Study of some redox reactions of neptunium and plutonium for the stabilization of particular oxidation states in alkaline media
- Institute of Physical Chemistry, Moscow (Russian Federation); and others
Reprocessing of irradiated fuel at the Hanford Site produced large volumes of alkaline high-level wastes containing long-lived isotopes of Np, Pu, and Am. Technologies for processing this waste require knowledge of the redox properties of the actinides in alkaline media. However, data on the alkaline redox reactions of Np and Pu in the lower oxidation states are particularly limited. To fill this gap, the redox behavior of Np(IV,V) and Pu(IV,V) in 0.5 to 14 M NaOH has been investigated using O{sub 2}, O{sub 3}, S{sub 2}O{sub 8}{sup 2-}, MnO{sub 4}{sup -}, Fe(CN){sub 6}{sup 3-}, FeO{sub 4}{sup 2-}, ClO{sup -}, BrO{sup -}, and H{sub 2}O{sub 2} as oxidants and N{sub 2}H{sub 4}, NH{sub 2}OH, SO{sub 3}{sup 2-}, S{sub 2}O{sub 4}{sup 2-}, (NH{sub 2}){sub 2}CSO{sub 2}, hydroquinone, and ascorbate as reductants. Suspensions of Np(IV) hydroxide in alkaline solution interact with all the named oxidants. For O{sub 2} and H{sub 2}O{sub 2}, hydroxo- and peroxo-complexes of Np(V) are the main reaction products. With the other oxidants, Np(V) appears as an intermediate which oxidizes further to Np(VI) and Np(VII) compounds. Freshly prepared Pu(IV) hydroxide reacts, but more slowly, with the same oxidants as Np(IV). Reduction of Np(V) to Np(IV) in alkaline media occurs only with NH{sub 4}, NH{sub 2}OH, and S{sub 2}O{sub 4}{sup 2-} of the named reductants. Elevated temperatures and excess reductant are required to achieve rapid rates. Reduction of Pu(V) occurs more easily than that of Np(V); all named reductants, with the exception of sulfite, are successful at appropriate conditions.
- OSTI ID:
- 370550
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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