Performance of Charcoal-Impregnated Filter Paper Type CP-20 for Collecting Airborne Radioiodine

Two types of charcoal-impregnated filter paper CP-20A and CP-20B manufactured by Toyo Filter Paper Co., Ltd., Tokyo were tested for their collection performance on airborne iodine generated during 131l production at the lsotope Test Production Plant, which is successively filtered through traps in the cell and through two installed air cleaning systems. In order to observe the effect brought upon the collecting efficiency by differences in charcoal granule size, the CP-20A and -20B were impregnated with activated charcoal granules of about 2μ and about 70μ in the average diameter. This paper describes the experimental results and discussions on the dependence of collecting efficiency on (1) the nature of the airborne iodine, (2) the relative humidity of the sampling air, (3) the sampling period, and (4) the face velocity. In general, better performance for collecting airborne iodine was shown by the CP-20B as compared with the CP-20A.