Behavior Of Radioactive Cesium Research Articles

Interactions between micaceous minerals weathering and cesium adsorption

The environmental behavior of radioactive cesium (RCs) in contaminated areas is generally governed by soil and sediment components and natural weathering conditions. In this study, desorption tests and spectroscopic approaches were used to explore the interaction between the weathering of micaceous minerals (i.e., biotite and phlogopite) and the adsorption of Cs+ and the critical role of weathering in the environmental behavior of RCs. Results showed that the reaction sequence between weathering and Cs+ adsorption significantly affected the surface species of Cs+ and the structure of biotite and phlogopite. Regardless of whether it occurred before, after, or during Cs+ adsorption, weathering generated more high-affinity adsorption sites, namely, interlayer sites (ITs) and frayed edge sites (FESs), to different extents, and then facilitated the uptake of Cs+ at FESs and ITs on micaceous minerals in a poorly exchangeable state. Cs+ stabilized the micaceous mineral structure once it was absorbed within collapsed interlayers by hindering cation exchange and preventing further destruction during weathering. As important weathering factors, high temperature and Ca2+ content promoted the binding of Cs+ in the interlayers of biotite and phlogopite by enhancing interlayer cation exchange. These findings are beneficial for a better understanding of the environmental behaviors of RCs in the hydrosphere and pedosphere.

Accumulation capability for cesium differs among bacterial species: A comprehensive study using bacteria isolated from freshwater and coastal sediment

The fate and behavior of radioactive cesium (Cs) in the water environment are of great concern. The involvement of bacteria regarding their accumulation capability for this element is the most fundamental factor that needs to be clarified even for exploring the interactions between many environmental factors that involve together in governing the transport and distribution of Cs. As the first systematical study that aimed to evaluate the accumulation capability of environmental bacteria for Cs, bacteria in the sediment of a freshwater reservoir and coastal water environment were isolated and multiplied for contact experiment with Cs under different temperature conditions (5, 25, and 35 °C). The accumulation concentration of Cs in bacteria from freshwater sediment varied in 3.95 × 10−6 to 5.68 × 10−4ng-Cs/cell, and that from coastal sediment in 1.52 × 10−6 to 7.41 × 10−4ng-Cs/cell, indicating obvious differences among bacterial species. Bacteria of coastal sediment possessed higher accumulation capability for Cs than bacteria from freshwater sediment, and temperature dependency was confirmed for bacteria from coastal sediment. The findings of this study have great reference value for better understanding and controlling the fate and behavior of radioactive Cs associated with bacteria in the water environment.

Investigation on the form and behavior of radioactive cesium in sewage sludge

Investigation on the form and behavior of radioactive cesium in sewage sludge

Influence of the type of furnace on behavior of radioactive cesium in municipal solid waste thermal treatment

Municipal solid waste (MSW) contaminated by radioactive cesium (r-Cs) has been incinerated since the Fukushima Daiichi Nuclear Power Plant accident. Eight thermal treatment plants with four different types of furnaces were comprehensively investigated to provide fundamental data to improve our understanding of the behavior of r-Cs in various types of MSW thermal treatment facilities. R-Cs tended to distribute to the fly ash (FA) more than to the residue from the bottom of the furnace (bottom ash, incombustibles or slag). The r-Cs concentrations in the FA depended on the type of furnace and followed the order; fluidized-bed incinerator < stoker type incinerator < gasification melting furnaces. Shaft-type gasification melting furnace separated r-Cs selectively into FA and simultaneously discharged decontaminated slag. The leaching rate of r-Cs from FA was high, 30–100%, and independent of the type of furnace, whereas r-Cs in the residue from the bottom of the furnace scarcely dissolved in water. Heat recovery ash e.g. gas cooler ash was characterized by intermediate r-Cs concentrations and leachabilities compared with bottom residue and FA in stoker type and fluidized-bed incinerator. In the case of shaft-type gasification melting furnace, however, heat recovery ash showed similar property to FA due to a cyclone followed by heat recovery process. We evaluated whether baghouses (air- pollution control equipment) successfully removed r-Cs from flue gas. In all cases, r-Cs in flue gas was below the limit of detection after baghouse. We concluded that different types of furnaces affected r-Cs distributions, but flue gases from baghouse systems of all types of furnaces were safe.

Behavior of radioactive cesium during incineration of radioactively contaminated wastes from decontamination activities in Fukushima

Large volumes of decontamination wastes (DW) generated by off-site decontamination activities in Fukushima Prefecture have been incinerated since 2015. The behavior of radioactive cesium during incineration of DW was investigated at a working incineration plant. The incineration discharged bottom ash (BA) and fly ash (FA) with similar levels of radiocesium, and the leachability of the radiocesium from both types of ash was very low (<1%). These results are significantly different from those obtained for the incineration of contaminated municipal solid waste (CMSW) reported in earlier studies. The source of radiocesium in DW-FA is chiefly small particles derived from DW and DW-BA blown into the flue gas, not the deposition of gaseous synthesized radiocesium compounds on the surfaces of ash particles in the flue gas as observed in CMSW incineration. This source difference causes the behavior of radiocesium during waste incineration to differ between DW and CMSW.

土壌中放射性セシウムの経時的な変化(1.環境動態, 放射能土壌汚染対策)

土壌中放射性セシウムの経時的な変化(1.環境動態, 放射能土壌汚染対策)

Behavior of radioactive cesium in agricultural environment

Behavior of radioactive cesium in agricultural environment

Behavior of Radioactive Cesium through Paddy Field Works

Behavior of Radioactive Cesium through Paddy Field Works

下水処理場における放射性セシウムの挙動調査および溶出試験

福島第一原子力発電所事故に伴い飛散した放射性物質が，東北·関東を中心とする多くの下水処理施設において検出されている。本研究では，放射性物質により下水汚泥が高濃度に汚染されるメカニズムを解明するため，関東・東北地方の4箇所の下水処理場を対象に，流入状況の調査および各処理過程における放射性核種分析を行った。さらに，放射性物質を含む下水汚泥の埋立処分のための知見を得るため，下水汚泥焼却灰及び溶融スラグについて，溶出試験を行い，放射性セシウムの溶出特性を調査した。その結果，下水処理場内に流入した放射性物質は主に反応槽内において保持されていること，大部分の放射性物質が浮遊物とともに汚泥側に移行していることが示された。また，溶出試験において，本試験に供した12検体のうち9検体については，溶出液の放射性物質は検出限界値以下であり，残り3検体については，溶出率が0.5－2.7％と極めて小さかった。

Migration of 134Cs in unsaturated soils at a site in Egypt

To demonstrate the safety performance assessment for the disposal of 134Cs radionuclide in a geological formation, several investigations were required to calculate the possible release of radionuclides into groundwater. This research examined the sorption behavior of radioactive cesium (134Cs) in natural groundwater. Cesium chloride (10-6 to 10-2 mol.l-1) was used as a carrier, traced with 134Cs radionuclide. Distribution coefficients of radiocesium for sorption and desorption were measured on natural soil samples of different grain size fractions (l400 to l36 mm). Cesium sorption and desorption were found reversible at cesium chloride concentrations between 10-6 mol.l-1 to less than 10-3 mol.l-1. Sequential extraction procedures showed that the cesium sorption on soils were of various types: those easily desorbed, ion-exchanged, bound to carbonate, iron oxides, and organic matter. To demonstrate the safety performance assessment for the disposal of 134Cs radionuclide in a geological formation, several investigations were required to calculate the possible release of radionuclides into groundwater. This research examined the sorption behavior of radioactive cesium (134Cs) in natural groundwater. Cesium chloride (10-6 to 10-2 mol.l-1) was used as a carrier, traced with 134Cs radionuclide. Distribution coefficients of radiocesium for sorption and desorption were measured on natural soil samples of different grain size fractions (l400 to l36 mm). Cesium sorption and desorption were found reversible at cesium chloride concentrations between 10-6 mol.l-1 to less than 10-3 mol.l-1. Sequential extraction procedures showed that the cesium sorption on soils were of various types: those easily desorbed, ion-exchanged, bound to carbonate, iron oxides, and organic matter.

Production of134Cs thermo-generated aerosols

This paper presents observations made on the behavior of radioactive cesium in laboratory conditions.134Cs-loaded aerosols are generated from UO2 pellets in an electric oven and allowed to deposit on small spruce trees. The transfer of radioactivity to the plants has been studied. In another series of experiments, trees are submitted to artificial rain contaminated by the radioactive aerosols. The two modes of contamination are compared.