Cherenkov Counting Research Articles

Comparison of quench correction methods for 90Sr/90Y assessment in waters after nuclear incident

One important matter of environmental radioactivity monitoring is the accuracy and precision of the 90Sr/90Y measurement techniques. When Cherenkov counting is carried out in coloured waters, the reduction in detection efficiency can cause significant errors in the obtained results. Two colour quench correction methods were considered in this study: the conventional SCR (Sample Channels Ratio) technique and the Muonic peak method. The latter indicates the quench level via the position of the muonic peak in the cosmic background spectrum. So far, there have been no reports about the Muonic peak method’s implementation in Cherenkov counting of 90Sr/90Y in waters. The performance, limitations, advantages, and drawbacks of two methods have been compared based on the analysis of coloured spiked test samples. The Muonic peak method provided similar accuracy as the SCR method in test samples. The adequacy and effectiveness of both techniques have been confirmed during 90Sr routine monitoring in the event of a nuclear emergency or radioactive leakage from nuclear facilities.

TDCR Cherenkov counting for determining 90Y activity in blood samples

TDCR Cherenkov counting for determining 90Y activity in blood samples

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.

LSC screening of coloured water samples for simultaneous 137Cs and 90Sr/90Y measurements during nuclear emergencies

Simultaneous screening of 137Cs and 90Sr/90Y levels in coloured water samples by Liquid Scintillation Counter Quantulus 1220 via Cherenkov counting has been investigated. Ionic liquid 1-butyl-3-methylimidazolium salicylate with wavelength-shifting properties has been added to the counting vials, which significantly improved detection efficiency. The results of 137Cs activities obtained via LSC method have been compared with conventional gamma-spectrometric measurements. The performance and limitations of the method have been demonstrated on coloured samples spiked with known 137Cs and 90Sr/90Y activities. In the case of a nuclear accident, this method can be used without sample pre-treatment so that results are obtained within 2 h. The method provides results with up to 80% relative deviation from true 137Cs and 90Sr/90Y activities in the case of highly quenched samples. Its application is limited to the prompt screening of a larger number of samples when it is necessary to efficiently detect radioactive contamination of water.

137Cs direct measurement in water via LSC techniques

This work explores the screening technique of 137Cs concentration dissolved in water via the Cherenkov counting method on a Liquid Scintillation Counter Quantulus 1220. In the event of a nuclear emergency or the potential radioactive leakage from the power plants, the prompt detection of two long-lived fission products, 90Sr/90Y and 137Cs, is of the greatest radiological concern. Here we present an innovative, rapid, and simple LSC method for 137Cs content determination that enables quick evaluation of the radioactive contamination status of water samples without any sample pre-treatment. The novelty in the presented Cherenkov counting technique is the addition of ionic liquid 1-butyl-3-methylimidazolium salicylate in a sample vial. Its presence in the amount of ∼1 g increases efficiency up to ∼30% via a wavelength-shifting mechanism, thus reducing the detection limit of the method more than 4 times. Without the ionic liquid's addition, the method's main parameters were detection efficiency of 6.98(11)% and a detection limit of 2.6 Bq L−1 for 300 min of counting in a 20 mL sample volume. Interference with 90Sr/90Y, a radionuclide that can contribute to the Cherenkov radiation spectrum, was also investigated. The method of distinguishing individual radionuclides (137Cs and 90Sr/90Y) in the cumulative Cherenkov spectrum is presented as well.

A method for determining 212Bi by TDCR Cherenkov counting

A method for determining 212Bi by TDCR Cherenkov counting

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.

Novel approach for strontium preconcentration from seawater and rapid determination of 89,90Sr in emergency situations

A novel approach for rapid 89,90Sr determination in seawater samples is developed. For the first time in the radioanalytical application, the features of the synthetic zeolite Z4A and a highly selective material for Sr separation were synergically employed. Seawater composition significantly reduces Sr yield on highly selective solid-phase extraction materials, making the preconcentration step essentially important but laborious and time-consuming. To address this issue, the ability of zeolite 4A to concentrate the Sr from the seawater matrix was employed. With the proposed method, two important goals were achieved: (i) simple preconcentration of Sr that can be conducted directly at the sampling site, enabling a rapid procedure for 89,90Sr determination in emergencies, and (ii) high and stable Sr recoveries (89 ± 4%) necessary for lowering detection limits. Strontium is effectively separated from 1 L of seawater in less than 1.5 h, which is especially important in emergency situations, such as the Fukushima Daiichi Nuclear Power Plant accident. Minimum detectable activities achieved for 89Sr:90Sr activity ratio ∼10:1 were 0.74 Bq/L for 89Sr, and 1.47 Bq/L for 90Sr, detected by Cherenkov counting, 36–38 h after separation, and 30 min counting time.

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

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

Improving the efficiency counting of Cherenkov detector by using high transmittance photonic crystal materials

In this study, a new type of photonic crystal (PC) designed as a transmitter. The transmittance spectra of the one-dimensional (1D) photonic crystal which are consist of silicon dioxide/magnesium fluoride (SiO2/MgF2). We are simulated the results using different incident angles, and the results showed a high transmittance (99.5%) within the wavelength range of (200–700 nm). Simulations of two-dimensional (2D) photonic crystals were studied, as well as the transmittance values were investigated. As a transmitter, photonic crystals in a one-dimensional array of SiO2 and MgF2 with periodicities N = 5 were employed around the wall of the Cherenkov counter vial. The high transmittance of the SiO2/MgF2 PC allows Cherenkov light to pass without any losing in its initial incident intensity which improves the Cherenkov counting efficiency, which is utilized in a wide range of applications. By replacing the traditional polyethylene (generally used to fabricate the walls of the counter vial) with the high transmittance photonic crystal SiO2/MgF2 which is allow to the most of the emitted Cherenkov radiation to reach the photomultiplier tube without any losing in its way to the tube. Subsequently, the efficiency of the Cherenkov counter was improved. Comparing the counting efficiency for both the polyethylene and the SiO2/MgF2 photonic crystal, it was found that the counting efficiency will be increased by 15% in one-dimension and 9.5% in two-dimensions if the polyethylene walls of the vial were replaced by SiO2/MgF2.

Simultaneous determination of actinides and 90Sr in large-size soil and sediment samples

A simultaneous analytical method for sequential separation and determination of actinides and 90Sr in large-size environmental samples has been developed. In this method, successive co-precipitation steps were firstly conducted to remove matrix elements, then sequential column separation method was applied for simultaneous separation and purification of actinides and 90Sr/90Y. By using vacuum box technology, the total analytical time was minimized and batch processing allowed analyzing 12 samples in four days. The activity of 90Sr was obtained immediately by measuring its daughter radionuclide (90Y) with triple-to-double coincidence ratio (TDCR) Cherenkov counting, while the concentrations of Pu isotopes and 241Am could be measured by alpha spectrometry and mass spectrometric techniques. The overall recoveries of Pu, Am, Sr and Y were higher than 70% for the entire procedure, while the recovery ratios of Sr/Y were between 0.95 and 1.04 before chromatographic separation. The developed method was verified using 20 g and 50 g of environmental soil samples spiked with certified reference materials IAEA-384 or IAEA-385 and standard solution of 90Sr/90Y, and good agreement between the expected values and measured results has been achieved.

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.

A comparative study of alternative methods for 210Pb determination in environmental samples

The accurate determination of the levels of 210Pb in environmental samples (e.g. atmospheric aerosols, waters, soils, biota, etc.) is essential due to its multiple applications in geochronology, radiation protection, groundwaters flows, air masses movement, etc. For this purpose, it has been developed a novel and thorough study of three alternative radiometric measuring methods of 210Pb activity concentrations in several types of samples. The three selected methods were low-level gamma spectrometry (210Pb), alpha-particle spectrometry (via 210Po), and Cherenkov counting (via 210Bi). This study has been performed in terms of precision, linearity and proportionality as well as spent time, type of matrix, and showing the most appropriate method of measure in each case. Several kinds of samples were analyzed such as atmospheric filters, soils, sediments and phosphogypsum (PG) matrices. These samples contain different 210Pb activity concentrations and were measured by the three techniques carrying out radiochemical procedures when necessary. There were not significant differences in the results obtained for the samples analyzed by the three methods. The major precision was obtained by using alpha-particle spectrometry, but this method is more expensive and time consuming.

ЗАСТОСУВАННЯ МЕТОДІВ СТАНДАРТИЗАЦІЇ СПЕКТРІВ БЕТА-ВИПРОМІНЮВАНЬ В РІДИННО-СЦИНТИЛЯЦІЙНОМУ ЛІЧЕННІ

The features of beta spectra standardization for modern liquid scintillation counting (LSC) us-ing Quantulus 1220TM alpha beta spectrometer are considered. The range of tasks is tritium meas-urement, beta-spectrometric determination of strontium-90, determination of strontium-90 by Che-renkov counting, determination of lead-210 in aerosol filters, radiocarbon studies. The purpose of the study was to summarize and analyze the peculiarities of the application of the methods of spectra standardization of beta-emitters in the study of radioactivity of environmental objects based on liquid scintillation counting. Materials and methods: liquid scintillation counting, LSC, Cherenkov counting, radiochemi-cal preparation of samples, spectra decomposition of beta-emitters. Results: Methods for spectra standardization of beta-emitters samples were analyzed in the study of 3H, 14C, 90Sr, 210Pb in environmental objects using a modern Quantulus 1220TM liquid scintil-lation spectrometer. The acceptability, effectiveness and scope of application of the methods of stand-ardization and spectra decomposition for beta-emitters for liquid scintillation counting and Cerenkov counting are grounded.

Synergy of flow injection system and molecular recognition technology products for rapid determination of 89,90Sr and 210Pb

A rapid, automated separation procedure was developed for radioactive strontium and lead isotope determination. This system includes a portable automated system for the preconcentration and sequential elution of targeting isotopes with an Na2H2EDTA solution from solid phase extraction materials, AnaLig®Sr-01 and SuperLig®620, provided by IBC Technologies. Strontium and lead were separated from the majority of matrix constituents to obtain pure fractions of Pb and Sr prior to radiometric detection. In case of barium presence, it can also be fully isolated and completely separated from Sr. The automated procedure can be successfully used for preconcentration and separation from high as well as low radioactivity samples. With only a 1 mL column filled with SuperLig®620, it is possible to isolate Sr and Pb with 100% recovery from 1 L to 2 L of sample at a flow rate of up to 10 mL min−1 within several hours. 89,90Sr isotopes can be further determined by Cherenkov counting, while 210Pb isotopes can be determined by either gamma spectrometry or liquid scintillation counter. The method was tested and validated using certified standard materials and proficiency test samples. The synergy of automated separation and detection procedures enables the determination of the low level activity of 90Sr and 210Pb in a short time with detection limits of 20 mBq L−1 for both isotopes. The proposed method enables lower labour costs, minimal size of apparatuses and columns, low separation time, and reduced secondary waste production. The automated procedure may be easily implemented in laboratories worldwide and can also be used at sampling sites.

Half-life determination of 213Bi and 209Pb by means of Cherenkov counting and detection with a NaI detector

An 225Ac source was prepared and combined with a dedicated setup to collect recoil atoms which are ejected as a consequence of alpha decay. Some targets were made of acrylic glass and were then placed in custom-built triple-to-double coincidence ratio (TDCR) counters to measure the Cherenkov counting rates as a function of time. Half-lives of 213Bi and 209Pb were derived from the data. In addition, polyethylene films were used as targets to collect recoil atoms. These films were then measured in a well-type NaI detector to detect gamma rays. The analysis of the data yielded an independent result for the half-life of 213Bi. Combining the results of both measurement techniques, T1/2(213Bi) = (45.60 ± 0.09) min was obtained as a final value for the half-life of 213Bi. The half-life of 209Pb was found to be T1/2(209Pb) = (195.1 ± 2.6) min.

210Pb/210bi detection in waters by cherenkov counting – perspectives and new possibilities

The measurement of 210Pb activity concentration via its product 210Bi, high-energy beta emitter capable of producing Cherenkov radiation in waters, by liquid scintillation counter Quantulus 1220 has been explored. Without the chemical pre-treatment, the detection limits have been evaluated and possibilities to further decrease MDA value have been considered. Prolonging the counting time coupled to the sample's evaporation prior to counting can enable the achievement of the detection limits below maximal permitted levels recommended by the international legislation. The impact of sodium salicylate addition to the counting vials on the detection efficiency and consequently MDA value has been tested. Sodium salicylate application is associated with the certain complications during sample preparation, here we propose salicylate-based ionic liquids instead. We present an innovative experiment that explores the influence of the addition of a synthesized 2-hydroxypropan-1-amminium salicylate to the counting vials in order to decrease MDA parameter. Furthermore, the interference with 226Ra Cherenkov spectra was assessed and the possibility to evaluate its contribution to 210Pb/210Bi spectra has been proposed. The potential of 210Pb screening in the samples without the chemical isolation of 210Pb has not been thoroughly considered in the literature so far. 210Pb screening of a few spiked samples and real samples collected in the vicinity of mine was carried out, thus the obtained results demonstrate the method's evaluation and set its limitations.

Verification of 90Sr determination in marine animals

90Sr is considered as a hazardous radionuclide for humans. When it is consumed, it would be eventually accumulated in bone and its daughter, 90Y, could then harm bone marrow. To monitor 90Sr in the environment especially in marine food samples it is very important for Thailand as the consumption of marine animals is high and these animals are also exported all over the world and play an important part of the economy. To measure 90Sr in our food samples, a liquid extraction technique using bis-2-etylhexyl-phosphoric acid to separate and purify yttrium followed by Cherenkov counting to determine 90Y in secular equilibrium to 90Sr were developed at the Office of Atoms for Peace’s laboratory. The analytical performance was validated for all criteria i.e. accuracy, precision and trueness. 90Sr determination in spiked mussel samples with various activity concentrations in a range of 2 – 1000 Bq kg−1 dry weight were performed for statistical evaluation. The results had a relative bias within the accepted relative bias of ± 25% i.e. in the range from 10.36 to 16.98 and passed all criteria. This could confirm our analytical approach for 90Sr determination in marine animals and foodstuffs was accepted. Moreover the method is cost-efficient, simple and fast to analyse 90Sr in the samples.

Comparison of different methodologies for the 90Sr determination in environmental samples

The paper describes different isolation/separation and detection procedures for 90Sr determination in the environmental samples which are routinely used in Laboratories A and B. In this context, four different methods for strontium isolation and two methods for detection were tested and compared by 90Sr determination in proficiency test samples (water, soil, vegetation) and animal bone samples. The chromatographic isolation of Sr on Sr resin, AnaLig®Sr01 resin gel, strong base anion exchange resins in nitrate form and combination of strong base anion exchange and Sr resin were used for the examination of the impact of sample matrix constituents on efficiency of strontium isolation (chemical yield), while Cherenkov counting of 90Y and counting of 90Sr(90Y) on proportional counter were used for the quantitative 90Sr determination. The chemical yields obtained with different isolation methods were compared with the emphasis on its influence on reliability of the 90Sr determination in different kinds of samples. The results show that the efficiency of strontium isolation depends on type of sample and separation methodology. The strontium yield on Sr resin column decreases with the increase of Sr, Ca and Na concentration. In the presence of 1 g of Ca and 1 g of Na, the yield of 85% was obtained for 5 mg of Sr carrier and dropped below 50% with further increase of Sr and other elements. However, the yield can be increased to 75% if Na and part of Ca are separated from Sr on the anion exchange column with alcoholic solution of nitric acid and by final separation of Ca from Sr on the Sr resin column. In the presence of large amounts of Ca, Na and other elements, isolation efficiency on the Sr resin column significantly decreases in comparison with other methods. The average yield for isolation from vegetation samples on the Sr resin column is only 21%. For the soil samples the highest average yield (78%) is obtained for the isolation in the combination of anion exchange and Sr resin columns. For the isolation from bone samples the average yields over 80% are on AnaLig®Sr01 and anion exchange resins columns, while Sr resin was not used for separation due to high content of Ca in samples. The results of the 90Sr determination in proficiency testing (PT) samples show that the accuracy of the determination does not depend on high chemical yield but depends on accuracy of yield determination. The analysis of z-values shows that 96% of obtained z-values range from 0 to ±2 while 77% of z-values range between 0 and ± 1. Ninety percent of obtained results of 90Sr determination deviate less than 20% from assigned values in PT provider reports. The results of 90Sr determination in animal bone samples using different methods are in good agreement. The results obtained by Cherenkov counting in both laboratories vary from −3.1–14.5% while results obtained by determination via 90Y and counting on i-Matic vary between −10.0 and −2.9%. These deviations are in accordance with deviations obtained with PT samples. Activity concentrations of 90Sr in wild boar bone samples range from 4 to 30 Bq kg−1 while in deer bone samples from 2 to 8 Bq kg−1.

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

In order to determine radiostrontium with a satisfactory chemical yield, calculated by an external standard, and a low level of MDC a radioanalytical method has been optimized, for environmental and biological samples. Samples were mineralized and extracted by chromatography with prepackaged columns for Cherenkov effect measurement, via daughter radionuclide 90Y, generated by 90Sr. When also 89Sr is present, 90Y is eluted by the same column to subtract its contribution to total Cherenkov counts and determine separately 89Sr and 90Sr (via 90Y) activity. By a fitting experimental data with an exponential equation the eventual presence of other β-emitter radionuclides was ascertained.