Some effects of pH on inorganic iodine volatility in containment

Abstract

The behaviour of iodine in containment in the event of an accident involving fission product release would be strongly dependent on pH. High pH leads to a lower rate of radiolytic oxidation, and in alkaline conditions the thermally stable form is IO 3 −. Much of the work on effects of pH on radiolytic oxidation reported in the literature may have been misinterpreted because of post-irradiation reaction and in this report some new experiments are described which were designed to overcome these problems involving sparged irradiated solutions of CsI spiked with 131I. The rate of radiolytic oxidation has been measured as a function of pH between pH 4.6 and pH 9 and iodide concentrations between 10 −4 and 10 −6 mol dm −3. Also discussed in the paper are factors which can affect the pH of the sump water and the effects of high pH in sprays. It is concluded that high pH is beneficial and it is important not only to achieve high pH but also to maintain it.