Formation of Methyl Iodide in the Radiolysis of Aqueous Cesium Iodide and Acetic Acid Solutions

Abstract

Volatile compounds of radioactive iodine, including methyl iodide, are released into the environment in the cases of serious accidents at nuclear power plants. The aim of this study was to find a conceivable mechanism of the radiation-chemical formation of methyl iodide in aerated aqueous solutions of cesium iodide and acetic acid. This provides the basis for subsequent investigations aimed at preventing the formation of methyl iodide. The radiation-chemical yield of methyl iodide formation in 10–3M CsI solutions containing CH3COOH (0.1 mol/l) decreased with increasing the pH. This fact is primarily explained by a decrease in the steady-state concentration of molecular iodine with increasing the pH. An increase in the pH of irradiated solutions up to pH ≥ 9 was found not only to prevent the formation of methyl iodide but also to enhance its radiation-chemical degradation.