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.     

Determination of 90Sr and 210Pb in deer bone samples by liquid scintillation counting after ion-exchange procedures

This work describes a procedure for the isolation of ⁹⁰Sr and ²¹⁰Pb from deer bones by anion exchange methods and their sequential measurement by LSC. To prevent collection of Pb on the Sr·Spec^® resin we first separated Pb on a Dowex anion exchange column. Sr, which is not held back on the Dowex column, was then purified using Sr·Spec^® resin: first Ca and the Ra isotopes were eluted with 3 M HNO₃ and then Sr was eluted with distilled water. With this 2-steps procedure pure ²¹⁰Pb and ⁹⁰Sr spectra can be achieved. The chemical yield of both steps was determined by ICP-MS. Our ⁹⁰Sr results show satisfying agreement with data obtained by a shorter Sr·Spec^® method and also by the “classical” ⁹⁰Sr determination using fuming nitric acid. Also ²¹⁰Pb results were checked by re-measuring bone samples with already known ²¹⁰Pb activities. Further our method was verified on the reference sample IAEA-A-12.     

Assay of89Sr in plant and soil samples by liquid scintillation counting

The Sr in plant and soil samples is converted to SrCl₂ by digestion with HNO₃ and HCl. The recovery of this digestion is 90% with a reproducibility of about 4%. SrCl₂ is solubilized in toluene by forming a complex with di-n-propyl phosphate (DNP). The DNP-toluene reagent was found to be a highly effective carrier of SrCl₂, and to have properties suitable for highly efficient liquid scintillation counting. An efficiency of 95% was obtained for⁸⁹Sr counting. The factors affecting the utility of the method are discussed.     

Determination of90Sr in environmental and biological materials with combined HDEHP solvent extraction-low liquid scintillation counting technique

Low level⁹⁰Sr in environmental and biological samples is determined using a combined HDEHP solvent extraction-liquid scintillation procedure. Yttrium-90 is selectively extracted from nitric acid solution into 5% di(2-ethylhexyl) phosphoric acid (HDEHP) in toluene, and⁹⁰Y in the organic phase is measured directly using an ultra low level liquid scintillation spectrometer.The working program of the Quantulus counter has been optimized. As the counting efficiency using liquid scintillation counting is high and the stripping and precipitation of Yttrium-90 oxalate is omitted, this procedure is simpler and more timesaving than traditional methods. The chemical recoveries of⁹⁰Y were 85.1% for soil, 75.7% for milk and 65.3% for bone. The detection limit is 8 mBq.     

Urine strontium-90 (Sr-90) manual and automated pre-analytical separation followed by liquid scintillation counting

Journal of Radioanalytical and Nuclear Chemistry - Responding to a radiological or nuclear incident may require assessing tens to hundreds of thousands of people for possible radionuclide...     

Removal of the impurities from environmental water samples for tritium measurement by liquid scintillation counting

Liquid scintillation counting is the most popular method for tritium measurement, however, it takes much time and a lot of doing to distill off the impurities before mixing the sample water and liquid scintillation cocktail. We have investigated the possibility of an alternative method to the distillation. We have found out that the filtration can be an alternative to distillation for the environmental water samples before electrolytic enrichment.     

Determination of 90Sr in urine samples and 89Sr/90Sr in water samples by chemical separation and Cherenkov counting with LSC system

Journal of Radioanalytical and Nuclear Chemistry - In order to determine radiostrontium with a satisfactory chemical yield, calculated by an external standard, and a low level of MDC a...     

Optimization of liquid scintillation counting techniques for the determination of carbon-14 in environmental samples

The goal of this work was to optimize the liquid scintillation counting techniques for the determination of¹⁴C in stack effluent gases and in environmental samples such as biological and air samples. Carbon-14 activities in most environmental samples were measured with the direct CO₂ absorption method. The highest figures of merit were found through the variation of Carbosorb E and Permafluor V ratio, and measurement windows. The best condition was an 1:1 volume ratio. Average 2.35 g of CO₂ was reproducibly absorbed in the 20 ml mixture within 40 minutes. The counting efficiency determined by repeated analysis of NIST oxalic acid standard and the background count rate were measured to be 58.8±1.4% and 1.88±0.06 cpm, respectively, in case of saturated solution. The correction curves of counting efficiency for partially saturated solutions and for saturated solutions with quenching were prepared, respectively. The overall uncertainty of the sample specific activity for near background levels was estimated to be about 7% for 4 hours counting at 95% confidence level. Stack effluent gas samples were measured by a gel suspension counting method. After precipitation of CO₂ in the form of BaCO₃, 140 mg of which was mixed with 6 ml H₂O and 12 ml of Instagel XF. The counting efficiency was measured to be 71.5±1.7% and the typical sensitivity of this technique was about 510 mBq/m³ for a 100 min count at a background count rate of 4.7 cpm. For the benzene counting method measurements were performed with a mixture of 3 ml benzene and 1 ml of scintillation cocktail (5 g of butyl-PBD in 100 ml of scintillation-grade toluene) in a low potassium 7 ml borosilicate glass vial. The counting efficiency and the background count rate were measured to be 64.3±1.0% and 0.51±0.05 cpm, respectively. The long-term stability of samples has been checked for all the counting techniques over a two week period, during which no apparent change in counting efficiency and background level was found.     

Modified 2-window approach for rapid determination of 90Sr and 90Y at low quench level using liquid scintillation counting

⁹⁰Sr is a product of nuclear fission, the radioactivity of which can be determined by liquid scintillation counting (LSC). Because the LSC spectra of ⁹⁰Sr and its daughter ⁹⁰Y overlap each other, the following methods are usually used: (1) measuring immediately after ⁹⁰Sr/⁹⁰Y separation; (2) waiting to reach radioactive equilibrium; (3) adopting the conventional 2-window approach; and (4) using the spectra deconvolution technique. The first one requires ⁹⁰Sr/⁹⁰Y separation and immediate measurement; the second one is time-consuming; the third one is valid only for samples with the same quench level as the calibration standard; the last one is somewhat complicated, and in some cases it is not convenient to export the experimental data to some deconvolution software. Therefore, we have developed a modified 2-window approach to rapidly determine ⁹⁰Sr and ⁹⁰Y in either equilibrium or disequilibrium at low quench level. The key modification of the approach is to provide an LSC spectrum of pure ⁹⁰Y with the same quench level as the sample to be determined. This modification eliminates the need to conduct ⁹⁰Sr/⁹⁰Y separation for the sample itself, to prepare the quench curves, and to fit the LSC spectra with some deconvolution software.     

Radiometric analysis of <Superscript>90</Superscript>Sr in fish bone ash samples by liquid scintillation counting after separation by extraction chromatographic resin

Studies on the extraction behavior and immobilization of cadmium by greener reagents have important bearings in today’s science. No-carrier-added (NCA), ¹⁰⁹Cd radionuclide is a potential candidate towards radiopharmaceutical studies for both in vivo and in vitro applications and is also used in industrial and environmental studies. Herein, we have studied the adsorption and desorption characteristics of cadmium in both NCA and bulk concentrations into calcium alginate using radiochemical method. Various isotherms like Langmuir, Freundlich, Temkin and Dubinin–Radushkevich have been studied and compared to match the adsorption phenomenon. A spontaneous endothermic physisorption process is expected from thermodynamic parameters.     

Uranium determination in water samples by liquid scintillation counting after cloud point extraction

The aim of this study is the radiometric determination of uranium in waters by liquid scintillation counting (LSC) after pre-concentration of the element by cloud point extraction (CPE). For CPE, tributyl phosphate (TBP) is used as the complexing agent and (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol (Triton X-114) as the surfactant. The measurement is performed after phase separation by mixing of the surfactant phase with the liquid scintillation cocktail. The effect of experimental conditions such as pH, reactant ratio (e.g. m(TBP)/m(Triton), ionic strength (e.g. [NaCl]) and the presence of other chemical species (e.g. Ca²⁺ and Fe³⁺ ions as well as humic acid and silica colloids) on CPE has been investigated. According to the experimental results the total method efficiency is (13 ± 2)% and the chemical recovery (50 ± 10)% at pH 4 and reactant ratio (V(TBP)/V(Triton) = 0.1). Regarding the other parameters, generally Ca²⁺ and Fe³⁺ ions as well as the presence of colloidal species in solution (even at low concentrations) results in significant decrease of the chemical recovery of uranium. On the other hand increasing NaCl concentration leads to enhancement of chemical recovery. The detection limit under optimum experimental conditions has been found to be 0.5 Bq L^?1 indicating that the method could be applied only to waters samples with increased uranium concentration. Moreover, the negative effect of the chemical species found in natural waters limits the applicability of the method with the respect to environmental radioactivity measurements.     

Measurement of radon emanation of drainage layer media by liquid scintillation counting

Slab-on-ground is a typical base floor construction type in Finland. The drainage layer between the slab and soil is a layer of sand, gravel or crushed stone. This layer has a minimum thickness of 200 mm and is sometimes even 600 mm thick, and thus may be a significant contributor to indoor air radon. In order to investigate radon emanation from the drainage layer material, a simple laboratory test was developed. Many organic solvents have high Ostwald coefficients for radon, i.e., the ratio of the volume of gas absorbed to the volume of the absorbing liquid, which enables direct absorption of radon into a liquid scintillation cocktail. Here, we first present equations relating to the processes of gas transfer in emanation measurement by direct absorption into liquid scintillation cocktails. In order to optimize the method for emanation measurement, four liquid scintillation cocktails were assessed for their ability to absorb radon from air. A simple apparatus consisting of a closed glass container holding an open liquid scintillation vial was designed and the diffusion/absorption rate and Ostwald coefficient were determined for a selected cocktail. Finally, a simple test was developed based on this work.     

Measurement of63Ni in highly radioactive Hanford waste by liquid scintillation counting

Characterization of high-activity radioactive waste stored in underground tanks at Hanford requires determining⁶³Ni (100 y). This low-energy -emitter (E_max 67 keV) must be separated with a high degree of radiochemical purity large amounts of other fission and activation products. The method to be discussed involves multiple precipitation steps with several holdback carriers added, followed by precipitations with dimethylglyoxime, ion exchange, and electrodeposition. The⁵⁹Ni activity is determined by low-energy photon spectrometry. The sample is then stripped from the counting disk with HNO₃, converted to the chloride form, and the⁶³Ni -spectrum is measured with high efficiency by liquid scintillation counting.Pacific Northwest Laboratory is operated for the U.S. Department of Energy under Contract DE-AC06-76RLO-1830.     

Rapid and accurate determination of89/90Sr in radioactive samples by Cerenkov counting

An improved and rapid method for determination of⁹⁰Sr via its daughter nuclide,⁹⁰Y, in aqueous samples from the low-level radioactive wastes by Cerenkov counting was established. This technique is applicable to beta particles maximum energies greater than 0.263 MeV in aqueous solution. A comparison of⁹⁰Sr determination by Cerenkov counting and standard wet chemical separation techniques indicates a high degree of correlation and excellent agreement. For a 20 ml aqueous sample following the prescribed experimental conditions and a 60 min counting interval, the detection limit was 0.20 dpm/ml (0.10 pCi/ml), and the relative deviation is less then 5%.     

Alpha-radiometry of seawater by liquid scintillation counting

Summary Liquid scintillation counting of the alpha-radionuclides after pre-concentration by cation-exchange represents a simple and robust method for the determination of total alpha-radioactivity in seawater. The total efficiency and the minimum detectable activity were calculated to be 95% and 30 mBq, respectively, for a liter sample and 1000-minute measuring time. The method has been applied successfully for the determination of alpha-radioactivity in seawater from five different coastal areas in Cyprus. The average alpha-radioactivity and uranium concentration were found to be 124±8 mBq ^. l^-1 and 3.2±0.2 mg ^. l^-1, respectively.     

Determination of U/U atom ratio in uranium samples using liquid scintillation counting (LSC)

A correlation has been developed for the determination of ²³⁵U/²³⁸U atom ratio in uranium samples using liquid scintillation counting (LSC). The ²³⁵U/²³⁸U atom ratio determined by thermal ionization mass spectrometry (TIMS) was correlated to the ratio of (i) α-count rate and (ii) Cerenkov count rate due to ^234mPa in the sample; both measured by LSC. This correlation is linear over the range of ²³⁵U/²³⁸U atom ratio encountered in the nuclear fuel samples, i.e. the low enriched uranium (LEU) samples with ²³⁵U < 20 atom%. The methodology based on this correlation will be useful for the quick determination and verification of ²³⁵U/²³⁸U atom ratios in fuel samples using cost effective technique of LSC.     

Measurement by ultra low level liquid scintillation counting following the Chernobyl accident

The situation in Austria following the Chernobyl accident is described shortly as well as applications of measurements with the ultra low level liquid scintillation counter Quantulus concerning milk, precipitation, surface water and drinking water. Data on the measurement of tritium are presented.     

Standardization of 90Y solution by mean of a Cherenkov counting in comparison with a liquid scintillation counting technique

Journal of Radioanalytical and Nuclear Chemistry - This paper presents the standardization of 90Y solution using the Cherenkov method measuring in the TDCR counters. The counting efficiencies for...     

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.