添加剂对放射性废物处置场中U及90Sr的分配系数研究

A ROLE OF GEOCHEMICAL BARRIER OF ADDITIVE MATERIELS FOR U AND 90SR IN A RADIOACTIVITY WASTES DISPOSAL SITE

通过滞留实验评价放射性废物处置场盖层不同基础物料与添加剂对放射性U与^90Sr的屏障效果，以确定不同基础物料及添加荆配合条件下U与^90Sr的分配系数Ka。滞留实验成果表明天然深褐色含腐殖质含角砾砂质亚粘土对U与^90Sr的Kd分别为1838．13和36．16，为良好的基础物料，添加Na2S和Na2CO3后可增大对^90Sr的滞留，添加碳质砂岩粉可增加对U的滞留。在还原条件下，洪积物及泥石流堆积物以及残积成因含角砾粉砂土基础物料在添加Na2S后，^90Sr的Kd为3069．30～3494．28；添加Na2CO3后，^90Sr的Kd为81．22～22203．6。洪积物及泥石流堆积物的泥、砂和砾石混合物、变质碳质粉砂岩风化物、残积成因砂质亚粘土和坡积物砂质亚粘土等4类基础物料添加FeS2、腐殖土后对U和^90Sr的滞留效果总体较差；净水剂、磷灰岩和粉煤灰3类添加剂对U和Sr的屏障效果以负面影响为主，不宜用作屏障添加剂。实验结果表明U与Sr的迁移-固定性能相反，在放射性元素迁移途径上宜分别建造U，Sr屏障，且优先处置U放射性元素。

Effects of basic and additive materials on selection of radioactivity wastes disposal cover in site on retardation of U and ^90Sr are evaluated. The distribution coefficients （Kd） of U and ^90Sr are made under different conditions. Kd of U and ^90Sr for brown arenaceous clay with humus is 1 838.13 and 36.16, respectively. Kd of ^90Sr increases and Ka of U decreases when Na2S or Na2CO3 is added into the clay. Kd of U increases when carbonaceous sandstone powder is added into the clay. Kd of ^90Sr varies from 3 069.30 to 3 494.28 when Na2S is added into diluvial,debris flow and residual deposits. Kd of ^90Sr changes from 81.22 to 22 203.6 when Na2CO3 is added. Small effects on Kd of U and ^90Sr are founded while four basic materials of mixture of diluvial and debris flow deposits,metamorphic carbonaceous siltstone, native sabulous clay and slope sabulous mild clay, add FeS2 or humus soil. Negative effects on retardation of U and ^90Sr occur while AlCl3, phosphate or fly ash is added in the mother soil samples. These three materials are unfit for disposal cover additive material. Reverse characteristics of migration-adsorption between U and ^90 Sr are found while the additives of Na2S or Na2COa are used. Along U and ^90Sr migration route,a separate type of geochemical barrier for U need to be set up first,then another type geochemical barrier for ^90Sr.