Effect of humidity on the trapping of radioiodine by impregnated carbons

Abstract

The performance of some coal-based carbons and coconut shell-based carbons, of high or low porosities, impregnated with either potassium iodide (KI) or triethylenediamine (TEDA) have been evaluated over a wide range of relative humidities (RH). Carbon beds have been dosed with methyl iodide (131I) under standard conditions and figures of merit (K-values) have been obtained from the penetration of the beds. The K-value of an impregnated carbon has been found to decrease with increasing RH and, at a particular RH, carbons impregnated with TEDA exhibit K-values which are consistently higher than the K-values of the same carbons impregnated with KI. The performance of coal-based impregnated carbons was found to be superior to that of comparable shell-based carbons at RH greater than 70%. A shell-based carbon impregnated with KI was found to perform better than a KI-impregnated coal-based carbon at 40% RH. The same shell-carbon impregnated with TEDA performed worse than the TEDA-impregnated coal-carbon at 40% RH. Pore size distribution measurements have revealed characteristic differences between the structures of coal-based and shell-based carbons: the relative performances of the examined carbons are discussed in terms of these differences.