Industrial activities that utilize nuclear technology can cause radioactive contamination in the ecosystems. In particular, cesium (Cs) has problems, such as neurological diseases, when it is exposed and accumulated in the bodies of animals, plants, and humans for a long time. Therefore, the development of simple and economical adsorbents for Cs removal is required. In this study, the surface of petroleum residue pitch was modified using NaClO and it was used to remove Cs from an aqueous solution. Batch experiments and characterization of the modified adsorbent were performed to determine the adsorption mechanism between the adsorbent and Cs. From these results, chemical and monolayer adsorption were found to occur at the carboxyl groups on the adsorbent surface, along with a cation exchange reaction occurred due to the sodium ions on the surface. Through this modification process, the total acidity, including phenolic, lactonic and carboxylic functional groups, was improved to 1.563 mmol/g and the maximum adsorption capacity of Cs for the modified adsorbent was 65.8 mg/g.

One of the issues currently facing nuclear power plants is how to store spent nuclear waste materials which are contaminated with radionuclides such as 134Cs, 135Cs, and 137Cs. Bioremediation processes may offer a potent method of cleaning up radioactive cesium. However, there have only been limited reports on Cs+ tolerant bacteria. In this study, we report the isolation and identification of Cs+ tolerant bacteria in environmental soil and sediment. The resistant Cs+ isolates were screened from enrichment cultures in R2A medium supplemented with 100 mM CsCl for 72 h, followed by microbial community analysis based on sequencing analysis from 16S rRNA gene clone libraries (NCBI’s BlastN). The dominant Bacillus anthracis Roh-1 and B. cereus Roh-2 were successfully isolated from the cesium enrichment culture. Importantly, B. cereus Roh- 2 is resistant to 30% more Cs+ than is B. anthracis Roh-1 when treated with 50 mM CsCl. Growth experiments clearly demonstrated that the isolate had a higher tolerance to Cs+. In addition, we investigated the adsorption of 0.2 mg L-1 Cs+ using B. anthracis Roh-1. The maximum Cs+ biosorption capacity of B. anthracis Roh-1 was 2.01 mg g-1 at pH 10. Thus, we show that Cs+ tolerant bacterial isolates could be used for bioremediation of contaminated environments.

전 세계적으로 원자력 발전소는 442기가 가동 중이며, 62기가 충원될 예정이다. 원자력 발전소의 증가에 따라 방사성 폐기물 유출에 대한 위험성도 증가하였다. 이러한 이유 때문 에, 방사성 폐기물의 처리는 인간, 동물, 식물을 포함하는 자 연 생태계를 보전하는 관점에서 중요하다. 또한, 방사성 폐 기물 유출은 그 지역뿐만 아니라 전 세계적으로 심각한 문 제를 야기한다. 본 연구는 입체 배양세포에 방사성 핵종원 소 (세슘, 스트론튬, 코발트)를 처리하였고 이에 대한 영향력 을 확인하였다. 입체 배양 구조체는 아가로오스 하이드로겔 을 이용하여 제작했으며 암세포 및 정상세포 (HeLa, HepG2, COS-7)를 사용하여 입체 배양을 실시 하였다. 입체 형태로 세포를 배양한 후 세슘, 스트론튬, 코발트 농도 변화에 따라 세포 생존능력을 분석하였다. 이때 입체 배양세포에서 생존 능력이 단층 배양세포 보다 최대 42% 우수한 것을 확인하였 다. 입체 배양구조체는 세포가 형태 및 생리학적으로 in vivo 환경인 조직과 비슷하게 배양을 가능하게 하였다. 따라서, 입체 배양구조체는 기존의 단층 배양 한계점인 in vivo 환경 에 적용시킬 수 없다는 한계를 극복하였다. 본 입체 배양 기 술이 중금속 독성평가 및 단시간 내에 다수의 물질 분석을 수행하는 고속 대량 스크리닝 기술에 활용될 것으로 기대한 다.

This study was evaluated the applicability of the membrane filtration process (Micro Filtration (MF), nanofiltration membranes (NF), reverse osmosis (RO)) on the major radioactive substances, iodine (I-) and cesium (Cs+) using membranes produced in Korea and domestic raw water. Iodine (I-) or cesium (Cs+) in the microfiltration membrane (MF) process could not be expected removal efficiency by eliminating marginally at the combined state with colloidal and turbidity material. At the domestic raw water (lake water, turbidity 1.2 NTU, DOC 1.3 mg/L) conditions, nanofiltration membrane (NF) and reverse osmosis (RO) showed a high removal rate of about 88 ~ 99% for iodine (I-) and cesium (Cs+) and likely to be an alternative process for the removal of radioactive material.

Increasing resource use is the primary motivator for the development of technology industries, which is leading to severe consequences, such as the release and disposal of radioactive waste containing radionuclides in the environment. Cesium (137Cs) is one of the most hazardous radionuclides in the environment. In particular, the steel manufacturing process produces hazardous waste in the form of electric arc furnace dust contaminated with 137Cs. In this study, the tolerances of five legume species to different activity concentrations of 137Cs in both seed germination and initial seedling growth were compared. To determine 137Cs tolerance, several parameters related to the growth and development of legumes were measured. Among the five legumes studied, Crotalaria juncea L. was the most 137Cs tolerant at 50,000 Bq·L−1. Sesbania javanica Miq. and Vigna mungo L. Hepper were moderately tolerant to 30,000 Bq·L−1 137Cs. After 10 days, the stress tolerance indices in all legume species decreased by more than 50% at activity concentrations greater than or equal to 20,000 Bq·L−1 137Cs. This approach allows the selection of desirable traits, making more-effective application possible in the phytoremediation of 137Cs through stress tolerance. In conclusion, legumes are promising candidates for the phytoremediation of environmental pollutants.

The nuclear fuel that melted during the Fukushima nuclear accident in 2011 is still being cooled by water. In this process, contaminated water containing radioactive substances such as cesium and strontium is generated. The total amount of radioactive pollutants released by the natural environment due to the nuclear accident in Fukushima in 2011 is estimated to be 900 PBq, of which 10 to 37 PBq for cesium. Radioactive cesium (137Cs) is a potassium analog that exists in the water in the form of cations with similar daytime behavior and a small hydration radius and is recognized as a radioactive nuclide that has the greatest impact on the environment due to its long half-life (about 30 years), high solubility and diffusion coefficient, and gamma-ray emission. In this study, alginate beads were designed using Prussian blue, known as a material that selectively adsorbs cesium for removal and detection of cesium. To confirm the adsorption performance of the produced Prussian blue, immersion experiments were conducted using Cs standard solution, and MCNP simulations were performed by modeling 1L reservoir to conduct experiments using radioactive Cs in the future. An adsorption experiment was conducted with water containing standard cesium solution using alginate beads impregnated with Prussian blue. The adsorption experiment tested how much cesium of the same concentration was adsorbed over time. As a result, it was found that Prussian blue beads removed about 80% of cesium within 10-15 minutes. In addition, MCNP simulation was performed using a 1 L reservoir and a 3inch NaI detector to optimize the amount of Prussian blue. The results of comparing the efficiency according to the Prussian volume was shown. It showed that our designed system holds great promise for the cleanup and detection of radioactive cesium contaminated seawater around nuclear plants and/or after nuclear accidents. Thus, this work is expected to provide insights into the fundamental MCNP simulation based optimization of Prussian blue for cesium removal and this work based MCNP simulation will pave the way for various practical applications.

The radioactive cesium, released from the normal operation or the accidental operation of nuclear facilities, should be regularly monitored for environmental regulatory compliance. The 135Cs/137Cs isotopic ratios, potentially useful for long-term tracking Cs transport in seawater, can be used as a tool of understanding how radionuclides are transported from different nuclear production source terms and distributed in the ocean. The ultra-high sensitive mass spectrometers (TIMS, SF-ICP-MS and TQ-ICP-MS) have been used to measure the 135Cs/137Cs isotopic ratios. However, the radiochemical separation of Cs from the seawater matrix is essential for the analysis of Cs using the mass spectrometers. An automated radiochemical procedure for the separation of Cs in seawater was developed for the analysis of 135Cs/137Cs isotopic ratios using a sequential column chromatography with AMPPAN and AG50Wx8 cation exchange resins. National Instrument’s LabVIEW is a graphical programming language and a powerful tool for the instrument control. A virtual instrument system for the automated separation of cesium isotopes was developed by the state machine of the fundamental design patterns in LabVIEW. In this study, the conceptual designs of an automated separation system of cesium isotopes, its virtual instrument system based on the LabVIEW state machine architectures and an automated radiochemical procedure were described for the purification of cesium isotopes at trace levels found in seawater discharged from the various nuclear facilities.

Wide-area surface decontamination is essential during the sudden release of radioisotopes to the public, such as nuclear accidents or terrorist attacks. A spray coating composed of a reversible complex between poly (vinyl alcohol) (PVA) and phenylboronic acid-grafted poly (methyl vinyl ether-alt-mono-sodium maleate) (PBA–g–PMVE–SM) was developed to remove radioactive cesium from surfaces. The simultaneous spay of PVA and PBA–g–PMVE–SM aqueous polymer solutions containing Cs adsorbent to contaminated surfaces resulted in the spontaneous formation of a PBA–diol ester bond-based gel-like coating. The Cs adsorbent suspended in the gel-like coating selectively removed Cs-137 from the Cs-contaminated surface. The used gel-like coating were removed from surfaces by simple water rinsing. This recovery way has advantages compared with costly incineration to remove the organic materials for final disposal/storage of the radioactive waste. Thus, our spray coating is suitable for practical wide-area surface decontamination. In radioactive tests, the hydrogel containing Cs-adsorbent showed substantial Cs-137 removal efficiencies of 96.996% for painted cement and 63.404% for cement, which are 2.33 times better than the values for the commercial surface decontamination coating agent DeconGel.

Low- and intermediate level waste (LILW) repository in Gyeongju, Korea is in operation and the radioactive waste should satisfy the waste acceptance criteria (WAC) of the repository. Among the WAC of the Gyeongju LILW repository, the leachability index criterion is considered to be the criterion that is directly related to the isolation of the radionuclides from biosphere. Cesium, strontium, and cobalt should satisfy the leachability index larger than six by following the ANS 16.1 leaching test method. Several research were performed for the leachability index of Cs, Sr, and Co by following the ANS 16.1 leaching test method. However, the test condition of the previous research is expected to be different to the condition of the actual waste. Due to the radioactivity of the radionuclide such as Cs, Sr and Co, most of the research applied the surrogate of those radionuclides. The concentration of those nuclides was generally measured by the inductively coupled plasma (ICP) equipment, however, high concentration compared to the disposal limit of those nuclides due to the detection limit of the ICP was applied. From the Freundlich and Langmuir adsorption isotherms, the adsorption of the nuclides differs according to the concentration of the nuclides. As the leachability index of the nuclides is affected by the adsorption of the nuclides on the binding material, the effect of nuclide concentration is expected to be not ignorable. Therefore, the leachability index difference according to the nuclide concentration should be compared to avoid over- or underestimation of the leachability index. In this study, the difference in the leachability index according to the concentration of nuclides is aimed to be checked. Cs, Sr, and Co, which should satisfy the leachability index criterion in the WAC of the Gyeongju repository, were selected as target nuclides. Three concentrations were selected to compare the leachability index: 0.1 mol, 0.001 mol and below the regulatory exemption concentration. The concentration of non-radioactive nuclides in the leachant was measured by ICPOES and ICP-MS while the concentration of radionuclides was measured by HPGe. The result of this study can be applied as background data enhancing the WAC or disposal concentration limit of the radionuclides in Gyeongju LILW repository.

The sustainability of the nuclear power industry hinges increasingly on the safe, long-term disposal of radioactive waste. Despite significant innovations and advancements in nuclear fuel and reactor design, the quest for a permanent solution to handle accumulating radioactive waste has received comparatively less attention. Conventionally, two widely recognized solidification methods, namely cementation for low and intermediate-level waste and vitrification for high-level waste, have been favored due to their simplicity, affordability, and availability. Recently, geopolymers have emerged as an appealing alternative, gaining attention for their minimal carbon footprint, robust chemical and mechanical properties, cost-effectiveness, and capacity to immobilize a broad spectrum of radionuclides, including radioactive organic compounds. This study delves into the synthesis of metakaolin-based geopolymers tailored for the immobilization of fission products like cesium (Cs) and molybdenum (Mo). The investigation unfolded in two key steps. In the initial step, we optimized the alkali content to prevent the occurrence of efflorescence, a potential issue. Remarkably, as the Na2O/Al2O3 ratio increased from 0.82 to 1.54, we observed significant enhancements in both compressive strength (11.45 to 27.07 MPa) and density (up to 2.23 g/cm3). This suggests the importance of careful adjustment in achieving the desired geopolymer characteristics. The second phase involved the incorporation of 2wt% of Cs and Mo, both individually and as a mixture, into the geopolymer matrix. We prepared the GP paste, which was poured into cylindrical molds and cured at 60°C for one week. To scrutinize the crystallinity, phase purity, and bonding type of the developed matrix, we employed XRD and FTIR techniques. Additionally, we conducted standard compressive strength tests (following ASTM C39/C39M-17b) to assess the stacking durability and robustness of the developed waste form, vital for storage, handling, transportation, and disposal in a deep geological repository. Furthermore, to evaluate the chemical durability, diffusivity and leaching of the GP waste matrix, we employed the ASTM standard Product Consistency Test (PCT: C 1285-02) and American nuclear society’s devised leaching test (ANS 16.1). It is noteworthy that the introduction of Cs and Cs/Mo in the GP matrix led to a reduction of more than 50% and 60% in compressive strength, respectively. This outcome may be attributed to the interference of Cs and Mo with the geopolymerization process, potentially causing the formation of new phases. However, it is crucial to emphasize that both developed matrices exhibited an acceptable normalized leaching rate of less than 10-5 g·m-2·d-1. This finding underscores the promising potential of the GP matrix for the immobilization of cationic and anionic radioactive species, paving the way for more sustainable nuclear waste management practices.

Radionuclides in low- and intermediate-level radioactive wastes from the decommissioning process of nuclear power plants were generally immobilized by cementation methods. Ethylenediaminetetraacetic acid (EDTA), which is extensively used as a decontamination agent, can affect the behaviors of radionuclides immobilized in cement waste forms. In this study, the effects of EDTA contained in simulated radioactive decommissioning wastes on the leaching characteristics of immobilized Co and Cs and the microstructure evolution of cement waste form. Co leaching was accelerated by the formation of Co–EDTA complexes with high mobility and solubility. Cs leaching was hindered by the ion competition with other metal–EDTA complexes for releasing from the cement waste form. Cs leaching was also retarded by carbonated layer at edge of the cement waste form, which process is facilitated by the presence of EDTA. Finally, the effects of EDTA on the leaching characteristics of immobilized Cs and Co and the microstructure evolution of the cement waste form should be considered to ensure the safety of disposal for lowand intermediate-level radioactive wastes.

The mobility of radionuclides is largely determined by their radiological properties, geochemical conditions, and adsorption reactions, such as surface adsorption, chemical precipitation, and ion exchange. To evaluate the safety assessments of radionuclides in nuclear sites, it is essential to understand the behavior and mechanism of radionuclides onto soils. Since nuclear power plants are located in coastal areas, the chemical composition of groundwater can vary depending on the intrusion of seawater, altering the adsorption distribution coefficient (Kd) values of radionuclides. This study examines the impact of seawater on the Kd values of clay minerals for cesium (Cs) and strontium (Sr). The results of Cs+ adsorption experiments showed a broad range of Kd values from 36 to 1,820 mL/g at an initial concentration of 1 mg/L and a high sorption coefficient of 15-613 mL/g at an initial concentration of 10 mg/L. Montmorillonite, hydrobiotite, illite, and kaolinite were ranked in terms of their CEC values for Cs+ adsorption, with hydrobiotite having the highest adsorption at 1 mg/L. The results of Sr adsorption experiments showed a wide range of Kd values from 82 to 1,209 mL/g at an initial concentration of 1 mg/L and a lower adsorption coefficient of 6.68-344 mL/g at an initial concentration of 10 mg/L. Both Cs+ and Sr2+ demonstrated lower Kd values at higher initial concentrations. CEC of clays found to have a significant impact on Sr2+ Kd values. Ca2+ ions showed a significant impact on Sr2+ adsorption distribution coefficients, demonstrating the greater impact of seawater on Sr2+ compared to Cs+. These findings can inform future safety assessments of radionuclides in nuclear sites.

Radioactive contaminants, such as 137Cs, are a significant concern for long-term storage of nuclear waste. Migration and retention of these contaminants in various environmental media can pose a risk to the surrounding environment. The distribution coefficient (Kd) is a critical parameter for assessing the behavior of these contaminants and can introduce significant errors in predicting migration and remediation options. Accurate prediction of Kd values is essential to assess the behavior of radioactive contaminants and to ensure environmental safety. In this study, we present machine learning models based on the Japan Atomic Energy Agency Sorption Database (JAEA-SDB) to predict Kd values for Cs in soils. We used three different machine learning models, namely the random forest (RF), artificial neural network (ANN), and convolutional neural network (CNN), to predict Kd values. The models were trained on 14 input variables from the JAEA-SDB, including factors such as Cs concentration, solid phase properties, and solution conditions which are preprocessed by normalization and log transformation. We evaluated the performance of our models using the coefficient of determination (R2) value. The RF, ANN, and CNN models achieved R2 values of over 0.97, 0.86, and 0.88, respectively. Additionally, we analyzed the variable importance of RF using out-of-bag (OOB) and CNN with an attention module. Our results showed that the initial radionuclide concentration and properties of solid phase were important variables for Kd prediction. Our machine learning models provide accurate predictions of Kd values for different soil conditions. The Kd values predicted by our models can be used to assess the behavior of radioactive contaminants in various environmental media. This can help in predicting the potential migration and retention of contaminants in soils and the selection of appropriate site remediation options. Our study provides a reliable and efficient method for predicting Kd values that can be used in environmental risk assessment and waste management.

Bentonite is a potential buffer material of multi-barrier systems in high-level radioactive wastes repository. Montmorillonite, the main constituent of the bentonite, is 2:1 type aluminosilicate clay mineral with high swelling capacity and low permeability. Montmorillonite alteration under alkaline and saline conditions may affect the physico-chemical properties of the bentonite buffer. In this study, montmorillonite alteration by interaction with synthetic alkaline and saline solution and its retention capacity for cesium and iodide were investigated. The experiments were performed in three different batches (Milli-Q water, alkaline water, and saline water) doped with cesium and iodide for 7 days. Alteration characteristics and nuclide retention capacity of original- and reacted bentonite was analyzed by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM), Nuclear Magnetic Resonance (NMR) and Cation Exchange Capacity (CEC) analysis. From the results, cesium retention occurred differently depending on the presence of competing ions such as K, Na, and Mg ions in synthetic solutions, while iodide was negligibly removed by bentonite. Montmorillonite alteration mainly occurred as cation exchange and zeolite minerals such as merlinoite and mordenite were new-formed during alkaline alteration of the montmorillonite. CEC value of reacted bentonite increased by formation of the zeolite minerals under alkaline conditions.

The removal of cesium (Cs) from contaminated clay minerals is still a challenge due to the limited efficiency of the process. Thus, this study aimed to enhance the removal for Cs+ ions during the conventional acid washing process by incorporating a bead-type adsorbent. Polyacrylonitrile-based nickel potassium hexacyanoferrate (NiFC-PAN) was utilized as the Cs adsorbent to selectively adsorb Cs+ ions in a strongly acidic solution that contained competing ions. To enable easy separation of clay particles and protect the adsorbent from harsh environmental conditions, PAN was deliberately constructed as large beads. The synthesized adsorbent (NiFC/PAN in a 2:1 ratio) displayed high selectivity for Cs+ ions and had a maximum capacity of 162.78 mg/g for Cs+ adsorption in 0.5 M HNO3 solution. Since NiFC-PAN exhibited greater Cs selectivity than the clay mineral (hydrobiotite, HBT), adding NiFC-PAN during the acid washing substantially increased Cs desorption (73.3%) by preventing the re-adsorption for Cs+ ions on the HBT. The acid treatment in the presence of NiFCPAN also significantly decreased the radioactivity of 137Cs-HBT from 209 to 27 Bq/g, resulting in a desorption efficiency of 87.1%. Therefore, these findings suggest that the proposed technique is a potentially useful and effective method for decontaminating radioactive clay.

The magnetic Cs adsorbent functionalized with hierarchical titanium-ferrocyanide were fabricated for the highly efficient magnetic removal of radioactive cesium from water. The new magnetic Cs adsorbent has a core–shell structure that comprises a Fe3O4 core, an interlayer of SiO2, and a titanium-ferrocyanide-shell with hierarchical nanostructure. At first, the magnetic Fe3O4 nanoparticles synthesized via a hydrothermal reaction were coated with SiO2. Then, TiO2 were coated on the surface of SiO2 coated magnetic nanoparticles. Finally, the hierarchical titanium-ferrocyanide composed of 2-dimensional TiFC flakes was fabricated on the surface of core-shell MNP@SiO2@TiO2 microparticles using a TiO2 sacrificial template via a simple reaction with potassium ferrocyanide (FC) based on the Kirkendall-type diffusion. The resulting magnetic Cs adsorbent shows higher adsorption capacity of 416 mg/g than other magnetic Cs adsorbents (below 200 mg/g) because of the increased effective surface area of hierarchical titanium-ferrocyanide. Therefore, our Magnetic Cs adsorbent functionalized with hierarchical titanium-ferrocyanide has excellent potential for the treatment of various 137Cs-contaminated sources.