An automatic weather station to be installed on a detached island as a data collection platform of the Geostationary Meteorological Satellite system was developed, and tested during the last one year, and a successful result has been obtained. The main design philosophies of this system are a) to minimize the electric power consumption in order to operate with the smallest power source b) to make maintenance intervals more than one year c) to manufacture at low cost.
The definition of high level radioactiv e waste and other high level radioactive matter not suitable for dumping at sea has been given by IAEA (1975). Since this definition is based on the report by WEBB and MORLEY (1973), a critical study is made on their report. The result of study shows that owing to the assumption of a very small value of the horizontal eddy diffusion coefficient (104 cm2/s) for the sake of safety for these nuclides, the limiting environmental capacity for such nuclides as 226Ra and 239Puwith longer half-lives is extremely overestimated. And due to a very small value of a daily intake of marine foods (6 g/d) and a larger value of the ratio of nuclidic concentrations between the top of the deep layer and the surface layer (100), the environmental capacity is also overestimated for every nuclide. It is proposed that the definition of high level radioactive waste should be reassessed carefully by experts in various countries.
Evaluation on deep sea disposal of r a dioactive waste into the North Pacific on the basis of diffusion process is done using a simplified model. The results of calculation by employing different sets of diffusion coefficients on the horizontal and vertical directions show that for the smaller diffusion coefficients discrepancies between relative concentration of nuclides and the law of radioactive disintegration are greater. For larger coefficients, concentration above the site of release approaches mean, homogeneous concentration which satisfies the rule of radioactivity. From oceanographic and radiologica l view points, it is concluded that 102 cm2/s and 108 cm2/s respectively of diffusion coefficient of the vertical and horizontal directions are appropriate and reasonable in the North Pacific for the purpose of dose evaluation. A New definition of the high-level radioactive waste and other matter i s given as follows (a) 10 Ci/t for b/r,. emitter (except tritium),1 Ci/t for 90Sr plus 137Cs, (b) 104 Ci/t for tritium, (c) No long-lived a emitter may be dumped.
(1) The reason for the remarkably high rate of deposition of radioactive fallout in the winter season (winter peak) along the Japan Sea side of the northern part of Honshu is studied, on the basis of observations at Akita (39°43'N,140°06'E). The results of study show that when the wind is west to north-west and vertical instability of the air is high, the specific radioactivity in rain and snow water in Akita reaches five to eight times that under other weather conditions. The winter peak in radioactive fallout along the Japan Sea coast can be explained by abundant precipitation amount, the prevailing wind blowing from the west to north-west originated in the Siberian continent, and vertical instability in the lower troposphere due to warming of the cold air of continental origin during its passage over the warm current of the Japan Sea. (2) The causes of the smaller amount of radioactive fallou t at Osaka than that in other regions are studied. The ratio of 90Sr fallout between Tokyo and Osaka is 1.4and that between Akita and Osaka is 2.7. Since rainfall amounts at Osaka and Tokyo are almost the same, the difference in 90Sr fallout between the two cities is due to other meteorological factors. It is made clear that in Osaka, owing to its local topography,72% of the total rainfall is associated with winds from the N to ENE. In Osaka a wind with the west to north-west component carrying radioactive dusts seldom blows. This seems to be a main reason for smallness of the radioactive fallout amount there.