Rn-219标准源的研制及其准确测量研究

Rn-219 is a kind of radioactive gas, it can break away from its mother nuclide into the atmosphere. Rn-219 and its daughters nuclide come into being aerosol easily, when the aerosol is breathed into the human body, it can produce internal exposure. There are plenty of Rn-219 at some place such as high enriched uranium storage and spent fuel cooling pool, people have attached any importance to the radioprotection of Rn-219 and its daughters. Research Some natural radioactivity nuclides for example Ac-227 and Ra-223 can be applied as a tracer in the field of science such as Groundwater Transference,Isotopic Oceanography. Ac-227 nuclide is required to monitor at surveying naturally occurring radioactive material (NORM), for measuring these nuclides. We can measure their daughter Rn-219, and it is very expediently for sample preparation. A method of measuring Rn-219 accurately and a standard Rn-219 source is needed for working all of these tasks. The interferences nuclides were transformed anion by different kind of acid and acidity,it can be removed from the matrix by chromatography. And an efficient and fast method for separating and collecting Ac-227 from uranium ore is founded,by which the radionuclide purity of Ac-227 is more than 95%. Using the identity of actinium ion which can be adsorbed by some carrier, the standard radioactive Rn-219 source is developed,the emanation coefficient of the source is more than 90%,and its the uncertainty is less than 5%. An accurate method of measuring Rn-219 is founded.The sample flow rate is more and the volume of the scintillation chamber is larger, the detection limit is about 10Bq/m3.

Rn-219为放射性气体，能脱离母体进入大气中。Rn-219与其子体易形成放射性气溶胶，其进入人体会产生内照射。高浓铀贮存库、乏燃料冷却池等场所有大量Rn-219存在，对其防护受到人们的重视；地下水迁移、同位素海洋学研究中可用Ac-227、Ra-223等天然核素作为示踪剂，天然放射性物质（NORM）的辐射监测对Ac-227提出新要求，可通过测其子体Rn-219来实现对这些核素的测量，且制样方便。所有这些工作都需要对Rn-219准确测量及Rn-219标准源。本课题通过利用不同酸类、酸度将干扰核素调成不种离子，并与色谱法相结合，建立高效、快速从铀矿石中提取Ac-227方法，Ac-227放射性纯度＞95%；利用锕离子能吸附在某些载体上这一特性，研制出Rn-219标准放射源，射气系数＞90%，不确定度＜5%；用大流量、大体积闪烁室的方法建立起测准确测定Rn-219的方法,检测下限为10Bq/m3。

Rn-219为放射性气体，能脱离母体进入大气中。Rn-219与其子体易形成放射性气溶胶，其进入人体会产生内照射。高浓铀贮存库、乏燃料冷却池等场所有大量Rn-219存在，对其防护受到人们的重视；地下水迁移、同位素海洋学研究中可用Ac-227、Ra-223等天然核素作为示踪剂，天然放射性物质（NORM）的辐射监测对Ac-227提出新要求，可通过测其子体Rn-219来实现对这些核素的测量，且制样方便。本课题取得以下研究结果：建立起提取高放射性纯度的Ac-227方法，该方法能获得高放射性纯度的Ac-227，其放射性纯度达到99.5%；利用γ能谱法通过对Ac-227的4个子体核素Th-227、Ra-223、Rn-219和Bi-211的活度进行测量，该方法能对Ac-227进行准确定值；研制出射气系数高且稳定的Rn-219放射源，在温度5℃-55℃、相对湿度大于40%时，射气系数均为92.5%，且射气系数稳定；利用Rn-219标准源对闪烁室进行刻度，得到相应条件下的Ｋ值；建立分离、测量Rn-219 、Ra-223、Ac-227方法。本课题研究结果可应用于天然放射性物质（NORM）的辐射环境监测、地下水迁移、同位素海洋学研究等领域中。