Leaching Rate of High-Level Radioactive Waste Glass

采用MCC浸出试验方法对模拟放射性废玻璃进行了静态浸出试验。用B（n，α）Li反应辐照过的玻璃和未辐照过的玻璃在40 ℃ ~ 150 ℃的温度下，在某些溶液中浸出长达60天。采用电感耦合等离子体光谱法（ICP）和/或γ-能谱法分析了渗滤液中各元素的浓度。采用化学分离法对渗滤液中的~（13）Cs进行分离，提高了γ能谱法的准确度<134>。在对渗滤液进行化学分离后，分析了几种γ射线强度较弱的其他核素<134>。用扫描电镜和X射线微区分析仪对浸出后的玻璃表面进行了观察，浸出液分析结果表明，废玻璃中的元素可分为两类。第1组元素为硅、硼、钠、铯和钾，各元素浓度随时间呈抛物线增加，浸出受扩散控制。第2组含铁、锰，各元素浓度很小，随时间变化基本恒定，浸出受溶解度控制。玻璃表面观察结果表明，在玻璃表面形成了沉淀层，沉淀层的厚度（1）与浸出液中硅的浓度（NL）成正比; 1=q（NL-NL^0），其中，NL^0表示沉淀开始时渗滤液中硅的浓度，认为硅在沉淀层中的释放受扩散控制硅的浸出行为可以用Wallace和Wicks提出的模型来解释。辐射对浸出行为的影响不被认可。在不同的溶液中，各试验结果的浸出行为也相差不大。

Static leach test of simulated radioactive waste glass was carried out by means of MCC leach test method. The glass irradiated with B(n,alpha)Li reaction and the non-irradiated glass were leached In some kinds of solution at the temperatures from 40ﾟC to 150ﾟC, for up to 60 days. The concentration of each element in leachate was analyzed by inductively coupled plasma spectroscopy (ICP) and/or gamma-spectrometory. The accuracy of gamma-spectrolletry method was improved by chemically separating the ^<134>Cs from the leachate. Several additional nuclides, which had weak intensity of gamma-ray, were analyzed after chemically separating the ^<134>Cs from the leachate. The leached glass surface was observed by scanning electron microscopy and X-ray microanalysis.The results of leachate analysis showed elements In the waste glass were classified into two groups. Group 1 contains silicon, boron, sodium, cesium and potassium; the concentration of each element in group 1 increased parabolically with time, the leaching was suggested to be controlled by diffusion. Group 2 contains iron and manganese; the concentration of each element in group 2 was very little and constant against time, the leaching controlled by solubility. The results of the glass surface observation showed the precipitation layer was formed on the glass surface and the thickness of this layer(1) was proportional to the concentration of silicon in the leachate (NL); 1=q(NL-NL^0), where NL^0 means the silicon concentration in the leachate when the precipitation started.The release of silicon was considered to be controlled by diffusion in the precipitated layer in the short range of the leaching time (-60days).Leaching behavior of silicon could be explained by the leaching model based on the model by Wallace and Wicks. Radiation effect on leaching behavior was not recognized. There was also little difference of leaching behavior among the results in some kinds of solution.