射气-闪烁法测定地下热水的镭-226和氡-222浓度

Concentrations of Ra-226 and Rn-222 in Thermal Groundwater Measured by Emanation-scintillation Method

地下热水中放射性浓度较高的226 Ra 和222 Rn 对于研究地下热水的形成和循环具有重要的意义.阐明了实验室测定地下热水226 Ra 和222 Rn 放射性浓度的射气闪烁法的仪器组成、测试原理、测试步骤、水样前处理和结果换算,讨论了在测试过程中各仪器和试验方法所需参数的选取及确定的具体操作.结果表明：在本试验中,所用放射性测试仪器 FD-125型氡钍分析仪的最佳阈电压为2 V,对应的最佳工作高压为450 V；所采用的3个闪烁室的校正因子分别为0.005428、0.005567和0.005060；进行前处理提取水样226 Ra时,pH 值应控制在2．5~3．0之间,可确保方法回收率最大.

High radioactive concentrations of 226 Ra and 222 Rn in thermal groundwater are of important significance in studying formation and circulation of thermal groundwater. The experimental apparatus,measurement principle and steps,pre-treatment of water samples and result calculations of the emanation-scintillation method to measure the radioactive concentrations of 226 Ra and 222 Rn in thermal groundwater in laboratory were described,and the determination of parameters used in the experimental devices and the measuring methods were discussed.The results show that the optimal threshold electric pressure for the radioactive FD-125 radonvthorium analyzer used in the experiment is 2 V,and the corresponding optimal working high electric pressure is 450 V;the collection factors for the three scintillation chambers used are 0.005 428,0.005 567 and 0.005 060,respectively;when 226 Ra is extracted from water sample in the pre-treatment,the pH values are controlled in the range of 2.5-3.0 in order to obtain the maximum method recovery rate.