Radiolytic oxidation

Progress made under the Radiolytic Oxidation contract to the end of 1987 is reviewed. In the experimental programme further evidence has been obtained for the oxidation of neptunium(IV) under gamma irradiation in granite and bentonite equilibrated waters. No evidence has been found for radiolytic oxidation of neptunium in concrete equilibrated water with a pH value greater than 12. Pertechnetate is reduced to a less soluble oxidation state when a solution in contact with 3:1 BFS/OPC cement is gamma-irradiated under argon. Modelling work has found good agreement for the simulation of aqueous chemistry between the thermodynamic code (PHREEQE) and a kinetic code using a FACSIMILE program. Preliminary simulations of radiolysis under repository conditions have been made using FACSIMILE. (author)