【作者】 时燕华；

【导师】 葛良全；

【作者基本信息】 成都理工大学 ， 辐射防护与环境保护， 2011， 硕士

【摘要】 在环境放射性检测项目中,土壤中锶―90含量分析是较为繁琐和分析结果稳定性差的,通常通过测量与⁹⁰Sr处于平衡的子体⁹⁰Y的活度来推算⁹⁰Sr的活度。在⁹⁰Sr分离过程中,关键是锶与同族元素钙、钡及镭之间的分离,尤其是锶与钙的相互分离。其次就是从⁹⁰Sr和其他放射性核素中分离出放射性纯的⁹⁰Y,以便进行β活度的测定。本课题结合了国家标准GB/T6764^GB/T6766 1986和GB/T1222.1 1989水和生物灰中对放射性⁹⁰Sr化学分析方法,对江西省国家监控点位土壤样中⁹⁰Sr进行了二―（2―乙基己基）磷酸酯萃取放置法的测定,在前人的研究成果基础上提出了适合测定50g土壤样中⁹⁰Sr活度浓度测定的分析程序,并用一般较为常用的快速法从锶的化学回收率、钇化学回收率、加标实验、空白试验以及⁹⁰Y探测效率等方面与之对比验证,取得如下成果:1、一般放置法是将土壤中锶―钇进行分离,除去土壤中本身带有的⁹⁰Y,将⁹⁰Sr保留下来放置14天以上使新衰变得到的⁹⁰Y与之达到放射性平衡,再将钇分离出来进行测量,得出⁹⁰Sr的活度浓度。本课题在利用快速法分离锶钇之后又进行了两次锶钇分离,并从放置法分析得到的钇化学回收率上看出色层柱对钇的损失较小,这使其分离更为彻底,将溶液中⁹⁰Y的再次生成所受到的干扰降低。2、两次加标验证实验中,标准锶钇活度浓度为8.693Bq/ml,本方法分析程序测定出的标准锶钇活度浓度为7.514Bq/ml、7.823Bq/ml,加标活度回收率为86.44%、90.00%;锶回收率为67.95%、61.40%,钇的化学回收率为53.02%、58.25%,相对误差为13.56%、10.01%,平均标准偏差为11.74%,而一般快速法锶钇活度为5.938Bq/ml、4.098Bq/ml,加标活度回收率为68.31%、47.14%,钇的化学回收率34.57%、30.79%,相对误差为31.69%、52.86%,平均标准误差为43.40%,可见放置法的实验效果比一般快速法的更为理想和准确。3、分析得出的江西省国家监控点位土壤样中⁹⁰Sr的活度,在放置法的相较快速法测得的值较大,这是由于快速法测定的是在土壤中原有的⁹⁰Y,而该⁹⁰Y含量在分离的化学前处理中有较大损失,而放置法所测定的再次生成⁹⁰Y至生成到仪器测定的过程较为简单,处理方便,钇含量损失较少。而这两种方法的准确性从图5 1中放置法、快速法钇回收率与锶回收率的测定值吻合度可以看出。4、低本底α、β测量仪对⁹⁰Y探测效率的验证实验中,放置法的探测效率一路、二路分别为0.2707、0.3120,完全满足仪器的要求。5、在最后的土壤锶浓度计算中,本课题在前人所编写的放置法计算公式上引入了β标准源效率的修正值参与计算,这是根据不同仪器对β粒子的探测灵敏度而修正的,本次实验中的二路低本底α、β测量仪（BH1216Ⅲ型）中修正后的β标准源效率分别为0.2833、0.3126,这也符合仪器中要到达0.2500的要求。引入该值后使加标试验中的标准活度更接近真实值。本次土壤中⁹⁰Sr的放置法分析程序的研究,从活度、回收率等发面上的测定都取得取得较为满意的结果,验证了该方法的可行性,且达到了较好精度和准确性。更多还原

【Abstract】 In the environmental radioactivity,the soil content of ⁹⁰Sr analysis is more complicated with poor stability.Usually in equilibrium by measuring the daughter ⁹⁰Y’s activity to calculate the activity of the ⁹⁰Sr,and the key is the separation of the same group elements strontium and calcium,barium and radium ,especially strontium and calcium from each other.The second is how pure ⁹⁰Y to be isolated from the ⁹⁰Sr and other radioactive,for the determination ofβactivity.The subject is basded on the national standard GB/T6764^GB/T6766 1986 and GB/T1222.1 1989,and National Surveillance Point of Jiangxi soil samples ⁹⁰Sr,carried out a二―（2―ethylhexyl） phosphoric acid method of determination of place in the results of previous studies and made on the basis of 50g soil samples for determination of activity concentration in the determination of ⁹⁰Sr analysis procedures.The Placed Method was proved with the Rapid Method of the chemical recovery of Sr,Y’s chemical recovery, standard addition experiments,blank tests and the detection efficiency and ⁹⁰Y contrast verification,achieved the following results:1、The general Placed Method is to remove ⁹⁰Y form the soil,the ⁹⁰Sr is placed more than 14 days to get the new decay of radioactive ⁹⁰Y for achieving a balancethen. Separated and measure the new Y once again,which is obtained in the activity concentration of ⁹⁰Sr.The issue separate the two times Sr and Y after use of the Rapid Method.Followed by The Placed Method obtained,the loss of the chemical recovery of ⁹⁰Y is more smaller Y,which will make the disruption of the re ⁹⁰Y was reduced.2、In the two adding the standard experiments,the activity concentration of Sr―Y was 8.693Bq/ml.The standard Sr―Y activity concentration of the Placed Method were 7.514Bq/ml and 7.823Bq/ml;of spiked recovery were 86.44% and 90.00%;Sr’s recovery were 67.95% and 61.40%;the chemical recovery of Y were 53.02% and 58.25%,relative error were 13.56% and 10.01%,the average standard deviation was 11.74%,while the Sr―Y activity of the general Rapid Method was 5.938Bq/ml, 4.098Bq/ml,spiked recovery wre 68.31% and 47.14%,34.57% ;the chemical recovery of Y was 30.79%,the relative erroris were 31.69% and 52.86%,the average standard deviation was 43.4%,which was showing that the experimental results of the Place Method more desirable than the Rapid Method’s.3、Drawn from the analysis of soil samples of national surveillance points in Jiangxi Province,the ⁹⁰Sr’s activity by the placed method compared to the fast method is the larger measured value,which is due to the Rapid Method get the ⁹⁰Y have a greater loss in the separation of the chemical pre treatment.In the other hand, Generation ⁹⁰Y was measured by the process of the placed method is more simple,convenient,and the loss of ⁹⁰Y contentless.The accuracy of these two methods is showed in Figure5 1,It can be seen that Sr recovery rate fit with by the Placed Method is very different it fit with the Y recovery rate by Rapid Method.4、In detection efficiency of ⁹⁰Y verification experiment of the low backgroundα、βmeasuring instrument,the detection efficiency of the Placed Method were 0.2707、0.3120 and meet the requirements for instruments fully.5、In the final Sr concentration calculation of the soil,the Placed Method’s formula was added theβmeasuring standard rate beyond the prepared previous method.The correction value involved in the calculation,which is based on theβparticles of the different of the instruments and the detection sensitivity.This experiment use the two Road of low backgroundα、βmeasuring instrument （BH1216Ⅲtype） and the revised efficiency ofβwere 0.2833、0.3126。It is consistent with the instrument requirements to reach 0.2500.After the introduction of it,test value is closer to the true value in the standard test.The study of the process in the soil analysis of ⁹⁰Sr by the Placed Method obtained the satisfactory results from the determination of the activity and recovery rates and so on.The study also achieved the feasibility and good precision betteraccuracy of the placed method更多还原