Radioactive Cesium Research Articles

Dissolution, Mechanical Properties, and Thermal Stability of Microparticles Containing Radioactive Cesium on Plant Litter Derived from the Fukushima Daiichi Nuclear Power Plant Accident

Most of the radioactive cesium (134Cs and 137Cs), which originated from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, has remained in the soil and on plants as water-insoluble microparticles (termed as CsMPs) and maintained relatively high radioactivity levels in the district. However, it has been reported that the radioactive Cs has been absorbed by plants. To interpret this phenomenon, the authors investigated CsMPs to determine if they become soluble during filtration and dialysis experiments. Moreover, other physical properties, such as mechanical properties and thermal stability, were observed during the course of the relevant experiments. These properties can be obtained by using carbonized charcoal litter with CsMPs.

Uncertainty derived from elemental analysis and its effect on the separation of radioactive waste into low-level radioactive waste and waste for clearance

Radioactive cobalt (Co), cesium (Cs), and europium (Eu), produced by neutron-capture reactions of the corresponding trace elements, are the main radioactive components of concrete waste in the decommissioning of aged nuclear power stations. The uncertainty regarding the activity of individual nuclide produced by activation is a main factor for efficient separation of radioactive wastes. Major and trace elements in the geostandard reference JG-3, aggregates collected from quarries, and cements, were analyzed by four different methods to evaluate experimentally the uncertainty. Neutronactivation analysis, a non-destructive technique, and analysis by using instruments such as an inductively coupled plasma mass spectrometry (ICP-MS) following sample digestion by alkali fusion have uncertainties of 30% for the content of major and trace elements. ICP-MS measurements following digestion by HF or K2S2O3 showed a poorer precision, especially for the trace elements. The Monte Carlo simulation using PHITS code was performed to estimate the depth profiles and uncertainty for the radionuclides produced by activation in the concrete including the uncertainty derived from the elemental analyses and local variability. On the basis of the uncertainty, we evaluated the boundary depth between low-level radioactive waste and waste for clearance in a bioshield for the prudent separation.

Direct comparison of bacterial communities in soils contaminated with different levels of radioactive cesium from the first Fukushima nuclear power plant accident

The Great East Japan Earthquake caused a serious accident at the first Fukushima nuclear power plant (NPP), which in turn released a large amount of radionuclides. Little attention has been paid to in-situ soil microorganisms exposed to radioactive contamination by the actual NPP accident. We herein investigated bacterial communities in the radioactive cesium (Cs)-contaminated and non-contaminated soils by high-throughput sequencing. The uppermost and ectorhizosphere soil samples were collected from the base of mugwort grown in the same soil type with the same soil-use history in order to compare the bacterial communities at geographically separated areas. The concentrations of radioactive Cs in the soils ranged from 10 to 563,000 Bq 137Cs/kg dry soil, with the highest concentration being detected at 1 km from the NPP. Alpha-diversity indices, i.e., Chao1, Shannon and Simpson reciprocal, of the sequence data showed the lower bacterial diversity in the most highly Cs-contaminated soil. Principal coordinate analysis with principle components 1 and 3 based on unweighted UniFrac distances indicated the significant difference in bacterial communities of the most contaminated area from those of the other areas. Operational taxonomic unit-based assay revealed higher abundance of the radio-resistant Geodermatophilus bullaregiensis relative in the most contaminated soil. Thus, it was strongly suggested that the radioactive accident facilitated the growth and/or survival of radio-resistant bacteria in the Cs-contaminated soils. The results of this study show that information on the soil type, vegetation and soil-use history enhances the direct comparison of geographically distant soil bacterial communities exposed to different levels of radioactive contamination.

Calculations for ambient dose equivalent rates in nine forests in eastern Japan from 134Cs and 137Cs radioactivity measurements

Understanding the relationship between the distribution of radioactive 134Cs and 137Cs in forests and ambient dose equivalent rates (H˙∗(10)) in the air is important for researching forests in eastern Japan affected by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. This study used a large number of measurements from forest samples, including 134Cs and 137Cs radioactivity concentrations, densities and moisture contents, to perform Monte Carlo radiation transport simulations for H˙∗(10) between 2011 and 2017. Calculated H˙∗(10) at 0.1 and 1 m above the ground had mean residual errors of 19% and 16%, respectively, from measurements taken with handheld NaI(Tl) scintillator survey meters. Setting aside the contributions from natural background radiation, 134Cs and 137Cs in the organic layer and the top 5 cm of forest soil generally made the largest contributions to calculated H˙∗(10). The contributions from 134Cs and 137Cs in the forest canopy were calculated to be largest in the first two years following the accident. Uncertainties were evaluated in the simulation results due to the measurement uncertainties in the model inputs by assuming Gaussian measurement errors. The mean uncertainty (relative standard deviation) of the simulated H˙∗(10) at 1 m height was 11%. The main contributors to the total uncertainty in the simulation results were the accuracies to which the 134Cs and 137Cs radioactivities of the organic layer and top 5 cm of soil, and the vertical distribution of 134Cs and 137Cs within the 5 cm soil layers, were known. Radioactive cesium located in the top 5 cm of soil was the main contributor to H˙∗(10) at 1 m by 2016 or 2017 in the calculation results for all sites. Studies on the 137Cs distribution within forest soil will therefore help explain radiation levels henceforth in forests affected by the FDNPP accident. The merits of this study are that it modelled multiple forests for a long time period, with the important model inputs being informed by field measurements, and it quantified how the measurement uncertainties in these inputs affected the calculation results.

CORRELATION BETWEEN RADIOACTIVE CESIUM AND THE INCREASE OF PANCREATIC CANCER: A HYPOTHESIS

Worldwide, both the incidence and death rates of pancreatic cancer (PC) are increasing. While the exact cause of PC is not known, certain risk factors are associated with the disease, including tobacco smoking, obesity and diabetes. The present author studied associations between radioactive cesium (137Cs) and increases in PC. There is a correlation between the geographical map of the incidence of and mortality from PC and the map of nuclear plants, related nuclear accidents and nuclear tests with consequent radioactive fallout, of which 137Cs, with its half-life of about 30 years, is one of the most relevant components. Published data in medical literature at World, European and Italian levels are reviewed and compared. In human and animal bodies, cesium ions behave like potassium ion (K+). Cs+ is absorbed from plants and fruit competitively with K+ and is localized mainly inside cells. 137Cs is present in the environment for at least 10-20 times its half-life, i.e. about 300-600 years. Autoradiographic studies in mice have shown that 137Cs is concentrated in significant quantities in the pancreas, in particular in exocrine cells, where most PCs featuring high malignancy originate. The pancreas and the salivary glands secrete cesium into the intestine thus eliminating about 14% of absorbed Cs with the feces, whereas the remaining 86% is eliminated by kidney with the urine. Some previous studies between radioactive Cs and tumors in general have been also reported.

Relationship between zeolite structure and capture capability for radioactive cesium and strontium

Zeolites are widely used for capturing radioactive Cs+ and Sr2+, but the important structural factors determining their performance have not been clearly understood. To investigate the structure-property relationship, we prepared thirteen zeolites with various structures and Si/Al ratios. Ion-exchange experiments revealed that Cs+ exhibited an enhanced affinity to zeolites with high Si/Al ratios, which could be explained by the dielectric theory. Notably, zeolites containing 8-membered ring (8MR) showed extra-high Cs+ selectivity. Structural analysis using X-ray diffraction proved that Cs+ with an ionic diameter of 3.6 Å was selectively coordinated within 8MR having a cavity diameter of 3.6–4.1 Å. Such unique size-selective Cs+ coordination is analogous to ion complexation by macrocyclic organic ligands (e.g., crown ethers). Divalent Sr2+ showed decreasing affinity to zeolites as the Si/Al ratio increased, because of the increasing average Al–Al distance distribution. Sr2+ exchange exhibited an insignificant dependence on zeolite structures due to its strong hydration, which inhibited close interaction with zeolite frameworks. In terms of kinetics, Sr2+ exchange was significantly slower than Cs+ exchange because of the bulkiness of hydrated Sr2+ ions. Therefore, the micropore channels with large apertures (e.g., 12-membered ring) were beneficial for achieving fast ion-exchange kinetics, especially in the case of Sr2+.

Changes in radioactive cesium concentrations from 2011 to 2017 in Fukushima coastal sediments and relative contributions of radioactive cesium-bearing microparticles

Sedimentary cesium-137 concentrations around the Fukushima Daiichi Nuclear Power Plant (FDNPP) were measured from 2011 to 2017 at eight stations. Although high values were observed until 2013, decreasing trends were observed at the surface sediments of seven stations. We isolated 25 radioactive Cs-bearing microparticles (CsMPs; 1.0–5385 Bq per particle). The contribution ratio of CsMPs to each sample ranged from 4.1% to 99.5% (median 58.8%), with the contribution ratio of the CsMPs in the southern part of the FDNPP was low compared to that from the northern part. In the southern part of the FDNPP, small CsMPs that could not be isolated in this study were present in large quantities immediately after the accident, and gradually diffused away and/or were dissolved over time. In contrast, the CsMPs in the northern part of the FDNPP have most likely accumulated over time, as suggested by the silty nature of the sediments there.

Assessing of cesium removal from wastewater using functionalized wood cellulosic adsorbent

Sustainable materials are urgently desired for treatment of radioactive cesium (Cs) contaminated water to safe-guard the public health. Apart from the synthetic ligand-based materials, the Mangrove charcoal modified adsorbent was fabricated for assessing of Cs removal from waste sample. The raw charcoal was oxidized using nitrification approach and diverse oxygen containing carboxyl, carbonyl and hydroxyl functional groups were introduced. After modification, the adsorbent characteristics were drastically changed as compared to the charcoal during the measurement of FTIR, N2 adsorption-desorption isotherms and SEM micrographs. The data clarified that charcoal modified adsorbent was exhibited high Cs transport through the inner surface of the adsorbent based on bonding ability. The adsorbent was shown comparatively slow kinetics to Cs ion; however, the adsorption capacity was high as 133.54 mg/g, which was higher than the crown ether based conjugate materials. The adsorption data were followed to the Langmuir adsorption isotherms and the monolayer coverage was possible due to the data presentation. The presence of high amount of Na and K were slightly interfered to the Cs adsorption by the charcoal modified adsorbent, however; the Na and K concentration was 350–600 folds higher than the Cs concentration. Then the proposed adsorbent was selective to Cs for the potential real radioactive Cs contaminated water. The volume reduction was established rather than desorption and reuses advantages. More than 99% volume reduction was measured by burning of Cs adsorbed adsorbent at 500 °C for ensuring the safe storage and disposal of used adsorbent. Therefore, the charcoal modified adsorbent may open the new door to treat the Cs containing wastewater.

Discharge of suspended solids and radiocesium into stream water in a forested watershed before and after line thinning with spur road construction

In an experimental watershed located around 120km southwest of the Fukushima Daiichi Nuclear Power Plant with a drainage area of 59.9ha, suspended solids (SS) and radioactive cesium discharge from a forested headwater catchment were monitored before and after line thinning. The lower slopes in the experimental watershed were covered with plantation conifer trees (Japanese cedar), while the upper slopes were covered with deciduous trees. In 2012, line thinning was carried out at a thinning rate of 35% across 17% of the northeastern part of the watershed and across the remaining part in 2013. Spur roads were constructed along all tributaries without water, and logged trees were dragged and grappled using forestry machinery and transported along these roads to timber yards using forwarder-type forestry vehicles. A V-notch weir and a water level gauge were installed at the watershed outlet and stream water was sampled twice a month during base flow, whereas during flood flow, stream water samples of 1L were collected every hour using an automatic water sampler. These samples were filtered through 0.5μm glass fiber filters to measure the SS concentration. SS concentration data was collected for 21 floods before thinning and for 37 floods after thinning. A time-integrated SS sampler was installed in the stream close to the weir and SS samples were collected every two or three months to measure their Cs-137 concentrations. SS concentrations before (from July 2010 to August 2012) and after thinning (from October 2013 to December 2018) were compared, where the maximum SS concentrations before and after thinning were 211 and 790mgL-1, respectively. It was discovered that some SS concentrations during flood flow were higher after carrying out thinning than before. Some ΣLss values (specific cumulative load of SS in a flood event) also showed the same results as the SS concentrations. Thus, it was clear that SS discharge immediately increases after thinning, but as it increases Cs-137 export is limited. This is related to a change in SS source brought about by the process of thinning, a decrease with time in the Cs-137 concentration in organic solid expected from that in litter, and a regrowth of vegetation on spur roads, protecting them against soil erosion. Therefore, it was concluded that thinning does not drastically increase Cs-137 export from a forested watershed.

Post-decontamination treatment of MXene after adsorbing Cs from contaminated water with the enhanced thermal stability to form a stable radioactive waste matrix

Safe and stable immobilization of spent adsorbents is a crucial step in nuclear and radioactive waste management. This study provides the first example of the green immobilization of simulated radioactive cesium-adsorbing MXene (Ti3C2Tx) by using hydroxyapatite (HAp) ceramic as a host matrix. The MXene-HAp (MX-HAp) composite exhibited a significantly enhanced thermal stability than that of the pure Cs-adsorbing MXene. The immobilization process was carried out by cold sintering at a low temperature (200 °C), which prevented the possible oxidation and chemical degradation of the spent adsorbent. The developed composite ceramic matrix was highly dense (3 ± 0.01 g·cm−3), mechanically strong (microhardness 2.2 ± 0.2 GPa), and chemically stable. The normalized leaching rate of simulated radioactive cesium was calculated to be 2.02 (±0.09) × 10−4 g·m−2·d−1. Thus, the thermal stability of MXene was enhanced using the HAp dried ceramic powder and non-volatile immobilization of the dried MX-HAp composite was achieved by cold sintering. The reported immobilization process showed no adverse effects on the stoichiometry of the composite matrix materials and no volatilization loss of the adsorbed simulated radionuclide was observed. This study is set to take the green immobilization process for spent adsorbents to the next level by combining MXenes and HAp to develop different types of composite materials.

Performance of in situ gamma-ray spectrometry in the assessment of radioactive cesium deposition around the Fukushima Daiichi nuclear power plant

In situ gamma-ray spectrometry using diverse survey platforms has been conducted in contaminated areas with various dose rate levels around the Fukushima Daiichi nuclear power plant (FDNPP). Six survey sites, including two evacuation zones around the FDNPP, were selected for ground-based gamma-ray spectrometry using HPGe (high purity Ge) and LaBr3(Ce) detectors to assess the radioactive cesium deposition in the ground. Laboratory analysis of soil samples taken by depth from the sites was performed to evaluate the depth profile of radioactive cesium. The diverse levels of radioactivity of 137Cs were then distributed to six survey sites from 30 to 3000 kBq·m−2 in the measurement period of October 2018. Finally, a method to directly calculate the depth profile using in situ measurement was introduced so as to have representation over a wide area, and the results were successfully compared with those of sample analysis at one point in the site. Except for the sites with relatively high lateral inhomogeneity of radioactive cesium, about 30% difference between two depth profiling methods using samples and in situ measurement was shown in the calculated radioactivity of 134Cs and 137Cs in the ground.

Paper Sludge Carbon as an Adsorbent for Fukushima Radiocontaminated Paddy Soil

Radiocontaminated soil in a paddy field in the Iitate village in Fukushima was treated with an industrial paper sludge carbon (PSC) prior to growing rice in May 2011. The results showed that the sum of the activity concentrations of 134Cs and 137Cs in the polished rice harvested in October 2011 was 30 Bq·kg−1, a level much lower than the Japanese governmental safeguard value of 100 Bq·kg−1. Upon contacting with the contaminated soil, the contents of calcium, magnesium, copper, potassium, and barium in the PSC were decreased. Among the PSCs impregnated with various chlorides and sulfates of the previously mentioned minerals, potassium chloride, copper sulfate, magnesium sulfate, and potassium sulfate yielded higher decontamination degrees compared to the original PSC. The results imply that radioactive cesium in the soil exchanges cations with these minerals.

Radiocesium concentrations in invertebrates and their environmental media at two distances from the Fukushima Dai-ichi Nuclear Power Plant during 3–6 years after the 2011 accident

Activity concentrations of the radioactive cesium (134Cs and 137Cs) were investigated in invertebrates at two sites of moderately high and higher air radiation dose rates, 14 km and 11 km distances, respectively, from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) from 2013 to 2016. At a14-km point, the 134+137Cs concentrations of soils in coniferous and broadleaf forests increased from 2013 to 2014, and thereafter declined until 2016. The 134+137Cs concentrations of the phytophagous beetle Anomala cuprea (Hope) rapidly decreased by 76.1% from 2013 to 2014, reflecting reduction in those of broadleaves. The 134+137Cs concentration levels of the carnivorous beetle Dolichus halensis (Schaller) showed a relatively low levels. The 137Cs concentrations of the necrophagous beetle Eusilpha japonica (Motshulsky) and coprophagous beetle Onthophagus lenzii (Harold) remained constant without reduction from 2013 to 2016. Average 134+137Cs concentrations throughout four years were the highest in the geophagous crustacean (Armadillidium vulgare Latreille), followed by necrophagous beetle and coprophagus beetle. The 134+137Cs concentrations in earthworms with gut contents were significantly correlated with those in soils at each habitat from 2014 to 2015 at a14-km point, and the concentration levels at an 11-km point in 2015 were remarkably high (898 kBq kg−1). Transfer factors (TFs) in earthworms ranged from 1.02 to 2.66 at a 14-km point and 0.66 to 5.0 at an11-km point. The transfer and chronological changes of radiocesium in invertebrates were discussed in relation to food habits through trophic levels in woodlands and pasturelands.

Validation of measurement comparability of NaI(Tl) scintillation detectors for radioactive cesium in brown rice sample by interlaboratory comparison

The interlaboratory comparison that 148 laboratories participated was performed to understand the validity and variability of measurements with NaI(Tl) scintillation detectors for samples near the standard limit for radioactive cesium in general foods in Japan. Brown rice grains with certified massic activity of radioactive cesium were used as test samples. The medians of the reported massic activities of radioactive cesium, 134Cs, and 137Cs in brown rice grains agreed with the reference values. On the point of view for inspection, more than 92% of the reported values were within the acceptable range.

Elution control of radioactive cesium in MSWI fly ash using water repellent treatment

Radioactive cesium found in municipal solid waste incineration (MSWI) fly ash can be easily eluted through contact with environmentally sourced water, such as rainwater. Dissolution suppression treatment of radioactive cesium, such as through cement solidification or geopolymer solidification, has been previously studied. Treatment through solidification requires the addition of a fixation agent, which results in an increase in the volume of fly ash following solidification. It is likely that the level of security at the landfill site will be high. In an attempt to simply suppress the elution of water-soluble radioactive cesium from MSWI fly ash without an increase in volume, we examined a water-repellent treatment method using four types of water repellents. Our results indicate that when the incinerated fly ash is impregnated and mixed with a commercially available water repellent, such as a silane-based oligomer, an alkyl alkoxysilane compound, or a fatty acid, it is possible to suppress the elution of radioactive cesium without a corresponding increase in fly ash volume.

Production of textile crops in conditions of radioactive contamination

After the accident at the Chernobyl Nuclear Power Plant, a large part of the lands of the Polissya Zone became contaminated with radionuclides, which were withdrawn from land use according to current regulations, thus we have analyzed the current state of the branches of flax and hemp growing in Ukraine. Chernobyl accident has led to radioactive contamination of large areas of agricultural land, and therefore more and more attention is paid to the work of scientists aimed at reducing radioactive contamination. The possibility of growing bast crops under different levels of radioactive contamination is substantiated, the elements of technology of cultivation and primary and deep processing of flax and hemp are considered, which allow to significantly reduce radioactive cesium 137Cs input into crop production and its content in various types of products of processing of these crops.Specific countermeasures are proposed to achieve this goal, namely: in the cultivation of flax and hemp, to introduce phosphorus-potassium fertilizers that reduce the intake of radionuclides into products grown under different levels of radioactive contamination, flax sowing should be carried out in conjunction with sparsely shrubby grasses, using for this purpose seed rate of 15–20 kg of grass seeds. When aging stalks to the straw, to rotate the strips, which reduces the accumulation of radionuclides by reducing the mass of dusty impurities and avoiding direct contact of primary processing products with soil. It is recommended to rinse the flax or hemp straw in a water stream on a squeezing-washing machine before processing on the scutching-and-breaking machine

Using Dates Leaves Midribs to Prepare Hierarchical Structures Incorporating Porous Carbon and Zeolite A Composites for Cesium137Cs Ion Exchange

This study synthesized zeolite 4A, and hierarchical composite structure consisting of zeolite 4A- carbon were successfully prepared. Hydrothermal method was used to grow a layer of zeolite 4A over porous carbon surfaces to enhance mass transfer and increase surface area of zeolite. The products then were used to remove radioactive cesium137Cs from liquid wastewater. Iraqi dates leaves midribs (DM) were used as locally available agricultural waste to prepare low- cost porous carbon, using carbonization method in tubular furnace at 900C for two hours. Hierarchical porous structures including zeolite are prepared by mechanically activating the carbon surface via Ultrasonicating nanoparticles suspension of ground zeolite type 4A.For preparing nanoparticles suspension, commercial zeolite has been milled using 0.3-0.4 mm diameter glass balls as grinding media. Nanoparticles of zeolite 4A acting as seeding (nucleation centers) increase the crystallization of amorphous aluminosilica gel on modification carbon surface. The products of the syntheses zeolite 4A and the hierarchal composite materials (DMZ) were characterized using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Nitrogen sorption (BET) and Energy dispersive X-ray spectrometer (EDX) to check the morphology, structure, surface area, and the chemical composition respectively. The products were used to treat radioactive wastewater contaminated with radioactive cesium 137Cs collected from destroyed building of the Radiochemistry Laboratories (RCL) in AL-Tuwaitha Nuclear Site. The activity concentration for the contamination water pre and after the treatment were measured using gamma spectroscopy system supplied with a high purity germanium detector (HPGe) with 60% relative efficiency. The results showed that the radioactivity concentration after the treatment process decreased significantly from 4800 Bq/L to 186 and Bq/L,121 Bq/L using 0.045 gm from synthesized zeolite 4A and DMZ respectively.

Removal of Radioactive Cesium in Secondary Wastewater after Soil-washing Process

Objectives : Secondary wastewater is generated as the soil washing process proceeds to restore contaminated soil near the nuclear power plants (NPPs). In this study, we tried to evaluate the possibility of removing radioactive cesium from secondary wastewater through the adsorption process using illite.Methods : To treat radioactive cesium present in wastewater, as an adsorbent, we used illite collected from Yeongdong, Chungbuk, and weathering illite artificially weathered by high temperature and acid treatment (60℃, 0.01 M HCl). Before and after weathering, the adsorption rate of illite at low concentrations of cesium and the desorption rate of adsorbents were compared and evaluated using a 1.5 ppm of competitive potassium ion similar to that of groundwater.Results and Discussion : When the illite was artificially weathered, the amount of frayed edge sites increased as the interlayer ions in the illite eluted. As a result of the adsorption and desorption experiments, it was confirmed that the adsorption rate of weathering illite increased by about 11% in acid condition (pH 3) and about 26% in neutral condition (pH 6.2), and the desorption rate of weathering illite decreased by about 6% in acid and neutral conditions, compared to Yeongdong illite. Yeongdong illite and weathering illite showed higher adsorption rate under neutral condition than acidic condition, because the surface of the illite became negatively charged at high pH so the reactivity with cesium present as a cation increased.Conclusions : The artificial weathering process has improved the performance of illite as an adsorbent. We expect that weathering illite can be used as an effective adsorbent for the removal of radioactive cesium from NPP.

Isolation, characterization and source analysis of radiocaesium micro-particles in soil sample collected from vicinity of Fukushima Dai-ichi nuclear power plant

Radioactive caesium was released during the accident of Fukushima Dai-ichi nuclear power plant (FDNPP) into the surrounding environment. In the current work, radiocaesium micro-particles (CsMPs) and radiocaesium-rich soil particles were selectively separated from soil particles as well as from each other using autoradiography-based procedure. The applied separation scheme is based on water dilution followed by drying of the soil sample prior to imaging plate autoradiography. The SEM/EDS investigation of the individual CsMPs showed that these particles have a silicate glass structure and vary in shape with a diameter less than 10 μm. For the first time, a two-stage formation mechanism was suggested for a CsMP based on shape and structure heterogeneity of its two parts. Perfect spherical core might be formed in the first stage with a remarkable lower content of Al, and relatively higher concentrations of Si and K than an outer angulated structure, which might be attached to the core sphere during a late stage.The radiocaesium-rich soil particles have bigger size than CsMPs and have a plate-like structure with cleavages inside the grains, which suggest that these particles might be a weathered biotite. The average radioactivity ratio of 134Cs/137Cs (dated March 11, 2011) in the investigated particles was found to be 1.05 ± 0.01, which confirmed that the radiocaesium in CsMPs and in the contaminated soil particles has the same source of origin, which could be unite 3 of FDNPP.

Effective removal of radioactive cesium from contaminated water by synthesized composite adsorbent and its thermal treatment for enhanced storage stability

A composite adsorbent for the removal of radioactive cesium (137Cs) was synthesized by immobilizing potassium cobalt ferrocyanide in the micro pores of the zeolite chabazite. The synthetically optimized composite adsorbent demonstrates a rapid cesium adsorption rate under both salt-free and high-salt conditions with a high distribution coefficient of cesium (≥105 mL/g). Although both components have the same ion-exchange reaction between potassium and cesium, the reaction by ferrocyanide component was predominant, which derived hundred times higher distribution coefficient of the composite adsorbent than that of pure chabazite. A thermal stabilization process was studied for improving the storage and/or disposal stability of the spent adsorbent. The formation of a eutectic system within the spent adsorbent reduced the stabilization temperature to 1000 °C from 1200 °C. Accordingly, the leaching of cesium was remarkably reduced by the remineralization to the stable pollucite. The stable impregnation of ferrocyanide component in the chabazite pores derived the reduction of cesium volatility enabling the high temperature stabilization method. Our experimental results provide evidence that the composite adsorbent has clear advantages on the cesium removal from contaminated water and its stabilization via thermal-treatment.