The measurement of222Rn in drinking water by low-level liquid scintillation counting

Radon-222 (Rn) has universally been found in well water. Non-stagnant ground water is collected at the well head while the well is pumping. The water is adjusted to a slow, non-aerated, steady flow through a clear tube, and a 500 ml glass bottle is filled. The sample is tightly capped after a high meniscus has developed. In the laboratory, standard 22 ml glass vials are filled with 10 ml of a toluene based mineral oil LS cocktail. Then, two 5 ml sample aliquots are pipetted into the vial. Vials are capped tightly, shaken vigorously, and placed in the liquid scintillation (LS) counter. Secular equilibrium is established in approximately 4 hours, after which samples are counted for 100 minutes each. The counting efficiency for Rn and progeny ranges between 315 to 345 percent depending on the chosen spectral window. The average background is about 6 cpm. A total of 28 wells were tested for Rn in the Carefree-Cave Creek, Arizona, USA area. The area's geometric average Rn concentration was found to be 46.5 Bq·l^–1. The associated estimated lung dose is 0.51 mSv·y^–1.Deceased 1 June 1991.     

Gross alpha/beta analyses in water by liquid scintillation counting

Summary The standard procedure for analyzing gross alpha and gross beta in water is evaporation of the sample and radioactivity determination of the resultant solids by proportional counting. This technique lacks precision, and lacks sensitivity for samples with high total dissolved solids. Additionally, the analytical results are dependent on the choice of radionuclide calibration standard and the sample matrix. Direct analysis by liquid scintillation counting has the advantages of high counting efficiencies and minimal sample preparation time. However, due to the small sample aliquants used for analysis, long count times are necessary to reach required detection limits. The procedure proposed consists of evaporating a sample aliquant to dryness, dissolving the resultant solids in a small volume of dilute acid, followed by liquid scintillation counting to determine radioactivity. This procedure can handle sample aliquants containing up to 500 mg of dissolved solids. Various acids, scintillation cocktail mixtures, instrument discriminator settings, and regions of interest (ROI) were evaluated to determine optimum counting conditions. Precision is improved and matrix effects are reduced as compared to proportional counting. Tests indicate that this is a viable alternative to proportional counting for gross alpha and gross beta analyses of water samples.     

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.     

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.     

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.     

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.     

Simultaneous determination of alpha and beta-emitting nuclides by liquid scintillation counting

The determination of - and -emitting nuclides has been studied with a commercial liquid scintillation counter /Tri-Carb 2200CA/ equipped with Pulse Shape Analysis /PSA/. The results indicated that the efficiency for -emitters is virtually 100% and discrimination for -emitters is more than 99.9%. Liquid scintillation counting with PSA can be used for the determination of - and -emitting nuclides simultaneously.     

Thorium determination in water samples by liquid scintillation counting after its separation by cloud point extraction

The aim of this study is the separation and pre-concentration of thorium from aqueous solutions by cloud point extraction (CPE) and its the radiometric determination by liquid scintillation counting (LSC). For CPE, tributyl phosphate (TBP) was used as the complexing agent and (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol (Triton X-114) as the surfactant. The radiometric measurements were performed after phase separation by mixing of the surfactant phase with the liquid scintillation cocktail. The effect of experimental conditions such as pH, ionic strength (e.g. [NaCl]) and the presence of other chemical species (e.g. Ca²⁺ and Fe³⁺ ions, and humic acid colloids) on the CPE separation recovery have been investigated at constant reactant ratio (m(TBP)/m(Triton) = 0.1). According to the experimental results the maximum chemical recovery is (60 ± 5)% at pH 3. 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. Generally, the method could be applied successfully for the radiometric determination of thorium in water solutions with relatively increased thorium content.     

Rapid determination of 226Ra in drinking water samples using dispersive liquid-liquid microextraction coupled with liquid scintillation counting

A new radioanalytical method was developed for rapid determination of ²²⁶Ra in drinking water samples. The method is based on extraction and preconcentration of ²²⁶Ra from a water sample to an organic solvent using a dispersive liquid-liquid microextraction (DLLME) technique followed by radiometric measurement using liquid scintillation counting. In DLLME for ²²⁶Ra, a mixture of an organic extractant (toluene doped with dibenzo-21-crown-7 and 2-theonyltrifluoroacetone) and a disperser solvent (acetonitrile) is rapidly injected into the water sample resulting in the formation of an emulsion. Within the emulsion, ²²⁶Ra reacts with dibenzo-21-crown-7 and 2-theonyltrifluoroacetone and partitions into the fine droplets of toluene. The water/toluene phases were separated by addition of acetonitrile as a de-emulsifier solvent. The toluene phase containing ²²⁶Ra was then measured by liquid scintillation counting. Several parameters were studied to optimize the extraction efficiency of ²²⁶Ra, including water immiscible organic solvent, disperser and de-emulsifier solvent type and their volume, chelating ligands for ²²⁶Ra and their concentrations, inorganic salt additive and its concentration, and equilibrium pH. With the optimized DLLME conditions, the accuracy (expressed as relative bias, B _r ) and method repeatability (expressed as relative precision, S _B ) were determined by spiking ²²⁶Ra at the maximum acceptable concentration level (0.5 Bq L⁻¹) according to the Guidelines for Canadian Drinking Water Quality. Accuracy and repeatability were found to be less than −5% (B _r ) and less than 6% (S _B ), respectively, for both tap water and bottled natural spring water samples. The minimum detectable activity and sample turnaround time for determination of ²²⁶Ra was 33 mBq L⁻¹ and less than 3 h, respectively. The DLLME technique is selective for extraction of ²²⁶Ra from its decay progenies.     

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.     

Simultaneous determination of 152Eu and 241Am in liquid solution by liquid scintillation counting

¹⁵²Eu and ²⁴¹Am are the most frequently used radiotracers in the separation studies on trivalent minor actinides and lanthanides. In almost all those studies, the determination of ¹⁵²Eu and ²⁴¹Am has been based on measuring their γ radiation by using a NaI(Tl) scintillation detector and/or a germanium detector. In this study, based on measuring the β particles and mono-energy electrons from ¹⁵²Eu and the α particles from ²⁴¹Am, we provide a new option to simultaneously determine the radioactivities of ¹⁵²Eu and ²⁴¹Am by liquid scintillation counting (LSC) with the aid of α/β discrimination. If the count rate ratio of ²⁴¹Am to ¹⁵²Eu is within the range of 100:1–1:100, the radioactivities of ¹⁵²Eu and ²⁴¹Am in mixed samples can be simultaneously determined by LSC with the errors less than 5 %. In addition, the interferences of ²⁴¹Am on Eu are divided into two parts: inside and outside the ²⁴¹Am region of interest. Only if the count rate ratio of ²⁴¹Am to Eu is more than 10:1, should the latter interference be in consideration.     

Quantification of99Tc by liquid scintillation counting: An evaluation of chemical quenching by liquid chromatographic eluents

The feasibility of utilizing liquid scintillation counting as a detection method for the liquid chromatographic analysis of⁹⁹Tc is evaluated. The chemical quenching of constituents commonly found in liquid chromatographic mobile phases is investigated, and quench corrections are presented. Quantification of⁹⁹Tc is achieved over a concentration range of 10^–3 to 10^–8M on quiescent KTCO₄ solutions, with sample volumes of 0.3 ml, yielding a counting efficiency from 51 to 59% for a narrow 150 channel window. The potential for the double isotope labelling of technetium complexes and the implications of the liquid scintillation counting of⁹⁹Tc in flowing eluents are discussed.     

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.     

Recent progress and application of low level liquid scintillation counting

The use of an ultra low level liquid scintillation counter with extremely low background, MCA technique, storage and software evaluation of pulse height spectra has given very low LLD's, the possibility of - and -spectrometry to some extent and time saving optimization of counting conditions. Quick and very simple but yet accurate analytical methods could be worked out worked out for environmental measurements: Environmental levels of tritium,¹⁴C in several assimilation products,²²²Rn and²²⁶Ra in water without any sample pretreatment. Suggestions for possible further applications in environmenial monitoring and low level counting are given.     

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.     

Increasing the sensitivity of241Pu determination for emission and immission control of nuclear installations by aid of liquid scintillation counting

A radiochemical procedure was developed and optimized which allows sensitive²⁴¹Pu measurement in various sample materials. As a first step, Pu isotopes are separated from matrix elements, purified radiochemically, electroplated, and measured by -spectrometry. The electrodeposited Pu is then redissolved in nitric acid and extracted with trioctylphosphinic oxide/cyclohexane. The organic phase is mixed with scintillator cocktail (PPO/Xylene) and Pu is measured with a liquid scintillation counter. The detection limit of the optimized procedure for a counting time of 100 minutes is 50 mBq²⁴¹Pu per sample at a 95% confidence level.     

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.     

Absolute liquid scintillation counting of35S and45Ca using a modified integral counting method

The disintegration rates of³⁵S and⁴⁵Ca samples were determined by the modified integral counting method, which extrapolates the integral count rate to the zero detection threshold of a liquid scintillation spectrometer. The agreement between the extrapolated value and the standardized disintegration rate of the sample is very satisfactory.