【作者】 吉艳琴；

【导师】 罗上庚； 李金英；

【作者基本信息】 中国原子能科学研究院 ， 核燃料循环与材料， 2001， 博士

【摘要】 核设施的运行，不可避免有放射性物质弥散到环境中。随着核能的开发应用，为评价放射性废物对坏境的影响及确定放射性废物安全处置方案，长寿命放射性核素的环境行为越来越受到各国环境科学工作者的关注。研究环境中铀、镎、钚等长寿命放射性核素的精密测定，对保护公众安全和保护环境，对了解核设施的历史操作情况和现状，都具有重要意义。 环境样品基体复杂，铀、镎和钚等锕系元素含量非常低，在复杂的生态条件下，这些核素常常具有复杂多变的化学形态，要准确测定其含量，必须要有灵敏可靠的检测方法。传统的放化分析方法主要包括α谱测量法、中子活化分析法、液体闪烁法、固体径迹法和γ谱法等，这些方法有制源过程复杂、测量时间较长、易受环境天然放射性元素的掩盖等缺陷，在许多方面已不能满足辐射防护与分析监测的要求。 随着新型分析技术的不断发展，痕量与超痕量非放射性检测技术已逐步应用于测量环境样品中放射性核素。电感耦合等离子体质谱(ICP-MS)具有灵敏度高、干扰少、检测限低、测量时间短、可进行多核素同时测量等特点。自八十年代以来，国外对ICP-MS测量环境样品中的铀、钍、镎和钚的研究表明，ICP-MS在测量长寿命放射性核素方面是最有发展前景的测量技术之一。任何分析技术的发展都有其局限性，ICP-MS也有不足之处，如测量环境样品中痕量水平的镎和钚时，存在一定干扰等。建立简便、快速的化学分离预处理技术，是ICP-MS成功应用于环境样品中痕量与超痕量放射性核素分析的关键。本文主要研究了以下内容： (1)国内率先开展微波消解溶样-ICP-MS同时直接测定土壤样品中U和Th 根据微波消解法处理样品速度快、试剂用量少等特点，引入微波消解法处理土壤样品；用209Bi做内标排除基体干扰；用2％(v/v)HN03消除ICP-MS测量时产生的记忆效应；用IAEA标样验证了分析方法的准确度等。分析了四种土壤样品，获得U、Th含量的相对标准偏差低于10％。 (2)环境样品中U同位素丰度比的ICP-MS测量方法研究 研究了TOPO萃取色层分离环境样品中U的方法。通过色层柱体积、上柱酸度、洗涤酸度，以及不同洗脱剂的条件实验，确定了分离流程，获得U的全程回收率约98％， 中国原子能科学研究院博士学位论文 摘 要 对土壤样品的去污因子为 l．4 X 10’－l．8 X 10’。 通过对不同丰度铀同位素标样的测量研究，确定了ICPMS测量铀同位素的质量偏 倚系数，比较研究了扫描和跳峰两种数据采集方式，获得刀’U／23b精密度忧于 1％、 ”‘U／2”U、”6U／235U、“勺123勺和’“U／23’U优于 5％。两种方式测量实际样品的结果吻 A （）首次建立了 TOA革取色层分离－ICPMS测量环境样品中锋的方法 关于TOA应用于分离环境样品中的痕量锋，只有液－液摹取法见诸报道。我们建立 了 TOA＄取色层法分离和 ICP－MS测定环境样品中刀Np的方法。该方法操作简便、 快速、准确、可靠，对模拟土壤样品分离锋的回收率接近 100％，刀佃p的检测限为 0．46 pg mL‘＊．2 x 10－’Bq rnL－‘卜对刀8U的去污因子超过 10＼ 完全适合于环境样品中痕量 ‘’hp的检狈。 （4）革取色层分离－ICPMS测量环境样品中的钎 在国家标准方法（GB ZIg刁－89）的基础上，通过改变样品上柱流速、用加热的 0．02mOIL－’HZCZO。＋0．16md’HNO。洗脱色层柱，使土壤样品中的针的凹收率为 （91．7。8．3）％。改进了国标方法。 （5）在国内首次用 ICP－MS测定了针的同位素丰度比值，成功地将同位素稀释法 应用于ICP－MS测量环境样品中的环 采用优化的仪器条件，测定了‘“Pu／239PU的比值。将同位素稀释法应用于 ICP－MS， 测量了环境样品中＊的含量。通过对IAEA标准样品的测定，检验了该方法的准确性。 用该方法测定了核设施的实际样品。 （6）环境样品中痕量锋和钎的ICP－MS同时测量方法研究 经TO A革取色层柱分离环境样品中的基体，通过两次上柱，将Np和PU同时洗脱， 实现了1＊－＊S同时测定帅和h的含量。以IAEA标样进行了验证，PU的测定值与 标样的推荐值较好吻合（标样中无Np的标推值人初步证明ICP－MS同时测定Np和 Pll的可行性。更多还原

【Abstract】 Small amounts of radioactive materials are lost inevitably to the environment during any processing of nuclear material. With the development of nuclear power industry the corresponding waste has been grown. In order to evaluate the radioactive waste, which could affect the environment, and to devise projects for the nuclear waste disposal, the behaviour of long-lived artificial radionuclides in the environment are subject to detailed studies and are of increasing concern to environmental researchers. By analyzing radionuclides such as uranium. neptunium and plutonium in environmental samples, which were collected in the immediate environment of a nuclear process or nuclear site, researchers can detect evidence of the corresponding nuclear activities. Results from such research can also supply reliable information to assure the public safety and protect the environment.The concentration of neptunium and plutonium is extremely low in environmental samples. Additionally such samples have a complex matrix composition, which is to be taken into account for a proper analysis. Conventional radiochemical methods such as alpha spectrometry, neutron activation analysis, liquid scintillation system, fission track and gamma spectrometry for the quantitative determination of neptunium and plutonium often require complicated and time-consuming sample preparation and separation procedures. Due to the large amount of the complex and often unknown matrix, the analysis may also be covered by naturally occurring radionuclides.With the development of new analysis techniques, non-radioactive methods are increasingly used for the determination of trace or ultratrace radionuclides hi environmental samples. Inductively coupled plasma mass spectrometry (ICP-MS) has some advantages, such as high sensitivity, low detection limits, short analysis time, less chemical interferences and multi-elemental capability. Since 1980s, ICP-MS has been used overseas for the determination of uranium, thorium, neptunium, and plutonium in environmental samples. ICP-MS is one of the most suitable analysis techniques for the measurement of the long-lived radionuclides. However, ICP-MS is susceptible to spectral interference and non-spectral interference ormatrix effects. Therefore the set up of a simple, fast separation procedure is the key to success when traces of radionuclides are measured by ICP-MS. The main topics of research presented in this paper are as follows (points 1 to 6):(1) A microwave acid-digestion - ICP-MS method was established for the direct determination of U and Th in soil samples:A microwave acid-digestion method, which is characterised by faster digestion and smaller reagent consumption than traditional approaches for the dissolution of soil samples has been developed. The matrix effects of soil have been effectively corrected by using 209Bi as an internal standard. The memory effect during aspiration of the liquid sample into the ICP-MS has been eliminated by using 2% (v/v) HNOs. The results obtained from soil standards of IAEA are in good agreement with recommended values. This method was applied to four real soil samples. The results show a standard precision of below 10%.(2) Studies on the method of determination of uranium isotopes ratios in environmental samples:An efficient separation procedure for uranium from environmental samples by TOPO chromatographic extraction has been developed. The procedure has been optimized experimentally for the size of the column, different concentrations of nitric acid for column load, column rinse and the different types of eluent. Uranium was recovered with approximately 98% efficiency by the improved and optimized procedure. The decontamination factors for the soil matrix is approximately 1.4 x 103 up to 1.8 x 105.The instrumental mass bias is usually calculated from the analysis of reference materials with certified isotope abundance ratios. For both scan and jump mode the isotope discrimination correction was evaluated and the accuracy was compared. The results s更多还原