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.     

High pressure Marinelli for counting low activity compressed gas samples

Quantification of low-activity noble gases in air is typically accomplished through separation of the noble gas from air followed by radiometric assay. This work is aimed at quantification of radioactive noble gas in air without extraction. A high pressure aluminum Marinelli counting vessel was designed and fabricated that can be placed on a coaxial high purity germanium detector for gamma counting. Characterization of the performance of this Marinelli using MCNP modeling, large excesses of activity, and low-activity noble gas in air is discussed. Minimum detectable concentrations achieved during a 24 h count are: 5, 10, 50, and 1 Bq/m³ for ¹³³Xe, ^133mXe, ^131mXe, and ¹³⁵Xe, respectively.     

Direct and precise determination of environmental radionuclides in solid materials using a modified Marinelli beaker and a HPGe detector

A simple but precise detection method was studied for the determination of natural radionuclides using a conventional HPGe detector. A new aluminium beaker instead of a plastic Marinelli beaker was constructed and examined to reach radioactive equilibrium conditions between radon and its daughter elements without the escape of gaseous radon. Using this beaker fifteen natural radionuclides from three natural decay series could be determined by direct γ-ray measurement and sixteen radionuclides could be determined indirectly after radioactive equilibrium had been reached. Analytical results from ground water were compared with those from conventional α spectroscopy and the results agreed well within 12% difference. Nitrogen gas purge was used to replace the surrounding air of the detector to obtain a stable background and reducing the interference of radon daughter nuclides in the atmosphere. The use of nitrogen purging and the aluminium Marinelli beaker results in an approximately tenfold increase of sensitivity and a decrease of the detection limit of ²²⁶Ra to about 0.74 Bq kg^–1 in soil samples. Received: 12 October 2000 / Revised: 12 December 2000 / Accepted: 13 December 2000     

Validation testing of the Genie 2000 Cascade Summing Correction

Summary To validate the accuracy and precision of the Cascade Summing Correction method, over 800 archived measurements of calibrated sources (filter paper, 20 cm³ liquid scintillation vial, 400 ml beaker and Marinelli beaker) containing cascading (⁸⁸Y and ⁶⁰Co) and non-cascading isotopes from 133 different ISOCS/LabSOCS characterized high purity germanium detectors have been analyzed. Comparing the corrected results for the cascading isotope activities to the known activities shows the method is effective and accurate. Evaluation of the accuracy as a function of the amount of correction reveals a small systematic error for which a variable precision adjustment is recommended. Requirements to filter true coincidence X-rays by are verified.     

Total versus effective total efficiency in the computation of coincidence summing corrections in gamma-ray spectrometry of volume sources

For the evaluation of coincidence summing effects for volume sources an effective total efficiency (ETE) is used instead of the common total efficiency (TE). In this paper ETE is computed by the Monte Carlo method. The differences between ETE and TE are analyzed and their origin is discussed. Measured values for the coincidence summing correction factors for a standard solution containing ¹⁵²Eu in a one liter Marinelli beaker are compared with computed values obtained from appropriate values of ETE. It is shown that the procedure for the evaluation of the coincidence effects is reliable. As a consequence it can be concluded that ¹⁵²Eu volume sources can be successfully used for efficiency calibration even in the case of high-efficiency detectors and close source-to-detector distances.     

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.     

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.     

Variation of the detection efficiency of a Ge detector with the height of the sample in Marinelli beaker

Several two and three parameter analytical functions were fitted to the measured detection efficiencies () of a Ge detector for a Marinelli beaker filled with samples up to different heights (H). From these, the expression =308E ^–0.82/((H–6.1)²+107), gave the best fit. The measured and calculated efficiencies were compared and for 70 determinations, a relative standard deviation of only 7.6% was obtained.     

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.     

Degradation of chlorpyrifos by ionizing radiation

Summary A survey was carried out to determine radioactivity concentrations and associated dose rates from the naturally occurring nuclides ²³² Th, ²³⁸U and ⁴⁰K in various surface soil formations of Alhkraje city. Samples were collected from different areas of the study, sieved through a fine mesh, sealed in 0.5-liter plastic Marinelli beaker, and measured in the laboratory for 24 hours each. From the measured g-ray spectra, radioactivity concentrations were determined for ²³² Th ranging from 5.32±2.59 to 16.40±2.04 Bq ^. kg^-1, ²³⁸U (2.87±0.18 to 18.83±0.81 Bq ^. kg^-1), ⁴⁰K (211.33±55.04 to 378.97±36.46 Bq ^. kg^-1) and ¹³⁷Cs (0 to 3.19±1.02 Bq ^. kg^-1). Absorbed dose rates in air doors were calculated to be in the range of 15.29±2.65 to 30.00±3.24 nGy ^. h^-1, the corresponding effective dose rates per person outdoors were estimated to be between 21.00±0.95 to 36.83±2.11 mSν^. y^-1, assuming a 20% occupancy factor.     

The effect of different sample-calibrant composition in gamma-ray spectrometry for the assessment of the radiation dose rate in the luminescence dating of sediments

One of the basic steps in luminescence dating is the determination of the annual radiation dose. Among the suitable determination methods in the case of sediment dating is HPGe gamma-ray spectrometry, primarily yielding the concentrations of K, Th and U via measurement of gamma-rays emitted by ⁴⁰K and by ²³²Th and ^235,238U and their decay products. These determinations involve both large-volume samples (with cylindrical or Marinelli geometry) and low-energy gamma-rays (down to the ²¹⁰Pb 46.5 keV line). In view of this, calculations have been made in the present work in order to investigate possible inaccuracies related to gamma-ray attenuation, which may be different in samples and calibrants which have considerably different composition (elemental concentration and packing density). The calculations are based on the introduction of correction factors containing “effective solid angles” (proportional to the peak detection efficiencies), which are believed to give “correct” concentration results. It was found that, in some cases, significant errors could be committed when not performing proper corrections. Therefore, it is concluded that in practice this possible source of inaccuracy should be kept in mind, thus making it necessary to have a fair knowledge of the properties of the materials (samples and calibrants) under investigation. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Direct and precise determination of environmental radionuclides in solid materials using a modified Marinelli beaker and a HPGe detector.

A simple but precise detection method was studied for the determination of natural radionuclides using a conventional HPGe detector. A new aluminium beaker instead of a plastic Marinelli beaker was constructed and examined to reach radioactive equilibrium conditions between radon and its daughter elements without the escape of gaseous radon. Using this beaker fifteen natural radionuclides from three natural decay series could be determined by direct gamma-ray measurement and sixteen radionuclides could be determined indirectly after radioactive equilibrium had been reached. Analytical results from ground water were compared with those from conventional alpha spectroscopy and the results agreed well within 12% difference. Nitrogen gas purge was used to replace the surrounding air of the detector to obtain a stable background and reducing the interference of radon daughter nuclides in the atmosphere. The use of nitrogen purging and the aluminium Marinelli beaker results in an approximately tenfold increase of sensitivity and a decrease of the detection limit of 226Ra to about 0.74 Bq kg(-1) in soil samples.     

Low-background Germanium spectrometry the bottom line three years later

Three years ago, state-of-the-art low-background germanium spectrometry was discussed, and speculations were advanced as to the origin of the remaining background. Some of those speculations have been shown to the incorrect. Contemporary lead shielding contains 100 Bq/kg of²¹⁰Pb. Our 450-year-old lead was shown to contain <100 mBq/kg A high purity electroformed copper Marinelli shield was placed around the detector with no efffect on the background, which implied that the source is other than the 450-year-old shield. A new limit on the²¹⁰Pb in this old lead shield is <9 mBq/kg. Electroformed copper components were found to contain²²⁶Ra and²²⁸Th contaminations at levels of 3500 and 110 Bq/kg, respectively. High purity H₂SO₄, recrystallized CuSO₄, and a BaSO₄ scavenge in the electroforming bath have reduced these contaminations to <25 and 9 Bq/kg, respectively. In copper, cosmic ray induced nuclear reactions are now the dominant source of raioactivity. For example,⁵⁸Co can be readily measured after only a 24-hour exposure at sea level. A new germanium spectrometer containing 2150 grams of 87.44% enriched⁷⁶Ge has been fabricated to mitigate the effect of cosmogenic⁶⁸Ge in the background. Current background spectra are presented, and potential sources identified.     

Neutron activation analysis for determination of trace elements in sediments in the Sea of Galilee,Israel

The feasibility of applying both thermal and epithermal neutron activation analysis for simultaneous determinations of elemental composition in sediments, collected from the Sea of Galilee (Kineret Lake), Israel, during 1988–1993, was experimentally investigated. In the present work, the concentrations of 30 elements (Al, Ba, Br, Ca, Ce, Co, Cs, Cr, Eu, Fe, Hf, K, La, Lu, Mg, Mn, Na, Nd, Rb, Sc, Si, Sr, Ta, Tb, Th, Ti, U, V, Yb and Zn) in sediments were determined. The validity of the method was checked by analyzing the U.S. NBS Standard Reference Material SRM-1633a; the elemental content found agreed well with the published certified data. Aluminium was determined by reactor neutron activation analysis (RNAA) taking into account the contribution of silicon to the total²⁸Al activity by the²⁸Si(n,p)²⁸Al reaction. Measurements of irradiated mixtures of Si and Al showed that the dependence of log SiAl mass ratio vs. log cadmium ratio (R _Cd) of²⁸Al is almost linear. The data can be analyzed more accurately by a parabolic correlation (log Si:Al mass ratio vs logR _Cd). The concentrations of fission radionuclide¹³⁷Cs, an activation radionuclide¹³⁴Cs (derived from Chernobyl accident) and the naturally occuring radionuclides⁴⁰K,²²⁶Ra and²³²Th in sediments were also measured by -ray spectrometry using Marinelli (Reentrant) Beaker-Sample Containers.     

Effects of inhomogeneity and contamination in k<Subscript>0</Subscript>-INAA of low (K,Th, U)-content sand for the annual radiation dose determination in luminescence dating

It was demonstrated that for the determination of the annual radiation dose for use in luminescence dating of sediments, one should be aware of possible material inhomogeneities when applying analysis methods (such as k ₀-INAA) with sample intakes of the order of the gram (to be compared with Ge gamma-ray spectrometry in cylindrical or Marinelli geometry, the latter involving ∼1.5 kg material). Moreover, when trying to remove the inhomogeneity, care should be taken to avoid contamination of the elements investigated, especially in the case of low (K, Th, U)-content sand with a considerable abrasive action (such as the Ossendrecht coversand dealt with in the present work). Whereas contamination was indeed shown to happen when grinding the material in a porcelain mortar, a satisfactory technique proved to be agate-ball milling.     

Radon exhalation and natural radiation exposure in low ventilated rooms

In the first part of this paper, the influence of radon (²²²Rn) exhalation rate from walls and air exchange upon its concentration in room air was considered using a simple mathematical room model. The exhalation rates have been determined in ten low ventilated rooms of ten villas in Jeddah city (Western Province) of Saudi Arabia. An electroprecipitation method has been applied for the determination of the ²²²Rn gas concentration in these rooms. The mean ²²²Rn gas concentration was found to be 46.80±8.80 Bq m^?3. The mean ²²²Rn exhalation rate was estimated to be 20.11±6.90 Bq m^?2 h^?1. The mean inhalation dose due to the exposure to ²²²Rn gas was calculated to be 1.18±2.30 mSv y^?1.The second part of this paper deals with a study of natural radionuclide contents of samples collected from the building materials of these rooms under investigations in part one. Analyses were performed in Marinelli beakers with a gamma spectroscopy system to quantify radioactivity concentrations. The collected samples revealed the presence of the uranium–radium (²²⁶Ra) and thorium (²³²Th) radioisotopes as well as ⁴⁰K. The mean activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K was determined to be 48.30±5.08, 43.90±5.63 and 223.90±7.55 Bq kg^?1, respectively. These activities amount to a radium equivalent (Ra_eq) of 125.96±15.90 Bq kg^?1 and to a mean value of external hazard index (H_ex) of 0.34±0.04.     

A Dynamic Link Library for calculating true-coincidence summing correction factors

A Dynamic Link Library (DLL) was created for calculating true-coincidence correction factors in γ- and X-ray spectrometry applications. Calculations are done by Monte-Carlo method on the basis of the Evaluated Nuclear Structure Data File (ENSDF). In calculations the emission of cascade gammas, as well as γ-X, γ-γ ₅₁₁ and X-X coincidences are appropriately taken into account. A set of measurement geometries implemented includes combinations of coaxial, planar, low and broad energy as well as well-type detectors with point, disk, spherical, cylindrical and Marinelli beaker sources. Together with true-coincidence correction factors full-energy-peak efficiencies are calculated and reported. The DLL was tested by comparing its results with experimental data and results of similar calculations.     

Some improvements in the estimation of137Cs in urine by the AMP-chlorostannate method

An accurate and reliable method has been developed for the estimation of radiocesium in urine. Initially cesium is adsorbed on ammonium phosphomolybdaste (AMP) precipitate and separated by ion exchange from other contaminants. Cesium thus separated is estimated as cesium chlorostannate, Cs₂SnCl₆, from a 50 (v/v)% solution of concentrated HCl in ethyl alcohol. While the results are in good agreement with the values obtained by γ-spectrometry using a Marinelli beaker in its range of applicability, the present method has a much lower detection limit. It is observed that the method has significant advantages over the methods available with respect to analysis time, accuracy and detection limits.