Nuclear Technology / Volume 150 / Number 3 / June 2005 / Pages 303-314
Technical Paper / Radioisotopes
The decomposition of aqueous colloidal suspensions of AgI induced by ionizing radiation was investigated under various conditions using 188Re as an in situ beta-radiation source. The suspensions were stabilized by an initial excess of either I- or Ag+ ions. Although the results were somewhat scattered, the following trends were observed. With an initial excess of I- and under strong oxidizing conditions (N2O sparging) at pH 2, ~65% AgI was decomposed into nonvolatile and volatile iodine (ratio 2:1) for doses of ~20 kGy, and up to ~80% was decomposed (mostly nonvolatile iodine) at pH 5. Chloride ions greatly enhanced the volatile and lowered the nonvolatile fractions. Little decomposition (<10%) was obtained with air sparging at both pH 2 and pH 5. Chloride ions increased the maximum decompositions to ~60% (~47% volatile) and ~20% (mainly nonvolatile iodine), respectively. With an initial excess of Ag+ with N2O sparging and at pH 2 and pH 5, very little volatile iodine was produced. The maximum decomposition was ~20% after ~20 kGy. Chloride ion addition at pH 2 had greatly enhanced the volatile iodine yield. The relevance of these results to the possible release of iodine to the environment following a nuclear reactor accident is discussed.