Radiolysis of boiling water

•The radiolysis of boiling water was investigated.•H2 and O2 gases were formed with a stoichiometric ratio (2:1) in ultra-pure water.•The concentration of H2O2 was negligible in the liquid phase.•Addition of NaCl enhanced the gas evolution.•Deterministic chemical kinetics simulation reproduced the experimental results.

γ-radiolysis of boiling water has been investigated. The G-value of H2 evolution was found to be very sensitive to the purity of water. In high-purity water, both H2 and O2 gases were formed in the stoichiometric ratio of 2:1; a negligible amount of H2O2 remained in the liquid phase. The G-values of H2 and O2 gas evolution depend on the dose rate: lower dose rates produce larger yields. To clarify the importance of the interface between liquid and gas phase for gas evolution, the gas evolution under Ar gas bubbling was measured. A large amount of H2 was detected, similar to the radiolysis of boiling water. The evolution of gas was enhanced in a 0.5 M NaCl aqueous solution. Deterministic chemical kinetics simulation elucidated the mechanism of radiolysis in boiling water.