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Weather-Caused Vertical Migration of Radioactive Nuclides in Unsaturated Soils

Author(s): Satoshi Imamura; Kuniaki Sato; Masahiro Munakata; Yo Ito

Linked Author(s): Kuniaki Sato

Keywords: Radioactive nuclides; Migration; Weather condition; Unsaturated soil

Abstract: The violent shaking, the ensuing tsunami flood and the earthquake-caused disaster at Fukushima atomic power plants in the Eastern Japan Great Earthquake of 2011 (11th of March) brought serious misfortune not only on the local inhabitants but also on many people in and around the earthquake-stricken wide areas as a result of the never before experienced contamination with radioactive fallout. The extent and seriousness of the damages have been unprecedented in the history of the country. Full-scale operations of land remediation practices based on a new state law (enforcement date, January, 2012) have given us the obligation of keeping “the standards of radioactive contamination” on environments and people’s health. One of required tasks to remedy contaminated soils with radio elements is to place the spotlight upon solute migration/dispersion hydraulics in unsaturated porous media. In the past, a lot of dispersion-related subjects focused on hydraulic dispersion in the flow through saturated porous media and groundwater flows. Thus, those results on hydraulic dispersion in saturated flows fell short of our expectations. The study aims to illuminate the hydraulics of radio elements migration in unsaturated soils through laboratory experiments. Three elements (typical fission products, cesium: alkali metal, strontium: alkaline earths, and cobalt: transition element) without radioactivity were used as tracers, because of the similarity of chemical behavior regardless of the presence of radioactivity. Different weather conditions are simulated artificially by rainfall and sunlight simulator on marking contaminants in unsaturated zone above the groundwater table. Mathematical models of the weather-caused vertical migration consist of coupled masses of water and tracers, and heat conservation equations in unsaturated porous media. Analytical solutions of the basic equations at steady state are derived, and compared with those of experimental results without a conflict of radioelement migration mechanism. oC58. 9 27 sC132 55 rS87 38


Year: 2013

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