SOME EFFECTS OF PH ON INORGANIC IODINE VOLATILITY IN CONTAINMENT

The behaviour of iodine in containment in the event of an accident inv olving fission product release would be strongly dependent on pH. High pH leads to a lower rate of radiolytic oxidation, and in alkaline con ditions the thermally stable form is IO3-. Much of the work on effects of pH on radiolytic oxidation reported in the literature may have bee n misinterpreted because of post-irradiation reaction and in this repo rt some new experiments are described which were designed to overcome these problems involving sparged irradiated solutions of CsI spiked wi th I-131. The rate of radiolytic oxidation has been measured as a func tion of pH between pH 4.6 and pH 9 and iodide concentrations between 1 0(-4) and 10(-6) mol dm(-3). Also discussed in the paper are factors w hich 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 importan t not only to achieve high pH but also to maintain it.