^(99)Tc在甘肃某处置场及周边区域的吸附-解吸特性与赋存形态研究  

Adsorption-Desorption Characteristics and Occurrence Speciation of^(99)Tc in a Disposal Site and Its Surrounding Area

作　　者：王鹏 王赵明 石云峰[2] 杨彪[2] 梁鹏亮 谢添 张艾明[2] 陈超[2] WANG Peng;WANG Zhao-ming;SHI Yun-feng;YANG Biao;LIANG Peng-liang;XIE Tian;ZHANG Ai-ming;CHEN Chao(China Institute of Nuclear Informationand Economics,Strategy Institute of Nuclear Industry,Beijing 100048,China;China Institute for Radiation Protection,Taiyuan 030006,China)

机构地区：[1]中国核科技信息与经济研究院,北京100048 [2]中国辐射防护研究院核环境模拟与评价技术重点实验室,太原030006

出　　处：《核电子学与探测技术》2023年第2期339-347,共9页Nuclear Electronics & Detection Technology

摘　　要：^(99)Tc半衰期长,赋存形态多样且容易被生物吸收利用,是高放废物处置中最需要考虑的放射性核素之一。以^(99)Tc为研究对象,在甘肃某处置场实地取样,针对不同岩样开展吸附-解析试验。试验结果表明,^(99)Tc在6种岩土样中的分配系数值为0.70~34.2 L/kg,差距较大。其中^(99)Tc在中-微风化大理岩、强风化大理岩中的吸附效果较好;在砂岩、花岗岩等岩体中的吸附效果较差且吸附可逆性较强。进一步利用PHREEQC软件,研究改变氧化还原电位pE、pH条件下^(99)Tc在处置库预选区地下水中的赋存形态变化。计算结果表明,pH对^(99)Tc的赋存形态影响较小,在pH=2~13时,TcO_(4)^(-)是其主要存在形态。pE值对^(99)Tc的赋存形态影响较大,pE<-3.2时,99 Tc的优势赋存形态为Tc(OH)_(4),当地下水pE>-3.19时,^(99)Tc主要以99 TcO_(4)^(-)形态存在。pE值为-3.5--3.0时,地下水中还有少量Ⅳ价^(99)Tc:TcO(OH)_(4)、(TcO(OH)_(2))^(2),Ⅶ价TcO_(4)^(-)。^(99)Tc has a long half-life,various forms of occurrence,and is easily absorbed and utilized by organisms,so it is one of the most important radionuclides to be considered in the disposal of high-level radioactive waste.In this study,^(99)Tc was taken as the research object,and samples were taken from a disposal site in Gansu,and adsorption-desorption experiments were carried out for different kinds of soil samples.The test results show that the distribution coefficients of^(99)Tc in the six kinds of soil samples are between 0.70 and 34.2 L/kg,with a large gap.Among them,the adsorption effect of^(99)Tc in mediumslightly weathered marble and strongly weathered marble is better;in sandstone,granite and other rock masses,the adsorption effect is poor and the adsorption reversibility is strong.The PHREEQC software was further used to study the morphological changes of^(99)Tc in the groundwater of the pre-selected area of the repository under the conditions of changing the redox potential pE and pH.The simulation results show that pH has little effect on the occurrence form of^(99)Tc.In the range of pH=2~13,^(99)Tc hasⅦvalence as the main form.The pE value has a great influence on the occurrence form of^(99)Tc.When pE-3.2,the dominant form of 99Tc is Tc(OH)_(4).When the groundwater pE-3.19,^(99)Tc mainly exists in the form of^(99)TcO_(4)^(-).In the pE value range of-3.5~-3.0,there are a small amount ofⅣ-valent TcO(OH)_(4),(TcO(OH)_(2))_(2),andⅦ-valent TcO_(4)^(-)in groundwater.

关 键 词：^(99)Tc 高放废物处置 吸附解析 赋存形态 

分 类 号：X591[环境科学与工程—环境工程]