Radioactive Cesium Research Articles

Characterising Radioactive Caesium Leaching from Incineration Ash of Municipal Solid Waste in Fukushima and the Inhibitory Effect of Acid Clay

Following the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident caused by the 2011 Tōhoku earthquake and tsunami, radioactive caesium (r-Cs) was detected in the ash generated by municipal solid waste (MSW) incineration facilities in Fukushima Prefecture. This has led to concerns of r-Cs leaching and subsequent environmental contamination during recycling or landfill disposal. Therefore, it is crucial that the relevant authorities have a thorough understanding of r-Cs leaching behavior to establish suitable prevention methods. In this study, we collected r-Cs-contaminated fly and bottom ash (FA and BA) samples from five MSW incineration facilities in Fukushima Prefecture and conducted tests to clarify their basic physical properties and r-Cs leaching properties. We also examined the possibility of preventing r-Cs leaching by adding 5 wt% acid clay to the FA. FA had greater chloride content and r-Cs leaching rate than BA and was found to absorb moisture and deliquesce when stored under high-humidity conditions. However, the addition of acid clay effectively prevented r-Cs leaching upon contact with moisture. From the results, we propose some specific recommendations to counter the leaching of r-Cs from FA at MSW incineration facilities, which will limit r-Cs leaching during recycling or landfill processes.

Double-Walled Metal-Organic Framework with Regulable Pore Environments for Efficient Removal of Radioactive Cesium Cations.

An anion double-walled metal-organic framework [Co2Li4(BTC)3(DMF)(H2O)·(CH3)2N]n (1) based on heterobimetallic Li+ and Co2+ ions was successfully constructed. Utilizing selective destruction and formation of Co-O/Co-N bonds in the metal chains, [Co2Li4(BTC)3(py)(H2O)·(CH3)2N]n (2) and [Co2Li4(BTC)3(pi)(H2O)·(CH3)2N]n (3) with the same skeleton but distinct pore structures can be surprisingly obtained. Additionally, compounds 2 and 3 can be transformed into [Co2Li4(BTC)3(H2O)2·(CH3)2N]n (4) by soaking them in an ethanol solution. This kind of single-crystal-to-single-crystal transformation successfully regulates the pore structure of MOFs and enriches the diversity of the pore wall on the premise of retaining the original framework. Most impressively, compound 1 shows high adsorption capacity for Cs+ cations and is a good candidate to selectively accommodate Cs+ among the common alkali metal ions, which is future identified by single-crystal X-ray diffraction and inductively coupled plasma mass spectrometry (ICP-MS) test. Meanwhile, compound 1 can selectively adsorb methylene blue (MB) and crystal violet (CV) molecules over Rhodamine B (RMB).

Simultaneous removal of radioactive cesium and strontium from seawater using a highly efficient Prussian blue-embedded alginate aerogel

Radioactive cesium (137Cs) and strontium (90Sr) contaminants in seawater have been a serious problem since the Fukushima accident in 2011 due to their long-term health risks. For the effective and simultaneous removal of radioactive cesium (137Cs) and strontium (90Sr) from seawater, a Prussian blue (PB)-immobilized alginate aerogel (PB–alginate aerogel) was fabricated and its adsorption performance was evaluated. PB nanoparticles were homogeneously dispersed in the three-dimensional porous alginate aerogel matrix, which enabled facile contact with seawater. The PB–alginate aerogel exhibited Cs+ and Sr2+ adsorption capacities of 19.88 and 20.10 mg/g, respectively, without substantial interference because Cs+ and Sr2+ adsorption occurred at different adsorption sites on the composite. The Cs+ and Sr2+ adsorption onto the PB–alginate aerogel was completed within 3 h due to the highly porous morphology of the aerogel. The Cs+ and Sr2+ adsorption behaviors on the PB–alginate aerogel were systematically investigated under various conditions. Compared with Cs+ adsorption, Sr2+ adsorption onto the PB–alginate aerogel was more strongly influenced by competing cations (Na+, Mg2+, Ca2+, and K+) in seawater. 137Cs and 90Sr removal tests in real seawater demonstrated the practical feasibility of the PB–alginate aerogel as an adsorbent.

Securely anchored Prussian blue nanocrystals on the surface of porous PAAm sphere for high and selective cesium removal

Prussian blue (PB) has been well known as a pigment crystal to selectively sequestrate the radioactive cesium ion released from aqueous solutions owing to PB cage size similar to the cesium ion. Because the small size of PB is hard to deal with, the adsorbents containing PB have been prepared in the form of composites causing low sequestration efficiency of cesium. In this study, securely anchored PB nanocrystals on the surface of millimeter-sized porous polyacrylamide (PAAm) spheres (PB@PAAm) have been prepared by the crystallization of PB on the Fe3+ adsorbed PAAm. The securely anchored PB nanocrystals have been demonstrated to be selective and efficient adsorbents for sequestration of the radioactive cesium. The well-interconnected-spherical pores and millimeter-sized diameter of the PB@PAAm adsorbents facilitated permeation of Cs+ into the adsorbent and ease of handling respectively. Especially the well-interconnected-spherical pores allowed that PB@PAAm showed 90% of its maximum Cs+ adsorption capacity within 30 min. The PB@PAAm showed an outstanding Cs+ capture ability of 374 mg/g, high removal efficiency of 85% even at low concentration of Cs+ (10 ng/L), and superior selectivity of Cs+ against interference ions of Na+, K+, Mg2+, and Ca2+.

Effective washing removal of radioactive cesium from soils using adsorbents: a proposed adsorbent-coexistence method

Effective washing removal of radioactive cesium from soils using adsorbents: a proposed adsorbent-coexistence method

Field Research Report on Radioactive Cesium Contained in Persimmon Growing at Orchards of Fukushima Eight Years after the Nuclear Power Plant Accident

Parts of the experimentally processed persimmon on the collection date (purchase date) in September of this year exceeded 100 Bq per kg, which is the standard value of the radioactivity concentration of foods set by the Ministry of Health, Labor and Welfare, Japan. As such, measures have been taken to avoid shipping of Anpo-gaki from that area as radioactive substances released into the environment from the explosion of the nuclear power plant in March 2011 remain in the environment.

Facile synthesis of silica‐polymer monoliths using nonionic triblock copolymer surfactant for efficient removal of radioactive pollutants from contaminated seawater

AbstractHere, we introduce a highly porous functional mesoscopically silica‐polymer composite based on silica monolith‐conjugated thiourea/formaldehyde copolymer. The developed nanostructure enables selective and fast removal of the radioactive pollutants strontium (Sr[II]) and cesium (Cs[I]) ions from contaminated seawater. The silica/polymer composite was synthesized by introducing thiourea/formaldehyde solution into tetramethoxy orthosilicate/triblock copolymer emulsion. The chemical and textural features of the synthesized silica/thiourea‐formaldehyde polymer composite (SiO2‐TUF) were characterized using Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscope, high‐resolution transmission electron microscope, energy dispersive X‐ray analysis, dynamic light scattering, thermal analysis, and N2 adsorption/desorption measurements. The synthesized microporous SiO2‐TUF showed excellent cesium and strontium ions removal ability, reaching a maximum adsorption capacity of 78.2 and 40.3 mg g−1 for Sr(II) and Cs(I), respectively. When tested with seawater contaminated with radioactive cesium and strontium, SiO2‐TUF was able to selectively target Sr(II) and Cs(I) ions. Among the different types of adsorption isotherms investigated, Sips isotherm showed the best fit with R2 > 0.990. The kinetic studies showed that the pseudo‐second‐order model gave the best description of the uptake process.

Integrated and Portable Probe Based on Functional Plastic Scintillator for Detection of Radioactive Cesium

The highly reliable and direct detection of radioactive cesium has gained potential interest due to in-situ detection and monitoring in environments. In this study, we elucidated an integrated and portable probe based on functional plastic scintillator for detection of radioactive cesium. A functional plastic scintillator with improved detection efficiency was fabricated including CdTe (cadmium telluride) material. Monolith-typed functional plastic scintillator having a diameter of 50 mm and a thickness of 30 mm was manufactured by adding 2,5-diphenyloxazole (PPO, 0.4 wt%), 1,4 di[2-(5phenyloxazolyl)]benzene (POPOP, 0.01 wt%), and CdTe (0.2 wt%) materials in a styrene-based matrix. To evaluate the applicability of the plastic scintillator manufactured to in-situ radiological measurement, an integrated plastic detection system was created, and the measurement experiment was performed using the Cs-137 radiation source. Additionally, detection efficiency was compared with a commercial plastic scintillator. As results, the efficiency and light yield of a functional plastic scintillator including CdTe were higher than a commercial plastic scintillator. Furthermore, the remarkable performance of the functional plastic scintillator was confirmed through comparative analysis with Monte Carlo simulation.

Adsorptive Removal of Cesium Ions Using Prussian Blue Immobilized Coffee Ground Biochar

Objectives: Among various radioactive contaminants, radioactive cesium is one of the most harmful radionuclides that causes human health issues due to its high emission of gamma-ray, high solubility, high mobility, high fission yield, and long half-life. Different kinds of adsorbents have been developed for the removal of cesium from radioactive wastewater. Especially, biochar has attracted great attention as a potential adsorbent in the treatment of pollutants and for water purification. In addition, Prussian blue is a cubic lattice structure that contains a cage size similar to the hydrated cesium ionic radius, indicating it can selectively remove cesium ions. Therefore, the aim of this study is to investigate the cesium adsorption performance of synthesized Prussian blue-immobilized coffee ground biochar (PB-CGBC) under various experimental conditions for cesium removal from radioactive wastewater.Methods: After wasted coffee ground was washed and dried, it was heated at 400℃ with 10℃/min of heating rate and 5 h of retention time in a furnace with little or no available air. The PB-CGBC was synthesized using a facile co-precipitation method. Fourier transform-infrared spectroscopy, X-ray diffractometer, field emission-transmission electron microscope, Brunauer-Emmett-Teller, and zeta potential analyzer were used to analyze physico-chemical characteristics and surface structure of the synthesized adsorbents. The kinetic and equilibrium experiments of cesium adsorption on PB-CGBC were carried out and the effect of pH, temperature, initial cesium concentration, and contact time were also investigated in a batch system.Results and Discussion: The characteristic analysis clearly confirmed the successful synthesis of PB-CGBC, indicating its abundant functional groups and special surface structure. In the batch study, it was found that the cesium adsorption onto the PB-CGBC was exothermic nature. The Elovich kinetic model and Temkin isotherm also provided a good correlation with the cesium adsorption reaction onto the PB-CGBC. The maximum adsorption capacity of PB-CGBC for cesium was 129.57 mg/g at 15℃ and pH 8 at 40 mM of an initial cesium concentration, which was one of the highest values among those of previously reported adsorbents.Conclusions: In this study, the PB-CGBC was synthesized by immobilizing Prussian blue to the surface of coffee ground biochar and successfully applied for the adsorptive removal of cesium ions. Based on the experimental results, the synthesized PB-CGBC can be served as a great adsorbent for treatment of wastewater polluted with radioactive cesium.

Encapsulation of cesium with a solid waste-derived sulfoaluminate matrix: A circular economy approach of treating nuclear wastes with solid wastes

It is of great importance to safely dispose nuclear wastes with the development of nuclear industries. Past approaches to this problem have included immobilizing radioactive cesium in Portland cement-based matrices; however, the leaching rates of cesium are relatively high, especially as the leaching temperature increases. This paper explores a high-efficiency and cost-effective approach for encapsulating cesium using a sulfoaluminate cement (SAC) matrix, which was prepared via synergetic use of industrial solid wastes. Leaching results showed that, the apparent diffusion coefficient values of cesium were only ~1.4 × 10−15 cm2/s and ~5 × 10−18 cm2/s at 25 ℃ and 90 ℃ leaching conditions, respectively. These values were several orders of magnitude lower when compared with previously reported values, indicating the excellent encapsulation performance of the solid-waste-based SAC for cesium. Moreover, the heavy metals contained in the industrial solid waste were also effectively immobilized. A mechanistic analysis revealed that cesium was encapsulated in the SAC matrices stably by a physical effect. Finally, a life cycle assessment and economic analysis indicated that this approach was environmental-friendly, cost-effective, and energy-saving. This work provides a promising strategy for effective encapsulation of cesium and synergetic treatment of industrial solid wastes.

Fixed Point Observations and Characterization of Radioactive Caesium in Tama River

Fixed Point Observations and Characterization of Radioactive Caesium in Tama River

Two newly identified Haematococcus strains efficiently accumulated radioactive cesium over higher astaxanthin production

In this study, we investigated the morphological, genomic and bioaccumulation characteristics of two isolated Haematococcus strains (namely Goyang and Sogang), which were newly discovered in South Korea. Morphological analysis revealed that the isolated strains were unicellular and bi-flagellated green microalgae that formed thickened walls at the palmelloid or red-cyst phase. Phylogenetic analysis of 18S rRNA and rbcL gDNA sequences demonstrated that both strains were taxonomically related to the genus Haematococcus. The two strains showed growth pattern that was similar to a typical Haematococcus strain, and accumulated astaxanthin within 48 h of exposure to intensive light. Both red-cyst cells effectively removed radioactive cesium to more than 50% within 48 h from low-level cesium-contaminated water of 5 Bq/ml concentration. The cesium-accumulation mechanism is largely associated with the replacement of cellular potassium in thick cell walls during biouptake, and the cesium-removal rate highly depends on the corresponding astaxanthin accumulation involving the potassium-transporting protein (P-type ATPase).

Quantitative modeling of radioactive cesium concentrations in large omnivorous mammals after the Fukushima nuclear power plant accident

Large quantities of radionuclides released by the Fukushima nuclear power plant accident entered terrestrial and marine ecosystems. The resulting radioactive contamination of large omnivorous wild mammals such as wild boar (Sus scrofa) and Asian black bear (Ursus thibetanus) varied greatly depending on location, season, and time after the accident. Quantitative modeling of how such factors influence radionuclide burdens in these species is important for enhancing current knowledge of chronic radionuclide exposure consequences in mammalian populations, and for assessing potential human risks from consumption of contaminated animal meat. Here we modeled the time course of radioactive cesium (134Cs + 137Cs) concentrations in boar and black bears from Fukushima Prefecture over ~ 7 years after the accident, using nonlinear robust and quantile regressions and mixed-effects modeling. To estimate predictive performance, models fitted to the full data set were compared with those fitted only to the first 3.5 years of data, and tested on the last 3.5 years of data. Ecological half-lives for radioactive cesium, and magnitudes and phase shifts for sinusoidal seasonal oscillations in cesium burdens, were estimated by each analysis method for each species. These results can improve the understanding and prediction of radionuclide concentrations in large mammals that inhabit radioactively contaminated areas.

Chemical State Analysis of Heavy Metals and Radioactive Cesium in Municipal Solid Waste Incineration Fly Ash Contaminated with Radioactive Cesium Released by the FDNPP Accident.

The chemical states of heavy metals and radioactive Cs were estimated in fly ash sampled at Fukushima prefecture, Japan. Estimating the speciation of incinerator fly ash is important to ensure an appropriate and efficient management of fly ash generated from disaster-related waste. In this study, fly ash collected at a waste incineration facility in Fukushima prefecture was treated using a sequential extraction test. The test results indicated that the solubility behavior of radioactive Cs was similar to that of NaCl and KCl, and approximately 60% of radioactive Cs was included as water-soluble chloride compounds in the fly ash sample. Most heavy metals eluted in three fractions, in the extraction steps for carbonate-bound, free oxide, and bound to organic matter species. The chemical states of elements in the three non-water-soluble fractions and residue showed minimal elution into the environment. Therefore, most heavy metals in the fly ash exhibited minimal elution into the environment.

STUDY ON REMOVAL OF CESIUM FROM CONTAMINATED SOIL BY ELECTROPHORESIS USING POTASSIUM ACETATE AS ELECTROLYTE

9 years have passed since a large amount of radioactive materials were diffused by the nuclear accident at the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company. The decontamination works have almost been completed, and some of the contaminated soil whose topsoil was stripped and collected was transported to the intermediate storage and incineration facilities. However, the contaminated soil containing the radioactive cesium stored in the temporary storage place has not decreased significantly. Additionally, the transportation of the intermediate storage and incineration facilities have an agenda from the viewpoint of cost. Therefore, it is needed to investigate the method of decontamination by which the radiation dose of contaminated soil can be reduced below 8000 Bq/kg at the temporary storage place. Considering the decontamination in the actual temporary storage place, electrophoresis is the simple method as a decontamination method, and it is desirable to utilize zeolite with ion-exchange property as an inexpensive adsorbent. Ammonium acetate has been considered to be effective as an electrolyte because it has ammonium ion that has high ion-exchange reaction with cesium ion. However, an efficient decontamination cannot be achieved since the adsorption of cesium ions to zeolite is inhibited by ammonium ions. The purpose of this study is to discuss the efficient removal of cesium by using zeolite as an adsorbent and potassium acetate as an electrolyte through the electrophoresis test. From the test results, it is turned out that potassium acetate is suitable to extract cesium efficiently in electrophoresis.

Kinetic and equilibrium studies of Cs-137 sorption on calcium-doped Prussian blue

Since the Fukushima plant accident took place in 2011, a large amount of radioactive cesium ions have been released and their separation from wastewater has been a major concern. Herein, we have synthesized a Cs-137 adsorbent: calcium-doped Prussian Blue (Ca-PB), using a simple solution co-precipitation technique. The adsorbent was characterized by FTIR and XRD, and systematically evaluated the kinetics and adsorption equilibrium for Cs+ adsorbed to Ca-PB. The experimental data were followed by a pseudo-second order kinetic model and well adapted to Langmuir’s isothermal model. The research showed that Ca-PB can be used to treat water contaminated by Cs-137 in extremely acidic conditions.

Insight into cesium immobilization in contaminated soil amended with biochar, incinerated sewage sludge ash and zeolite

Radioactive cesium (Cs) in the soil represents a severe threat to human health and the environment. Plant uptake is an important pathway for the migration of Cs to the human food chain. It is therefore essential to find effective amendments for reducing the phytoavailability of Cs. In this study, we aimed to evaluate the effectiveness and possible mechanisms of biochar (BC), incinerated sewage sludge ash (ISSA) and zeolite (ZL) on the immobilization of Cs in the contaminated soil. Greenhouse pot experiment was conducted using Napier grass ( Pennisetum purpureum ) to investigate the effects of BC, ISSA and ZL (10% application rate, w/w) on the soil properties, plant biomass, the accumulation and distribution of Cs in the grass grown on the contaminated soil added with Cs as a rate of 100 mg kg −1 . The results showed that all amendments enhanced the grass growth, with the maximum biomass recorded in the ISSA treatment. The concentrations of Cs in the leaf blade, leaf sheath and root of grass significantly decreased with all amendment applications. Especially the BC application showed the lowest Cs concentration in grass, decreased by up to 95% compared to control (no amended soil). Moreover, the obtained results in terms of pH, cation exchange capacity, surface charge, specific surface area and potassium concentration of amendments and potting soils highlighted the remarkable efficiency of biochar to adsorb Cs and reduce the plant uptake of Cs providing key evidences for Cs immobilization. • Cs immobilization in soil amended with three sorbent materials was investigated. • The additions of BC, ISSA and ZL significantly restricted the Cs transfer to plant. • The BC showed the most significant inhibition effect on the plant uptake of Cs. • Cs was immobilized by BC due to its high sorption capacity and K concentration.

Effect of dissolved soil organic matter on cesium adsorption by zeolite and illite

In controlled landfill sites, soil layers are installed around radioactive waste to prevent the leaching of radioactive cesium (Cs). The Cs retention capacity of soil has been reported to be enhanced by mixing clay minerals. However, several studies have indicated that dissolved soil organic matter (DSOM) inhibits the Cs sorption by clay minerals. Therefore, this study assesses the effect of DSOM on the Cs sorption by zeolite and illite. Excitation emission matrix fluorescence spectroscopy was used for DSOM in the soil solution before and after contact with clay minerals. The results show that DSOM sorption onto clay minerals, particularly fulvic acid, inhibited Cs sorption. Batch sorption tests were conducted to obtain the sorption isotherms using two sample solutions, namely, soil and ionic solutions. Soil solution, which contained DSOM, was prepared by mixing soil and ultrapure water and filtration using a 0.3-μm glass fiver filter. Ionic solution was prepared by removing DSOM larger than 500 Da from the soil solution using dialysis. The amount of sorbed Cs in the soil solution was lower than that in the ionic solution. Comparing the Freundlich coefficients (KF) between the soil and ionic solutions, we found that the KF values of zeolite and illite for the ionic solution accounted for 6.4- and 4.4-fold higher than that for the soil solution, respectively.

Treatment of Radioactive Liquid Waste Using Bentonite

Radioactive liquid waste contaminated with cesium-137 found in the radiochemistry laboratories at Tuwaitha site, south of Baghdad, was treated in this work. Bentonite was used as a sorbent material for the removal of radioactive cesium-137 from liquid waste by ion exchange method. The results indicated that the best removal efficiency obtained was 95.13% with experimental conditions of 2 h mixture time, 0.04 g sorbent mass, and pH=10 for the radioactive liquid. It was found that the experimental results match well with Langmuir and Freundlich models, with better matching with the latter.

Estimation of Effect of Radiation Dose Reduction for Internal Exposure by Food Regulations under the Current Criteria for Radionuclides in Foodstuff in Japan Using Monitoring Results.

This study examined the effect of food regulations under the current criteria (e.g., 100 Bq/kg for general foods) established approximately a year after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Foods are monitored to ensure that foods exceeding the standard limit are not distributed; ~300,000 examinations per year have been performed especially since FY2014. This study comprehensively estimated the internal exposure dose resulting from the ingestion of foods containing radioactive cesium using the accumulated monitoring results. Committed effective dose was conservatively calculated as the product of the radioactive concentration randomly sampled from test results, food intake, and dose coefficient. The median, 95th, and 99th percentile of the dose were 0.0479, 0.207, and 10.6 mSv/y, respectively, in the estimation with all test results (without regulation), and 0.0430, 0.0790, and 0.233 mSv/y, respectively, in the estimation with results within the standard limits (with regulation) in FY2012. In FY2016, the dose with and without regulation were similar, except for high percentile, and those doses were significantly smaller than 1 mSv/y, which was adopted as the basis for the current criteria. The food regulation measures implemented in Japan after the FDNPP accident have been beneficial, and food safety against radionuclides has been ensured.