A PULSE-RADIOLYSIS STUDY ON THE KINETICS OF O-2(-) AND HO2- REACTIONSWITH NP(VI) AND NP(VII) IN ALKALINE-SOLUTIONS

Reactions of O-2(-) in aerated solutions containing 1 x 10(-4) mol/l N p(VI) or Np(VII) were studied at pH 9.2-13.7. To eliminate the reactio ns OH + O-2(-) and O- + O-2 --> O-3(-), HCOONa was introduced into all of the Np(VI) solutions and into Np(VII) solutions with pH > 10.7. Th e reaction Np(VI) + H2O2 was examined in solutions containing 2 x 10(- 4) mol/l each of Np(V) and H2O2 and saturated with N2O, and the reacti on of Np(VII) with H2O2 was studied in N2O-saturated solutions contain ing 1 x 10(-4) mol/l Np(VII). A change in pH from 9.2 to 13.7 decrease d the rate constants of all of the reactions from 10(4)-10(5) to 10(2) -10(3) l mol(-1) s(-1). This decrease is associated with a drop in red ox potentials of the Np(VI)/Np(V) and Np(VII)Np(VI) pairs.