LS Counter Research Articles

Simultaneous 137Cs and 90Sr/90Y detection in water on an LS counter: A quick response in a case of radiation emergency

This research investigates the possibility to simultaneously measure 137Cs and 90Sr/90Y content in water by Liquid Scintillation Counter Quantulus 1220. The method relies on the Cherenkov counting and does not require sample pre-treatment. During nuclear emergencies, a potential radioactive release should be promptly detected, and this technique ensures measurement results 2 h after the sample's arrival to the laboratory. 137Cs and 90Sr/90Y concentrations were determined with and without 1-butyl-3-methylimidazolium salicylate ionic liquid's addition, which increased detection efficiency via wavelength-shifting mechanism. The results of analysis were obtained with relative deviations up to 70% from the true activities without IL's addition, but their accuracy was improved (with relative deviations up to 40%) after the addition of 1 g of ionic liquid to the counting vials.

In Search for an Ionic Liquid with the Best Performance during 210Pb/210Bi Cherenkov Counting in Waters on an LS Counter.

The research presented in this paper aims to investigate the performance of several newly synthesized ionic liquids during 210Pb/210Bi detection in water on a liquid scintillation spectrometer Quantulus 1220 via Cherenkov counting. These experiments have been triggered by the recent reports that certain ionic liquids can act as wavelength shifters, thus significantly increasing the detection efficiency of Cherenkov radiation. The benefit of ionic liquid's addition to the analysed samples is reflected in the detection limit's decrement during 210Pb quantification, which is pertinent considering naturally low levels of 210Pb in aqueous samples. Firstly, it was discovered that ionic liquid, 1-butyl-3-methylimidazolium salicylate, is more efficient than the previously explored 2-hydroxypropylammonium salicylate. Consequently, the impact of a few other ionic liquids on Cherenkov counting efficiency with the same cation group (1-butyl-3-methylimidazolium benzoate, 1-butyl-3-methylimidazolium 3-hydroxybenzoate and 1-butyl-3-methylimidazolium 4-hydroxybenzoate) was also explored to test their potential influence. Molecular simulations have been carried out to reveal which structures of ionic liquids assure wavelength-shifting behavior. The obtained results confirmed that, among the investigated ones, only ionic liquids with the salicylate anion exhibited a wavelength shifting effect.

In Search for an Ionic Liquid with the Best Performance During 210pb/210bi Cherenkov Counting in Waters on a Ls Counter

In Search for an Ionic Liquid with the Best Performance During 210pb/210bi Cherenkov Counting in Waters on a Ls Counter

Cherenkov Radiation Detection on a LS Counter for 226Ra Determination in Water and Its Comparison with Other Common Methods.

Reliable determination of 226Ra content in drinking water, surface water and groundwater is required for radiological health-risk assessment of populations and radiation-dose calculations after ingestion and inhalation. This study aimed to determine 226Ra presence in the untreated water samples on a liquid scintillation counter via Cherenkov radiation detection. Cherenkov counting is a faster, simpler, less expensive technique than other commonly used methods for 226Ra determination. Step-by-step optimization of this technique on the Quantulus detector is presented in this paper. Improvement of detection limit/efficiency in the presence of sodium salicylate was investigated in this study. The main parameters of the method obtained were detection efficiency 15.87 (24)% and detection limit 0.415 Bq/L achieved for 1000 min of counting in 20 mL of sample volume. When 1 g of sodium salicylate was added, efficiency increased to 38.1 (5)%, with a reduction in the detection limit to 0.248 Bq/L for 500 min of counting. A satisfactory precision level of Cherenkov counting was obtained, the results deviating between 5% and 20% from reference values. The precision and accuracy of the Cherenkov counting technique were compared to liquid scintillation counting (EPA Method 913.0 for radon determination) and gamma spectrometry (the direct method for the untreated water samples on HPGe spectrometer). An overview of the advantages/disadvantages of each technique is elaborated in this paper.

Study on quench effects in liquid scintillation counting during tritium measurements

Quench effects can cause a serious reduction in counting efficiency for a given sample/cocktail mixture in liquid scintillation counting (LSC) experiments. This paper presents a simple experiment performed in order to test the influence of quenching on the LSC efficiency of 3H. The aim of this study was to investigate the behavior of several quench agents with different quench strengths (nitromethane, nitric acid, acetone, dimethyl-sulfoxide) added in different amounts to tritiated water in order to obtain standard sets for quench calibration curves. The OptiPhase HiSafe 2 and OptiPhase HiSafe 3 scintillation cocktails were used in this study in order to compare their quench resistance. Measurements were performed using a low-level LS counter (Wallac, Quantulus 1220).

A high-sensitivity method for the measurement of 222Rn based on liquid scintillation counting of polycarbonate powder.

This work describes a technique for the measurement of 222Rn by absorption in polycarbonate (PC) powder and liquid scintillation counting (LSC). The work is an improvement of the recently proposed method for 222Rn measurements by LSC of exposed PC grains. It is demonstrated that the use of PC powder as a 222Rn sampler improves 13.6 times the sampling efficiency and leads to 6.5 times smaller minimmal detectable activity concentrations (MDAC) compared with the PC grains used so far. For a 40-h exposure of 7.4-g PC powder to 222Rn in air, the MDAC with a RackBeta 1219 LS counter is 62 Bq m(-3) (assuming a 8-h sample counting time and 24-h background time). For the same conditions the estimated 222Rn MDAC with a Quantulus 1220 LS counter is 20 Bq m(-3). The proposed technique is suitable for radon in air and radon in soil-gas measurements.

Optimization of low-level LS counter Quantulus 1220 for tritium determination in water samples

Liquid scintillation counting (LSC) is the most commonly used technique for measuring tritium. To optimize tritium analysis in waters by ultra-low background liquid scintillation spectrometer Quantulus 1220 the optimization of sample/scintillant ratio, choice of appropriate scintillation cocktail and comparison of their efficiency, background and minimal detectable activity (MDA), the effect of chemi- and photoluminescence and combination of scintillant/vial were performed. ASTM D4107-08 (2006) method had been successfully applied in our laboratory for two years. During our last preparation of samples a serious quench effect in count rates of samples that could be consequence of possible contamination by DMSO was noticed. The goal of this paper is to demonstrate development of new direct method in our laboratory proposed by Pujol and Sanchez-Cabeza (1999), which turned out to be faster and simpler than ASTM method while we are dealing with problem of neutralization of DMSO in apparatus. The minimum detectable activity achieved was 2.0Bql−1 for a total counting time of 300min. In order to test the optimization of system for this method tritium level was determined in Danube river samples and also for several samples within intercomparison with Ruđer Bošković Institute (IRB).

Experimental study of the influence of the counter and scintillator on the universal curves in the cross-efficiency method in LSC

The cross-efficiency method in LSC is one of the approaches proposed for the extension of the Système International de Référence (SIR) to radionuclides emitting no gamma radiation. This method is based on a so-called “universal cross-efficiency curve”, establishing a relationship between the detection efficiency of the radionuclide to be measured and the detection efficiency of a suitable tracer. This paper reports a study at LNHB on the influence of the scintillator and of the LS counter on the cross-efficiency curves. This was done by measuring the cross-efficiency curves obtained for 63Ni and 55Fe vs. 3H, using three different commercial LS counters (Guardian 1414, Tricarb 3170 and Quantulus 1220), three different liquid scintillator cocktails (Ultima Gold, Hionic Fluor and PicoFluor 15 from Perkin Elmer®), and for chemical and colour-quenched sources. This study shows that these cross-efficiency curves are dependent on the scintillator, on the counter used and on the nature of the quenching phenomenon, and thus cannot definitively be considered as “universal”.

An improved method for 85Kr analysis by liquid scintillation counting and its application to atmospheric 85Kr determination

Atmospheric 85Kr concentration at Fukuoka, Japan was determined by an improved 85Kr analytical method using liquid scintillation counting (LSC). An average value of 1.54 ± 0.05 Bq m −3 was observed in 2008, which is about two times that measured in 1981 at Fukuoka, indicating a 29 mBq y −1 rate of increase as an average for these 27 years. The analytical method developed involves collecting Kr from air using activated charcoal at liquid N 2 temperature and purifying it using He at dry ice temperature, followed by Kr separation by gas chromatography. An overall Kr recovery of 76.4 ± 8.1% was achieved when Kr was analyzed in 500–1000 l of air. The Kr isolated by gas chromatography was collected on silica gel in a quartz glass vial cooled to liquid N 2 temperature and the activity of 85Kr was measured with a low-background LS counter. The detection limit of 85Kr activity by the present analytical method is 0.0015 Bq at a 95% confidence level, including all propagation errors, which is equivalent with 85Kr in 1.3 l of the present air under the analytical conditions of 72.1% counting efficiency, 0.1597 cps background count rate, and 76.4% Kr recovery.

Radionuclide metrology using liquid scintillation counting

Liquid scintillation counting (LSC) techniques can be used for radionuclide standardization when the calculation of detection efficiency is possible. This is done using a model of the physicochemical processes involved in light emission and also of the statistics of photon emission: the free parameter model. This model can then be applied in two ways: by deducing the free parameter from the measurement of a tracer (the CIEMAT/NIST method) or by calculating this free parameter from coincidence ratio in a specific LS counter (the TDCR method). The purpose of this paper is to describe both these models and some practical issues that need to be addressed if LSC is to be effectively used in radionuclide metrology.

Standardization of 222Rn by LSC and comparison with [formula omitted]- and [formula omitted]-spectrometry

Liquid scintillation counting (LSC) was used for the measurement of 222Rn in equilibrium with its daughters, with detection efficiency close to 5. The appropriate corrections were considered, including one related to the probability that the 165-μs half-life 214Po decays during the dead time of the counter initiated by the disintegration of his parent nuclide, 214Bi. The dead-time determination of a commercial LS counter is also presented using a 222Rn standard source. The LSC 222Rn sources were prepared by transfer of 222Rn produced by a solid 226Ra source into LSC cocktail frozen at 77 K, flame-sealed afterwards. They were measured using the LNHB triple coincidence counter with adjustable extending-type dead-time unit, between 8 and 100 μs; two different procedures were used to calculate an effective dead time and then to deduce the counting rate extrapolated to zero dead-time value. The LSC results were compared with those obtained by cryogenic α -particle spectrometry (LNHB system) and by γ -ray spectrometry for the same radon source in the LSC vial; the geometry transfer coefficient was calculated using the ETNA software. Measurement results and uncertainties are discussed.

A rapid field extraction method for determination of radon-222 in natural waters by liquid scintillation counting

A simple and robust method for determination of 222Rn in natural waters is described. A 1.3-L water sample is collected in a plastic (PET) water bottle and shaken with 20 mL mineral oil scintillant for 4 minutes. Radon preferentially migrates to the mineral oil, and the 222Rn activity is determined by counting 222Rn and the short-lived daughter products 214Po and 218Po using an ultra-low-level LS counter via α/β separation technique. The PET method achieves a detection limit of ~3 mBq L−1, making it an ideal method for analysis of surface water and groundwater samples.

Low-level measurements of tritium in water

Using a liquid scintillation counter, an experimental procedure for measuring low-level activity concentrations of tritium in environmental water has been developed by our laboratory, using the electrolytic tritium enrichment. Additionally, some quality tests were applied in order to assure the goodness of the method. Well-known water samples collected in the Tagus River (West of Spain) and the Danube River (Bulgaria), both affected by nuclear plant releases, were analysed and results were compared to previous data. The analytical procedure was applied to drinking water samples from the public water supply of Seville and mineral waters from different springs in Spain in order to characterize its origin. Due to the very low levels of tritium in the analysed samples, some results were reported as lower than the minimum detectable activity concentration (MDA). However, the count rate of these measurements was over the background count rate of LS counter in all the cases. For that reason, an exhaustive discussion about the meaning of the MDA, using an experimental essay, was made in order to establish a rigorous criterion that leads to a reliable value in the case of low-level measurements.

A simple computing program for application of the TDCR method to standardization of pure-beta emitters

The Triple to Double Coincidence Ratio (TDCR) method is an absolute LSC method for the activity determination of many radionuclides. The method is based on a statistical description of the phenomena in a triple photomultiplier LS counter. The TDCRB-1 program was developed to calculate the radioactive concentration of a solution and is based on the TDCR method data processing. The program, in FORTRAN language has a modular structure, which easy enables to understand its functioning. The outline of the theory, a structure and algorithm of the program, as well as an example of the output results, are presented.

Determination of 222Rn and 226Ra in aqueous samples using a low-level liquid scintillation counter

A method for measuring 222Rn and 226Ra in aqueous samples has been studied. The technique uses low-level liquid scintillation counting from vials containing an insoluble high efficiency mineral oil scintillation cocktail. A Wallac 1220 TM Quantulus LS counter was used for all the experiments. The optimum pulse-shape discrimination value was evaluated by using the minimum detectable activity criterion for each condition of measurement. Experiments on the optimum volume and sample-cocktail ratio, the influence of shaking, type of vial and diffusion of radon from vials were carried out. The study was applied to the determination of very low levels of 222Rn and 226Ra from aqueous environmental samples. The results reached using this method were very satisfactory and even better than from other more laborious procedures.

Instrumentation and Software for Low-Level Liquid Scintillation Counting Radiocarbon Dating

In China, the development of 14C dating is closely related to that of liquid scintillation counting (LSC). New demands are continuously made on LSC by 14C dating, and at the same time, the development of LSC promotes 14C dating. Benzene synthesis for 14C sample preparation was first developed in China in 1974 by the 14C Laboratory of the Department of History, Peking University. This has laid the foundation for 14C dating by β counting with LS counters. Initially, we used a modified conventional LS counter. Despite its poor detection efficiency and high background, it did make a great contribution to 14C dating and LSC in China. Additional 14C laboratories were established for the fields of archaeology, geology, geography, vertebrate paleontology, marine geology and seismology, for which 14C dating is becoming an important research tool. At present, over 50 14C laboratories have been established in China; 90% of the labs use LS counters for β counting, most of which are manufactured in China. 14C dating in China has been primarily concerned with sample synthesis techniques. Since 1979, we have developed three types of LS counters. One is of conventional design; the others are with anticoincidence shielding. We describe here an anticoincidence-shielded LS counter.

Simon Fraser University Radiocarbon Dates II

This list reports measurements made on archaeologic samples by our laboratory from September 1980 to May 1982. Results of measurements made during that period which lack review by submitters will be reported in a subsequent date list. Dates were obtained by liquid scintillation counting of benzene using the laboratory procedure outlined previously (R, 1982, v 24, p 344–351). All dates are expressed in 14C years relative to ad 1950 based on the Libby half-life for 14C of 5568 yr. The laboratory standard continues to be ANU sucrose. Data analysis is now performed with the aid of an RT-11 microcomputer interfaced with our Packard model 3255 LS counter. Dates have been corrected for isotopic fractionation only when the δ13C value is given. No corrections have been made for natural 14C variations. The following descriptions of samples are based on information provided by the submitters.