570. 放射性浮遊ヨウ素サンプリングにおける各種添着活性炭カートリッジおよび濾紙の捕集性能

Abstract

In order to improve the performance of a commercially available charcoal filtel paper (Toyo Roshi, Type CP-20) and of a charcoal cartridge (Toyo Roshi, Type CHC-50) for collecting airborne radioiodine under high relative humidity, the charcoals were impregnated with triethylenediamine (TEDA), stannous iodide (SnI2), potassium iodide (KI+I2) or else with potassium thiocyanate (KSCN). The impregnated charcoals were examined for their dependence of collection efficiency on the properties of airborne iodine, on the sampling period and on the face velocity, and the results were compared with unimpregnated charcoal as reference. The airborne radioiodine used as samples was obtained from the exhaust ventilation systems at the 131I production plant, and from the fuel reprocessing test plant, both belonging to the Japan Atomic Energy Research Institute.The charcoals impregnated with TEDA or SnI2 were found to show greatly improved performance compared with the unimpregnated charcoals; the collection efficiency of the charcoal cartridge and of the charcoal filter paper was maintainted at levels above 85 and 80%, respectively, over a period of 14hr of sampling. It was found, however. that the collection performance was impaired by the presence of chemically reactive gases such as NO2 and organic vapor. The charcoals impregnated with (KI+I2) and with KSCN showed almost no improvement in their collection efficiencies.