An Application of the Photochemistry of Uranyl Ion to Nuclear Fuel Reprocessing

从应用于乏核燃料后处理的角度研究了铀酰离子（UO_2^<2+>）在硝酸中的光化学反应。通过与奎宁在硫酸中的发光量相比较，测定了铀酰离子在硝酸中激发的荧光量子产率。结果表明，产率为10^<-3>数量级，并测定了硝酸的浓度依赖性。添加剂的存在对发射有很大的影响，并确定了一些添加剂的淬火参数。评价值与文献报道一致。此外，还提出了一种简单的方法来评估在淬灭剂作为杂质存在的情况下，从淬灭测量中得到的铀酰离子的绝对浓度。测定了硝酸中乙醇光还原铀酰离子为铀离子（U^<4+>）的量子产率。根据硝酸和乙醇的浓度依赖性、氧及其伴生离子[H^+]和[NO^<3->]的影响，推导了光化学反应的机理。最后指出，乙醇光还原铀酰离子可用于核燃料后处理新技术的开发。

Photochemical reactions of uranyl ion (UO_2^<2+>) in nitric acid have been investigated from a point of applications to a spent nuclear fuel reprocessing.Quantum yields of fluorescence from excited uranyl ion in nitric acid were determined by comparing with the photoemission of quinine in sulfuric acid taken as a refernce. It was found that the yields is an order of 10^<-3> and concentration dependence of nitric acid was measured. The emission is strongly affected by the presence of additives and quenching parameters for some additives were determined. The evaluated values were consistent with reported. Further, a simple method is proposed to evaluate the absolute concentration of uranyl ion from the quenching measurements in the presence of quenchers as impuruties.Quantum yield of photoreduction of uranyl ion to uranous ion (U^<4+>) by ethanol in nitric acid was determined. On the basis of the concentration dependence of nitric acid and ethanol, and effects of oxygen, and concomitant ions of [H^+] and [NO^<3->], mechanism of the photochemical reactions was derived. Finally, it is concluded that photoreduction of uranyl ion by ethanol could be used for developing new techniques of the nuclear fuel reprocessing.