PHOTOCHEMICAL REACTION IN NITRIC ACID SOLUTION CONTAINING Pu(III),Fe(II) AND N_2H_5

The photochemical reaction in nitric acid solution containing Pu(III), Fe(II) and N2H5+ is studied to explore its possible application in spent nuclear fuel reprocessing. A GGH-120 Hg lamp is used as the light source. The effects of various factors on the photo-reaction are investigated.Experimental results show that Fe(II), N2H5+ and Pu(III) are oxidized rapidly and completely during the course of irradiation. The initial rate of photooxidation of Fe(II) and N2H5+ is proportional to the power of light, [Fe(II)] and [N2H5+]0.5 respectively. In the nitric acid solution, HNO2 is produced during the irradiation, but in the system containing N2H5+ with or without Fe(II), HNO2 is not detected until the complete oxidation of Fe(II) and N2H5+.Photooxidation of Pu(III) occurs via the following three stages: (1) slow oxidation of Pu(III) to Pu(IV) .The initial rate of photooxidation is proportional to [Pu(III)],increases with the increase of [NO3-]and[H +], and decreases with the increase of [UO22+]; (2) rapid oxidation of Pu(III) to Pu(IV);(3) disproportionation of Pu(IV) to Pu(III) and Pu(VI) .It is observed that the yield of Pu(VI) increases with the increase of [HNO3], but the yield is considerably reduced when Fe(III) is present in the system.