Yasuhiro TETSU
A stady on the relationship of radioactive substance flowing into the river and hydrologic
Minjiao Lu
Happening accident at the Fukushima nuclear power plant, radioactive substance was released. Radioactive substance falling to the ground were transported and flowing into the river. I compare radioactive substance in the sludge generated from the water purification plant and precipitation in the basin. I predict the time and precipitation of radiation dose below the clearance level. The results would help in treated with water purification plant. I use a radioactive substance amount in the sludge generated from the five water purification plant in Saitama Prefecture. The study basins are the Tone River water system and Ara River water system.
From emissions and half-life, I should consider only for cesium-134 and cesium-137. Continuous release after accident is negligibly small in comparison with the release at the time of accident. Radioactive substance was almost outflow within six months after deposition. In this half-year, effect of half-life was small and effect of rainfall was greater. In the later, effect of half-life was relatively large. Rainfall intensity has a significant effect on the outflow of radioactive substance. Clearance level has been defined as 100 Bq/Kg. Sludge is consdered safe below it. Of the five water purification plants, the two plants had been below the clearance level. The two places have water intake from Ara River water system that low radioactive contamination. Part of the water treatment plant was predicted to take 5 years to below the clearance level. From now on, half-life has a significant effect on the reduction of radioactive substances in rivers
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