放射性废物处置某场址地球化学工程屏障研究

Study on the geochemical engineering barrier at a disposal site for radioactive wastes

针对某放射性废物处置场址的天然屏障性能差,提出建造折叠式"之"字形地球化学工程屏障,将处置物释放出的核素垂向固定在场址范围内。屏障的机理是,核素铀、锶的迁移形式分别为:UO2(CO3)22-和Sr2+,而性能相反,且处置层为表生强氧化带,降水入渗强烈,不宜建还原性屏障;故对铀和锶依次建造:阴离子吸附屏障和阳离子吸附屏障,形成可连续渗流的双重屏障。屏障的砂土物料取自场址附近,成本极低。经室内模拟实验结果表明,铀和锶等核素通过其屏障时的分配系数值都在103量级。

Because of the poor performance of a natural barrier and the sensitive social problem for a radioactive waste disposal site, the authors suggest to construct a folded ＂Z＂-shaped geochemical engineering-barrier to ensure a complete safety of groundwater around the site. The barrier can vertically fix the radionuclides （released from radioactive waste） within the disposal site so as to insure the environment safety and easily construct the barrier and monitor it. According to local conditions, the transferring forms of uranium and strontium are UO2（CO3）2^2- and Sr^2＋, respectively, but their performances are opposite, and the disposal layers are strong surface oxidation zones and the rain infiltration is also intensive, so reductive barriers should not be built. Therefore, the barriers for uranium and strontium are orderly constructed, anion adsorption barrier （ Ⅰ ） and cation adsorption barrier （Ⅱ）, to make up of the double barriers enabling a continuous infiltration. The sand materials for barrier construction can be taken from the disposal site nearby and the cost is very low. The results of simulation experiment in the laboratory show that the distribution coefficients are in the 103 magnitude when uranium and strontium radionuclides pass through the barriers. This study can provide a technical support for protecting the disposal site safety and economically treating radioactive wastes.