Fundamental Study of "The Third Phase" formed in Extraction Processes of Nucler Fuel Reprocessing

用元素分析的方法，系统地研究了Zr和TBP辐射耗尽产物HDBP、H_2MBP、H_3PO_1体系中“第三相”的形成条件、组成和结构。X-射线衍射、红外光谱和核磁共振氢谱。证实了第三相的重要来源之一是Zr离子与TBP贫化产物的络合作用。还阐明了以下几点：(1)当耗尽的产物相互共存时，在低酸溶液中对前沉淀的形成存在协同效应。(2)析出物的形成取决于HDBP/Zr的摩尔比。(3)当摩尔比约为2时，生成的沉淀物的化学式为：Zr(NO_3)_2(HDBP)_2(OH)_2。(4)Zr-H_2MBP体系的…用扩展X射线吸收精细结构(EXAES)方法研究了磷酸一正丁酯和磷酸二正丁酯这两种主要的“第三相”析出物中围绕着Zr的局域结构。凝胶和干燥样品对磷酸一正丁酯和磷酸二正丁酯的傅里叶变换光谱相同。在磷酸一正丁酯体系中，析出物以桥连磷的形式存在于锆离子、磷酸-锆离子之间。在二丁基磷酸二丁酯中没有桥联磷酸盐，而在Zr(IV)-二丁基磷酸酯中没有桥联羟基。这一事实表明了本报告(I)部分所述的磷酸一正丁酯的16A^ﾟ距离的层状结构。至于随着磷酸三丁酯含量的增加，磷酸二丁酯沉淀的再溶解现象，见(I)部分。二丁基磷酸二丁酯中桥联磷酸盐的缺失起着重要的作用。通过元素分析推测其化学结构。红外光谱。从EXAFS的现有结果中详细证实了(I)中的~1H-核磁共振和X-射线衍射谱。证实了水溶液中不存在锆离子。较少

Formation conditions, compositions and structures of precipitates or "the third phase" were systematically examined in the systems of Zr and radiation depleted products of TBP, such as HDBP, H_2MBP, H_3PO_1, by means of elemental analysis. X-ray diffraction, infrared spectra and ^1H-NMR. It was confirmed that one of the most important origins for the third phase is a complexation between Zr ion and the depleted products of TBP. Followings were also elucidated:(1) When the depleted products co-exist with each other, the cooperative effects on the pre- cipitate formation appear in low acid solutions. (2) Precipitate formation depends on the mole ratio of HDBP/Zr. The amount of precipitate reaches the maximum at the mole ratio of approximately 2 and decreases with increasing concentration of HDBP and finally disappeals at approximately 10. (3) Precipitate formed at the mole ratio of approximately 2 has the chemical formula, Zr(NO_3)_2(HDBP)_2(OH)_2. (4) Precipitates of the Zr-H_2MBP syste … More m begin to appear at the concentration of H_2MBP in one order of magnitude smaller than of HDBP in Zr HDBP system.EXAES (Extended X-ray Absorption Fine Structure) measurement was carried out for the study of the local structure around Zr in precipitates of Zr(IV)-monobutylphosphate and Zr(IV)- dibutylphosphate, which are one of the main species of so-called "The Third Phase". Both gelatinous and dried samples show the same Fourier transform spectra for Zr(IV)-monobutyl- phosphate and Zr(IV)-dibutylphosphate. The precipitates in Zr(IV)-monobutylphosphate have the bridging phosphate between Zr ions, Zr-phosphate-Zr. as well as the bridging hydroxyl between Zr ions, Zr-OH-Zr, while no bridging phosphate in Zr(IV)-dibutylphosphate. This fact indicates the layer structure with 16A^^ﾟ distance for Zr(IV)-monobutylphosphate described in Part (I) of the present reports. As for the re-dissolution of Zr(IV)-dibutylphosphate precipitates with increasing tributylphosphate observed in Part (I). the absence of the bridging phosphate in Zr(IV)-dibutylphosphate plays an important role. The chemical structures pospuiated by elemental analysis. infrared spectra. ^1H-NMR and X-ray diffraction in Part (I) were confirmed in detail from the present results of EXAFS. It was confirmed ZrO^<2->, zirconyl ion, does not exist in aqueous solutions. Less