Abstract: The PUREX process is the only reprocessing process applied on an industrial scale in the world. One of the key technologies of this process is to adjust the valence of plutonium(Pu), neptunium(Np) and technetium(Tc). Traditionally the valence of these elements should be adjusted by chemical methods. Chemical methods, however, might meet difficulties such as the valence adjustment of Np in nitric acid solution. Compared with the chemical methods, photochemical methods offer the remarkable advantages such as simpler steps, less secondary wastes, easier remote control techniques and low requirements for radioactive resistance of materials, etc. The combination of photochemical methods and solvent extraction offers a potential for the separation of metal elements, and it is also possible to separate and recover metal elements by using photochemical methods to reduce metal ions to atoms. In addition, exposure of UO₂ under UV light can significantly promote the dissolution rate of UO₂ at room temperature in nitric acid solution.