热电离过程中铀的化学形态及微观形貌研究  

Study on the Chemical and Microscopic Morphology of Uranium in the Process of Thermal Ionization

作　　者：张继龙 杨丽芳 王未然 黎春 纪建臣 骆无瑕 武朝辉 邵阳[3] 李汐 谭俊龙 ZHANG Jilong;YANG Lifang;WANG Weiran;LI Chun;JI Jianchen;LUO Wuxia;WU Zhaohui;SHAO Yang;LI Xi;TAN Junlong(State Nuclear Security Technology Center,Bejing 102401,China;East China University of Technology,Nanchang Jiangxi330013,China;Institute of HighEnergyPhysics,Chinese Academy of Sciences,Beijing100049,China)

机构地区：[1]国家核安保技术中心,北京102401 [2]东华理工大学,江西南昌330013 [3]中国科学院高能物理研究所,北京100049

出　　处：《世界核地质科学》2022年第4期766-773,共8页World Nuclear Geoscience

摘　　要：热电离质谱在分析铀同位素时由于存在质量分馏效应,影响铀同位素准确测量,通常对质量分馏效应采用外标校正法,但此方法要求测量过程中标准物质和样品应产生一致的质量分馏行为。研究了涂样和热电离过程中铀的形态变化以及涂样方式对铀电离效率的影响。通过控制不同涂样加热温度,制备出硝酸铀酰、三氧化铀和八氧化三铀等3种形态的铀样品。采用扫描电镜和拉曼光谱分析技术,结合热电离质谱,研究了硝酸铀酰、三氧化铀和八氧化三铀等样品在热电离过程中发生的形态变化,以及铀的电离效率和铀氧化物离子的产率。研究发现:(1)在真空环境下加热超过一定温度后,硝酸铀酰、三氧化铀和八氧化三铀均会转化成二氧化铀,然后以二氧化铀固态形式进行热蒸发和电离。(2)双铼带结构下,铼蒸气会沉积到铀样品表面并逐渐形成包覆层,样品原子逐渐以扩散方式渗透出包覆层实现电离。(3)当样品被制备为八氧化三铀时铀金属离子电离效率最高。进一步完善了铀在铼灯丝上的蒸发和电离机理,为铀同位素测定过程中提高样品的利用率和测量准确性提供了实验依据。The accuracy of uranium isotopes analysis is affected by the mass fractionation while applying thermal ionization mass spectrometry.Generally,the mass fractionation could be eliminated by the way of applying the external standard method.However,this method requires consistent fractionation behavior of standard material and sample during measurement.In order to control the mass fractionation effects on the accuracy of measurement,the uranium morphological changes before and after thermal ionization procedure and the effect of coating method on the ionization efficiency of uranium were studied.Uranium samples in the forms of uranyl nitrate,UO3and U3O8were prepared under different controlled heating temperatures.The morphological changes of uranyl nitrate,UO3and U3O8during thermal ionization process,the ionization efficiency of uranium and the yield of uranium oxide were studied by scanning electron microscopy,raman spectroscopy and thermal ionization mass spectrometry.Results were found as follows:(1) Under the condition of vacuum environment and a certain temperature,uranyl nitrate,UO3and U3O8samples could be rapidly converted to UO2.After then,the thermal evaporation and ionization of uranium started in the form of solid UO2.(2) Under the double rhenium band structure,rhenium vapor could condense onto the surface of uranium sample and form a coating layer.The uranium atoms were gradually permeated out of the coationg layer and ionized by the way of diffusion.(3) The highest ionization efficiency was found when the sample was prapered to the form of U3O8.The uranium evaporation and ionization mechanism on rhenium filament were further improved by our study,which could provide experimental basis for improving the sample utilization and the accuracy of measurement.

关 键 词：热电离 铀同位素 铀氧化物离子 硝酸铀酰 八氧化三铀 二氧化铀 

分 类 号：O657.63[理学—分析化学]