地质水泥固化体中Sr(Ⅱ)、Cs(Ⅰ)、U(Ⅵ)的长期浸出行为研究

Study on Leaching Performance of Sr(Ⅱ),Cs(Ⅰ) and U(Ⅵ) in Geological Cement

以深圳航天科技创新研究院研制的地质水泥为固化基材,通过考察Sr(Ⅱ)、Cs(Ⅰ)、U(Ⅵ)在地质水泥固化体中2.5a内的浸出率Rn、累积浸出分数Pt以及物相、显微结构等参量的变化,研究了模拟核素的浸出规律和机理,并构建了其长期浸出模型。在整个浸出周期内,浸出试验始终在碱性环境中进行,这对地质水泥吸附核素有利;浸出液的电导率在核素浓度达到平衡后仍在缓慢变化,说明除核素外,水泥固化体中的其余离子也参与了溶浸,这也从XRD的测试结果得到了证实;第42d时Sr(Ⅱ)、Cs(Ⅰ)、U(Ⅵ)的Rn和Pt值均低于国家限定标准,表明地质水泥对这3种核素均具有较好的固化能力,其中对U(Ⅵ)和Sr(Ⅱ)的滞留远高于Cs(Ⅰ);一维衰变浸出模型能很好地预测地质水泥固化体中Sr(Ⅱ)、Cs(Ⅰ)、U(Ⅵ)长达2.5a的浸出行为。

Geological cement was invoked as the basic material for solidification.The leaching rate(R n),cumulative leaching fraction(P t),phase,micro-structure and other parameters of Sr(Ⅱ),Cs(Ⅰ)and U(Ⅵ)in the geological cement solidified body during the leaching period of up to 2.5 years were investigated.Leaching rules and mechanisms of three simulated nuclides were studied,and the long-term leaching model was constructed.The experimental results show that the leaching experiment is always carried out in an alkaline environment during the whole leaching cycle,which is beneficial to the adsorption of nuclides by geological cement.The conductivity of leaching solution still changes slowly after the concentration of nuclides reaches equilibrium,which indicates that other ions in cement solidified body also participate in dissolution leaching,which is confirmed by XRD test result.The R n and P t values of Sr(Ⅱ),Cs(Ⅰ)and U(Ⅵ)at 42 d are all lower than the national standard,indicating that the cement has good solidification ability for these three nuclides,but the retention ability for U(Ⅵ)and Sr(Ⅱ)is much higher than that for Cs(Ⅰ).The one-dimensional decay leaching model can predict the long-term leaching behavior of Sr(Ⅱ),Cs(Ⅰ)and U(Ⅵ)in the solidified geological cement over a period of up to 2.5 years.