Behavior Of Cs Research Articles

Applying multiple processes nonequilibrium model to investigate cesium transport in crushed granite

Abstract Understanding the movement of radionuclides (RN) in the subsurface environment is of paramount importance, particularly when it comes to the planning and assessment of facilities devoted to the disposal of radioactive waste. Comprehensive mathematical models serve as indispensable tools in this regard, demanding a profound and thorough understanding of the intricate mechanisms underlying radionuclide transport. The effective application of these models is contingent upon accurately determining the required input parameters. This is a critical aspect to consider given the inherent physical and chemical variations exhibited by the subsurface environment. These variations can induce significant effects on the movement of RNs below ground, potentially altering the predicted outcomes of radionuclide transport. This paper presents the findings of a comprehensive investigation that was conducted utilizing both advective-dispersive experiments (ADE) and multiple processes nonequilibrium (MPNE) inversion. These methodologies were employed using the advanced HYDRUS code, which is highly regarded in the field. The research specifically focuses on the transportation mechanisms of Cesium (Cs), a common radionuclide, in a medium of crushed granite. The study considers varying conditions, including different flow rates and column lengths, to provide a broad understanding of the behavior of Cs. The findings reveal that the transport behavior of Cs is not only influenced by the different flow rates and column lengths but is also significantly affected by the diffusive mass transfer and nonequilibrium sorption. These factors collectively contribute to our understanding of the complex processes involved in radionuclide transport.

Enhanced prediction of Cs removal by CST from Hanford tank waste with K accountability

AbstractThe treatment of Hanford tank waste is one of the most challenging environmental cleanup activities to date. To expedite the processing of liquid waste stored in underground tanks in Washington State it is necessary to remove the significant dose contributor, 137Cs. Crystalline silicotitanate ion exchanger is currently used to remove 137Cs from the aqueous phase of Hanford tank wastes in preparation for vitrification at the Waste Treatment and Immobilization Plant (WTP). Improving the understanding of potassium impacts on ion exchange behavior of Cs will help in the operation of a critical component of one of the most complex treatment processes in the world today. Optimization of this process can result in significant cost savings and less waste production. Toward this effort, a series of batch contact tests varied in potassium concentration were conducted to look at the impact of potassium concentration on Cs distribution. Experimental distribution ratios (Kd) were compared to the distribution ratios predicted using the ZAM model. A significant underprediction of Cs capacity in the presence of potassium was seen with the existing model. A revision of the equilibrium constants was determined and provided a statistically better fit for determining the Cs Kd values in tank waste matrices.

Effects of Large-Scale Wildfires on the Redistribution of Radionuclides in the Chornobyl River System.

Wildfires in radiologically contaminated areas raise significant concerns due to potential radionuclides redistribution and increased public radiation exposure. This study examined the impact of the 2020 Chornobyl wildfire on the redistribution of radionuclides, specifically 137Cs and 90Sr, in the Chornobyl River system. We determined the quantities and speciation of 137Cs and 90Sr in charred residues and soil after wildfires and analyzed the riverine concentrations of these radionuclides based on long-term monitoring data. Our findings indicate that the inventories of 137Cs and 90Sr in the charred residues and soil decreased with increasing distance from the nuclear power plant, which is consistent with the initial deposition patterns. However, the transfer of 137Cs and 90Sr from soil to charred residues did not correspond to the distance, type of contamination source, or fire type. Speciation analysis revealed that the water-soluble fractions of 137Cs and 90Sr in the charred residues were significantly higher than those in the soil, implying increased mobility. Following the wildfires, no significant increase in 137Cs concentration was observed in a river catchment in Chornobyl. However, 90Sr concentrations showed a significant increase, exceeding the permissible levels in drinking water (2 Bq/L) in Ukraine. This increase is attributed to hydrologically driven mobilization processes: (1) during snowmelt in spring and (2) the transport of soluble 90Sr from charred residues and surface soil into the river during high suspended solid concentration events. Collectively, our findings highlight the importance of continuous monitoring of radionuclide dynamics in postwildfire environments to better assess potential radionuclide redistribution and radiation exposure risks. These results provide valuable insights into the behavior of 137Cs and 90Sr in river systems affected by wildfires, contributing to a more accurate understanding of their environmental impacts and potential countermeasures.

Optical, AC conductivity and antibacterial activity enhancement of chitosan-silver nanocomposites for optoelectronic and biomedical applications

This study is aimed to prepare and investigate the optical, electrical and antibacterial activity of the environmentally friendly (green) chitosan (Cs)/silver nanocomposites. TEM demonstrated that AgNPs have a spherical shape with particle size ranged from 3 nm to 25 nm. UV analysis spectra of Cs and Cs/Ag nanocomposites showed that, increasing the content of AgNPs led to a noticeable increase in the values of Urbach energy (E U ) and a dramatic decrease in both the indirect (E ig ) and direct (E dg ) optical bandgap energies. It is found that (E ig ) and (E dg ) are decreased from (4.72/5.31 eV) to (2.47/4.19 eV). The formation of the AgNPs is verified by the existence of surface plasmon resonance (SPR) peak at ∼ (421–450) nm. Wemple-DiDomenico and Sellmeier oscillator models are employed and displayed a clear enrichment in the dispersion energy (E d ) and oscillator energy (E 0) as well as the linear and nonlinear optical parameters of Cs. It is observed that the linear (χ(1)) and nonlinear (χ(3) and n2) parameters are enhanced from 0.083, 0.868 × 10−14 and 1.584 × 10−12 to 0.153, 9.762 × 10−14 and 4.088 × 10−12. The novel results in our study nominate Cs/Ag nanocomposites for applications in linear/nonlinear optical devices. AC conductivity behavior of Cs and Cs/Ag nanocomposites is analyzed based on Jonscher’s law and the analysis showed that the overlapping large polaron tunneling (OLPT) is the dominant conduction mechanism for our samples. It is clear that the values of dielectric constant (ε′) of Cs and Cs/Ag nanocomposites are higher confirming the presence of interface polarization (IP) relaxation. Moreover, it is found that the antibacterial activity of Cs against Gram-negative (P. aeruginosa) and Gram-positive (B. thuringiensis) bacteria is found to be enhanced with increasing the content of Ag NPs. These results suggested that Cs/Ag nanocomposites will be good source for preparing bio-nanocomposites for use in many biomedical and industrial applications.

Sorption behavior of Cs(I), Co(II), and Ni(II) from aqueous solutions using carboxymethyl cellulose/clay sorbent

Sorption behavior of Cs(I), Co(II), and Ni(II) from aqueous solutions using carboxymethyl cellulose/clay sorbent

Chemical implication of the partition coefficient of 137Cs between the suspended and dissolved phases in natural water

After the Fukushima Daiichi nuclear power plant accident, the terrestrial environment became severely contaminated with radiocesium. Consequently, the river and lake water in the Fukushima area exhibited high radiocesium levels, which declined subsequently. The partition coefficient of 137Cs between the suspended sediment (SS) and dissolved phases, Kd, was introduced to better understand the dynamic behavior of 137Cs in different systems. However, the Kd values in river water, ranging from 2 × 104 to 7 × 106 L kg−1, showed large spatiotemporal variability. Therefore, the factors controlling the 137Cs partition coefficient in natural water systems should be identified. Herein, we introduce a chemical model to explain the variability in 137Cs Kd in natural water systems. The chemical model includes the complexation of Cs+ with mineral and organic binding sites in SS, metal exchange reactions, and the presence of colloidal species. The application of the chemical model to natural water systems revealed that Cs+ is strongly associated with binding sites in SS, and a major chemical interaction between 137Cs and the binding sites in SS is the isotope exchange reaction between stable Cs and 137Cs, rather than metal exchange reactions with other metal ions such as potassium ions. To explain the effect of the SS concentration on Kd, the presence of colloidal 137Cs passing through a filter is significant as the dominant dissolved species of 137Cs in river water. These results suggest that a better understanding of stable Cs dissolved in natural water is important for discerning the geochemical and ecological behaviors of 137Cs in natural water.

First-principles study on the diffusion behavior of Cs and I in Cr coating

First-principles study on the diffusion behavior of Cs and I in Cr coating

Investigation of sorption behavior of 137Cs in a river–sea system boundary area after the Fukushima Dai-ichi nuclear power plant accident

The radiocesium (137Cs) distribution between dissolved and particulate phases was examined in river water and coastal seawater as a function of the 137Cs sorption behavior on suspended particles. Dissolved 137Cs activity concentrations in the Tomioka River (salinity <0.1), about 10 km south of Fukushima Dai-ichi Nuclear Power Plant, and in coastal seawater at Tomioka fishery port (salinity >30), Fukushima Prefecture, from June 2019 to October 2021 were 3.6–20 Bq/m3 (geometric mean 11 Bq/m3) and 2.4–86 Bq/m3 (13 Bq/m3), respectively. Although the suspended particle concentration was lower in the river than in seawater, the mean 137Cs activity on suspended particles was 11,000 Bq/kg-dry in the river versus 3200 Bq/kg-dry in seawater. Proportions of ion-exchangeable, organically bound, and refractory fractions of 137Cs on suspended particles were determined by sequential extraction. The ion-exchangeable fraction accounted for 0.3–2.0% (average: 1.2%) and 0.4–1.3% (0.8%) at the river and port sites, respectively. The organically bound fraction accounted for 0.3–4.8% (1.8%) and 0.1–5.5% (2.1%) at the river and port sites, respectively. In both areas, the refractory fraction accounted for >90% of 137Cs. Therefore, the small labile 137Cs fraction on suspended particles in coastal seawater indicates that the mobility of 137Cs to marine biota is quite low. SynopsisThis study is the first to examine radiocesium sorption forms on suspended particles in coastal seawater near the Fukushima Dai-ichi Nuclear Power Plant. It suggests immobility of 137Cs in suspended particles being incorporated to marine biota.

Sorption behavior of cesium ions to Mg-containing calcium silicate hydrate in a co-precipitation process

The sorption behavior of Cs to Mg-containing calcium silicate hydrate (C–S–H) was examined to consider C–S–H formation under the water-saturated conditions around a radioactive waste repository. The amount of Cs sorption was slightly lower for Mg-containing C–S–H than for C–S–H, because Mg leads to a decrease in sorption sites by facilitating the polymerization of silicate chains. However, the apparent sorption distribution coefficient Kd of Cs on C–S–H with a Ca/Si molar ratio of 0.8 and Mg contents up to 20% was estimated to be 3.4–6.1 mL/g. Furthermore, the amount of Cs sorption was not decreased by the presence of Ba. The apparent Kd obtained in this study was about 10 times higher than that conventionally estimated for host rocks in the plutonic repository, indicating that C–S–H retains the effect of Cs immobilization even when it contains Mg.Graphical abstract

First-principles molecular dynamics study on the behaviors of Cs in a mixed system of liquid metal and LiCl-KCl molten salt.

The structure and dynamic properties of Cs in the mixed system of LiCl-KCl molten salt and a liquid metal (Bi and Pb) electrode are investigated through first-principles molecular dynamics simulation. It is found that the dynamic properties of different ions in molten salt could be significantly affected when the liquid metal electrode is coupled and this influence varies with the type of liquid metal applied. The microstructures of the mixed systems of molten salt and liquid metal electrode: MS-Cs-Bi, MS-CsCl-Bi, MS-Cs-Pb, and MS-CsCl-Pb, are also investigated by the bond angle distribution function, Voronoi tessellation analysis, five-fold symmetry parameter, and bond-orientational order parameter. The comparison study of the microstructures of the mixed systems when different liquid metal electrodes are applied provides information on the liquid metal electrode selection when conducting electrolysis. The present study represents the first demonstration of the study of a mixed system of salt and liquid electrode for practical applications and would be greatly beneficial to the development of pyroprocessing of spent nuclear fuel.

Evaluation of the impact of the 137Cs supply from rivers to coastal waters off Fukushima on the 137Cs behavior in seabed sediment

The accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) caused a radioactive contamination in seabed sediment. The 137Cs supply from rivers could be an important process for the long-term behavior of 137Cs in seabed sediment. In this study, a ten-year simulation of the 137Cs behavior in seabed sediment was conducted using an oceanic dispersion model combined with a prediction model of 137Cs behavior in land and river. In the waters north of FDNPP, the simulation results suggested that the 137Cs supply from rivers had a great impact on the concentrations in coastal sediment due to the initial low concentrations in seabed sediment and the large supply of 137Cs from rivers. In the waters near FDNPP and south of FDNPP, the simulation results suggested that the impact of the 137Cs supply on the temporal variation of 137Cs concentration in coastal sediment was relatively small due to the large initial adsorption from seawater. Overall, these results indicated that 137Cs supply from rivers had an impact on the spatiotemporal distribution of 137Cs concentrations in seabed sediment on a decadal time scale and the impact was especially great in the waters north of FDNPP.

Temporal changes of 137Cs concentrations in the Far Eastern Seas: partitioning of 137Cs between overlying waters and sediments

Deep-ocean sediments, similarly to seawater, are important reservoirs of 137Cs, an anthropogenic radionuclide with a relatively long half-live found in the Earth system. To better understand the geochemical behaviour of 137Cs in the ocean, we examined the temporal changes of 137Cs activity concentrations in the overlying waters and in sediments from the Far Eastern Seas (Sea of Japan, SOJ, and Okhotsk Sea, OS) during the period of 1998–2021. The 137Cs activity levels showed exponential changes during the observed period. The decay-corrected change rates of 137Cs in deep waters of SOJ exhibited a slow increase, while 137Cs levels in seawater and sediment in OS decreased gradually. This reflects a topographical difference, as SOJ is a semi-closed sea, whereas OS receives continuously inflow of subarctic waters. It was confirmed that 137Cs released after the Fukushima Dai-ichi Nuclear Power Plant accident was rapidly transported into the deep waters of the SOJ. To elucidate the transfer processes of 137Cs from seawater to sediment, we discussed the temporal changes of the partition coefficients (Kd) of 137Cs between the overlying water and the surface sediment. In shallow areas (< 1500 m water depth), Kd values were almost constant within the sampling periods, although the temporal changes in the Kd values occurred in deeper waters (> 2500 m depth). The Kd values increased with increasing depth, which may reflect a pressure effect as a possible mechanism. These findings suggest that chemical processes may be important factors controlling the transport of 137Cs between seawater and sediment, although more complicated phenomena occurred in deep waters and sediments of the SOJ (> 3000 m depth).

The migration behavior of cesium during plasma gasification melting process of spent radioactive resins by thermodynamic calculation

Plasma gasification melting is an effective method of spent radioactive resin disposal. However, the equilibrium distribution and migration of Cs during the plasma gasification melting process is still unclear. In this study, the volatilization behavior of Cs during the plasma gasification melting process of spent resins was investigated by thermodynamic model. The composition of the stable phase and the release of Cs from the stable phase in the three systems of Cs-C-O, Cs-S-O and Cs-N-O were calculated by HSC Chemistry. The possible composition of Cs during the plasma gasification melting process of spent resins was determined. At the same time, the thermodynamic simulation of spent resins in the temperature range of 300–1800 °C was carried out, and the morphological distribution of Cs during the plasma gasification melting process of spent resins was calculated and analyzed, which will provide theoretical guidance for subsequent experimental research. The results showed that Cs2CO3, Cs2SO4 and Cs2O were identified as the stable phases of each system at 1200 °C in air atmosphere. The existent forms of Cs in the three stages of plasma pyrolysis, gasification and melting are different. In the plasma pyrolysis and melting stage, Cs mainly enters the gas phase in the form of gaseous Cs and CsOH. In the plasma gasification stage, Cs mainly enters the gas phase in the form of gaseous Cs and Cs2SO4. By comparing with the results of some literature, the accuracy of thermodynamic calculation is proved. The migration and transformation law of Cs during the plasma gasification melting process of spent radioactive resins is revealed.

Sorption behaviour of 137Cs and 152+154Eu onto bentonite phosphate modified with nickel: kinetics, isotherms, and chromatographic column application

Abstract Using batch and column procedures, the present work investigated the sorption behaviour of 137Cs and 152+154Eu by bentonite phosphate modified with nickel (BPN) sorbent. The kinetic data obey pseudo-1st-order for 137Cs and follow pseudo-2nd-order for 152+154Eu. Various sorption isotherm models were used to analyze equilibrium data. The thermodynamic functions reflect an endothermic and spontaneous sorption process. HCl (about 95.35 %) and CaCl2 (about 98.13 %) showed the optimum eluents for the complete recovery of both 137Cs and 152+154Eu, respectively. Finally, column data show that 137Cs and 152+154Eu may be loaded on BNP sorbent and separated from an aqueous solution using a variety of HCl concentrations as eluent. The obtianed results revealed that BNP sorbent is suitable for recovering 137Cs and 152+154Eu from low-level radioactive waste effluents (LLW).

Effects of EDTA on the leaching behaviors of Cs(I) and Co(II) from cement waste forms

Cementation is extensively employed for immobilizing radionuclides in low- and intermediate-level radioactive wastes generated during the decommissioning of nuclear power plants. Ethylenediaminetetraacetic acid (EDTA), used as a decontamination agent during the decommissioning process, can be introduced into the cement waste form containing radionuclides. This study investigated the effects of the EDTA present in simulated radioactive decommissioning wastes on the leaching behaviors of Co and Cs immobilized in the cement waste form. Co leaching was facilitated by the formation of highly mobile Co–EDTA complexes. However, Cs leaching was impeded by the competition for leaching with other metal–EDTA complexes. Moreover, the EDTA-induced carbonated layer with a dense pore structure played a crucial role as a retardation barrier for the Cs leaching. The calcite contents of the samples with 8 wt% EDTA were approximately three times higher than those of the samples without EDTA. The introduced EDTA affected the leaching behaviors of both Co and Cs, as well as the microstructure evolution of the cement waste form. Nevertheless, the addition of EDTA had a relatively low positive effect on the efficiency of Cs immobilization, but also an obvious negative effect on the efficiency of Co immobilization, regardless of the concentration of EDTA. Finally, an EDTA dosage of 1 wt% in the cement waste forms containing Co or Cs is suggested as a potential waste acceptance criterion for solidified low- and intermediate-level radioactive waste.

Origin and pathway of a subsurface maximum of 137Cs detected in the winter of 2012 after the Fukushima accident

This study investigates the dispersion behavior of 137Cs and evaluates its origin (atmospheric deposition or direct ocean release) from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident using a Lagrangian particle tracking model. The ocean circulation fields based on the Modular Ocean Model Version 5 (MOM5) were adopted for the simulation. The MOM5 results represented the formation and migration of subtropical mode water (STMW) comparable with observations and reanalysis data. Particularly, anticyclonic eddies south of the Kuroshio extension promoted surface mixing over 300 m in the cooling season. The particle tracking simulation reproduced well the maximum subsurface activity between 142 and 146°E, where STMW is deep owing to anticyclonic eddies, compared to the activity found via measurements conducted around 149°E in the winter of 2012. It also demonstrated that the 137Cs of the tropical and subtropical regions (10–35°N, 142–146°E) in the winter of 2012 almost entirely originated from atmospheric deposition.

Thirty-Year Prediction of 137Cs Supply from Rivers to Coastal Waters off Fukushima Considering Human Activities

The Fukushima Daiichi Nuclear Power Plant accident caused an accumulation of 137Cs in coastal sediment. The 137Cs supply from rivers to the ocean can affect the long-term fate of 137Cs in coastal sediment. Since the Fukushima coastal river basins include large decontaminated and evacuation order areas, considering the decontamination work and resumption of agriculture is important for predicting the 137Cs supply. We conducted a 30-year prediction of the 137Cs supply from the Fukushima coastal rivers to the ocean using a distributed radiocesium prediction model, considering the effects of human activities. In river basins with decontaminated and evacuation order areas, human activities reduced the total 137Cs outflow from agricultural lands, urban lands, and forest areas to the rivers and the 137Cs supply to the ocean by 5.0% and 6.0%, respectively. These results indicated that human activities slightly impacted the 137Cs outflow and supply. The 137Cs supply from rivers impacted by the accident to the coastal sediment was estimated to correspond to 11–36% of the total 137Cs in the coastal sediment in the early phase of the accident. Therefore, the 137Cs supply from rivers to the ocean is important for the long-term behavior of 137Cs in coastal sediment.

Sorption behavior of 137Cs, 152+154Eu and 131Ba from aqueous solutions using inorganic sorbent loaded on talc

Sorption behavior of 137Cs, 152+154Eu and 131Ba from aqueous solutions using inorganic sorbent loaded on talc

Performance of molybdenum vanadate loaded on bentonite for retention of cesium-134 from aqueous solutions

This article studied the sorption behavior of Cs(I) ions from aqueous solutions onto molybdenum vanadate@bentonite (MoV@bentonite) composite. MoV@bentonite has been fabricated using the precipitation method and was characterized by different analytical tools including, FT-IR, XRD, and SEM attached with an EDX unit. The sorption studies applied on Cs(I) ions include the effect of contact time, pH, initial metal concentrations, ionic strength, desorption, and recycling. The experimental results revealed that in the adsorption process carried out after equilibrium time (300 min), saturation capacity has a value of 26.72 mg·g−1 and the sorption of Cs(I) ions is dependent on pH values and ionic strength. Sorption kinetic better fit with the pseudo-second-order model; sorption isotherms apply to Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. Data of thermodynamic parameters indicate that sorption is spontaneous and endothermic. Recycling experiments show that MoV@bentonite could be used for 7 cycles and the best eluant for the recovery of Cs(I) ions is 0.1 M HCl (76.9%). All the obtained data clarify that MoV@bentonite is considered a promising sorbent for the sorption of Cs(I) ions from aqueous solutions.

Efficient and selective removal cesium from strong acidic medium by novel butenyl-calix [4]-crown 6 functionalized millimeter-sized mesoporous carbon spheres sorbent: Experimental and theoretical study

Eliminating the radioactive Cesium from high level waste (HLW) is crucial to avoid the radioactive pollution. Herein, a novel carbon-based recognizable material, butenyl-calix [4]-crown 6 functionalized millimeter-sized mesoporous carbon spheres (ButC[4]C6/MMCs), was prepared via “interpenetrating functionalization” strategy to remove Cs(I) from strongly acidic solution. ButC[4]C6 supramolecular was incorporated into the channels of MMCs and polymerized to form cross-linked IPN structure. The morphology and microstructure of the final product were characterized by SEM, NMR, FT-IR, TG-DSG and N2 adsorption–desorption isotherms. The adsorption behaviors of Cs(I) onto ButC[4]C6/MMCs were systematically investigated. ButC[4]C6/MMCs displayed an astonishing adsorption capacity (55.22 mg g−1), high selectivity and reusability at a low dose (2.0 g L-1) under 3.0 M HNO3 medium. Pseudo-second-order kinetic model, Brouers-Sotolongo model and thermodynamic study revealed that the adsorption process is a spontaneous endothermic chemical and heterogeneous adsorption process. Theoretical study revealed that the Cs(I) was tightly fixed in the calixarene cavity via cation-π interaction. This work proposes an effective approach to selectively remove Cs(I) from HLW by skillfully coupling supramolecular recognizer with millimeter-sized porous material to address radioactive pollution issue.