Gamma Radiolysis of Water Solutions Relevant to the Nuclear Fuel Waste Management Program

The gamma radiolysis of water was investigated for conditions relevant to studies of the geological disposal of nuclear fuel waste. Chemical kinetic calculations were carried out for seven systems: argon-purged water; O₂-purged water; N₂O-purged water; O₂-purged solution containing 0.01 mol/ℓ sodium formate; O₂-purged solution containing 0.01 mol/ℓ t-butanol; N₂O-purged solution containing 0.01 mol/ℓ Na₂CO₃; and argon-purged solution containing 0.169 mol/ℓ Cl⁻ ions. The initial pH in all systems was set at 9.5. The concentrations of the important oxidants and reductants, both molecular and radical species, are presented as a function of the dose rate and the radiolysis time. In almost all cases, radical species are at steady state after 20 h of irradiation. In argon-saturated solutions, concentrations of all radiolysis products are low (<4 × 10⁻⁸ mol/ℓ). In oxygen-saturated solutions containing formate, an H₂O₂ concentration as high as 1.7 × 10⁻³ mol/ℓ was calculated after 20 h of irradiation at a dose rate of 280 Gy/h.