Neptunium Valence Adjustment through Photochemically Induced Redox Reactions at Low Concentrations

Abstract

Photochemically induced redox reactions of Np(VI) and Np (IV) to Np (V) are experimentally studied in nitric acid solution of low Np concentration less than 10−4 mo].dm8 using a Kr-F excimer laser. The preparations of the initial solution of Np (VI) or Np (IV) are based on the addition of chemical redox reagents. The extraction chromatography is used to analyze the fraction of the neptunium valences. The result of redox experiments with laser radiation shows that the fractions of Np(V)/Np(VI) or Np(V)/Np(IV) photochemically increase up to the steady-state values against initially oxidizing or reducing conditions respectively. The steady- state values are different from those at thermal equilibrium states. It is concluded that, in low Np concentration as is observed in the normal Purex process, laser application to valence adjustment of Np gives another redox condition which is different from that determined thermochemically.