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

从乏燃料后处理的应用角度出发，研究了铀酰离子在硝酸中的光化学反应。以奎宁在硫酸中的光电发射为参照，测定了铀酰离子在硝酸中激发的荧光量子产率。结果表明，硝酸的产率为10^&lt；-3&gt；，并测定了硝酸的浓度依赖关系。添加剂的存在对发射有很大的影响，并确定了某些添加剂的猝灭参数。评价值与文献报道一致。在此基础上，提出了一种简单的方法来估算在有猝灭剂存在的杂质存在下的铀酰离子的绝对浓度，并测定了乙醇在硝酸中将铀酰离子光还原为铀离子的量子产率。根据硝酸和乙醇的浓度依赖性以及氧以及伴随离子[H^+]和[NO^&lt；3-&gt；]的影响，推测了光化学反应的机理。最后得出结论，乙醇光还原铀酰离子可用于开发核燃料后处理新技术。

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.