Measurement of <Superscript>3</Superscript>H,gross <Emphasis Type="Italic">α/β</Emphasis> and <Superscript>222</Superscript>Rn in drinking water using the new Quantulus GCT 6220

Since the introduction of the European Council Directive 2013/51 Euratom in October 2013, the analysis of drinking water has increasingly become the focus of many laboratories in Europe. The activity of tritium, radon and the gross α/β-activity is determined routinely. In order to cope with the increased sample numbers and to reach the necessary detection limits, sensitive measuring devices are required. This work was done with the new Quantulus GCT 6220 to test the sensitivity of this system for drinking water analysis. The results indicate that this instrument is very well suited for this type of analysis and counting times are typically below the required counting times of established systems.     

Standardization of calibration procedures for quantification of gross alpha and gross beta activities using liquid scintillation counter

Simultaneous measurement of gross alpha and gross beta activities by liquid scintillation counting technique using LKB Wallac Quantulus 1220 liquid scintillation counter (LSC) equipped with Pulse Shape Analyzer (PSA) is described. Three sets of pure alpha and pure beta standards simulating the activity concentration values of real samples in terms of α/β activity ratios were used to calibrate the LSC. Calibration methodology for the Quantulus 1220 with respect to the above measurements using ²⁴¹Am and ⁹⁰Sr/⁹⁰Y standards of respective activity concentrations of ~25 dpm and ~10⁴ dpm is described in detail. Also highlighted the need to calibrate the LSC using another set of ²⁴¹Am and ⁹⁰Sr/⁹⁰Y standards of low and high activity concentrations respectively. The practicability and working performance of these calibration plots was checked by the validation trials with test samples spiked with ²⁴¹Am and ⁹⁰Sr/⁹⁰Y covering range of α/β activity ratios from 1:1 to 1:50.     

Possible overestimation of the external standard quench parameter on Wallac 1220 Quantulus™ with high energetic beta-emitters

The 1220 Quantulus is equipped with an ¹⁵²Eu external source used to determine an external standard quench parameter SQP(E). The relationship between ⁹⁰Sr/⁹⁰Y counting efficiency and SQP(E) was found linear in a defined range of SQP(E) values. This function was fixed after many counting experiences made with ⁹⁰Sr/⁹⁰Y standards. The sasme equation is used for the measurement of ⁹⁰Sr in environmental samples. The first goal of this paper is to objectify an overestimation of the SQP(E) when high energetic beta-emitters like ⁹⁰Y are present (1 to 4% in routine conditions). The second one is to show how this artefact could induce a bias in the calculation of ⁹⁰Sr activity in environmental samples. The median of this overestimation is estimated around 6%. Another approach using ⁸⁵Sr standard is suggested to avoid this overestimation. Provided the chemical composition — and thus the quenching — is similar for the two standards, the counting efficiency measured with the ⁹⁰Sr/⁹⁰Y standard could be related to the SQP(E) value of the ⁸⁵Sr standard. Indeed this one appears to be more robust regarding to the range of activity and to the counting time of the external source.     

<Emphasis Type="Italic">ABCD</Emphasis>-<Emphasis Type="Italic">Tool</Emphasis>, a software suite for the analysis of α/β spectra from liquid scintillation counting

This paper presents the alpha/beta complete deconvolution tool (ABCD-Tool), a C++ application for the analysis of spectra from liquid scintillation counting (LSC) measurements. In addition to the basic algorithms for standard gross alpha/beta analysis and the determination of the counting efficiency, the software implements a recent unfolding technique based on Fourier transforms, which gives precise and reliable results even in the case of complex, strongly overlapping spectra. The application is designed to be used with alpha/beta spectra generated from Perkin Elmer Wallac Quantulus 1220. However, future upgrades are scheduled in order to extend the compatibility to spectra from other LSC instruments in commerce.     

The simple radiochemical determination of 90Sr in environmental solid samples by solvent extraction

Determination of ⁹⁰Sr in environmental solid samples is a challenging task because of the presence of so many other radionuclides in samples of interest. This problem was dealt with by radiochemical separation of strontium followed by yttrium separation and Cerenkov counting of the high-energy ??-particle emissions of ⁹⁰Y in order to quantitate ⁹⁰Sr. In this work, an improved method is described for the determination of ⁹⁰Sr in soil samples, through the separation of the daughter ⁹⁰Y at equilibrium. The procedure is based on the HDEHP solvent extraction in combination with liquid scintillation spectrometry (LSS). A low background Quantulus has been optimized for low level counting of Cerenkov radiation emitted by the hard ??-emitter ⁹⁰Y. The analytical quality of the method has been checked by analyzing IAEA Soil-375 reference materials. The analytical method has also been successfully applied to the determination of ⁹⁰Sr for moss-soil samples in inter-laboratory exercises through IAEA??s ALMERA network. The chemical recovery for ⁹⁰Y extraction ranged from 80 to 85% and the counting efficiency was 73% in the window 25?C400 keV.     

A modified method for the sequential determination of 210Po and 210Pb in Ca-rich material using liquid scintillation counting

This research describes methods for the sequential determination of ²¹⁰Pb and ²¹⁰Po activity concentrations in Ca-rich ash samples collected from oil shale-fired power plants in Estonia. The procedure involves digestion of Ca-rich ash samples in a microwave digestion system, radiochemical separation of ²¹⁰Pb and ²¹⁰Po and their measurements. All samples, blanks and standards were measured by liquid scintillation counting (Quantulus 1220). The method was tested using IAEA (International Atomic Energy Agency) RGU-1 and IAEA-444 reference materials. Spectral calibration/peak identification which included the optimization of α/β discrimination system (pulse shape analyser), and recovery have been made by ²⁰⁹Po and ²¹⁰Pb standard solutions.

     

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).     

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.     

A fast and very sensitive LSC procedure to determine Fe-55 in steel and concrete

This procedure for determining Fe-55 contributes to a safe and economically reasonable decommissioning of nuclear power plants. Co-60, Fe-55 and Ni-63 are the most abundant, long-lived radionuclides associated with contaminated piping, hardware, and concrete for several decades of years after shutdown. The analysis of Fe takes about three hours until the measurement with an anticoincidence shielded LSC Quantulus 1220 starts. The decontamination factors are ranging from greater than 10⁵ to 10⁹ for all important naturally and artificially occurring radionuclides except Sb. The chemical yield stays constant at a value of about 92% up to 0.1 g stable Fe in steel, concrete or other material. The detection limits (confidence level 95%) reach values of 8 mBq per sample or about 60 mBq/g steel and 1.5 mBq/g concrete at a counting time of 1000 minutes. Four to eight analyses are performed by one technician during eight hours.     

Calibration and optimization of alpha-beta separation procedures for determination of radium/radon in single- and two-phase liquid scintillation systems

Liquid scintillation alpha beta discrimination technique based on pulse shape analysis (PSA) was evaluated for determination of ²²⁶Ra and ²²²Rn in water samples. In view of the significance of calibration, for the reliable and precise determination of ²²⁶Ra and ²²²Rn concentrations in water samples, calibration procedures were standardized for single and two phase systems using Quantulus 1220 liquid scintillation counter. PSA optimization and efficiency calibrations were performed using ²²⁶Ra standard rather than conventionally used pure alpha and beta standards and substantiated by measuring the activity concentrations of ²²⁶Ra and ²²²Rn in the spiked water samples.     

Rapid measurement of 241Pu activity at environmental levels using low-level liquid scintillation analysis

A straightforward and rapid method has been developed for the determination of ²⁴¹Pu activities. Pu is chemically separated from the sample, purified and electrodeposited to produce a source for alpha spectrometric determination of ²³⁸Pu and ^239,240Pu. Pu is stripped from the disc with concentrated nitric acid and extracted into tri-octylphosphine oxide (TOPO)/toluene. The organic extract is then mixed directly with commercial liquid scintillation cocktail without any further purification procedures and the sample counted on a Wallac 1220 Quantulus liquid scintillation counter (LSC). ²⁴¹Pu activity is estimated via the ²⁴²Pu yield monitor acquired by alpha spectrometry measurement. Experimental results for the performance testing of a low-level liquid scintillation spectrometer and the data for the evaluation of the method using standard reference materials are presented.     

Liquid scintillation counters calibration stability over long timescales

Liquid scintillation spectrometry is widely used for the analysis of alpha and beta emitting radionuclides. Robust calibration of liquid scintillation (LS) spectrometers is fundamental to accurate LS measurement but at the same time is time consuming and costly, particularly if a wide range of radionuclides are analysed by the laboratory. The frequency of the calibration varies in different laboratories and is based on many practical and operational factors. This work summarizes the observations regarding variations in 1220 Quantulus spectrometers efficiency calibrations performed annually using various radionuclides: ³H ⁶³Ni, ⁵⁵Fe, ³⁶Cl, ⁴⁵Ca, ¹⁴⁷Pm, ²⁴¹Pu, ⁹⁹Tc for a period of 9 years and discusses the implication to calibration frequency.

     

A sensitive method based on HDEHP extraction and LSS for the determination of 90Sr in solid samples

An improved and rapid method is described for the determination of ⁹⁰Sr in environmental samples, through the separation of the daughter ⁹⁰Y at equilibrium. The procedure is based on the HDEHP solvent extraction in combination with liquid scintillation spectrometry (LSS). A low background QuantulusÔ has been optimized for low level counting of Cerenkov radiation emitted by the hard b-emitter ⁹⁰Y. The counting efficiency was 60% and the background 0.53 cpm. The reliability and reproducibility of the method have been checked using IAEA reference materials. The chemical recovery for ⁹⁰Y extraction ranges from 83 to 90%.     

Application of ultra-low level liquid scintillation to the determination of 222Rn in groundwater

A procedure for the determination of ²²²Rn in environmental water samples using liquid scintillation counting (LSC) was applied. The extractive scintillator RADONS^Ò and an ultra-low background 1220 QuantulusÔ were used. A minimum detectable activity of 0.1 Bq·l^?1 in 20 ml was found with low-diffusion polyethylene vials and 200 minute measurement time. Quenching effects and possible interferences due to the existence of other radionuclides in the extraction process were studied. The procedure was controlled by gamma-ray spectrometry of the ²²²Rn daughters. Applications to environmental samples collected from spas, wells, and public springs in Extremadura (Spain) are presented.     

222Rn and 226Ra activity concentrations in groundwaters of southern Poland: new data and selected genetic relations

Since 2008, the authors have been conducting research into ²²²Rn and ²²⁶Ra activity concentrations in shallow circulation groundwaters in southern Poland. Measurements have been performed with a liquid-scintillation method and ultra low-level liquid-scintillation spectrometers α/β Quantulus 1220. The research carried out so far has demonstrated that in the Sudetes groundwaters with high activity concentrations of ²²²Rn and ²²⁶Ra are common. In other studied areas in southern Poland no shallow circulation groundwaters with high radon or radium concentrations have been found yet. The conducted research has demonstrated that the activity concentration of ²²²Rn dissolved in shallow circulation groundwaters in the Sudetes depends chiefly on the amount of radon, which after being released as gas from reservoir rocks is dissolved in waters flowing through these rocks. At the same time, the concentration of ²²²Rn dissolved in some shallow circulation groundwaters in the Carpathians is influenced significantly by the amount of radon produced from the decay of its parent ion ²²⁶Ra²⁺ dissolved in these waters.     

Rapid determination of 89,90Sr in wide range of activity concentration by combination of yttrium, strontium separation and Cherenkov counting

The methodology for the rapid determination of ^89,90Sr in wide range of activity concentration is given. Methodology is based on simultaneous separation of strontium and yttrium from samples by mixed solvent anion exchange chromatography, mutual separation of ^89,90Sr from ⁹⁰Y by hydroxide precipitation and quantitative ^89,90Sr determination by Cherenkov counting within 3 days. It is shown that Y and Sr can be efficiently separated from alkaline, alkaline earth and transition elements as well as from lanthanides and actinides on the column filed by strong base anion exchanger in nitrate form and 0.25 M HNO₃ in mixture of ethanol and methanol as eluent. Decontamination factor for Ba, La and other examined elements except calcium is low and can not affect quantitative determination in predictable circumstances. Methodology for quantitative determination by Cherenkov counting based on following the changes of sample activity over time is described and discussed. It has been shown that ^89,90Sr can be determined with acceptable accuracy when ⁸⁹Sr/⁹⁰Sr ratio is over 10:1 and that separation of Y enables reliable determination of ⁸⁹Sr and ⁹⁰Sr in wide range of ⁸⁹Sr/⁹⁰Sr ratios (60:1) and in some cases in presence of other yttrium and strontium isotopes. The methodology was tested by determination of ^89,90Sr in Analytics crosscheck samples (nuclear waste sample) and ERA proficiency testing samples (low level activity samples). Obtained results shows that by using of low level liquid scintillation counter it can be possible to determine ⁸⁹Sr and ⁹⁰Sr in wide range of concentration activity (1–1,000 Bq/L/kg) with uncertainty below 10% within 2–3 days. Results also show that accuracy of determination of ⁸⁹Sr (and ⁹⁰Sr) strongly depends on the determination of difference between separation and counting time when activity ratio of ⁸⁹Sr/⁹⁰Sr is high. Examination the influence of media and vial type on background radiation and counting efficiency has shown that lowest limit of determination can be obtained by using of HNO₃ in plastic vials as counting media, because in this combination figure of merit is maximized. For the recovery of 50% and 100 min of counting time estimated MDA is 55 Bq and 90 Bq for ⁹⁰Sr and ⁸⁹Sr, respectively. Analysis of combined uncertainty shows that it mainly depends on uncertainty of efficiency and recovery determination, uncertainty of activities determination for both isotopes and level of background radiation.     

Efficient and Stable Thin-Film Luminescent Solar Concentrators Enabled by Near-Infrared Emission Perovskite Nanocrystals

A novel triphenylphosphine (TPP) treatment strategy was developed to prepare the near-infrared emission CsPbI₃ nanocrystal (NC)-polymer composite thin-film luminescent solar concentrators (LSCs) featuring high absolute photoluminescence quantum yield (PLQY), low reabsorption, and high stability. The PL emission of the LSCs is centered at about 700 nm with 99.4±0.4 % PLQY and narrow full width at half maximum (FWHM) of 75 meV (30 nm). Compared with LSCs prepared with classic CsPbI₃ NCs, the stability of the LSCs after TPP treatments has been greatly improved, even after long-term (30 days) immersion in water and strong mercury-lamp irradiation (50 mW cm⁻²). Owing to the presence of lone-pair electrons on the phosphorus atom, TPP is also used as a photoinitiator, with higher efficiency than other common photoinitiators. Large-area (ca. 75 cm²) infrared LSCs were achieved with a high optical conversion efficiency of 3.1 % at a geometric factor of 10.     

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.     

Efficient and Stable Thin‐Film Luminescent Solar Concentrators Enabled by Near‐Infrared Emission Perovskite Nanocrystals

A novel triphenylphosphine (TPP) treatment strategy was developed to prepare the near‐infrared emission CsPbI₃ nanocrystal (NC)‐polymer composite thin‐film luminescent solar concentrators (LSCs) featuring high absolute photoluminescence quantum yield (PLQY), low reabsorption, and high stability. The PL emission of the LSCs is centered at about 700 nm with 99.4±0.4 % PLQY and narrow full width at half maximum (FWHM) of 75 meV (30 nm). Compared with LSCs prepared with classic CsPbI₃ NCs, the stability of the LSCs after TPP treatments has been greatly improved, even after long‐term (30 days) immersion in water and strong mercury‐lamp irradiation (50 mW cm^?2). Owing to the presence of lone‐pair electrons on the phosphorus atom, TPP is also used as a photoinitiator, with higher efficiency than other common photoinitiators. Large‐area (ca. 75 cm²) infrared LSCs were achieved with a high optical conversion efficiency of 3.1 % at a geometric factor of 10.     

Further development of accelerator mass spectrometry for the measurement of <Superscript>90</Superscript>Sr at Lawrence Livermore National Laboratory

Based on the encouraging results of our initial efforts to develop a ⁹⁰Sr accelerator mass spectrometry capability, we have undertaken efforts to enhance our system. By changing some key operating parameters and constructing an optimized detector we were able to improve the discrimination of ⁹⁰Sr from the isobaric interference ⁹⁰Zr and reduce our instrumental background by nearly two orders of magnitude. Our current background (4 × 10⁶ atoms, 3 mBq) is comparable to that achievable by decay counting, but is still a factor of ten higher than what is theoretically predicted based on the efficiency of our system. Therefore, future plans include implementation of a time-of-flight system to improve the rejection of ⁹⁰Zr.