Confinement of airborne radioactivity. Progress report, January--December 1974

Several commercial activated carbons, marketed for iodine removal in reactor off-gas cleanup systems, were evaluated for iodine penetration at elevated temperatures (4 hr at 1800C), and the penetration data varied widely. Subsequent chemical analysis of the samples indicated a strong correlation between the atom ratio of iodine to potassium (I/K) in the carbon and the high-temperature performance data. Iodine penetration tests were also performed on several carbons in an intense gamma radiation field (greater than 107 rads/hr). Test data show that carbons intentionally exposed to high concentrations of DOP aerosol performed as well as unexposed carbons. Studies of the rate of evaporation of elemental iodine from aqueous solutions indicated that significant quantities of I2 might be expected to become airborne within a short period of time (5 hr) after release to open ponds. Addition of sodium thiosulfate to the solution substantially reduced the evaporative loss of iodine; however, the effects of high-intensity radiation fields on iodine-thiosulfate solutions remain to be evaluated. Small HEPA filters containing filter media of the type used in the Savannah River confinement system were exposed to reactor building air and a high-intensity radiation field. Following this exposure, they were tested for flow performance under simulated accident conditions. Radiation exposure slightly impaired the performance of new filters and improved the performance of service-aged filters. Service aging effects on filter performance were far more significant than radiation effects