Yields of primary species in the low-linear energy transfer radiolysis of water in the temperature range of 25–700 °C

Abstract

Monte Carlo track chemistry simulations were used to calculate the time-dependent yields (G values) for the radical (e_aq⁻, H˙, ˙OH) and molecular (H₂, H₂O₂) “primary species” formed in the low-linear energy transfer (LET) radiolysis of deaerated, pure water (H₂O) in the range of ∼1 ps to 1 ms between 25 and 700 °C, at 25 MPa pressure. Beyond the critical point, we used in the calculations the new supercritical water (SCW) radiolysis database of Liu et al., in particular their reported reaction rate constants. A striking conclusion of these simulations is the sharp increase in G(˙OH) and G(H₂), and the corresponding decrease in G(H˙), which are observed above 200 °C, due to the oxidation of water by the H˙ atom (H˙ + H₂O → ˙OH + H₂) in the homogeneous chemical stage of radiolysis. These results may have important implications for proposed Generation-IV SCW-cooled reactors for the control and management of water chemistry and for the maintenance of the structural integrity of materials.