Rapid determination of iodide ion content in chloride molten salt by ascorbic acid reduction

Abstract

Abstract Acidic conditions are typically used to dissolve fission product cations from the molten spent fuel. However, it is unfeasible to analysis iodide anion due to its memory effect. Proper pretreatment of the samples is therefore necessary. In the present work, an alternative method was developed to evaluate the efficacy of removing fission product iodine from molten salt spent nuclear fuel under acidic conditions. In the pretreatment stage, ascorbic acid with a mass fraction of 0.5wt% was used instead of dilute nitric acid with a volume fraction less than 2%. The iodide content in molten salt samples dissolved in different Cl/I concentration ratios was determined by ICP-MS and compared with ion chromatography(IC). The results showed that under 1 mg/L chloride ion concentration, the detection limit of this method was 0.255 µg/L, with a spike-and-recovery experience between 103.3% and 102.8% and a relative standard deviation of less than 3% (n = 6). When the concentration ratio of Cl/I in the molten salt was less than two orders of magnitude, the analytical value of this technique was comparable to the measurement result by IC. Furthermore, the accuracy of ICP-MS was superior to that of IC when the concentration ratio of Cl/I was higher than two orders of magnitude. Our results indicate that the improved pretreatment method with ascorbic acid can eliminate inaccuracies caused by the iodide memory effect, which is simple to operate and suitable for determining iodide content in chloride molten salt under acidic conditions.