Application of liquid scintillation inclusion techniques for the simultaneous determination of alpha and beta activities in composite samples – A preliminary study

Present work highlights liquid scintillation inclusion techniques as a tool for simultaneous determination of gross α and β activities in composite samples. This preliminary study comprises a preamble exercise to check whether Automatic Efficiency Control (AEC) and knee point inclusion techniques which are conventionally used for analysis of two β-emitting radio-nuclides in a mixture, can be implemented for quantification of gross α and β activities in composite samples. In inclusion techniques, two counting regions are set such that there are spill-up and spill-down of pulse events in each region from both types of radio-nuclides. AEC which is built-in feature in Packard Tri-Carb 2900 TR Liquid Scintillation Counter (LSC) provides automatic counting region adjustments for single and dual label samples according to the degree of quench present in sample. While knee point inclusion technique requires manual Lower Level (LL) and Upper Level (UL) discriminator setting to define two counting regions. In the present study, α/β spiked composite samples were treated as dual label samples with α and β radio-nuclides as two distinct entities contributing to the gross activities and analyzed employing AEC and knee point inclusion techniques. Instrument discriminator settings and regions of interest (ROI) were evaluated to determine optimum counting conditions for both the techniques. Three sets of pure alpha and pure beta standards simulating the activity concentrations of real samples in terms of α/β activity ratios were used to calibrate LSC. Calibration methodology for Packard Tri-Carb 2900 TR LSC with respect to the above measurements using ²⁴¹Am, ³⁶Cl and ⁹⁰Sr/⁹⁰Y calibration standards is explained in detail. The practicability and working performance of these techniques was checked by the validation trials with spiked synthetic samples covering range of α/β activity ratios from 1:1 to 1:50 and 50:1. Procedures have been tested by comparison with, established PSA technique and repeatability has been evaluated.     

Determination of gross alpha and beta activities in water samples by liquid scintillation counting

Liquid scintillation counting (LSC) has been proposed for the determination of the gross alpha and beta activities of aqueous samples because of its simplicity and low associated costs. In this paper, protocols for gross alpha and beta activities determination of the samples of waste water from the discharges of radiochemical laboratories and of the water samples from underground low-level waste repository monitoring wells are described. Lower limits of detection as low as 30 mBq L⁻¹ for gross alpha and 90 mBq L⁻¹ for gross beta activities are achieved for 10 000 s measurement of a sample produced by concentration of 1 L of the ground water.     

低本底α/β仪测量饮用水中总 α放射性活度的实验室质量控制

总α放射性活度检测可避免繁琐的低水平放射性核素鉴定,是饮用水放射性水平的初筛监测手段之一。近年调查显示：我国饮用水总α放射性活度稳定保持在较低水平。低水平的α放射性活度检测需要高质量实验室质量控制,以保证检测结果的准确度。实验采用低本底α/β仪,以α闪烁体为探测器,吸收样品核辐射α粒子能量,使有机闪烁体分子ZnS(Ag)发射荧光,通过统计单位时间内的闪烁体发射荧光数目正比于核衰变数目,由此感应有效厚度样品层辐射的α粒子计数信号,对饮用水中总α放射性活度浓度检测。首先,实验以表面α粒子发射率为2～20粒子数/s(2π 方向)的电镀源测定本底α计数效率(CPS)。然后,在最优化的本底值、工作源效率、串道率等参数条件下,运用标准曲线法测定标准源α计数效率(ε)。最后,结合CPS和ε代值计算质控样总α体积活度、计数平均值(或总体积活度平均值)和标准偏差s,并以±s为上辅助线(upper auxiliary limit, UAL)和下辅助线(lower auxiliary limit, LAL),以±2s为上警告线(upper warning limit, UWL)和下警告线(lower warning limit, LWL),以±3s为上控制线(upper control limit, UCL)和下控制线(lower control limit, LCL),绘制本底α计数、标准源α计数和质控水样总α体积活度的均数质量控制图,以考察CPS和ε对质控水样总α体积活度测量质量控制的影响。数据结果显示,以电镀239Pu为工作源,以241Am为标准源,样品放置时间24 h,测量时间60 min,铺样厚度4 mg·cm-2时,本底α计数率CPS=0.000 37 s-1,工作源探测效率η=94.35%,α→β串道率Fα=0.41%,标准源计数效率ε=7.25%(Y=1.323X-5.285,R2=0.991 5)。统计结果显示：40份空盘本底α计数的受控范围为-1.61~5.82,33个点落在UAL与LAL范围内,2个点落在UWL与UAL范围内,3个点落在LWL与LAL范围内,2个点落在UWL与UCL之间,本底测量受控良好;24份标准源α计数的受控范围523.7~644.3,14个点落在UAL与LAL范围内,5个点落在UWL与UAL范围内,5个点落在LWL与LAL范围内,标准源测量受控良好;20份质控水样总α体积活度受控范围为0.007 91~0.057 86 Bq·L-1,11个点在UAL与LAL范围内,5个点在UWL与UAL范围内,3 个点在LWL与LAL范围内,1个点在LWL与LCL之间,质控水样测量实验室质量控制良好。因此,以α闪烁探测器对低水平α放射性计数测量时,控制α本底计数和标准源计数效率,这两个α统计计数中的主要不确定度来源,可以实现水样中总α放射性活度检测的有效实验室质量控制。     

The natural radioactivity in water by gross alpha and beta measurements

An alternative method for evaluating gross alpha and beta radioactivity in water was developed by performing alpha counting using a surface barrier detector and gamma- ray spectrometry using a NaI(Tl) scintillation detector. Several experiments were realized under controlled conditions in the laboratory with the aim of establishing adequate calibration of the systems utilized for performing activity concentration measurements in water samples of variable salinity. Groundwater samples collected at several spas in São Paulo and Minas Gerais States in Brazil were submitted to the developed technique in order to assure its applicability in waters characterized by different Total Dissolved Solids content. The values obtained were compatible with the previous knowledge of the radioactivity of the studied water sources, thus indicating the reliability and usefulness of the method for generating information on investigations focusing environmental aspects and/or the evaluation of the drinking water quality in terms of radiological aspects.     

Relative x-ray transition probabilities to theK-shell forZ=81, 92, 94, and 96

Accurate intensity measurements of the majorK x-ray groups have been performed with high resolution Ge(Li) detectors in singles and coincidence arrangements and with a high-purity Ge detector of the intrinsic type. Previously reportedK x-ray intensities forZ=96 are in error due to the presence of a 121.5 keV γ-ray in the decay of²⁴⁹Cf. The present results are as follows: forZ=81,K _α2/K _α1=0.589±0.008, \(K_{\beta _1^\prime } /K_{\alpha ^1 } = 0.344 \pm 0.008, K_{\beta _2^\prime } /K_{\alpha _1 } = 0.102 \pm 0.004\) , andK _β/K _α=0.281±0.006; forZ=92 \(K_{\alpha _2 } /K_{\alpha _1 } = 0.611 \pm 0.008,K_{\beta _1^\prime } /K_{\alpha _1 } = 0.365 \pm 0.008, K_{\beta _2^\prime } /K_{\alpha _1 } = 0.125 \pm 0.004\) , andK _β/K _α=0.300±0.006; forZ=94, \(K_{\alpha _2 } /K_{\alpha _1 } = 0.610 \pm 0.008, K_{\beta _1^\prime } /K_{\alpha _1 } = 0.369 \pm 0.010, K_{\beta _2^\prime } /K_{\alpha _1 } = 0.127 \pm 0.004\) , andK _β/K _α=0.308±0.008; and forZ=96, \(K_{\alpha _2 } /K_{\alpha _1 } = 0.627 \pm 0.008, K_{\beta _1^\prime } /K_{\alpha _1 } = 0.372 \pm 0.009, K_{\beta _2^\prime } /K_{\alpha _1 } = 0.133 \pm 0.005\) , andK _β/K _α=0.310±0.008. The error limits are the 2σ statistical errors to which a systematic error in the detector efficiencies has been added linearly. The present results are compared with recent theoretical calculations.     

Fluctuations and a rigorous uncertainty relation of trigonometric operators of the phase and the number of photons of an electromagnetic field for general quantum superpositions of coherent states

The quantum-statistical properties of states of an electromagnetic field of general superpositions of coherent states of the form of N _α,β(α?+e ^iξ β? are investigated. Formulas for the fluctuations (variances) of Hermitian trigonometric phase field operators ? ≡ côs φ, ? ≡ sîn φ (the so-called “Susskind–Glogower operators”) are found. Expressions for the rigorous uncertainty relations (Cauchy inequalities) for operators of the number of photons and trigonometric phase operators, as well as for operators ? and ?, are found and analyzed. The states of amplitude \({N_{\alpha ,\beta }}\left( {\left| {{{\sqrt {ne} }^{i\varphi }}\rangle + {e^{i\xi }}\left| {{{\sqrt {{n_\beta }e} }^{i\varphi }}\rangle } \right.} \right.} \right)\), φ = φ_α = φ_β, and phase \({N_{\alpha ,\beta }}\left( {\left| {{{\sqrt {ne} }^{i{\varphi _\alpha }}}\rangle + {e^{i\xi }}\left| {{{\sqrt {ne} }^{i{\varphi _\beta }}}\rangle } \right.} \right.} \right)\), n = n _α = n _β, superpositions of coherent states are considered separately. The types of quantum superpositions of meso- and macroscales (n _α, n _β » 1) are found for which the sines and/or cosines of the phase of the field can be measured accurately, since, under certain conditions, the quantum fluctuations of these quantities are close to zero. A simultaneous accurate measurement of cosφ and sinφ is possible for amplitude superpositions, while an accurate measurement of one of these trigonometric phase functions is possible in the case of certain phase superpositions. Amplitude superpositions of coherent states with a vacuum state are quantum states of the field with a “maximum” level of the quantum uncertainty both in the case of a mesoscopic scale and in the case of a macroscopic scale of the field with an average number of photons n _α/β ≈ 0, n _β/α » 1.     

Radioactivity levels in surface water of lakes around Izmir/Turkey

The aim of this study is to determine the radioactivity levels as a baseline for further studies and to obtain the distribution patterns of radioactivity in lake surface water around Izmir/Turkey. In this study, surface water samples were collected from three lakes around Izmir–Turkey. Surface water samples were analyzed for pH, mV conductivity and alkalinity content. The gross alpha/beta and uranium concentrations were investigated in the collected lake water samples. Mean gross alpha and gross beta activity concentrations in the surface water were found to be between (0.03 and 2.62) Bq l⁻¹ for Karagol Lake, (0.75 and 2.35) Bq l⁻¹ for Golcuk Lake, (0.03 and 1.77) Bq l⁻¹ for Cakalbogaz Lake, respectively. Uranium concentration varied between (0.05 and 900) μg l⁻¹ for Karagol Lake, (0.05 and 0.95) μg l⁻¹ for Golcuk Lake and (3.33 and 10) μg l⁻¹ for Cakalbogaz Lake. Radioactivity contour maps were produced and their data were evaluated statistically.     

Classical Dynamics Based on the Minimal Length Uncertainty Principle

In this paper we consider the quadratic modification of the Heisenberg algebra and its classical limit version which we call the β-deformed Poisson bracket for corresponding classical variables. We use the β-deformed Poisson bracket to discuss some physical problems in the β-deformed classical dynamics. Finally, we consider the (α,β)- deformed classical dynamics in which minimal length uncertainty principle is given by \( [ \hat {x} , \hat {p}] = i \hbar (1 + \alpha \hat {x}^{2} + \beta \hat {p}^{2} ) \). For two small parameters α,β, we discuss the free fall of particle and a composite system in a uniform gravitational field.     

Fast determination of uranium and radium in waters of variable composition

The effects of uranium and its progeny radium are known to be harmful and their measurements in drinking water are necessary for careful monitoring. Fast and accurate methods for determination of uranium and radium in water samples with various salinity and activities concentrations have been developed. High Resolution Inductively Coupled Plasma Mass Spectrometry is used for direct measurement of uranium. Calibration is performed with ²³⁸U standards and ²⁰⁹Bi is used as internal standard to correct the matrix effects and plasma instability. The radium is determined by photon electron rejected alpha liquid spectrometry after a chemical separation procedure that includes co-precipitation of radium with barium sulphate, transformation of the sulphate to carbonate and extraction of radium in the scintillation cocktail. The minimal detectable activities of 3.5×10⁻⁸ Bq kg⁻¹ for uranium and 2.3×10⁻⁴ Bq kg⁻¹ for radium are obtained.     

Luminescent properties of a new In-based organic liquid scintillation system

A novel liquid scintillator system using metal β-diketonate chemistry based on loadings of indium, a target of current interest in low energy solar neutrino detection, is developed. The optical absorption, fluorescence and scintillation properties for this new system are described. The scintillation light output as found from the irradiation by low energy gamma-rays is presented. Notable light yields are found.     

Continuous thoron gas measurement using single scintillation cell – Correction for 212Pb deposition

Scintillation cells are used in continuous mode for thoron estimation using gross alpha counts. Such methods give rise to overestimation resulting from buildup of background counts due to the deposition of Lead (²¹²Pb). Here, the background counts in the cell for a specific counting period owing to previously deposited ²¹²Pb has been estimated using a model to get a time dependent correction factor. This correction for ²¹²Pb deposition has been utilized to estimate the current thoron concentration of the sample. The concentration obtained by this method is validated using the scintillation cell by grab sampling method and a continuous thoron monitor, RAD7.     

The beta branching ratio and conversion coefficients in the137Cs decay

The decay of¹³⁷Cs has been reinvestigated using several precision counting methods. The emission rate ofβ-particles plus internal conversion electrons was measured by the 4π-proportional counter method using vacuum evaporated sources free of self-absorption and checked by the liquid scintillation method. TheK-conversion coefficient was determined by the electron X-ray coincidence method using a magnetic spectrometer and a high resolution Si(Li) detector. TheK/(L+M+...) conversion ratio and a second less accurate value for the β-branching ratio were obtained from the recorded electron spectra. Theγ-ray emission rate of all sources was determined to within ±0.14%, on the average, with a calibrated NaI(Tl) crystal detector. As results the intensity of theβ-decay to the ground state of¹³⁷Ba could be determined to (5.4±0.3)% of the¹³⁷Cs decays, theK-conversion coefficient to 0.0916±0.0004, and theK/(L+M+...) conversion ratio to 4.41±0.04. From these values the γ-ray emission intensity is (85.1±0.4)% of the¹³⁷Cs decays and theK X-ray emission intensity is (8.13±0.10)% of the emittedγ-rays. All errors are discussed in detail.     

Radiochemical analysis of chlorine-36

The radioactive chlorine isotope, ³⁶Cl, decays with a half-life of 3×10⁵ years by emitting a beta particle (98 %) and by electron capture. The aim of this paper is to propose a radiochemical separation method of ³⁶Cl from the other beta-gamma emitters present in low and medium radioactive wastes such as spent ion exchange resins and evaporator concentrates, that arise from Nuclear Power Plants and particularly in the wastes that come from decommissioning activities of graphite reactors, in order to provide data for ³⁶Cl inventory calculations. The separation method proposed is based on an oxidation technique where chlorine is trapped by NaOH. ³⁶Cl beta emissions are measured by liquid scintillation counting by the dual label technique in order to avoid the contamination produced by ¹⁴C which is also trapped by NaOH and which is the main contaminant present in graphite samples. The sensitivity of this method is sufficient to achieve the needed thresholds for the radiological characterization of the radioactive materials to which this method can be applied.     

<Superscript>210</Superscript>Pb and <Superscript>210</Superscript>Po determination in environmental samples using liquid scintillation counting and alpha spectrometry

A simple radiochemical procedure has been developed to determine ²¹⁰Pb and ²¹⁰Po in environmental samples from the same matrix. Sediment samples are decomposed by leaching with mineral acids or by microwave digestion, while water samples are pre-concentrated. One part of the resulting solution, spiked with ²⁰⁹Po, is used for ²¹⁰Po determination by spontaneous deposition onto nickel disks (α-spectrometry). The other part is assayed for ²¹⁰Pb, separating the Pb either by anion-exchange (sediment samples), or by solvent extraction (water samples). The ²¹⁰Pb source is finally prepared by precipitation as oxalate and the chemical recovery determined by gravimetry. The ²¹⁰Pb activity concentration is determined by liquid scintillation. A standard sediment sample supplied by IAEA and spiked water samples were analysed to check the procedure. The ²¹⁰Pb and ²¹⁰Po measurements agreed well with the certifications, deviations being less than 10%. The mean recoveries for Pb and Po were (70±12)% and (77±8%) for sediments, and (70±10)% and (81±7)% for waters, respectively.     

Implications of Time Varying Cosmological Constant on Kaluza-Klein Cosmological Model

In this paper, the cosmological model with variable $\varLambda= \alpha \frac{\dot{R}^{2}}{R^{2}} + \beta\frac{1}{R^{2}}$ in Kaluza-Klein metric have been studied. Here α and β are dimensionless parameters. The solutions to Einstein field equations which assume that the Universe is filled with perfect fluid have been obtained by using the Gamma Law Equation p=(γ?1)ρ; in which the parameter γ is constant and power law equation A(t)=R ⁿ (t)—where A(t) is scale factor for extra dimension and R(t) is scale factor for space dimensions. The fifth dimension for the radiation dominated phases is more prominent with this model. Other physical parameters i.e. density, pressure, deceleration parameter, Hubble parameter have been determined for this model. It is observed physical parameters depends upon constants α, β and n. Neo-classical tests have also been studied in this paper.     

Increasing the performance of tritium analysis by electrolytic enrichment†

Several improvements are described for the existing tritium enrichment system at the Isotope Hydrology Laboratory of the International Atomic Energy Agency for processing natural water samples. The improvements include a simple method for pretreatment of electrolytic cells to ensure a high tritium separation factor, an improved design of the exhaust system for explosive gases, and a vacuum distillation line for faster initial preparation of water samples for electrolytic enrichment and for tritium analysis. Achievements included the reduction of variation of individual enrichment parameters of all cells to less than 1% and an improvement of 50% of the stability of the background mean. It resulted in an improved detection limit of less than 0.4 TU (at 2s), important for application of tritium measurements in the future at low concentration levels, and resulted in measurement precisions of±0.2 TU and±0.15 TU for liquid scintillation counting and for gas proportional counting, respectively.     

Synthesis and lithium ion insertion/extraction properties of hollandite-type MnO2 prepared by acid digestion of Mn2O3

Single-phase specimens of α-MnO₂ (hollandite-type) and β-MnO₂ (rutile-type) were synthesized by the acid digestion of Mn₂O₃ under reflux conditions. The type of polymorph of MnO₂ products was strongly dependent on the reaction temperature, type of acid used, and its concentration. The pH titration curve of α-MnO₂ displayed a monobasic acid behavior toward Li⁺, but β-MnO₂ showed a poor ion-exchange property. In contrast, both α-MnO₂ and β-MnO₂ acted as a rechargeable active material in a liquid organic electrolyte lithium cell. The initial discharge capacities of both electrodes exceeded 200 mAh/g (cut-off voltage: 2 V). After discharge–charge repetition, the α-MnO₂ structure was still retained without structure collapse, although the β-MnO₂ structure was destroyed. These findings show that Li⁺ ions can be inserted only into the hollandite-type tunnels in α-MnO₂ and cannot diffuse the rutile-type linkages in α-MnO₂ as well as those in β-MnO₂ without structure collapse.     

The tensor polarization of 5Li (32−) in the reaction α + d → α + p + n

At the Hamburger Isochronous Cyclotron the formation of the particle unstable ground state of ${}^5\text{Li(}\text{3}\text{2}{}^{\mathrm{?}}$ has been investigated in the reaction α + d → α + p + n at E_α = 28.3 MeV. The neutrons were detected in two liquid scintillation counters, while a large Si (Li) detector was used to observe the α-particles. In a first analysis, the tensor polarization parameters of the five-nucleon system ⁵Li are determined from the experimental data. The results are in quite good agreement with theoretical predictions of Hackenbroich et al.     

The in-situ solid-state NMR spectroscopy investigation of alcoholic lactose suspensions

The polymorphic forms of lactose in alcoholic suspensions have been determined by ¹³C CP-MAS NMR spectroscopy, employing hand-made glass inserts. Suspensions of alpha lactose monohydrate (Lα·H₂O) with particle size between 2 and 200 μm were prepared by 24 h reflux or by storage for 28 d in anhydrous ethanol without agitation. These suspensions were compared to an ethanolic sub-micron lactose suspension provided by a 3 M Health Care (Loughborough). The ¹³C CP-MAS NMR spectra indicated that Lα·H₂O dehydrated to stable anhydrous alpha lactose polymorph (Lα_S) whilst suspended in ethanol. In addition, strong ethanol ¹³C resonances were observed for some samples, indicating a liquid–solid interaction between the ethanol and lactose surface. Replacement of ethanol with anhydrous methanol, n-butanol and 3-methylbutan-2-ol implied that the solvent mediated dehydration of Lα·H₂O to Lα_S occurs as a result of sterically controlled interactions.