Scintillation Counting Techniques Research Articles

Activity standardization of 32Si at PTB

Within the scope of the SINCRON project, several 32Si solutions were measured by means of liquid scintillation (LS) counting techniques at PTB to determine the activity concentration. Initial results revealed limited long-term stability of the samples, and a discrepancy between the TDCR method and the CIEMAT/NIST efficiency tracing method was found. In some cases, the sample instability could not be completely avoided but there is evidence that the results of the first measurements which are carried out within a few days after sample preparation can be used for an activity determination, though with increased uncertainty. Various sample compositions were tested, and a systematic study of long-term measurements and further experiments indicates that the sample instability is due to an adsorption-like effect. The discrepancies between the two LS methods were significantly lower when measuring other 32Si solutions. The initially observed discrepancies are likely due to low-energetic radioactive impurities that can be present in some of the 32Si solutions. A spectral analysis supports the thesis that tritium is present in the first solution and even allows a rough quantification of the activity ratio A(3H)/A(32Si/32P). This value allows impurity corrections to be applied, which leads to a noticeable improvement in the agreement between TDCR and CIEMAT/NIST efficiency tracing. Finally, a new LS sample composition with 15 mL Ultima Gold and 1 mL of HCl (0.5 mol/L) was found to yield stable LS samples. The activity determinations presented in this paper represent a fundamental step towards a new 32Si half-life determination in the framework of the SINCHRON project.

222Rn calibration procedure for water analyses by liquid scintillation counting

PurposeAmong the several methods to measure 222Rn in water, the liquid scintillation counting (LSC) technique is one of the most sensitive and widely used when analysing non-saline waters by liquid extraction, providing excellent accuracy, precision and low-level detection limits. When using the liquid scintillation counter Tri-Carb 3170 TR/SL (Perkin-Elmer) it is not possible to make an automatic determination of the alpha/beta discrimination parameter, being necessary to evaluate the pulse decay discriminator (PDD) value manually to the 222Rn determination. In this work, we describe the steps to perform the calibration of that type of equipment.MethodsThe method consists in the preparation of standard samples from a 226Ra certified standard solution and the adjustment of the PDD value by hand until the percentage of alpha events reaches a plateau of a near-constant fraction of total events. The process consists in taking several measures between PDD 80 and 200 with 15 min counting time each. Within the plateau, the alpha/beta ratio was used to determine the plateau final range as well as the optimum PDD value. After that, the calibration standards and blanks were measured and the region of interest (ROI) was established by finding the maximum value for the figure of merit (FOM) in the upper and lower limits.ResultsThe optimal PDD value of 148 was established by the alpha/beta ratio, and after that, it was possible to measure 226Ra standards to perform the calibration. An efficiency of (9.758±0.035) × 10–1 was obtained. In routine measurements, a detection limit of about 0.50 Bq L–1 is achieved for a 120 min counting time. To evaluate the uncertainty budget, the uncertainties of the net count rate, the efficiency, the sample amount and the decay correction factor were considered.ConclusionsA method was developed for the calibration of LSC Tri-Carb 3170 TR/SL with the optimization of the PDD using a 226Ra standard solution. The acquisition to obtain the plot of the variation of the events fraction in each window (alpha and beta) in function of PDD allowed to evaluate a plateau where the fraction of events was at a minimum. Afterwards, it was possible to measure the set of 226Ra standards after the equilibrium with 222Rn and determine the efficiency for 222Rn with a detection limit of about 0.50 Bq L–1 in routine analyses.

Technical Carbon Black and Green Technology

Abstract Carbon black (CB) is produced through the incomplete combustion of biomass or thermal decomposition in an oxygen-deprived environment. Technical carbon black (TCB) primarily consists of elemental carbon and comes in various grades distinguished by surface area and nanostructure morphologies. However, TCB production raises sustainability concerns due to its reliance on non-renewable feedstock, significant CO2 emissions and high energy consumption. TCBs find extensive use as reinforcing fillers in the tire and rubber industries. Recent studies underscore the importance of eco-friendly alternatives. This research was carried out to monitor the renewability of the TCB samples by determining the 14C isotope concentration. Liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) radiocarbon techniques were employed for measuring the 14C isotope concentration, while isotope ratio mass spectrometry (IRMS) corrected standardised isotope fractionation correction. The investigation revealed that the examined TCB samples contain extremely low 14C concentrations, measuring <1 per cent modern carbon (pMC). This finding raises concerns regarding potential environmental ramifications.

STUDY OF BIO-BASED CARBON FRACTIONS IN TIRES AND THEIR PYROLYSIS PRODUCTS

ABSTRACTWasted tires are the great source of fuel and valuable components but could be a cause of environmental and land pollution. This study shows the detailed method for the determination of radiocarbon isotope (14C) concentration in tires and their pyrolysis products. Samples are taken from truck and passenger car tires in the form of shredded rubber, pyrolysis oil and recovered carbon black. Liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) techniques were used for the investigation at Gliwice Radiocarbon and Mass Spectrometry Laboratory, and National Laboratory for Age Determination, Trondheim, Norway. The results are in good agreement. Radiocarbon concentration of the rubber varies significantly because of its complex structure and composition within the tires. The 14C concentration values were found to be higher in pyrolytic oil compared to rubber, and greater in truck tires rather than car tires.

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

Activity standardization by means of liquid scintillation counting and determination of the half-life of 89Zr

A89Zr solution was measured by means of liquid scintillation counting techniques in order to determine the activity concentration. Two methods were used: the CIEMAT/NIST efficiency tracing method with 3H as a tracer, and the triple-to-double coincidence ratio method. The counting efficiencies were computed with a stochastic model. The very detailed investigation showed that a few corrections are particularly important: Asymmetries in the photodetector responses as well as the backscattering of high-energy gamma rays must be taken into account. Corresponding corrections have therefore been applied. In addition, a detailed uncertainty analysis was carried out and the uncertainties compared with those determined by other research groups.The activity concentrations obtained from the two methods agree well and a combined result was used to establish calibration factors for ionization chambers, which are important secondary standardization instruments. The ionization chambers were combined with a new high-precision current measurement device to provide outstanding linearity. Measurement data from one chamber were used to determine the half-life, which was found to be T1/2=(78.373 ± 0.023) h.

Determination of optimal PSA for the measurement of gross alpha and beta radioactivity in ‎water samples by LSC

Measurement and determination of gross alpha and gross beta radioactivity in water are important in all societies and countries of the world because of their adiobiological risks and is part of the goals of standards and public health organizations. Liquid scintillation counting technique is one of the best methods for simultaneously measuring alpha and beta-particle-emitting in water. In this technique, due to the overlap of spectra of alpha and beta, evaluation of the alpha and beta interference and the appropriate PSA value is very important for sample counting rate. The purpose of this work is to measure the activity concentration of gross alpha and beta in bottled water and compare them with the allowable limit and international standards. To achieve the goal of this research, the work was carried out in two phases. In phase 1, the alpha and beta interference and the appropriate PSA are obtained using two standard solutions of americium-241 and strontium-90 with activity of 21 and 40 Bq. In phase 2, The 10 bottled drinking water samples from different brands are analyzed using LSC. The results of the sample counting showed appropriate PSA value of 110 for the measurement of gross alpha and gross beta radioactivity in water. The measurement results showed that the gross alpha and beta activity concentrations were 41-62 mBqL-1 and 57-85 mBqL-1 which are below the allowable limit by comparing the standard limits.

Electrolytic enrichment method for tritium determination in the Arctic Ocean using liquid scintillation counter

A method of measuring the tritium in seawater based on electrolytic enrichment and ultra-low background liquid scintillation counting techniques was established. The different factors influencing the detection limit were studied, including the counting time, the electrolytic volume of the seawater samples, the selection of background water, scintillation solution and their ratio. After optimizing the parameters and electrolyzing 350 mL volume of samples, the detection limit of the method was as low as 0.10 Bq/L. In order to test the optimization of system for this method, of the 84 seawater samples collected from the Arctic Ocean we measured, 92% were above the detection limit (the activity of this samples ranged from 0.10 Bq/L to 1.44 Bq/L with an average of (0.30±0.24) Bq/L). In future research, if we need to accurately measure the tritium activity in samples, the volume of the electrolytic samples will be increased to further reduce the minimum detectable activity.

The effect of quench agent on urine bioassay for various radionuclides using QuantulusTM1220 and Tri-CarbTM3110

Following a radiological or nuclear incident, the National Response Plan has given the Department of Health and Human Services/Centers for Disease Control and Prevention the responsibility for assessing population’s contamination with radionuclides. In the public health response to the incident, valuable information could be obtained in a timely and accurate manner by using liquid scintillation counting techniques to determine who has been contaminated above background for alpha and beta emitting radionuclides. The calibration plays a major role in this process therefore, knowing the effect of quench agents on calibration is essential.

Determination of Bio Content in Polymers used in the Packaging of food Products

ABSTRACTThe ENEA Radiocarbon Laboratory (Bologna, Italy) has been operating since 1985; it is the oldest among such laboratories operating in Italy and has been active for about 30 years in the field of dating of different types of samples with the radiocarbon (14C) liquid scintillation method. This study shows the detailed procedure for radiocarbon analysis on bioplastic materials by means of the synthesis of benzene, which includes CO2 production and purification, synthesis of acetylene, and synthesis and collection of benzene. The changes made to the original design of the synthesis procedures and the operational parameters adopted to optimize the combustion of the plastic materials are described. The measurement of 14C activity was performed using the liquid scintillation counting technique by a QuantulusTM 1220 low-background counter. The δ13C content was compared with the percentage of 14C concentration for the characterization of the bio content in plastic used in the food packaging.

Assessment of radioactivity contents in bedrock groundwater samples from the northern region of Saudi Arabia.

Recognizing the vast uses of water in human life, the presence of α and β particles emitting radionuclides in groundwater of northern Saudi Arabia has been evaluated as a means of water quality assessment of the region. A liquid scintillation counting technique was used to determine the gross α/β, and 228Ra radioactivities in water samples, while the radioactivity concentrations of 234,238U and 226Ra were determined using alpha spectrometry after the separation process. Present results show that all water samples contain a higher level of gross α and β radioactivity than the WHO recommended limits; the average gross α activity is about 7 times greater than the limit value of 0.5 Bq L-1, while the average gross β activity value is about 3.5 times greater than the limit value of 1 Bq L-1. Correlations of TDS and pH with gross α and β radioactivity in the studied samples were investigated. The activity ratio of the measured U and Ra alpha emitters to the gross α radioactivity and the ratio of the measured β emitters to gross β radioactivity were also discussed. Furthermore, interesting information on thorium abundance and radioactive disequilibrium in U series were observed by studying the activity ratio of 228Ra/226Ra, 226Ra/238U, and 234U/238U. Although these samples are not directly used for human being drinking, and mainly used in irrigation, the higher gross α/β radioactivity may cause health risks to humans, since these radionuclides may enter the food chain through irrigation water. Thus, further radioactive risk assessment is highly recommended.

Mobility of chloride through cement-based materials under partially saturated conditions

This work presents two complementary techniques to study 36Cl and stable chloride diffusion through unsaturated cement-based materials for saturation degrees (Sw) ranging from 0.18 to 1. The first technique is based on steady-state through-diffusion method where suction (up to 9 MPa) is controlled using osmosis process. In the second technique, in-diffusion experiments are performed by putting into contact a spiked-fresh-cement paste with a CEM-V/A-hardened-cement paste (HCP) sample (initial water to cement ratio of 0.4) having a given water saturation imposed by saline solution method. After a controlled diffusion time, the 36Cl activity profiles within the samples are acquired by means of the abrasive peeling method and 36Cl activity is determined by liquid scintillation counting (LSC) technique. The application of the first technique resulted in data showing a sharp decrease of the effective diffusion coefficient (De) (by a factor of ten) between the experiments done on the fully-saturated HCP sample and the HCP sample at Sw = 0.85. Moreover, duplicate in-diffusion experiments carried out on HCP samples partially-saturated at Sw = 0.86 provided 36Cl De range well bracketing the one determined by the first approach at Sw = 0.85. Four other in-diffusion experiments were thus performed on HCP samples with saturation degrees down to 0.18. Interpretation of the experimental results showed a very small decrease of De values for Sw from 0.74 to 0.41 and a sharp decrease for Sw from 0.41 to 0.18. Lastly, comparison with the diffusive behavior of tritiated water (HTO) through unsaturated CEM V/A HCP samples clearly indicated that diffusion of chloride was more affected by desaturation than HTO. Its ionic form would restrict chloride to the liquid phase whom continuity is broken when dehydration is strong enough.

A comparison of two methods used for determination of tritium concentration in urine samples by liquid scintillation counter

Tritium (3H) emits low-energy beta particles with a maximum energy of 18.6 keV. Liquid scintillation counting technique (LSC) is mostly used for the detection and quantification of low-energy emitters like H-3. The most widely used method to determine the level of tritium in humans is testing urine. In this study, tritium activity concentrations in urine samples taken from 20 adults were measured. Their ages range from 23 to 50. Eight of them are female, and others are male. The tritium activity concentrations in urine samples were determined with two different methods. Also, two standard samples were used to compare urine samples. The efficiency values were found with two different methods (26.07% for the first method and 26.14% for the second method). According to the comparison results, the tritium concentration differences between these methods were found in a negligible level for urine samples and in an acceptable level for standard samples. The tritium activity concentrations in urine and standard samples were calculated using two different methods. According to the comparison results, these two methods can be used for determination of tritium concentrations in urine samples.

Activity standardization of 99mTc using liquid scintillation counting method

The Korea Research Institute of Standards and Science (KRISS) participated in the BIPM.RI(II)-K4.Tc-99 m comparison of activity measurements of 99mTc. We develop the national primary standard for 99mTc solution used during the comparison. We use two primary liquid scintillation counting techniques for the standardization: digital coincidence counting with the 4πβ(LS)-γ(NaI(T1))system and triple-to-double coincidence ratio counting. Both methods give consistent results for the specific activity of a 99mTc solution. Adopting the result from the DCC method as the reference value of the 99mTc measurement, we evaluate the standard uncertainty of 0.856% for the KRISS primary standard of the 99mTc activity. The K4 comparison result shows that the newly-established KRISS primary standard lies within the standard uncertainty with the key comparison reference value defined from other 99mTc measurements.

Estimation of Radionuclide Concentrations and Average Annual Committed Effective Dose due to Ingestion for the Population in the Red River Delta, Vietnam

Radioactivity concentrations of nuclides of the 232Th and 238U radioactive chains and 40K, 90Sr, 137Cs, and 239+240Pu were surveyed for raw and cooked food of the population in the Red River delta region, Vietnam, using α-, γ-spectrometry, and liquid scintillation counting techniques. The concentration of 40K in the cooked food was the highest compared to those of other radionuclides ranging from (23 ± 5) (rice) to (347 ± 50) Bq kg−1 dw (tofu). The 210Po concentration in the cooked food ranged from its limit of detection (LOD) of 5 mBq kg−1 dw (rice) to (4.0 ± 1.6) Bq kg−1 dw (marine bivalves). The concentrations of other nuclides of the 232Th and 238U chains in the food were low, ranging from LOD of 0.02 Bq kg−1 dw to (1.1 ± 0.3) Bq kg−1 dw. The activity concentrations of 90Sr, 137Cs, and 239+240Pu in the food were minor compared to that of the natural radionuclides. The average annual committed effective dose to adults in the study region was estimated and it ranged from 0.24 to 0.42 mSv a−1 with an average of 0.32 mSv a−1, out of which rice, leafy vegetable, and tofu contributed up to 16.2%, 24.4%, and 21.3%, respectively. The committed effective doses to adults due to ingestion of regular diet in the Red River delta region, Vietnam are within the range determined in other countries worldwide. This finding suggests that Vietnamese food is safe for human consumption with respect to radiation exposure.

Accurate Quantification of Radiosulfur in Chemically Complex Atmospheric Samples.

An ultralow-level liquid scintillation counting (LSC) technique has been used in measuring radiosulfur (cosmogenic 35S) in natural samples. The ideal half-life of 35S (∼87 days) renders it a new way to examine various biogeochemical problems. A major limitation of the technique is that complex chemical compositions in atmospheric samples may lead to color quenching of LSC cocktails, a serious problem prolonging the pretreatment time (>1 week) and hampering the accurate determination of 35S. For application of the technique where many of the most important atmospheric chemical processes are examined, significant interferences arise and accurate analysis in small samples is not possible. In this study, we optimized the LSC method to minimize/eliminate color quenching in high-sensitivity 35S measurements. The analytical performance of this new method was evaluated using control laboratory experiments and natural aerosol samples. Results show that the new method offers comparable accuracy as the traditional method for normal environmental samples [bias: <±0.03 disintegrations per minute (DPM)] and significantly shortens the pretreatment time to less than 3 days. For samples that were heavily contaminated by color-quenching agents, the accuracy of this new method is notably higher than that of the traditional method (maximum bias: -0.3 vs -1.5 DPM). With the growing use of radiosulfur in the field of Earth and planetary sciences, the accurate determination of 35S would provide a reliable field-based constraint for modeling 35S production in the atmosphere and allow a wide range of atmospheric, hydrological, and biogeochemical applications.

Rapid analysis method for the determination of 14C specific activity in irradiated graphite.

14C is one of the limiting radionuclides used in the categorization of radioactive graphite waste; this categorization is crucial in selecting the appropriate graphite treatment/disposal method. We propose a rapid analysis method for 14C specific activity determination in small graphite samples in the 1–100 μg range. The method applies an oxidation procedure to the sample, which extracts 14C from the different carbonaceous matrices in a controlled manner. Because this method enables fast online measurement and 14C specific activity evaluation, it can be especially useful for characterizing 14C in irradiated graphite when dismantling graphite moderator and reflector parts, or when sorting radioactive graphite waste from decommissioned nuclear power plants. The proposed rapid method is based on graphite combustion and the subsequent measurement of both CO2 and 14C, using a commercial elemental analyser and the semiconductor detector, respectively. The method was verified using the liquid scintillation counting (LSC) technique. The uncertainty of this rapid method is within the acceptable range for radioactive waste characterization purposes. The 14C specific activity determination procedure proposed in this study takes approximately ten minutes, comparing favorably to the more complicated and time consuming LSC method. This method can be potentially used to radiologically characterize radioactive waste or used in biomedical applications when dealing with the specific activity determination of 14C in the sample.

The distribution of tritium in aquatic environments, Lithuania

The aim of this study is to investigate mobile radionuclide tritium (3H or T) activity dynamics in aquatic environments related to Ignalina NPP (INPP) site and water bodies located in remote areas unaffected by the INPP. The 3H excess in the INPP environment was analyzed and compared to the variable 3H background level over the period of operation of the INPP (end of 1983 – end of 2009) and during the initial stage of decommissioning (2010–2017). 3H in the INPP vicinity has been studied in the water of artificial channels related to operation of the INPP and site drainage, in natural surface water bodies and, at a smaller scale, in unconfined groundwater. This study presents an extensive 3H data set extending back to 1980, i.e. before INPP operation started. To assess the contribution of global sources to 3H dynamics, monthly precipitation was also studied, along with water from the Baltic Sea, Curonian Lagoon and Nemunas River were studied as well, all three of these located in the Lithuanian maritime zone. The 3H activity concentration in water was measured using liquid scintillation counting (LSC) techniques (direct counting and counting after enrichment). During the period of INPP operation, 3H from liquid effluent could be clearly observed in discharge channels, occurring in rather low diluted conditions, as well as in Lake Druksiai, the cooling basin, at an even more diluted level. The highest 3H activity concentration in Lake Druksiai was observed in 2003 and reached 201.3 ± 1.3 TU at a time when 3H activity concentrations in background water bodies was 9.2 ± 3.5 TU. After the closure of the INPP, the 3H liquid effluent rate reduced by approximately two orders of magnitude (from 1012 Bq in 1991 to 1010 Bq in 2016) and when decommissioning activity commenced then the 3H activity concentration fell to that approaching the background level (19–27 TU) that can still be observed in industrial discharge and rainwater drainage channels. 3H as a result of leakage from the INPP can be observed in groundwater only in direct proximity to the INPP site near the radioactive waste storage zone.

Standardisation and half-life of 89Zr

The nuclide 89Zr is being tested for the labelling of compounds with long blood circulation times. It decays by beta plus emission (22.8%) and by electron capture (77.2%) to 89Y. Its half-life has been determined by following the decay rate with two measurement systems; an Ionisation Chamber and an HPGe detector. The combination of six results gives a value of T1/2 = 78.333 (38) h, slightly lower than the DDEP recommended value of 78.42 (13) h. This radionuclide has also been standardised by liquid scintillation counting, 4πγ counting and coincidence techniques.

Optimization of the liquid scintillation counting technique for the European interlaboratory comparison on gross α/β activity concentrations in water

A liquid scintillation counting (LSC) measurement method optimization for the gross α/β activity analysis in drinking waters with different chemical and radionuclide composition was performed. The optimized method was suitable to provide gross radioactivity results in drinking waters with the levels of the accuracy and precision similar to those obtained using other radioactivity screening techniques. Robust LSC results contributed to the calculation of gross α/β activity reference values of EC-JRC interlaboratory comparison water samples in 2012. Some of the most common errors in the determination of the gross radioactivity using the LSC are presented.