Removal of cesium radioisotopes from solutions using granulated zeolites

The influence of type of zeolite and the flow rate of solution through the column on the removal efficiency of radioactive cesium ions from solution has been investigated. The analysis of the change in the concentration of cesium ions in the solutions and distribution of cesium ions in the column fillings (granulated zeolites), after passing the solutions through the columns filled with various granulated zeolites (zeolite 4A, zeolite 13X, synthetic mordenite) was performed. On the basis of the results of this study, the conditions for the most efficient removal of cesium ions from solutions have been discussed.     

Mass selective separation applied to radioisotopes of cesium

A technique that uses the intrinsic mass‐based separation capability of a quadrupole mass spectrometer has been used to resolve spectral radiometric interference of two isotopes of the same element. In this work the starting sample was a mixture of ¹³⁷Cs and ¹³⁴Cs and was (activity) dominated by ¹³⁷Cs. This methodology separated and ‘implanted’ ¹³⁴Cs that was later quantified for spectral features and activity with traditional radiometric techniques. This work demonstrated a ¹³⁴Cs/¹³⁷Cs activity ratio enhancement of >4 orders of magnitude and complete removal of ¹³⁷Cs spectral features from the implanted target mass (i.e. 134). Copyright © 2016 John Wiley & Sons, Ltd.     

Uptake of cesium and strontium radioisotopes onto pillared clays

Pillared clays were characterised by thermal analysis and small-angle X-ray scattering. They were then examined for their ability to take up¹³⁷Cs and⁹⁰Sr/⁹⁰Y isotopes as a function of concentration and competing cations (Na⁺, K⁺, NH₄ ⁺, Ca²⁺, Mg²⁺) in the concentration range 10⁻¹ to 10⁻⁴ M. The radioisotope uptakes were quantified byK _d (ml/g) measurements.     

Determination of cesium in seawater by radiochemical methods

Radiochemical methods for the determination of cesium in seawater are described. Preliminary substoichiometric concentration with nickel hexacyanoferrate(II) and tetraphenylborate and application of selective radiochemical techniques are used. The cesium content in Atlantic Ocean samples is 0.74 ± 0.03 μg l^-1. The method is applicable on board ship. The approach should be generally useful.     

An improved method FO the determination of90Sr in large samples of seawater

The determination of⁹⁰Sr in large sample of seawater by its daughter product⁹⁰Y by means of solvent extraction with bis-2-ethylhexyl-phosphoric acid (HDEHP) ini n-heptane leads to²³⁴Th contamination. Two methods are described by which the²³⁸U daughter product²³⁴Th is separated from the Y³⁺ samples, either by a cation exchanger procedure or by a co-recipitation with Zr₃(PO₄)₄.     

Extraction-scintillation method for determining the concentration of radioisotopes

A method is presented for the determination of uranium isotopes in waters by the scintillation-extraction method. By extraction with tributyl phosphate (TBP) in toluene as a liquid scintillator it was established that the presence of TBP in the solvent does not affect the photo-yield substantially. The optimum measuring conditions and the sensitivity of the method have been studied.     

Determination of light hydrocarbons dissolved in seawater

A practical method for the on board determination of light (C1-C4) hydrocarbons dissolved in seawater has been developed. The gaseous hydrocarbons in seawater were extracted quickly with a vacuum sparge tower and determined gas chromatographically. By using two cryogenic columns at dry ice-ethanol temperature (-80 degrees C) connected in series, it was possible to completely collect the hydrocarbons. The precision and sensitivity were comparable to that of previous methods. The analysis was completed within 45 min for one sample and the sample volume was 500 ml. The method was successfully applied to the northern North Pacific water collected in summer 1997. The concentrations of C2-C4 hydrocarbons in surface seawater ranged from several to several tens pmol l(-1), within the range of concentrations in previous studies.     

Preparation and evaluation of composite ion-exchanger for the removal of cesium and strontium radioisotopes

Preparation conditions of composite ion-exchanger based on stannic molybdophosphate (SMP) and poly-acrylamide (PAA) have been described. Batch distribution coefficients for some ions were investigated at 25 °C. Sodium ion exchange capacity and breakthrough curves of cesium and strontium ions have also been determined. The results obtained from the experiments showed that the selectivity of SMP-PAA for cesium and strontium was greater than for other ions. Adsorption amounts of both ions were higher than 99% in demineralized water and their uptake rate were relatively rapid.     

Sorption characteristics of an economical sorbent material used for removal radioisotopes of cesium and europium

Application study for the evaluation of sorption characteristics of sawdust as an economical sorbent material used for decontamination of radioisotopes cesium and europium from aqueous solution has been carried out in the present work. In this respect, sawdust (untreated and treated by HNO₃) has been prepared from the commercial processing of wood for furniture production. Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by N₂ adsorption and DFT software. Radiotracer method onto sawdust from aqueous solutions was studied in a batch technique with respect to pH, contact time, temperature. The kinetics of adsorption of Eu³⁺ and Cs⁺ have been discussed using five kinetic models namely, pseudo-first-order model, pseudo-second-order model, Elovich equation, intraparticle diffusion model, and modified Freundlich equation that have been tested in order to analysis the experimental data. Kinetic parameters and correlation coefficients were determined. It was shown that the second-order kinetic equation could describe the sorption kinetics for two metal ions. The metal uptake process was found to be controlled by intraparticle diffusion. Thermodynamic parameters, such as ΔH, ΔG and ΔS, have been calculated by using the thermodynamic equilibrium coefficient obtained at different temperatures. The obtained results indicated that endothermic nature of sorption process for both ^152+154Eu and ¹³⁴Cs onto sawdust.     

Isolation of a suite of radionuclides from large volumes of seawater

A suite of radio-nuclides is isolated with favorable yields from seawater by precipitating with ammonium hydroxide only a fraction of the magnesium inherent in the medium. A large sample volume apparatus was assembled which provides for the separation of the precipitate from 3000 liters of sample in less than 15 min.     

Rapid determination of actinides in seawater samples

A new rapid method for the determination of actinides in seawater samples has been developed at the Savannah River National Laboratory. The actinides can be measured by alpha spectrometry or inductively-coupled plasma mass spectrometry. The new method employs novel pre-concentration steps to collect the actinide isotopes quickly from 80 L or more of seawater. Actinides are co-precipitated using an iron hydroxide co-precipitation step enhanced with Ti⁺³ reductant, followed by lanthanum fluoride co-precipitation. Stacked TEVA Resin and TRU Resin cartridges are used to rapidly separate Pu, U, and Np isotopes from seawater samples. TEVA Resin and DGA Resin were used to separate and measure Pu, Am and Cm isotopes in seawater volumes up to 80 L. This robust method is ideal for emergency seawater samples following a radiological incident. It can also be used, however, for the routine analysis of seawater samples for oceanographic studies to enhance efficiency and productivity. In contrast, many current methods to determine actinides in seawater can take 1–2 weeks and provide chemical yields of ~30–60 %. This new sample preparation method can be performed in 4–8 h with tracer yields of ~85–95 %. By employing a rapid, robust sample preparation method with high chemical yields, less seawater is needed to achieve lower or comparable detection limits for actinide isotopes with less time and effort.     

Rapid determination of radiostrontium in seawater samples

A new method for the determination of radiostrontium in seawater samples has been developed at the Savannah River National Laboratory (SRNL) that allows rapid pre-concentration and separation of strontium and yttrium isotopes in seawater samples for measurement. The new SRNL method employs a novel and effective pre-concentration step that utilizes a blend of calcium phosphate with iron hydroxide to collect both strontium and yttrium rapidly from the seawater matrix with enhanced chemical yields. The pre-concentration steps, in combination with rapid Sr Resin and DGA Resin cartridge separation options using vacuum box technology, allow seawater samples up to 10 L to be analyzed. The total ⁸⁹Sr + ⁹⁰Sr activity may be determined by gas flow proportional counting and recounted after ingrowth of ⁹⁰Y to differentiate ⁸⁹Sr from ⁹⁰Sr. Gas flow proportional counting provides a lower method detection limit than liquid scintillation or Cerenkov counting and allows simultaneous counting of samples. Simultaneous counting allows for longer count times and lower method detection limits without handling very large aliquots of seawater. Seawater samples up to 6 L may be analyzed using Sr Resin for ⁸⁹Sr and ⁹⁰Sr with a minimum detectable activity (MDA) of 1–10 mBq/L, depending on count times. Seawater samples up to 10 L may be analyzed for ⁹⁰Sr using a DGA Resin method via collection and purification of ⁹⁰Y only. If ⁸⁹Sr and other fission products are present, then ⁹¹Y (beta energy 1.55 MeV, 58.5 day half-life) is also likely to be present. ⁹¹Y interferes with attempts to collect ⁹⁰Y directly from the seawater sample without initial purification of Sr isotopes first and ⁹⁰Y ingrowth. The DGA Resin option can be used to determine ⁹⁰Sr, and if ⁹¹Y is also present, an ingrowth option with using DGA Resin again to collect ⁹⁰Y can be performed. An MDA for ⁹⁰Sr of <1 mBq/L for an 8 h count may be obtained using 10 L seawater sample aliquots.     

Separation of actinides, cesium and strontium from marine samples using extraction chromatography and sorbents

Plutonium concentrations in seawater of the western North Pacific observed over the period from 1985 to 1997 are reported. In the 1990's, surface ^239,240Pu concentrations in the western North Pacific were relatively homogeneous (around 3 mBq/m³), although surface ^239,240Pu before the 1980's showed a latitudinal distribution with highs in mid-latitudes and lows in the Equatorial region. Temporal variations of surface ^239,240Pu in three different sea areas were examined. In mid-latitudes (21°–35°N), surface ^239,240Pu exponentially decreased with an apparent residence time of 9.9 years, whereas in the subtropical and Equatorial areas, decrease rates of surface ^239,240Pu were slower than in mid-latitudes. The vertical profiles of ^239,240Pu in mid-latitudes of the western North Pacific showed a surface minimum, a subsurface maximum and decreased with increasing depth. The water column inventory of ^239,240Pu at the station (27°48'N, 130°44'E) was calculated to be 113 Bq/m².     

Determination of a strong organic ligand dissolved in seawater: Thorium-complexing capacity of oceanic dissolved organic matter

Studies have been made of loose water tritium (LWT) distribution and behavior in the soil samples taken from the region within a radius of 2 km to the HWRR stack of CIAE. The analytical results show that the LWT concentrations in most soil samples of the region are in the range from 24.8 Bq/l (3.6 Bq/kg) to 116 Bq/l (16.0 Bq/kg) with an average value of 58.1±24.8 Bq/l (10.3±4.5 Bq/kg). There are two areas with a higher LWT content; the first one (4.61 · 10⁴ m²) is located near HWRR with ahighest LWT concentration of 287 Bq/l (55.8 Bq/kg) and the second one (3.27 ·10⁵ m²) is located near Lab. A with a highest LWT concentration of 2.35 · 10⁴ Bq/l (2.56 · 10³ Bq/kg). It is estimated that the LWT inventories deposited in soil of the two areas are about 1.52 · 10⁹ Bq and 1.42 · 10¹⁰ Bq, respectively. The analytical results have been evaluated by comparing the possible tritium intake of the human body with the annual limit of intake recommended by ICRP, it can be concluded that the operations of all the nuclear facilities releasing tritium in CIAE are safe without causing any notable tritium contamination.     

Sorption of cesium on montmorillonite and effects of salt concentration

The sorption behavior of cesium on montmorillonite type clay was studied by using radioactivity measurements. Concentrations of Cs⁺ ions ranged from 10^–6 to 10^–2M. Cesium retention reduced with increasing salt concentration which was varied between 10^–4 and 10^–1M. Selectivity coefficients K_Cs–Na for the exchange between Cs and Na were calculated for different equivalent fractions of Cs on the solid phase. Using theK _Cs–Na values, free energy change was found to be 7.8 kJ/mol. The data could be fitted to a Freundlich isotherm, and empirical Freundlich parameters enabled the generation of a site distribution function. By fitting the data to the Dubinin-Radushkevich (D-R) isotherm, a mean energy of sorption of 8.6 kJ/mole was calculated which corresponds to the energy of ion exchange reactions. The values of energy changes calculated by using two different methods were in good agreement.     

On-line concentration and fluorescence determination HPLC for polycyclic aromatic hydrocarbons in seawater samples and its application to Japan Sea

An on?line concentration and fluorescence determination HPLC for polycyclic aromatic hydrocarbons (PAHs) in seawater was proposed. An online concentration column packed with octadecyl polyvinyl alcohol polymer, a pump and a column switching valve were introduced in the conventional HPLC with a fluorescence detector. Only 1.0-100?mL seawater sample was introduced into the concentration column at 1.0?mL?min(-1) without any other pretreatment except filtration. Then the trapped PAHs totally flew into the separation column and eluted separately to be detected fluorogenically. The proposed method had good linearity with correlation coefficients (r) ranged from 0.951 to 0.998, and limits of detection ranged from 0.002 to 0.50?ng?L(-1) for 15 PAHs as 100?mL seawater was loaded. The sensitivity of the method was 10 to 100 times higher than those reported by other works. The proposed method was applied to the determination of PAHs in the seawater samples collected in the Japan Sea with satisfactory results and to check the present benzo[a]pyrene concentration at the beaches in Noto peninsula, Japan polluted with C-heavy oil spilled from the tanker in 1997.     

Combining reverse osmosis and pulsed electrical current electrodialysis for improved recovery of dissolved organic matter from seawater

Dissolved organic carbon (DOC) in the oceans is one of the largest dynamic reservoirs of carbon on earth, comparable in size to the atmospheric reservoir of carbon (as CO₂) in the atmosphere, or to the amount of carbon in all terrestrial and aquatic biota. The concerted efforts of earth scientists, atmospheric scientists, and biologists who study global biogeochemical cycles and the earth's climate have yielded a rather detailed understanding of carbon in the atmosphere and in biota. Marine dissolved organic matter (DOM) is far less well characterized, principally because it exists as a highly diluted mixture of perhaps millions of organic compounds in a highly saline aqueous solution. Prior to 2007, only around 1/3 of marine DOM was typically recovered from seawater for research purposes, regardless of the method of isolation. In 2007, reverse osmosis (RO) and electrodialysis (ED) were coupled to achieve recoveries of 64–93% of marine DOM. The level of residual salts in the concentrated samples, however, still precluded the characterization of marine DOM by solid-state NMR, mass spectrometry, or even elemental analysis. This paper describes a major improvement to the RO/ED method, in which pulsed ED is used (at sea) to reach roughly 100-fold greater removal of salts compared to non-pulsed ED while maintaining comparable recoveries of DOM.     

Improved accuracy of determination of dissolved silicate in seawater using absorption spectrometry

We studied to develop a certified reference material of seawater for nutrient analysis whose relative combined standard uncertainty for dissolved silicate was <0.5 %. In order to precisely measure the content of dissolved silicate in seawater, widely used absorption spectrometry with the so-called molybdenum blue was investigated as one of the highly sensitive determination methods. For the absorption spectrometry, a batch mode and a continuous flow analysis (CFA) mode were used and the characteristics of the calibration curves in the both modes were examined in detail. The calibration curve in the batch mode could be explained by a first-order regression line, whereas that in the CFA mode fitted to a second-order regression line. Therefore, for measuring the silicate content of seawater whose matrix depends on its origin, a standard addition method in a batch mode is preferable, though strict control of the compositions of the solutions for the standard addition calibration curve are greatly important for getting good linearity of the curve. In addition, in the case of the standard addition method, it is important to measure the blank value including the background; in the present study, the origins related to the blank were discussed and evaluated. The relative combined standard uncertainty of 0.48 % could be achieved for the measurement of content of 28 μmol/kg silicate in seawater, providing that the volume ratio between each of the molybdenum blue colorimetric reagents and the seawater was kept constant among all the solutions for the standard addition calibration curve. The procedure was validated using artificial seawater with a known concentration of silicate. Such highly improved precision and trueness which reaches the recent target of the community related to analysis of nutrients in seawater is reported for the first time. The developed procedure will provide a good way of validation for the analysts who need measurement with high precision and trueness on the content of silicate in seawater and other samples.     

Fast determination of gold in large mass samples of gold ores by photoexcitation reactions using 10 MeV bremsstrahlung

The determination of gold is based on the photoexcitation reaction ¹⁹⁷Au(γ,γ’)^197mAu with the half-life of 7.73 seconds and energy of emitted gamma-rays of 279 keV. Three 100 ml aliquots of coarsely ground Au-ore (grains <2 mm) corresponding to ca. 150–180 g were irradiated for 20 seconds with bremsstrahlung of maximum energy 10 MeV produced by a microtron at the electron beam current of 30–40 μA, 1–10 times reactivation was applied. After 3 seconds of decay, samples were measured for 20 seconds using scintillation or semiconductor gamma-spectrometry with the detection limits for an ideal sample down to 0.5 μg·g⁻¹ and 0.1–0.2 μg·g⁻¹ of Au, respectively. Content of U and Th undergoing photo-fission increases the detection limits several times.