人类核活动向环境中释放了大量的长寿命放射性核素129I和99Tc，由于其裂变产额高、寿命长、易迁移等特点，其总浓度及其在环境中的赋存形态，一直以来在核废物处置和核环境安全监测中都受到极大的关注。环境中129I和99Tc的浓度极低，测量难度大，在我国的环境放射性调查中一直缺失相关的数据报道。本课题拟对大气气态碘的采集和分离技术，99Tc的干扰核素99Ru的去除，99Tc的靶源制备等关键技术难题进行研究，基于碘负离子和锝的氟化物负离子提取，优化AMS的关键仪器参数、样品化学分离纯化条件等，建立超痕量129I和99Tc及其形态的加速器质谱分析方法。本申请将首次在小型化AMS（3MV）上进行实际样品的99Tc分析。方法将用于分析大气中的129I及其形态、土壤和沉积物中的129I和99Tc及其形态，初步获得129I和99Tc的环境水平及其形态分布信息，为核废料处置和环境示踪研究提供科学依据。

Human nuclear activities have released large amount of long-lived radionuclides iodine-129 (129I) and technetium-99 (99Tc) to the environment. Because of high fission yields, long half-life, strong beta radiotoxicity, high mobility and volatility, concentrations and species of 129I and 99Tc have been always receiving great attention in nuclear waste disposal and nuclear safety monitoring. However, extremely low-level of the two radionuclides in the environment is hard to be measured, which is the main reason that rare data are available in the investigation of environmental radioactivity in China, in particular the level of 129I in the atmosphere and 99Tc in all kinds of environmental media. This study aim to mainly develop highly efficient trapping technique of gaseous iodine in atmosphere, removal of 99Ru isobar interference of 99Tc, target source preparation of 99Tc, and finally establish highly sensitive analytical method of accelerator mass spectrometry (AMS) for measurement of ultra-low level of 129I and 99Tc and their species in environmental samples. Using AMS detection, extraction of iodide and technetium fluoride negative ions, crucial AMS instrumental parameters, separation and purification of radionuclides, as well as conditions of speciation separation will be carefully optimized to achieve the best analytical performance. This study will firstly conduct measurement of 99Tc in environmental samples using a small (3 MV) AMS instrument in combination with chemical treatment. These established methods will be mainly applied on determination of 129I and 99Tc in air, soil and sediment, aiming to investigate the levels and the species distribution, at the service of the nuclear waste disposal, environmental radioactivity investigation and environmental tracing applications.