Measurement of radioactive samples in Marinelli beakers by gamma-ray spectrometry

Radioactivity measurement of environmental samples is frequently assayed by gamma-ray spectrometry using Marinelli beakers. In this work, self-absorption and coincidence summing effects arising in activity measurements for Marinelli beaker geometry have been studied with a Ge detector. Three types of Marinelli beakers which have capacities of 450 mL, 1 L, and 2 L were developed. Self-attenuation effects for density variation of radioactive samples in each type of the Marinelli beakers were measured as a function of gamma-ray energy, and also the results were compared with calculated values by mathematical model. Meanwhile, the coincidence summing effects of¹²⁵Sb and¹⁵⁴Eu nuclides were obtained from the determination of the full-energy peak and total efficiencies for a Ge detector.     

GESPECOR: A versatile tool in gamma-ray spectrometry

GESPECOR is a Monte Carlo based software developed for the computation of efficiency, of matrix effects and of coincidence summing effects in gamma-ray spectrometry. GESPECOR can be applied to coaxial and well-type HPGe or to Ge(Li) detectors and to various types of sources, including point, cylindrical, and spherical sources or Marinelli beakers. In this paper the structure of GESPECOR is presented and the procedures applied are described. The uncertainty of the results computed by GESPECOR is carefully analyzed. The analysis shows that GESPECOR is able to provide results with a well defined uncertainty, in a user friendly WINDOWS environment.     

电感耦合等离子体原子发射光谱(ICP-AES)法测定钢中硼时样品溶解损失及空白控制研究

用电感耦合等离子体原子发射光谱(ICP-AES)法研究了钢中硼的测定。实验发现,分析线在硼182.64nm处无硼铁基体空白值低于纯试剂(无铁)空白值。样品分析时,应进行无硼铁基空白实验,结果计算只能用此空白值。对普通玻璃烧杯和聚四氟乙烯烧杯的酸溶样品测定结果进行了比较,结果表明,测定结果和空白值相近且都很低,无硼普通玻璃烧杯也能满足钢中低含量硼的测定需要。通过对实验与报道结果比较分析表明,硝酸或王水加热溶解样品得到的溶液中硼没有损失,此溶液可测定钢中酸溶硼;用高氯酸发烟处理后,样品中酸不溶硼可能会溶解,但硼会挥发损失。因此,高氯酸发烟处理不能测定硼。     

A computer program for calculating Ge(Li) detector counting efficiencies for Marinelli beakers

A novel computing method has been developed to calculate the absolute photopeak efficiency of a Ge(Li) detector for Marinelli beakers of different heights and diameters and with variable density. For each point in the cylindrical sample the detection efficiency is calculated taking into account the distance from the detector and gamma-ray attenuation and the efficiency is integrated numerically over the volume of the sample. The detector is approximated as a point detector with an experimentally determined effective interaction depth. It is necessary to measure the absolute efficiency for a point source located on the detector axis and on a line beside the detector parallel to the axis. The computer program calculates the absolute counting efficiency for Marinelli beakers of any geometry and for any density. The measured and calculated values for three different densities give a good (–2.2%) overall agreement.     

Neutron activation analysis of snow and ice in Antarctica

In order minimize the possible contamination during storing and pre-treatment of such pure samples as ice and snow collected in Antarctica, trace elements in experimental tools such as bottles, beakers, tubings and filters were determined by neutron activation analysis. By using well certified tools, ice and snow samples from Antarctica and high mountains in China and in Japan were analyzed. Relative concentrations of volatile elements such as Zn, Cd, As, Sb or Ag to Al or Fe which are major components in the earth crust were found to be 10 to 1000 times higher than in the ordinary soil for the samples from Antarctica and Mt. Naimonanyi in China.     

A study of adsorption characteristics of traces of chromium(III) and (VI) on selected surfaces

The adsorption losses of chromium(III) or (VI) on the walls of Pyrex, flint glass and polyethylene beakers have been investigated. Chromium(III) or (VI) solutions were stored in beakers at different hydrogen ion concentrations, and losses due to adsorption were measured at various contact times by counting the γ-ray activity from chromium-51 radiotracer. At pH 6.95, chromium(III) solutions showed the greatest instability, particularly in polyethylene beakers, where losses up to 25% were observed at the end of the 15-day contact period. Chromium(VI) showed a completely different pattern; losses less than 1% were observed at the end of 15 days on all the three types of containers.     

Contamination problems from glass beaker inner surface in low level <Superscript>210</Superscript>Po analysis

It was found that heating of diluted nitric or hydrochloric acids in many years stored glass beakers can result in mBq quantities of ²¹⁰Po leached from beaker walls to the solution. In the case of freshly bought beakers acid leaching of ²¹⁰Po was not observed. We suppose that acid leachable ²¹⁰Po in old beakers is mainly due to implantation of radon progenies (from air) into superficial layers of glass beaker walls.     

Determination of four additives in aluminum electrolyte by ICP-OES with wet digestion

A method to quantify K, Ca, Mg and Li in aluminum electrolyte by ICP-OES with wet digestion was developed. The samples were digested using aqua regia in PTFE beakers and heated by electric hot plate. The levels of four additives, namely KF, CaF₂, MgF₂ and LiF in aluminum electrolyte were determined simultaneously by ICP-OES. The recovery rate of this method was 93.27%–103.51%. Accuracy was also proven through the measurement of standard sample of aluminum electrolyte. The developed method was applied to relative standard deviations for three digestion replicates of ten samples were in the range from 0.51% to 8.33%.     

Determination of four additives in aluminum electrolyte by ICP-OES with wet digestion

A method to quantify K, Ca, Mg and Li in aluminum electrolyte by ICP-OES with wet digestion was developed. The samples were digested using aqua regia in PTFE beakers and heated by electric hot plate. The levels of four additives, namely KF, CaF₂, MgF₂ and LiF in aluminum electrolyte were determined simultaneously by ICP-OES. The recovery rate of this method was 93.27%–103.51%. Accuracy was also proven through the measurement of standard sample of aluminum electrolyte. The developed method was applied to relative standard deviations for three digestion replicates of ten samples were in the range from 0.51% to 8.33%.     

Detection of metal ions by atomic emission spectroscopy from liquid-electrode discharge plasma

In this paper, the discharge ignited in a capillary connecting two beakers filled with electrolyte solution is investigated. During the experiment, an external electrical voltage is applied through two platinum electrodes dipped in the beakers. A gas bubble forms inside the capillary when the applied voltage is higher than 1000 V. Since the beakers are tilted slightly, after generation, the bubble moves slowly to the uphill outlet of the capillary due to buoyancy. When the bubble reaches the end of the capillary, it cracks and a bright discharge is ignited. The emission spectra of the discharge plasma are related to the metal ions dissolved in the solution and thus can be used for metal ion detection. An application of the system to measurement of water hardness is shown.     

Counting yield calibration of NaI(Tl) detectors for complex geometry samples by use of californium-252

The counting yield for large volume, complex geometry samples such as solutions in Marinelli beakers as counted on a large NaI(Tl) detector can be calibrated using radionuclides activated by neutrons form a²⁵²Cf source. Calibration may be done by using either a known neutron flux facility or by cross calibration of the activated material as a point source vs. sealed gamma-standard sources. The point source of activated material is dissolved after cross calibration to produce the large volume distributed source.     

Surface treatment of borosilicate glass beakers for prevention of sodium contamination

Pyrex glass beakers are treated with molten Ca(NO₃)₂-KNO₃ (20:80 mol %) mixture at 500°C for 3 h. Treated beakers can be used successfully in wet oxidation of SRM-1571 Orchard Leaves for sodium determination; at least 10 oxidations can be done without sodium contamination. Mass spectrometry is used to investigate the depth profiles of glass components within 60 nm of the glass surfaces and to clarify the mechanism of the sodium contamination.     

Activity of137Cs in some foodstuffs imported to the Slovak Republic

The results of radiocesium activity of some foodstuffs imported to the Slovak Republic in the period from January 1988 to July 1995 are presented. The analysed samples were homogenized, packed into 0.451 Marinelli beakers and then measured by direct semiconductor, -spectrometry for 10 000–50 000 seconds. The levels of¹³⁷Cs in various foodstuffs varied quite widely from Minimum Detectable Activity (MDA)=0.4 to 80.2 Bq/kg. Concentrations of¹³⁷Cs in fish and fish products were in general higher than those in beef and pork.     

Application of reference materials in the accurate calibration of the detection efficiency of a low-level gamma-ray spectrometry assembly for environmental samples

A new assembly dedicated for the low-level ψ-ray spectrometric measurements of environmental samples have been installed recently at the International Atomic Energy Agency's Laboratories, Seibersdorf. Calibration of the detection efficiency was performed by a set of 14 IAEA Certified Reference Materials, a standardized solution of¹³⁴Cs, solutions of 2 pure potassium salts, and 2 mixed radionuclide gamma reference standard solutions. These materials, in 1.3 liter Marinelli beakers, were measured by a large HPGe detector. The high precision and accuracy of the calibration procedure is shown by the high significance achieved in the linear fits of the efficiency results, which are traceable to certified and standard reference materials. Small biases between some calibrands were detected. A new corrected result is the 1.37±0.05 Bq/kg activity concentration of¹³⁷Cs in IAEA-A-14 Milk Powder.     

Experimental validation of some thermal neutron self-shielding calculation methods for cylindrical samples in INAA

Neutron self-shielding has been a factor of concern in the history of Instrumental Neutron Activation Analysis. When the sample to be analyzed cannot be made small enough in size and/or sufficiently diluted, this undesired phenomenon must be accounted for. Several analytical, semi-empirical and computational methods for estimating the thermal neutron self-shielding effects have been extensively discussed in the literature and this work aims at the experimental validation of some of these methods by neutron irradiation of cylindrical samples containing strong thermal neutron absorbers. The accuracy and the relative differences in the results between these methods are discussed for cylindrical samples with up to 40% thermal self-shielding, showing that a semi-empirical sigmoidal function can be more accurate in modeling this effect than other exact algorithms, where a maximum 2% relative difference to the experimental values was obtained.     

On the method of Dryak et al. for self-absorption correction calculations

An analytical expression for the equivalent thickness of a sample measured in a Marinelli geometry is reported. Using it as input in the formula proposed by Dryak et al.¹, self-absorption corrections for Marinelli beakers with arbitrary dimensions can be computed.     

226Ra uptake from soils into different plant species

Accumulation of ²²⁶Ra into different plant species from contaminated soils was measured on site within the area of an uranium mill. Marinelli beakers and Nal(Tl) spectrometer were used for measurement of dried and weighted samples. While the ²²⁶Ra activity concentration in soil on site ranged from 7.12 to 25.60 Bq·g⁻¹ (1 SD<±10%), in the plant species tested it ranged from 0.66 to 5.70 Bq·g⁻¹ (1 SD<±10%). No significant differences in ²²⁶Ra accumulation were found after cultivation of selected plant species in a glasshouse in relation to the outdoor experiments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of surface properties of the titanium dioxide porous films on the characteristics of solar cells

Porous films formed by cylindrical geometrically anisotropic fragments of TiO₂ have been produced by electrochemical anodization of titanium. The specific surface area and pore volume of the samples were determined by the BET method. It is shown that the samples have a bimodal pore-size distribution with maxima depending on the anodization voltage: by increase in voltage the inner diameter of the cylindrical pores grows, which leads to a decrease in the specific surface area. Dye sensitized solar cells were assembled on the basis of the obtained materials to study the effect of certain characteristics on the efficiency of solar energy conversion. The electrical transport properties of the films were studied by impedance spectroscopy.     

Carboxylated and decarboxylated nanotubes studied by X-ray photoelectron spectroscopy

Carbon nanotubes (CNTs) of the conic and cylindrical structure were studied by X-ray photoelectron spectroscopy in the initial state and after carboxylation and decarboxylation reactions. The O=C—O and C—O groups were revealed on the surface of the chemically modified samples. It was found that both the carboxylated and decarboxylated cylindrical CNTs contain a smaller amount of oxygen than the corresponding conic CNTs apparently due to differences in their structures.     

Analysis of small amounts of solid samples by spark-source mass spectrometry

Various elements were determined in solid samples weighing < 2 mg by spark-source mass spectrometry. The samples were fixed on the top of a cylindrical graphite electrode using a conductive silver paint. After baking, the samples were sparked against a tantalum or gold wire. The method was used for the determination of impurities in steel, iron, molybdenum and CdSe. For samples weighing ca. 1 mg, detection limits of the order of 1 μg g^?1 were obtained. A relationship between the relative sensitivity factor and physical properties is proposed.