乏燃料干法后处理过程的实时监测及关键问题研究

The real time monitoring technique of continuous analysis and determination is urgently developed without sample taken out from molten salts during electrorefining selected in spent fuel reprocessing because of high burn-up and strong radiation of reactor. The real time monitoring method for multicomponent complex system was first built by follow study: the qualitative analysis for single element and multi-elements were conducted by investigating the electrochemical behaviors of single element and multi-elements of U and key fission products; the quantitative analysis for single element and multi-elements in molten salts were performed using square wave voltammetry, standard curve and chemometric methods; and the multivariate calibration and multivariate resolution methods were carried out to examine the analysis results. Then, the key issues were solved through real time monitoring as follow: (1) the change of dissolution sequence, dissolution rate, ions concentration and valence state of U and key fission products with the time during anodic dissolution process; (2) the variation of reduction sequence, extraction rate and ions concentration, valence state of U and key fission products in molten salts with the time during cathodic electro-deposition; (3) the change of sequence and rate of removing the key fission products, concentration and valence state of key fission products with time in the process of molten purification. Base on the above results, the real time monitoring technique, having the advantages of rapid and accurate, was built, which can provide fundamental data and technology for remote monitor in the dry reprocessing of spent fuel.

基于反应堆燃耗深、辐射性强而选用的熔盐电解精炼法处理乏燃料方案，迫切需要无须样品处理就可进行连续分析测定的实时监测方法。因此，本项目拟首先通过研究U及关键裂片产物的单组分和多组分共存的电化学行为，对单组分和多组分进行定性分析；采用方波伏安法、标准曲线法、化学计量学方法对单组分和多组分体系进行定量分析；再采用多元校正法和多元分辨法对定量分析结果进行校验，建立多组分熔盐体系定量实时监测方法。然后通过实时监测解决以下关键问题：(1)阳极溶解过程中各组元的溶出顺序、溶出速度以及离子浓度、价态随时间的变化；(2)阴极电沉积过程中U和关键裂片离子的还原析出顺序、提取速率以及浓度、价态随时间的变化；(3)熔盐净化过程中去除关键裂片离子的顺序、速度以及浓度、价态随时间的变化。根据以上研究结果，建立并确定快速、准确、实时监测干法后处理过程的方法，为干法后处理远程监控提供必需的基础数据和技术。

基于反应堆燃耗深、辐射性强而选用的熔盐电解精炼法-干法后处理乏燃料方案，迫切需要无须样品处理就可进行连续分析测定的实时监测方法，只有先实现监测才能进行监控。由于干法后处理技术只有实现远程监控才能得到实际应用，因此，实时在线监测方法的建立是关系到干法后处理能否工业化所面临的一个关键问题。.(1). 研究了铀U、稀土元素RE（La，Ce，Nd，Sm，Eu，Gd等）和锆Zr在惰性W电极上的电化学行为，确定了铀U、稀土离子和锆Zr的析出电位、平衡电位和表观电位并对各元素进行了定性分析。研究关键裂片元素中两种离子共存时LiCl-KCl熔盐中的电化学行为，对二组分关键裂片元素共存时方波伏安曲线的重叠峰（波）解析，进行定性分析，采用电化学方法在线监测了电化学提取铀和稀土的进程，并通过ICP-AES分析对结果进行了验证。.(2).采用方波伏安法、标准曲线法、化学计量学方法（小波变换）对单组分铀U、关键裂片元素RE、Zr进行定量分析。采用小波变换对高度重叠双组分、半重叠双组分的方波伏安曲线进行了定量分析。结果表明，小波分析能够给出模糊峰亦或是不可见峰的位置和相对信号强度，也能对重叠度较高的失真信号进行解析，让难以定性定量的方波伏安曲线可以通过小波分析的方式定性定量分析。.(3).解决了以下关键问题：①实时监测了乏燃料阳极溶解过程中各组元阳极溶出的顺序，溶出的 U 和关键裂片离子的浓度、价态随时间的变化；②实时监测了 U、关键裂片离子在阴极电沉还原析出顺序、提取速率以及浓度、价态随时间的变化；③实时监测了熔盐净化过程中去除关键裂片（RE=La，Sm，Nd，Dy）离子的顺序、速度以及浓度、价态随时间的变化。. (4). 建立了快速、准确可靠、实时监测乏燃料干法后处理过程中铀、关键裂片（如稀土）离子浓度变化的方法，并研制了熔盐过程终点智能响应装置。