ABSTRACT
The yields of the radiolytic oxidation of U(IV) and of the U(VI) formation, measured by spectrophotometry, are found to be the same (G(-U(IV))(N2O) = G(U(VI))(N2O) = 8.4 x 10(-7) mol J(-1)) and almost double the H(2) formation yield (G(H(2)) = 4.4 x 10(-7) mol J(-1)) in the (60)Co gamma radiolysis of N(2)O-aqueous solutions in the presence of 2 mol L(-1) Cl(-) at pH = 0 (HCl). According to the mechanism of U(IV) radiolytic oxidation, we show that under the conditions of our experiments the U(V) ions do not disproportionate, but undergo a stoichiometric oxidation into U(VI) by H(+) with forming H(2).
ABSTRACT
Absorbance measurements find the yield of the oxidation of U(IV) to be (8.75 +/- 0.05) x 10(-7) mol J(-1) in the (60)Co gamma radiolysis of aqueous solutions containing 4.4 x 10(-3) mol L(-1) U(IV) in the presence of O(2) saturated 2 mol L(-1) Cl(-) at pH = 0. This high value of oxidation yield suggests that all primary radicals formed by water decomposition are scavenged in these solutions. Simulations using a nonhomogeneous stochastic kinetic track model agree with the experimental results and are used to explain the mechanism for scavenging radicals and oxidation of U(IV).