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 Co-60 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).