Analytical description of the hydrogen evolution from concrete under the effect of gamma radiation

Abstract

The formation of explosive gas mixtures due to the evolution of hydrogen from concrete structures for radiation protection of nuclear power buildings should be taken into account when designing and operating them. However, this requires methods for estimating and predicting the radiation evolution of hydrogen. This paper was done due to the lack of analytical methods for determining the gas evolution from concrete and their components under the influence of gamma radiation. In the work, based on the available experimental data, the model was selected, checked, and adjusted for an analytical description of the process of hydrogen evolution from concrete on aggregates that do not contain water under the influence of gamma radiation. When selecting the model, it was assumed that the evolution of hydrogen from concrete on aggregates that do not contain water under the effect of gamma radiation is mainly due to the radiation decomposition of evaporable water (free water and adsorbed water) from hardened cement paste (cement stone) and is determined by the amount of evaporable water in the material and the power of the absorbed dose of gamma radiation. It was taken into account that the amount of evaporable water during irradiation decreases with increasing time and temperature of irradiation. Verification of the possibility of using the selected model, its necessary adjustment and determination of the main parameters of this model was performed on the basis of available experimental data on the evolution of hydrogen from Portland cement stone under the influence of gamma radiation. We used experimental data on the release of hydrogen and water from cement stone containing and practically not containing evaporable water when irradiated with gamma rays with an average energy of 1.25 MeV at the absorbed dose rate of 0.87 kGy/h, 3.84 kGy/h and 7.05 kGy/h at temperatures of 25, 40 and 60 °C for up to 2 months. The dependence of the model parameters on the absorbed dose rate of gamma radiation and the irradiation temperature is shown. For cement stone dried at 120 °C to remove evaporable water, the amount of residual evaporable water (residual evaporable water or decomposed chemically bound water) was studied and determined.