁移扩散机理,探讨了辐射安全防护距离的计算方法,提出了关于铀矿通风尾气放射性污染的数值计算方法和预测评价方法。论文的主要工作体现在以下几个方面:(1)系统阐述了铀矿通风尾气排放特点和污染特征;分析了放射性污染问题主要研究方法的适用性及不足。在上述基础上,提出了研究铀矿通风尾气对周围环境放射性污染的数值计算方法和评价方法。(2)系统分析了各种影响大气中铀矿通风尾气放射性核素迁移扩散的因素,确定影响核素扩散的主要因素,为数值模拟和模型实验设计提供了理论依据。(3)研究了复杂地形下核素大气中迁移扩散的数值计算方法,探讨了复杂地形网格的划分、边界条件的确定、核素计算参数的选取等一些基本问题;提出了核素分相求解的计算方法,为后续数值模拟计算打下了基础。(4)针对铀矿通风尾气排放源特征、风速和下垫面粗糙度特点,采用数值方法研究了风场特性和粗糙度对复杂地形下铀矿通风尾气核素扩散的影响,揭示了不同因素影响下氡气的分布规律和影响区域,以及核素粒子的大气迁移特性,数值结果与现场实测值规律一致,吻合良好,为铀矿通风尾气对周围环境放射性污染和危害的预测与评价打下了基础。(5)采用缩比模型水槽实验方法,利用盐水溶液在水中的扩散来模拟氡气在大气中的扩散情况,并应用PIV技术、DIPT技术和流场显示技术研究了铀矿通风尾气核素大气扩散特性,揭示了铀矿通风尾气核素大气迁移扩散和浓度分布规律,并用实验结果验证了数值计算结果。(6)应用前述所建立的数值方法以及国家对铀矿区周围放射性污染的公众个人剂量限制标准,建立了辐射防护安全距离和铀矿区选址的评价方法;并利用指数平滑法建立污染预测模型,对铀矿井周围放射性核素污染进行了10年的预测评价;最后提出了针对我国铀矿通风尾气对环境污染的防护措施。更多还原

【Abstract】 Many radioactive radionuclides such as radon and its daughters, uranium dusts and radioactive aerosols, etc. are produced in process of uranic mining, which have caused the 83.3 percent dose of the total nuclear fuel cycle dose. A certain degree of pollution to surroundings is caused by the radionuclides about uranic well ventilation exhaust gas. Radionuclide migration in atmosphere is complicated, and it is concerned with the features of pollution sources, topography and geomorphological features of the migration region, as well as atmospheric wind fields, the climatic characteristics of different regions, precipitation and other factors. The research of radioactive radionuclides about uranic well ventilation exhaust gas is one of emphasis projects of contamination-controlling and environment-administering, which has a great significance to promote sustainable development of the nuclear industry.Supported by National Natural Science Foundation (Research on the forecast method of safety protection distance and radionuclides migration about uranic well ventilation exhaust gas), and based on the radionuclide diffusion characteristics of different wind speed properties and surface roughness degrees, numerical simulation and model experiment investigation on the migration status of radionuclides about uranic well ventilation exhaust gas are accomplished in this dissertation. In addition, the computation method of safety protection distance is discussed, and then the method of numerical computation, prediction and evaluation about uranic well ventilation exhaust gas are put forward finally.In summary, this dissertation includes the following main contents:(1) To investigate systematically the exhaust characteristics and pollution properties about uranic well ventilation, as well as the applicability and shortages of current major research methods about radioactive radionuclides. On that basis, the method of numerical computation, prediction and evaluation about uranic well ventilation exhaust gas are put forward.(2) To analyze systematically the various factors on the migration of radionuclides in atmosphere, and to decide the main factors, which creates the theoretical basis for numerical simulation and model experiment design. (3) Numerical computation methods for the migration of radionuclides in atmosphere under complex terrain are studied. And some basic questions are researched such as the grid division, boundary conditions setting and the selecting of radionuclides computation parameters, etc. Then the computation method of radionuclides phases-separating is brought forward, which creates the basis for the coming numerical simulation research.(4) Based on the source features, wind properties and surface roughness degrees characteristics about uranic well ventilation, the migration impact of wind properties and surface roughness features under complex terrain is researched for radionuclides by numerical simulation. And it is obtained the different factors of radon gas distribution and pollution regions, as well as the migration characteristics of radionuclide particles in atmosphere. And the numerical results are similar to the measurement results on the spot, which creates the basis for prediction and evaluation of radioactive pollution and harm on the surrounding environment about uranic well ventilation exhaust gas.(5) Using the method of small-scaled model water tank experiments, the diffusion of salt liquor in water is used to simulate the diffusion status of radionuclide in atmosphere. In addition, the PIV technology, DIPT technique and flow field visualization technique are used to investigate the diffusion characteristics of radionuclides about uranic well ventilation exhaust gas, and reveal its’ rules of migration-diffusion and concentration distribution. At last, the experimental results would be used to verify the numerical results.(6) Based on the above numerical methods and national public dose limit personal standards about uranic mining areas, the evaluation methods for radiation safety protection distance and uranium mine site-selecting are set up. Then the method of exponential smoothing is used to set up pollution prediction model and also it is used to make a ten-year prediction and evaluation on uranic well ventilation exhaust gas radioactive pollution. Finally, some suggestions for preventing and controlling the environmental pollution by radioactive ventilation exhaust gas are put forward.更多还原