New method for90Sr determination in liquid samples

A method has been developed for measuring⁹⁰Sr activity in liquid samples. After concentrating strontium from the sample by coprecipitation with calcium phosphate, the residue is dissolved in 8N HNO₃ and passed through an extraction chromatographic column (Sr.Spec) containing a new material that selectively retains strontium. This is eluted from the column with 0.05N HNO₃ and counted by liquid scintillation. Measurement is performed using a double window method, that allows a rapid and single determination of⁹⁰Sr.     

An improved method for technetium determination in environmental samples

Summary The recent developments of extraction chromatography and ICP-MS made easier the determination of ⁹⁹Tc in environmental samples. However, in the non-contaminated area, a pre-concentration procedure is necessary, because usually a large amount of sample is used for analysis. In this study, the ferrous ion (Fe²⁺) added as a reductant can make chemical yield from 50 to 80%, when larger than 100 liter water samples or 500 g soil samples are analyzed. The extraction chromatography with TEVA resin (EIChrom) and the measurement by ICP-MS have been developed using ^95mTc and ¹⁰³Ru as yield tracers. Detection limits of 3σ are 0.054 mBq/kg for 500 g soil and 0.032 µBq/lfor 500 l water. A pond named Hinotani, Mie Prefecture in the central part of Japan, was selected to be investigated as a natural system in a non-contaminated area. Surface soil near this pond, pond water and sediment were collected and analyzed for ⁹⁹Tc. In a high fall-out area, Okuetsu, Fukui Prefecture forest soil was collected and analyzed. The ⁹⁹Tc in the surface (0-5 cm) was 10.5±0.8 mBq/kg. The ⁹⁹Tc in Hinotani surface (0-5 cm) soil were 0.77±0.06 mBq/kg less than in Okuetsu. Technetium-99 has been determined in pond water, sediment (0-5 cm) and shrimps in the Hinotani pond, 0.25±0.02 mBq/l, 3.3±0.3 mBq/kg, 1.5±0.2 mBq/kg, respectively.     

On the reliability of a rapid method for the determination of90Sr in natural samples

A method for the rapid evaluation of⁹⁰Sr in environmental matrices has been developed. It is a one-day time-consuming procedure compared with 20–25 d of the traditional methods. It is based on a partial measurement of the sample activity and on data extrapolation. This work reports the methodology and its reliability.     

A simple radiochemical determination of90Sr in environmental samples

A simple procedure for the determination of⁹⁰Sr in environmental samples is described. The method uses the different solubilities of the oxalates of calcium and strontium in presence of a large excess of calcium. For this reason the method is especially suited for Ca-rich samples, as e.g., bones or soils. However, after addition of supplementary calcium it works equally well for other types of samples. The method was tested by analyzing the IAEA Certified Reference Materials soil, animal bone and algae.     

Studies on soil samples mineralization conditions preceding the determination of 90Sr

Some results of the extraction of strontium and yttrium from soil samples by concentrated nitric acid are described. The concentration of Sr and Y in the solid was determined by XRF method. The results obtained allowed to elaborate the conditions of acid leaching and to propose an analytical procedure for the determination of ⁹⁰Sr in samples without their total dissolution.     

A sensitive method based on HDEHP extraction and LSS for the determination of 90Sr in solid samples

An improved and rapid method is described for the determination of ⁹⁰Sr in environmental samples, through the separation of the daughter ⁹⁰Y at equilibrium. The procedure is based on the HDEHP solvent extraction in combination with liquid scintillation spectrometry (LSS). A low background QuantulusÔ has been optimized for low level counting of Cerenkov radiation emitted by the hard b-emitter ⁹⁰Y. The counting efficiency was 60% and the background 0.53 cpm. The reliability and reproducibility of the method have been checked using IAEA reference materials. The chemical recovery for ⁹⁰Y extraction ranges from 83 to 90%.     

Preparation of animal tissue samples for the determination of90Sr and actinides

A unique procedure permitting the determination of⁹⁰Sr and actinides in the same protion of sample, with good chemical yields of all analytes, is presented. Animal tissue samples containing bone are ashed, spiked with^{2 3 2}U,^{2 4 2}Pu,^{2 4 3}Am and^{8 5}Sr and solubilized. The actinides and strontium are gathered and separated by a series of coprecipitations with, cerium hydroxide and cerium fluoride. Actinide separation and determination and purification and determination of⁹⁰Sr are accomplished by a combination of several well-known procedures. The laboratory method consistently results in high chemical yields of all the analytes and overcomes interferences from phosphates and calcium.     

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.

     

An improved method for the determination of uranium isotopes in environmental samples by alpha-spectrometry

In order to improve the selectivity of the uranium isotopes determination in environmental samples, further studies have been carried out, including (1) interference of ²¹⁰Po with uranium isotope determination, (2) distribution coefficients of polonium between 5% TOPO in toluene and aqueous hydrochloric and nitric acids, (3) decontamination factor of uranium from polonium of the recommended procedure, and (4) leaching effect comparison of two different leaching procedures in a lichen sample. Based on the new findings, a more accurate extraction chromatographic/ a-spectroscopy method has been developed. For the method's validation, four kinds of reference materials supplied by the IAEA have been tested. It is observed that nearly all the ²³⁸U, ²³⁴U and ²³⁵U concentrations obtained are in good agreement with the recommended or information values, showing that the method can give reliable results. A comparison with existing uranium determination methods has also been made. It is concluded that due to involving preconcentration and chemical separation, the extraction chromatographic/a-spectroscopy method is a more selective, very sensitive and accurate, and low cost method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Rapid determination of 90Sr/90Y in water samples by liquid scintillation and Cherenkov counting

Strontium-90 (⁹⁰Sr) is a ubiquitous contaminant at nuclear facilities, found at high concentrations in spent nuclear fuel and radioactive waste. Due to its long half-life and ability to be transported in groundwater, an accurate method for measuring ⁹⁰Sr in water samples is critical to the monitoring program of any nuclear facility. To address this need, a rapid procedure for sequential separation of Sr/Y was developed and tested in groundwater samples collected from an area of riverbed affected by a ⁹⁰Sr groundwater plume. Sixteen samples, plus spike and water blanks, were analyzed. Five different measurements were performed to determine the ⁹⁰Sr and yttrium-90 (⁹⁰Y) activities in the samples: direct triple-to-double-coincidence ratio (TDCR) Cherenkov counting of ⁹⁰Y, liquid scintillation (LS) counting for ⁹⁰Sr following radiochemical separation, LS counting for ⁹⁰Y following radiochemical separation, Cherenkov counting for ⁹⁰Y following radiochemical separation and LS counting of the Sr samples for ⁹⁰Y in-growth. The counting was done using a low-level Hidex 300SL TDCR counter. Each measurement method was compared for accuracy, sensitivity and efficiency. The results following Cherenkov counting and radiochemical separation were in very good agreement with one another.     

An improved nephelometric method for the determination of small amounts of thiosulfate in aqueous samples

The procedure is based on decomposition of thiosulfate, with formation of sulfur, in the presence of 0.5 mol l^?1 nitric acid. Thiosulfate is determined in the range 15–100 mg l^?1, with a relative standard deviation of 5.4% and a mean relative error of 3.2%. These data are of the same order of magnitude as those obtained for the earlier silver/1,10-phenanthroline method. The present method has the advantage of being almost completely free from interferences; the only interference observed (sulfide) is easily eliminated.     

Rapid determination of strontium-90 in seawater

It is shown that Y₂O₃, YF₃, LaF₃, and CeF₃ help concentrate ⁹⁰Y from seawater. To determine ⁹⁰Sr, YF₃ is the best reagent because the effect of interfering lead and thorium radioisotopes is minimum in this case. It is proposed to preconcentrate ²¹⁰Bi on PbS to eliminate its interference. To determine ⁹⁰Sr we measure the Cherenkov radiation of ⁹⁰Y concentrated on YF₃ without prior elution.     

The simple radiochemical determination of 90Sr in environmental solid samples by solvent extraction

Determination of ⁹⁰Sr in environmental solid samples is a challenging task because of the presence of so many other radionuclides in samples of interest. This problem was dealt with by radiochemical separation of strontium followed by yttrium separation and Cerenkov counting of the high-energy ??-particle emissions of ⁹⁰Y in order to quantitate ⁹⁰Sr. In this work, an improved method is described for the determination of ⁹⁰Sr in soil samples, through the separation of the daughter ⁹⁰Y at equilibrium. The procedure is based on the HDEHP solvent extraction in combination with liquid scintillation spectrometry (LSS). A low background Quantulus has been optimized for low level counting of Cerenkov radiation emitted by the hard ??-emitter ⁹⁰Y. The analytical quality of the method has been checked by analyzing IAEA Soil-375 reference materials. The analytical method has also been successfully applied to the determination of ⁹⁰Sr for moss-soil samples in inter-laboratory exercises through IAEA??s ALMERA network. The chemical recovery for ⁹⁰Y extraction ranged from 80 to 85% and the counting efficiency was 73% in the window 25?C400 keV.     

Application of neutron activation analysis in chemical yield determination for89Sr and90Sr separation of environmental samples

For⁸⁹Sr and⁹⁰Sr determination in grass samples neutron activation analysis was employed as an advantageous method for yield measurements during the separation process. From the activity ratio found conclusions on the source of radioactivity are possible taking into consideration the dependence on reactor operating time.     

A novel approach to Ca-Sr separation in the determination of90Sr using inorganic exchangers: An application to environmental samples

A procedure for⁹⁰Sr determination in calcium rich samples is presented. It is based on the precipitation of calcium oxalate in homogeneous solution and under controlled conditions to minimize the coprecipitation of strontium. The latter is subsequently separated as carbonate and radiochemical purification is completed by ion exchange chromatography on two inorganic exchangers: PRTD (partially reduced tin dioxide) and CUCR (copper chromate). The procedure was applied to environmental samples such as ashed sediment, fish and vegetable and results are reported.     

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.