Computation of the effect of pH on spur chemistry in water radiolysis at elevated temperatures

Diffusion-kinetic model has been employed to calculate the effect of pH and associated ionic strength on the primary yields in the radiolysis of water from ambient temperature to 200°C. Account has been taken of the effect of ionic strength, I, up to 0.1 molźdm-3 in both acidic and alkaline solutions resulting from the addition of H+ and OH-,assuming the counter ions have unit charge. The primary yields are essentially independent of pH for I ? 10-4. AboveI = 10-4 molźdm-3 the primary yields of e-aq and H2 in acidic solutions decrease whereas the primary yields of the H atom, hydroxyl radical and hydrogen peroxide increase. At I >10-3 molźdm-3 in alkaline solutions, the OH radical and hydrogen peroxide are partially converted into Oo- and HO-2 , respectively. Increases in the total yields GoOH + GOo- and Ge-aq + GHo and a decrease in GH2O2 + GHO-2 have been found with increasing pH. At elevated temperatures the effect of pH is diminished. The temperature effect on the primary yields in acidic and alkaline solutions is nearly the same as in neutral water

A Numerical Simulation of Radiation Chemistry for Controlling the Oxidising Environment in Water-Cooled Nuclear Power Reactors

Maintaining the integrity of materials of light-water nuclear power reactors requires the development of effective methods to control and minimise the corrosive environment associated with the radiolysis of a coolant. In this study, the behaviour of the oxidising environment is simulated using a hybrid method. The hybrid method has advantages in that the production of radiolytic species under exposure of the coolant to ionising radiation is simulated while providing material and charge balances. Steady-state concentrations of stable and transient oxidising agents are calculated as a function of radiation composition and dose rate by numerical integration of the system of kinetic equations describing radiation chemistry of neutral water, the alkaline solution, and the hydrogenated systems at 300 °C. The importance of the reactions and equilibria constituting the radiolysis scheme of the coolant is assessed. The influence of the presence of a base and the injected H2 on the yield of key reactions responsible for the formation of the main oxidants H2O2 and O2 are discussed. Simulation indicated the synergic effect of H2 gas and base added to the coolant on diminishment of the steady-state concentration of oxidants

Correction: Swiatla-Wojcik, D. A Numerical Simulation of Radiation Chemistry for Controlling the Oxidising Environment in Water-Cooled Nuclear Power Reactors. <i>Appl. Sci.</i> 2022, <i>12</i>, 947

The author wishes to make the following corrections to this paper [...

3D Characterization of the Molecular Neighborhood of ^•OH Radical in High Temperature Water by MD Simulation and Voronoi Polyhedra

Understanding the properties of the •OH radical in aqueous environments is essential for biochemistry, atmospheric chemistry, and the development of green chemistry technologies. In particular, the technological applications involve knowledge of microsolvation of the •OH radical in high temperature water. In this study, the classical molecular dynamics (MD) simulation and the technique based on the construction of Voronoi polyhedra were used to provide 3D characteristics of the molecular vicinity of the aqueous hydroxyl radical (•OHaq). The statistical distribution functions of metric and topological features of solvation shells represented by the constructed Voronoi polyhedra are reported for several thermodynamic states of water, including the pressurized high-temperature liquid and supercritical fluid. Calculations showed a decisive influence of the water density on the geometrical properties of the •OH solvation shell in the sub- and supercritical region: with the decreasing density, the span and asymmetry of the solvation shell increase. We also showed that the 1D analysis based on the oxygen–oxygen radial distribution functions (RDFs) overestimates the solvation number of •OH and insufficiently reflects the influence of transformations in the hydrogen-bonded network of water on the structure of the solvation shell

3D Characterization of the Molecular Neighborhood of &bull;OH Radical in High Temperature Water by MD Simulation and Voronoi Polyhedra

Understanding the properties of the &bull;OH radical in aqueous environments is essential for biochemistry, atmospheric chemistry, and the development of green chemistry technologies. In particular, the technological applications involve knowledge of microsolvation of the &bull;OH radical in high temperature water. In this study, the classical molecular dynamics (MD) simulation and the technique based on the construction of Voronoi polyhedra were used to provide 3D characteristics of the molecular vicinity of the aqueous hydroxyl radical (&bull;OHaq). The statistical distribution functions of metric and topological features of solvation shells represented by the constructed Voronoi polyhedra are reported for several thermodynamic states of water, including the pressurized high-temperature liquid and supercritical fluid. Calculations showed a decisive influence of the water density on the geometrical properties of the &bull;OH solvation shell in the sub- and supercritical region: with the decreasing density, the span and asymmetry of the solvation shell increase. We also showed that the 1D analysis based on the oxygen&ndash;oxygen radial distribution functions (RDFs) overestimates the solvation number of &bull;OH and insufficiently reflects the influence of transformations in the hydrogen-bonded network of water on the structure of the solvation shell