[en] Aqueous plutonium photochemistry is briefly reviewed. Photochemical reactions of plutonium in several acid media have been indicated, and detailed information for such reactions has been reported for perchlorate systems. Photochemical reductions of Pu(VI) to Pu(V) and Pu(IV) to Pu(III) are discussed and are compared to the U(VI)/(V) and Ce(IV)/(III) systems respectively. The reversible photoshift in the Pu(IV) disproportionation reactions is highlighted, and the unique features of this reaction are stressed. The results for photoenhancement of Pu(IV) polymer degradation are presented and an explanation of the post-irradiation effect is offered

[en] Investigation of equilibrium and kinetics of the oxidation reactions in the Pu(3)-Pu(4)-V(5)-V(4) system is carried out. It is established that the equilibrium constant of the Pu³⁺+VO₂⁺+2H² reversible Pu⁴⁺+VO²⁺+H₂O reaction in HClO₄ solution at ion strength μ=1.6 and 25 deg C constitutes 7.2+-0.7 mol^-2xl². The rate of the direct reaction is expressed with the equation -d[Pu(3)]/dt=[Pu(3)][V(5)]/(1+k₁[H⁺])+k₂[H⁺]²x(k₁+k₂[H⁺]²), where k₁=203 and 180 mol^-1xlxmin^-1 and k₂=224 and 594 mol^-3l³xmin^-1 at 25 deg C and μ=1.6 and 3 respectively (k₁ and k₂ are equilibrium constants of VO₂⁺ ions protonation over the first and second stages). In HNO₃ at μ=2 and 25.4 deg C k₁=3500 mol^-1xlxmin^-1 and k₂=1.6x10⁴ mol^-3xl³xmin^-1. The reaction proceedes in two ways, in the slow stages of which Pu³⁺ ions interact with VO₂⁺ and VO³⁺ ions

[en] The polarographic behaviour of tetravalent uranium, neptunium and plutonium solvates (U(ClO₄)₄x9DMSO, Np(ClO₄)₄x8DMSO and Pu(ClO₄)₄x8DMSO) in dimethylsulfoxide on mercury drop electrode (m.d.e.) and rotating platinum electrode (r.p.e.) has been studied. All the three compounds undergo two-stage reduction, first to the three-valent state and then to an amalgam (on m.d.e.). On the r.p.e. there is one wave corresponding to the process An⁴⁺ + e → An³⁺. All the uranium reduction waves are irreversible. On the m.d.e. neptunium shows a reversible wave of reduction of Np⁴⁺ to Np³⁺. On the r.p.e. the waves of Np⁴⁺ and Pu⁴⁺ are almost reversible. Chloride-ions did not affect the reduction tetravalent U, Np and Pu. The potential shift of ion pairs U⁴⁺/U³⁺, Np⁴⁺/Np³⁺ and Pu⁴⁺/Pu³⁺ in DMSO as against water is explained in terms of pronounced solvation of tertravalent actinoid ions

[en] Stability constant of Pu(III)-fluoride complex in 1 M perchlorate medium containing about 0.1 M perchloric acid was determined using F-ion selective electrode. An iterative computational method developed earlier was used to overcome the difficulties associated with the calculation of Ej values in highly acidic medium. The average value of measured concentration stability constant was 1.18x10³. (author). 6 refs

[en] Absorption spectra in carbonate and bicarbonate media have been measured for various oxidation states of plutonium. The oxidation state of plutonium was adjusted electrochemically (Pu(VI)-V), Esub(f)=+0.11 V vs. SCE) to avoid contamination by redox reagents. In carbonate medium the spectra of Pu(VI) and Pu(V) showed marked differences from the spectra of the same oxidation state in acidic solutions. In bicarbonate the spectra of Pu(VI) and Pu(IV) also differed from the corresponding spectra in acidic media. Reduction to Pu(III) resulted in a precipitate in both carbonate and bicarbonate media. (author)

[en] Reactions of several actinide (An) perchlorates with e/sub aq/^- and OH radicals produced by pulse radiolysis of solutions of these compounds are reported. Kinetic data for the formation of a U(VI)--H₂O₂ complex are reported. Rate parameters for the reaction of the e/sub aq/^- with various actinides have been determined and their significance discussed