Testing and evaluation of absorbers for gaseous penetrative forms of radioiodine

A significant fraction of airborne radioiodine, encountered at times in operational areas of Ontario Hydro nuclear power generating stations, was found to be penetrative inorganic and organic species. Theoretical evaluation of iodine chemistry is presented in this paper based on analysis of operational iodine concentrations in station systems, areas and effluents under actual operating conditions. The theoretical evaluation and the operational experiments show that hypoiodous acid and organic iodides are the basic forms of airborne iodine which occur in the field and in station effluents. A method was developed for laboratory generation of HOI and its identity confirmed by use of specific absorbers. Six of the commercially available (and recently developed) absorbers were tested for HOI removal efficiency in the laboratory under conditions similar to those found in the field. Experimental equipment, methods used for the absorber testing and experimental conditions are described. It is evident from results of these measurements that charcoals have generally better initial absorption efficiency for hypoiodous acid than silver impregnated inorganic absorbers. Both technical and economical aspects of the operational use of the tested absorbers are discussed. (U.S.)