张洪铭 1杨琪 1李定明 1袁嘉瑶 1柳倩 1杨素亮 1田国新2
作者信息
- 1. 中国原子能科学研究院放射化学研究所,北京 102413
- 2. 中国原子能科学研究院放射化学研究所,北京 102413||清华大学核能与新能源技术研究院,北京 100084
- 折叠
摘要
Abstract
99Tc is a major radioactive fission product of 235U and 239Pu during the operation of nuclear reactors,and with a half-life time of 2.11×105 years it is also a long-term contributor to radiotoxicity of spent nuclear fuel.In PUREX spent fuel reprocessing,99Tc exists in the form of TcO4-in solution of spent fuel dissolution in nitric acid.TcO4-ion might be co-extracted with U(Ⅵ),Pu(Ⅳ),and other metal ions by TBP,then affects the efficiency of the uranium-plutonium separation cycle,giving a negative impact on the operation.Previous studies have shown that in PUREX,when HNO3 and HTcO4 coexist with U(Ⅵ)in aqueous solution,in addition to UO2(TBP)2(TcO4)2 and UO2(NO3)2(TBP)2 extracted complexes each just containing one type of anion,either NO3-or TcO4-,there might be another complex,(UO2)(TBP)2(TcO4)(NO3),being formed with mixed anions.While the UO2(NO3)2(TBP)2 complex has been structurally and thermodynamically studied with clear results,there is no clear experimental evidence for the composition and structure of the other two extracted complexes,UO2(TBP)2(TcO4)2 and UO2(TBP)2(TcO4)(NO3).In the present work,the composition of the complex formed from the reaction of hydrated uranyl perchlorate UO2(ClO4)2·(H2O)x with TBP is investigated with Raman spectroscopy to be UO2(TBP)4·(ClO4)2 in which only the four TBP molecules directly bond to uranyl but the two perchlorate anions do not.When NO3-and ClO4-coexist in the system,both UO2(NO3)2(TBP)2 and UO2(TBP)4·(ClO4)2 complexes are observed.In comparison of the Raman spectra of the sample from dissolving concentrated perchloric acid with that of UO2(ClO4)2·(H2O)x into TBP,it has been found that the characteristic peak of ClO4-at 928 cm-1 is independent of the existence of U(Ⅵ),and that U(Ⅵ)in the system does not directly interact with ClO4-,indicating that ClO4-only acted as a charge-balancing anion.For the complexes from dissolving UO2(ClO4)2·(H2O)x with different amounts of TBP,the Raman spectra suggest that only UO2(TBP)4·(ClO4)2 species is formed independently form the ratio of TBP to U(Ⅵ)used for preparing the samples.Dissolution of UO2(ClO4)2·(H2O)x in the organic phase of 30％TBP-kerosene loaded with varying amounts of UO2(NO3)2 yields light and heavy organic phases.It is confirmed by Raman spectra that UO2(NO3)2(TBP)2 is present in the system along with UO2(TBP)4·(ClO4)2,but there is no U(Ⅵ),TBP,NO3,ClO4-quaternary complexes formed.The results obtained in the present work for the complexes formed from TBP with U(Ⅵ),ClO4,and NO3 will provides helpful information for determining the composition of the extracted complexes in PUREX formed from TBP with U(Ⅵ),TcO4,and NO3,due to the similarity in size and charge between TcO4-and ClO4-.关键词
磷酸三丁酯/铀酰/高氯酸根/拉曼光谱Key words
tributyl phosphate/uranyl/perchlorate/Raman spectroscopy分类
核科学
