Annual γ-exposure around a nuclear site has been evaluated from short term plume-exposures with annual statistics of meteorological condition in which wind directions counted in a sector of 16 compass points are considered to be on the center of the sector. In this report, effects of wind direction frequency distribution in a sector itself on the γ-exposure are described. Correction coefficients to be applied to conventional calculation are obtained. Methods of calculation of plume-exposure and formula of frequency distribution in a sector are discussed.
Some characteristics of I2-gas relevant to its transportation in earths were investigated. The sorption was studied by passing 131I loaded I2-gas through thin beds of earth samples under various conditions of the temperature and relative humidity. Desorption was examined by sweeping these beds with dry air and by leaching with water. Some of the results are (1) sorption is large for dry earths, while it becomes much smaller with increase of moisture, (2) a variety of desorptivity was observed, still the remaining quantity at the end of water leaching was nearly independent of the kind of samples and of experimental conditions, and (3) sorption increases linearly at first and tends to saturation, where the limit of linearity will correspond to the adsorption with monomolecular layer. The transportation behavior was studied by passing I2-gas through a 35cm tube filled with the earth sample. The time-dependent distribution of iodine was obtained radiologically. The result is approximately expressed by a transport equation taking the Henry type adsorption and the chemisorption into account.
This review describes the chemical form and removal of airborne radioiodine released in a loss-of-coolant accident of light water reactor. The chemical form of the iodine is considered to be elemental and partially organic as methyl iodide. The airborne iodine is removed in the reactor containment by spray and air-filter systems, and the iodine leaked from the containment by another air-filter system. Those air-filter systems consist of impregnated chacoal, HEPA filter and additional installations. The materials impregnated on charcoal for removal of methyl iodide are triethylenediamine, KI and SnI2. Those charcoals, however, should be operated under the condition of relative humidity less than 97%. In order to use the charcoals with good performance, it is necessary to have information on the deterioration due to adsorption of impurities in the enviromental atmosphere.
The monitoring techniques for airborne radioiodine, based on the findings at JAERI and the works elsewhere are described: 1) Properties of the airborne radioiodine encountered in radiation work. 2) Performance of the iodine sampler consisting of a cellulose asbestos filter paper and a charcoal-loaded filter paper or charcoal cartridges, or the three. 3) Improvement of the sampler by use of charcoal impregnated with chemicals such as triethylenediamine (TEDA) or by dehumidification through heating the sampling air. 4) Practices of the monitoring in radiation protection. Problems in environmental monitoring of the airborne radioiodine from a light water power reactors and fuel reprocessing plants are also presented.