Determination of nanogram amounts of cesium by a concentration-dependent distribution method

Paper impregnated with Prussian blue sorbs cesium in low concentration to a different extent if varying initial concentrations of cesium are present. This dependence can be employed for the determination of submicrogram amounts of cesium. The selectivity and precision of the method are discussed. The method is applied to the determination of specific activity in “carrier-free” ¹³⁷Cs samples.     

有机铯化合物对人红细胞的跨膜行为研究

采用石墨炉原子吸收法检测氯化铯、天冬氨酸铯、3,5-二硝基水杨酸铯、5-氨基四唑铯的跨膜量，探讨有机铯化合物的跨膜机理以及阴阳离子间的相互作用对铯跨膜方式的影响。结果表明：铯化合物可通过多种方式跨膜，并具有动力学饱和特征；3,5-二硝基水杨酸铯、5-氨基四唑铯中有机阴离子的存在使铯很难以CsCO₃^-的形式依靠阴离子通道跨膜，NaHCO₃的加入有利于天冬氨酸铯中铯的跨膜；Ca²⁺通道抑制剂硝苯地平在日光下的降解产物促进了氯化铯中Cs⁺的跨膜但抑制了其他铯化合物中Cs⁺的跨膜。     

Interaction of the cesium cation with mono-, di-, and tricarboxylic acids in the gas phase. A Cs+ affinity scale for cesium carboxylates ion pairs

Humic substances (HS), including humic and fulvic acids, play a significant role in the fate of metals in soils. The interaction of metal cations with HS occurs predominantly through the ionized (anionic) acidic functions. In the context of the effect of HS on transport of radioactive cesium isotopes in soils, a study of the interaction between the cesium cation and model carboxylic acids was undertaken. Structure and energetics of the adducts formed between Cs⁺ and cesium carboxylate salts [Cs⁺RCOO⁻] were studied by the kinetic method and density functional theory (DFT). Clusters generated by electrospray ionization mass spectrometry from mixtures of a cesium salt (nitrate, iodide, trifluoroacetate) and carboxylic acids were quantitatively studied by CID. By combining the results of the kinetic method and the energetic data from DFT calculations, a scale of cesium cation affinity, CsCA, was built for 33 cesium carboxylates representing the first scale of cation affinity of molecular salts. The structural effects on the CsCA values are discussed.     

Separation du cesium et du baryum des terres rares dans la source d’ions d’un separateur electromagnetique d’isotopes

In a previous work we studied the separation of cesium from a lanthanum target bombarded by protons in the thermoionic ion source of an electromagnetic isotope separator. After irradiation the principal elements found in the targets were Cs, Ba, Ce and La. We have extended this method to the separation of cesium and barium from metallic lanthanum targets and from lanthanum oxides. It is based on the thermoionization efficiency and on the behaviour of the element studied in the heated cavity, which depends on its volatility if it is under metallic form, and on its reduction and on the volatility of resulting compounds if it is under compound form. In the metallic system we obtained on the collector successively cesium and barium with respective overall yields of about 5% and 0.2%. In the oxide system, we obtained cesium as Cs⁺ ions and simultaneously barium as BaO⁺ ions which are separated from Ba⁺ by 16 masses avoiding the interference with cesium isotopes. The overall yield of the barium separation is about 0.2%. A discussion on the value of barium ionization potential is given.      

Sorption of radiocesium on soils in the presence of electrolytes

The influence of background electrolytes (KCl, NH₄Cl, CTABr) in different concentrations on the sorption ability of radiocesium by measuring the distribution coefficient has been studied. Sorption isotherms of cesium for characterization of soil sorption ability were used. Sorption of cesium depends on its concentration and at least three different sorption sites are active in the sorption process. In the case of low cesium concentration, two very selective sites with high distribution coefficients are responsible for the sorption. With increasing cesium concentration in the aqueous phase, distribution coefficient is decreasing. Frayed edge sites of illite in soil and exchangeable potassium are probably responsible for nonlinear isotherms at low cesium concentrations. From sorption isotherms and determination of potassium by activation analysis, it was found that the capacity of very selective sites for different concentrations of background electrolyte was up to 7 mmol·kg^–1.     

A complementary cesium coolant concentration ratio for localizing defective PWR fuel rods during reactor operation

Rough techniques for pinpointing defective fuel pins during actual reactor operation were developed for nuclear power plants. These techniques are based on various fission product concentration ratios. Here, a new cesium concentration ratio,¹³⁴Cs/¹³⁶Cs, was tested in combination with the more usual cesium ratio¹³⁴Cs/¹³⁷Cs. This new cesium ratio confirmed the conclusions drawn from the ratio¹³⁴Cs/¹³⁷Cs and provided some additional information on the location of the defective fuel rods. Application of this second cesium ratio improves the reliability of the rough localization method.     

Rapid method to determine 89/90Sr in steel samples

The sorption and diffusion behavior of cesium was studied to support the interpretation of the ongoing in-situ experiments in the Olkiluoto test site. The distribution coefficients of cesium in the Olkiluoto pegmatitic granite, veined gneiss and their main minerals were obtained by batch sorption experiments and the diffusion of cesium was studied in rock cubes. The results were modelled with PHREEQC and Comsol Multiphysics. The distribution coefficients of cesium were largest in biotite and veined gneiss. The effective diffusion coefficients of cesium from the diffusion model were 3 × 10⁻¹³ m² s⁻¹ for veined gneiss and 4 × 10⁻¹³ m² s⁻¹ for pegmatitic granite.

     

Syntheses and crystal structures of three cesium salts: Cesium 5-sulfosalicylate, cesium 3,5-dinitrosalicylate and cesium 2,4-dinitrophenoxide monohydrate

In an attempt to probe a potential template role of the large alkali-metal cation cesium in organization of biorelevant ligands, 5-sulfosalicylate, 3,5-dinitrosalicylate and 2,4-dinitrophenol complexes of cesium were prepared and structurally investigated. The structures of cesium 5-sulfosalicylate, cesium 3,5-dinitrosalicylate and cesium 2,4-dinitrophenoxide monohydrate have been determined through X-ray diffraction analysis. The 5-sulfosalicylate anion has lost the proton at the −SO₃H group while the 3,5-dinitrosalicylate anion at −COOH group but both retains the usual intermolecular hydrogen bond between phenolic and carboxylic oxygen. In cesium 2,4-dinitrophenoxide monohydrate, the Cs⁺ cation is 12-coordinate by O atoms in anions and water molecules while the metal atoms in cesium 5-sulfosalicylate and cesium 3,5-dinitrosalicylate have coordination numbers 10 and 11, respectively, with an irregular coordination sphere made up exclusively of oxygen atoms. Even more in cesium 2,4-dinitrophenoxide monohydrate, the water molecules are in rare triply bridging positions between these cations. Both complexes have layer structures containing the cations and polar groups of the ligands in core domains sandwiched by the aromatic rings above and below. The organization of all layer structures appears to be governed mainly by steric effects and electrostatic forces with very little directional influence of the cations.     

Factors affecting interaction of radiocesium with freshwater solids

The paper aims at the analysis of principal factors affecting the interaction of radiocesium with freshwater solids, important for the migration of radiocesium in rivers. Uptake of radiocesium by bottom sediments and suspended solids from small streams was studied as a function of pH and composition of aqueous phase, of the concentration of cesium in water and of the composition of freshwater solids, using laboratory model experiments. pH had negligible effect on the uptake in the pH range 5–9, the uptake decreased at pH values less than 3–5 depending on the nature and concentration of the solids. Addition of cations suppressed the uptake in the order K⁺>Na⁺>Ca²⁺, the suppression began at 0.001, 0.01 and 0.1 mol.dm^?3 concentration, respectively. Increase in cesium concentration in water caused a decrease of radiocesium uptake, but at very low concentrations of cesium combined with higher concentration of sediment (2g·dm^?3) the uptake was independent of cesium concentration. Removal of carbonates, oxidic coatings and organic matter from a sediment did not affect the sorption properties of the sediment. The nature of the effects found confirms that cesium is sorbed mainly by clay components of freshwater solids. Results obtained are compared with literature data and conclusions are drawn on the importance of the factors studied for modelling of radiocesium migration in rivers.     

A new method for the radiochemical separation of rubidium and cesium

The analytical reactions of bismuth iodide and stannic chloride with cesium and rubidium are used for the radiochemical separation of these two elements. The method consists in precipitating potassium, rubidium and cesium as their cobaltinitrites, selective isolation of cesium as cesium bismuth iodide from glacial acetic acid, and subsequent separation of rubidium from potassium as chlorostannate from conc. HCl. The results obtained by the present method for the rubidium and cesium contents of the different U.S.G.S. standard rock samples are compared with those reported using methods of comparable accuracy. The suitability of the method for the analysis of fall-out samples for their radiocesium (¹³⁷Cs) contents has been demonstrated.     

Composite ion exchanger with ammonium molybdophosphate and its properties

An organic binding polymer based on polyacrylonitrile (PAN) was used for the preparation of the composite exchanger containing ammonium molybdophosphate (AMP) as the active component. Due to the improvement of granulometric properties of powdered AMP with a binding polymer, an exchanger suitable for the application in column operations was prepared. Study of the properties of the exchanger AMP-PAN proved that kinetics of cesium sorption, capacity of the exchanger for cesium and desorption of cesium are not influenced by the binding polymer. The composite exchanger AMP-PAN described is therefore suitable for the selective separation and concentration of cesium and purification of radioactive wastes from¹³⁷Cs.     

Catalytic Effect of Cesium Cation Adduct Formation on the Decarboxylation of Carboxylate Ions in the Gas Phase

The effect of Cs⁺ ligation on the decarboxylation of malonic acids (unsubstituted and methyl‐, dimethyl‐, ethyl‐, and phenyl‐substituted) in their carboxylate form was studied in the gas phase using tandem mass spectrometry. The study is based on the comparison of the decarboxylation of the bare monoanion (hydrogen malonates) and of the cesium adduct of the cesium salt (Cs⁺[cesium hydrogen malonates]) under collisional activation. Energy‐resolved dissociation curves of the negative and positive ions exhibit major differences. Decarboxylation of the cationic adducts of substituted malonic acid salts occurs at significantly lower collisional activation than for the corresponding bare hydrogen malonate anions. The conclusions from these experiments are supported by DFT calculations. The calculated activation parameters (enthalpy and Gibbs energy) confirm that the cesium cation coordination assists the decarboxylation of the carboxylate form.     

Emission intensity of cesium in flames of various gas compositions

The emission intensity of cesium at 852.1 nm has been studied in hydrogen flames burning with various mixtures of oxygen and nitrogen. A significant maximum was observed in the relative emission intensity of cesium at an oxygen to nitrogen ratio of 3:2 in the aspirating gas. The effect of Rb⁺, K⁺, Li⁺, Na⁺, and NH₄⁺ ions on cesium emission is much less pronounced in this optimum flame than in a pure oxy-hydrogen flame. The optimum flame (60% oxygen) yields a significantly better calibration curve than can be obtained in either the normal air-hydrogen or oxyhydrogen flame for 0–12 p.p.m. cesium concentrations; the graph is linear over this concentration range.     

The effect of dehydration on the position of cesium cations in the structure of CsNaFAU(Y) studied by powder X-ray diffraction and magic-angle spinning NMR spectroscopy

The influence of dehydration on the position of sodium and cesium cations obtained by ion exchange in the structure of FAU(Y) was studied by powder X-ray diffraction using synchrotron radiation and ²³Na and ¹³³Cs magic-angle spinning NMR spectroscopy. The sodium and cesium cations were found to be mobile in the hydrated samples. In dehydrated zeolites CsNaFAU(Y), cesium is predominantly localized in four crystallographic ion-exchange positions located in the large cavities and sodalite cages.     

Fast concentration of dissolved forms of cesium radioisotopes from large seawater samples

The method developed for cesium concentration from large freshwater samples was tested and adapted for analysis of cesium radionuclides in seawater. Concentration of dissolved forms of cesium in large seawater samples (about 100 L) was performed using composite absorbers AMP-PAN and KNiFC-PAN with ammonium molybdophosphate and potassium–nickel hexacyanoferrate(II) as active components, respectively, and polyacrylonitrile as a binding polymer. A specially designed chromatography column with bed volume (BV) 25 mL allowed fast flow rates of seawater (up to 1,200 BV h^?1). The recovery yields were determined by ICP-MS analysis of stable cesium added to seawater sample. Both absorbers proved usability for cesium concentration from large seawater samples. KNiFC-PAN material was slightly more effective in cesium concentration from acidified seawater (recovery yield around 93 % for 700 BV h^?1). This material showed similar efficiency in cesium concentration also from natural seawater. The activity concentrations of ¹³⁷Cs determined in seawater from the central Pacific Ocean were 1.5 ± 0.1 and 1.4 ± 0.1 Bq m^?3 for an offshore (January 2012) and a coastal (February 2012) locality, respectively, ¹³⁴Cs activities were below detection limit (<0.2 Bq m^?3).     

An XPS Study of the Promotion of Ru-Cs/Sibunit Catalysts for Ammonia Synthesis

The nature of surface cesium compounds in cesium-modified ruthenium-Sibunit catalysts for ammonia synthesis was studied by X-ray photoelectron spectroscopy (XPS). It was found that, on the reduction of promoted catalysts, cesium was incorporated into the micropores of Sibunit to form quasi-intercalation cesium-carbon bonds. In this case, the chemical state of cesium was close to its state in cesium suboxides. The subsequent interaction with atmospheric oxygen resulted in the oxidation of cesium, which occurred as cesium peroxide and cesium superoxide in the oxidized samples. Ruthenium occurred in a metallic state in the reduced samples. The activity of a Ru-Cs⁺/C(1) sample was higher than that of inactive Ru-Cs⁺/C(2). This is a consequence of the higher surface concentration of ruthenium, which is most likely due to an increase in the dispersity of metal particles, as well as of the higher probability of the interaction between the promoter and the active component due to a symbatic increase in the surface concentrations of both ruthenium and cesium.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 635–641.Original Russian Text Copyright © 2005 by Larichev, Prosvirin, Shlyapin, Shitova, Tsyrul’nikov, Bukhtiyarov.     

Solid electrolytes with cesium cation conductivity in the Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>-TiO<Subscript>2</Subscript>-Cs<Subscript>2</Subscript>O system

Solid solutions based on cesium monogallate CsGaO₂ are synthesized in the Ga₂O₃-TiO₂-Cs₂O system. Their crystalline structure and also temperature and concentration conductivity dependences are studied. The cesium cation character of conductivity is confirmed. The most conducting samples contain an excess of cesium oxide and have the structure of high-temperature γ-modification of KAlO₂. Their specific conductivity is (5.0–6.7) × 10^?3 S cm^?1 at 400 °C, (2.5–5.0) × 10^?2 S cm^?1 at 700°C at the activation energy of 33–35 kJ/mol^?1.     

Improved cesium sensitivity in electrothermal atomic absorption spectrometry

The sensitivity for cesium determination by electrothermal atomic absorption spectrometry is improved four-fold by the addition of a large excess of potassium nitrate. Zeeman background corrections is used to compensate for the large non-specific absorption signal resulting from the potassium. The characteristic concentration and detection limit are 0.44 and 2 μg l^?1, respectively, and the coefficient of variation is 2% at the 50 μg l^?1 level. The procedure is suitable for the rapid determination of cesium in leach solutions from nuclear waste fixation experiments.     

The effect of the synthesis method on the parameters of pore structure and selectivity of ferrocyanide sorbents based on natural minerals

Ferrocyanide sorbents were obtained via thin-layer and surface modification of natural clinoptilolite and marl. The effect of modification method on surface characteristics of these sorbents and their selectivity for cesium was studied. It was shown that the modification resulted in an increase of selectivity of modified ferrocyanide sorbents to cesium as compared with the natural clinoptilolite in presence of Na⁺, as well as in an increase of cesium distribution coefficients in presence of K⁺. The nickel–potassium ferrocyanide based on the clinoptilolite showed the highest selectivity for cesium at sodium concentrations of 10^?4—2 mol L^?1: cesium distribution coefficient was lg K _d = 4.5 ± 0.4 L kg^?1 and cesium/sodium separation factor was α(Cs/Na) = 250. In the presence of NH₄ ⁺, all modified sorbents showed approximately equal selectivity for ¹³⁷Cs. Probable applications of the sorbents were suggested.     

Adsorption studies of cesium on potassium copper nickel hexacyanoferrate(II) from aqueous solutions

Adsorption of cesium from aqueous solutions on potassium copper nickel hexacyanoferrate(II) (KCNF) has been investigated in batch experiments and optimized as a function of concentration of acids, salts and adsorbate using a radiotracer technique. The results are presented in terms of distribution coefficient, K_d (ml·g^–1). The uptake of cesium obeys a Freundlich adsorption isotherm over the concentration range of 3.7 to 37 mmol·l^–1 with b values of 0.77, 0.68 and 0.56 at temperatures of 293, 313, 333 K, respectively. The Langmuir adsorption isotherm is followed in the concentration range of 15 to 75 mmol·l^–1 in the same temperature range. The values of limiting adsorption concentration (C_m) have been found to be 2.58, 2.44 and 2.32 mmol·g^–1. The heat of adsorption was calculated as 26.43 kJ·mol^–1. The influence of a number of anions and cations on cesium retention has also been studied. Column experiments have been performed and breakthrough have been obtained under different operating conditions. The low cesium capacity of 1.1 mmol·g^–1 has been obtained under dynamic conditions as compared to batch experiments. Desorption of cesium from the column has been achieved (45.4%) by nitric acid solution of 8M concentration at a flow rate of 0.5 ml·min^–1.