Thermal Neutron Activation Analysis Research Articles

A Comparative Analysis of Radioactive Material Concentrations in Natural Sources Linked to Mining in Niger using two Measurement Methods

In the present work, we report the results of radioactivity measurements carried out in soils from the COMINAK and SOMAIR mining areas, using normal mode gamma-ray spectroscopy (NMGS) and thermal neutron activation analysis (TNAA). Radio activities were determined for two series radionuclides (U-238 and Th-232) and one non-series radionuclide (K-40) from measured gamma-ray spectra. The activity concentrations of U-238 and Th-232 were respectively determined from the average nuclide concentration [Pb-214 (295.2keV ; 19.20%), Pb-214(351.9keV ; 37.10%), Bi-214 (609.3keV ; 46.90%), Bi-214 (1120.2keV; 15.04%) and Bi-214 (1764.49 keV; 15.90%)] and [Pb-212 (238.6keV; 43.6%), Pb-212 (300.09 keV; 3.18%), and Ac-228 (911.2keV; 25.8%), Ac-228 (968.9keV; 15.8%), Ac-228 (338.32 keV; 11.27%)]. The activity concentrations of K-40 are determined directly by measuring gamma-ray transitions at 1460.8keV (100%) using a high-resolution pure germanium detector with good efficiency from the Egyptian Atomic Energy Authority. We find that the result found in NMGS technique and TNAA technique for COMINAK soil sample for U-238 and Th-232 are 2.32mg/Kg, 2.36mg/Kg and 11.67mg/Kg, 11.72mg/Kg respectively the results are getting closer. In SOMAIR soil sample the result found for U-238 is getting closer 1.35mg/Kg and 1.34mg/Kg respectively for NMGS and TNAA and also for Th-232 the result is close 7.2mg/Kg and 7.87mg/Kg respectively for NMGS and TNAA. The results obtained confirm that one of the samples (COMINAK soil) is more radioactive than the SOMAIR soil samples, and the results are similar for both NMGS and TNAA techniques, with the exception of thorium in the SOMAIR soil sample. This study will help to assess the environmental impact around the mining areas.

Feasibility of using 10 MeV electron LINAC for explosives detection based on thermal neutron activation analysis: a Monte Carlo study

In the present paper, we used the MCNPX code for the feasibility of the design of a conceptional explosives detection system based on a neutron source generated by a 10 MeV electron linear accelerator (LINAC). In this study, an optimized e–γ–n converter (as a suitable neutron source) has been used for explosives detection based on thermal neutron activation analysis (TNAA) (a nondestructive technique for materials analysis). After optimization, total and thermal neutron fluxes of 4.78 × 108 ± 0.63% (n/cm2 mA s) and 3.95 × 108 ± 0.69% (n/cm2 mA s) could be obtained, respectively. Twelve LaBr3 (3-inch) scintillator detectors have been simulated in order to calculate the response function (by the F8 tally) and to obtain a spectrum of prompt gamma of six common explosives (TNT, PETN, RDX, HMX, NG and EGDN). In these spectra, peaks of the prompt gamma of the hydrogen and nitrogen at 2.223 MeV and 10.829 MeV were observed, respectively, as the first indicator for explosives detection. The ratio of the counts under the peaks for H and N (as the second indicator for explosives detection) were also calculated. Finally, we verified the obtained results of the simulation with the theory and we showed that the results of theory and simulation have a good agreement. Therefore, the results revealed that using a 10 MeV LINAC can be a good alternative for TNAA and also for explosive detection.

Optimization of Am–Be millicuries neutron source in a small volume cylindrical water tank for NAA

The neutron activation analysis (NAA) is a very powerful method for multi-element analysis of samples. NAA technique needs to be developed for low neutron flux in millicuries using the 241Am-Be neutron source. To optimize sample and neutron source geometry for maximum γ-ray yield for neutron activation analysis. Gamma ray neutron activation analysis (NAA) has been set up where a 50-millicurie Am-Be neutron source is available. In this experimental setup, the neutron source is placed at the center of a cylindrical water tank of 40 x 40 cm in xyz plan, and thermal neutrons are produced at a distance of 1.2 cm from the source. The system is used for the activation analysis of sodium carbonate, sodium chloride and copper with the gamma ray emissions of 1.37, 1.73, 2.25 and 2.76 MeV for 24Na and 0.511 MeV for 64Cu having half lives of 15 hrs and 12.9 hrs, respectively. The thermal neutron activation analysis has been demonstrated by placing the samples at about 1.2 cm from the neutron source. HPGe and 3x3 inch NaI(Tl) gamma ray spectrometers have been used for the gamma ray spectrometry of these activated samples with the use of a Marinelli beaker. The geometry of the sample with respect to the neutron source has been optimized for the maximum γ-ray yield in NAA. The geometry of the sample with respect to the neutron source has been optimized for the maximum γ-ray yield in NAA. The increase in gamma ray flux distribution in the medium of water, due to the neutron source inside the tank, has been observed by a GM detector which is due to the production of short-lived 16N on activation of 16O in water. This system can also be used for prompt γ-ray analysis.

Application of medium energy plasma focus device in study of radioisotopes

Pulsed neutrons generated in a plasma focus device are used for the thermal neutron activation analysis (TNAA) of selected three elements having widely different half-lives varying from a few seconds to a few days [Dysprosium (Dy), Manganese (Mn) and Gold (Au)]. Neutron pulse having strength of (1.2±0.3)×109 neutrons/pulse with a pulse width of 46±5ns is produced by “MEPF-12” device operated at a filling gas (deuterium + 0.5% krypton) pressure of 3 mbar. The fast 2.45 MeV D–D neutrons are thermalized before irradiating the sample. The decay gammas from the radioisotopes 165mDy (T1/2=1.26min.), 56Mn (T1/2=2.58hrs.), and 198Au (T1/2=2.69days) produced via reactions, 164Dy(n,γ)165mDy, 55Mn(n,γ) 56Mn, and 197Au(n,γ) 198Au respectively are counted off-line in a lead shielded well type 76×76mm2 NaI(Tl) detector coupled to a calibrated 2048 channel analyzer. The values of half-lives evaluated from the measured decay gammas, 1.43±0.3min., 2.56±0.5hrs. and 2.84±0.6days respectively for the radioisotopes of Dy, Mn and Au, are seen to be close to the values reported in literature.

Optimization of Linac-based neutron source for thermal neutron activation analysis

A 20 MeV electron Linac based neutron beam has been shaped for neutron activation analysis (NAA) technique. A beam shaping assembly (BSA) has been simulated using MCNPX2.6 code to increase the thermal neutron flux and decrease the epithermal and fast neutrons as much as possible at the beam port for NAA facility. Final BSA containing 1.5 cm tungsten as photoneutron target, 7 cm BeD2 and 4 cm polyethylen as moderators surrounded by BeO as reflector as well as 6 cm PE as collimator layer provides 1.67 × 1010 (n/cm2 mA) at the beam port. The results of final configuration show that the proposed system leads to increasing of thermal to epithermal and thermal to fast neutron flux up to approximately 5.29, 6.22, respectively.

Determination of concentrations of Fe, Mg, and Zn in some ferrite samples using neutron activation analysis and X-ray fluorescence techniques

Mg–Zn ferrite is considered as one of the important materials with potential uses in many applications. In this work, samples of ferrite Mg(1-x)ZnxFe2O4 (where x=0.0, 0.2, 0.4, 0.6, 0.8 and 1) were synthesized by the sol–gel method for use in some hyperthermia applications. The composition and purity of the prepared samples hardly affected their properties. Therefore, the elemental concentration of these samples was measured by the X-ray fluorescence technique and thermal neutron activation analysis to check the quality of the prepared samples. The results of both methods were compared with each other and with the molecular ratios of the as-prepared samples. In addition, no existing elemental impurity, with considerable concentration, was measured.

Characterization of bauxite residue (red mud) for 235U, 238U, 232Th and 40K using neutron activation analysis and the radiation dose levels as modeled by MCNP

This study employs thermal and epithermal neutron activation analysis (NAA) to quantitatively and specifically determine absorption dose rates to various body parts from uranium, thorium and potassium. Specifically, a case study of bauxite residue (red mud) from an industrial facility was used to demonstrate the feasibility of the NAA approach for radiological safety assessment, using small sample sizes to ascertain the activities of 235U, 238U, 232Th and 40K. This proof-of-concept was shown to produce reliable results and a similar approach could be used for quantitative assessment of other samples with possible radiological significance. 238U and 232Th were determined by epithermal and thermal neutron activation analysis, respectively. 235U was determined based on the known isotopic ratio of 238U/235U. 40K was also determined using epithermal neutron activation analysis to measure total potassium content and then subtracting its isotopic contribution. Furthermore, the work demonstrates the application of Monte Carlo Neutral-Particle (MCNP) simulations to estimate the radiation dose from large quantities of red mud, to assure the safety of humans and the surrounding environment. Phantoms were employed to observe the dose distribution throughout the human body demonstrating radiation effects on each individual organ.

A new reflector structure for facility thermalizing D–T neutrons

A facility for thermalization of fast neutrons (14.2 MeV) emitted by compact deuterium–tritium (D–T) neutron generators (NGs) for thermal neutron activation analysis is proposed. Its final design is based on Monte Carlo calculations (MCNP5). To maximize the ratio between the thermal neutron flux and the total neutron flux and simultaneously to ensure the highest possible value of the thermal neutron flux at the output surface, the facility should consist of a two-layer reflector [tungsten (W)—the inner part, molybdenum—the outer part], a two-layer multiplier (W followed by lead), a moderator (polyethylene followed by magnesium fluoride) and a collimator (molybdenum and nickel near the output surface). For the D–T NG producing the maximum available neutron yield 1015 n s−1, the facility provides the thermal neutron flux 2.0 × 1011 n cm−2 s −1 and a slightly higher fast neutron flux 2.3 × 1011 n cm−2 s−1. To improve the ratio of the thermal neutron flux to the fast neutron flux (above 2.7) an addition of a silicon layer to the moderator and especially a proper adjustment and a threefold increase of the multiplier thickness is necessary.

Determination of macroconstituents and trace elements in naturally occurring radioactive material in oil exploration waste products

Naturally occurring radioactive materials (NORM) contain radionuclides, such as radium, thorium, and uranium. The existence of NORM remains an issue for oil and gas exploration because once the material becomes concentrated through technological activity, it becomes a radioactive contamination hazard or a radioactive waste. Pipes and tanks used to handle large volumes of produced water at some oil-field sites are coated with scale deposits that contain high levels 226Ra, 228Ra and 210Pb. Experiments were conducted using thermal and epithermal neutron activation analysis and Compton suppression for the determination of macroconstituents and trace elements in the radioactive scale sample.

Assessment of the associated particle prompt gamma neutron activation technique for total body nitrogen measurement in vivo

Total body nitrogen (TBN) can be used to estimate total body protein, an important body composition component at the molecular level. A system using the associated particle technique in conjunction with prompt gamma neutron activation analysis has been developed for the measurement of TBN in vivo. The system uses a compact D, T neutron generator (~107 n/s) coupled to an internal alpha-particle detector, and a counting system with six bismuth germinate detectors. 14 Subjects were scanned from shoulders to hips (20 min scan time, <0.4 mSv dose) generating complex spectra dominated by signals from C, O, H, and N, with significant peak overlap. Fractional contributions from these elements to regions of interests (ROI) spanning a 4–8 MeV range were determined by algorithms comparing ratios of interrelated ROIs. In addition, multi-component least squares fitting was done to further resolve individual peak activities (MATLAB R2011b). Total body potassium (TBK) was also measured using a whole body gamma counter. Predicted TBN values, based on fat-free mass estimated from TBK, were compared to measured TBN results. Measured versus predicted results for all subjects were not statistically different. Separating subjects by gender also showed no difference between measured and predicted values. The associated particle system showed good agreement with predicted TBN values, but measurement precision was not better than that commonly seen in traditional prompt gamma thermal neutron activation analysis systems.

Measuring activity of 235, 238U, 232Th and 40K in geological materials using neutron activation analysis

The radioactivity of the 235, 238U and 232Th isotope decay chains for geological samples can usually be assumed to be in equilibrium due to their age. Similarly, one can assume that the isotopic mass proportions are equal to natural isotopic abundance. Current methods used to ascertain activity in these decay chains involve alpha particle spectrometry, ICP-MS or passive gamma-ray spectrometry, all of which can be laborious and time consuming. In this research, we have used thermal and epithermal neutron activation analysis (NAA) of small sample sizes of various geological materials in order to ascertain these activities. By using NAA, we aim to obviate cumbersome sample preparation, the need for large samples and extended counting time. In addition to the decay chains of uranium and thorium, 40K was also determined using epithermal neutron activation analysis to determine total potassium content and then subtracting out its isotopic contribution.

Human telomeric G-quadruplex formation and highly selective fluorescence detection of toxic strontium ions

Strontium ions play important roles in biological systems. The inhalation of strontium can cause severe respiratory difficulties, anaphylactic reaction and extreme tachycardia. Strontium can replace calcium in organisms, inhibit normal calcium absorption and induce strontium "rickets" in childhood. Thus, the development of sensitive and selective methods for the determination of trace amounts of Sr(2+) in aqueous media is of considerable importance for environmental and human health protection. A number of methodologies, such as X-ray energy dispersive spectrometry, inductively coupled argon plasma atomic emission spectroscopy (ICP-AES), atomic absorption spectrometry (AAS) and instrumental thermal neutron activation analysis, have been reported. However, these methods are somewhat complex, costly, time consuming and, especially, need special instruments. Thus, the design of convenient and inexpensive approaches for the sensitive and selective detection of Sr(2+) with rapid, easy manipulation is in ever-increasing demand. To the best of our knowledge, using DNA conformational change to detect Sr(2+) has not yet been reported. Herein we utilized thiazole orange (TO) as a signal reporter to devise a simple Sr(2+) detection assay based on Sr(2+) induced human telomeric DNA conformational change in the presence of SWNTs. The limit of detection is 10 nM Sr(2+) (0.87 μg L(-1)), far below 4 mg L(-1), the U.S. Federal threshold in drinking water defined by the U.S. EPA.

Determination of silver using cyclic epithermal neutron activation analysis

A fast pneumatic transfer facility was installed in Nuclear Engineering Teaching Laboratory (NETL) of the University of Texas at Austin for the purpose of cyclic thermal and epithermal neutron activation analysis. In this study efforts were focused on the evaluation of cyclic epithermal neutron activation analysis (CENAA). Various NIST and CANMET certified materials were analyzed by the system. Experiment results showed 110Ag with its 25 s half-life as one of the isotopes favored by the system. Thus, the system was put into practical application in identifying silver in metallic ores. Comparison of sliver concentrations as determined by CENAA in CANMET certified reference materials gave very good results.

Trace elements in 11 fruits widely-consumed in the USA as determined by neutron activation analysis

While there is a lot of information on the elemental content of food for nutritional and pollution studies, the analysis of fruits has received little attention. We have investigated 11 commonly eaten fruits for their trace and minor element constituents by neutron activations including thermal and epithermal neutron activation analysis. Our results revealed that both blueberries and strawberries had the most of top two highest elemental concentrations followed by raspberries, oranges and mango. Bananas, grapes, plums, apples, pears, and cherries had the fewest or none of the most elevated elemental concentrations.

Evidence of tin and other anthropogenic metals in particulate matter in Lisbon, Portugal

Thermal and epithermal neutron activation analysis techniques were used to analyze 27 Teflon air filters which were exposed to ambient air in Lisbon, Portugal, in February 2007. Tin was detected which is strongly suggestive of an anthropogenic source. Arsenic, antimony and copper were shown to be highly correlated, which is also suggestive of anthropogenic pollution. Trace element analysis of short- and medium-lived isotopes was performed yielding concentration information of various elements. Analytical sensitivities were enhanced using a Compton suppression system. Enrichment factor analysis shows that arsenic, tin, zinc, copper and antimony are at elevated concentrations in the Lisbon atmosphere.

Determinação de paládio em amostras biológicas aplicando técnicas analíticas nucleares

This study presents Pd determinations in bovine tissue samples containing palladium prepared in the laboratory, and CCQM-P63 automotive catalyst materials of the Proficiency Test, using instrumental thermal and epithermal neutron activation analysis and energy dispersive X-ray fluorescence techniques. Solvent extraction and solid phase extraction procedures were also applied to separate Pd from interfering elements before the irradiation in the nuclear reactor. The results obtained by different techniques were compared against each other to examine sensitivity, precision and accuracy.

Thermal neutron activation analysis of essential and trace elements and organic constituents in Trikatu: An ayurvedic formulation

Trikatu, an Ayurvedic formulation of three dried powder spices, ginger, black pepper and pipali in equal proportion is widely used to promote digestion, assimilation and bioavailibility of food. It works synergistically, and hence, is more effective than an equal amount of any of its three ingredients taken separately. Five different brands and its three constituents were analyzed for 31 elements by instrumental neutron activation analysis (INAA) using 5-minute and 6-hour thermal neutron irradiation followed by high-resolution J-ray spectrometry. Heavy toxic metals Cd, Ni and Pb determined by atomic absorption spectrometry (AAS) were found below permissible limits. Most elements in different brands vary in a narrow range. Ginger is particularly enriched in Ca, Fe, Mg and Mn whereas black pepper is enriched in Cr, Se, P and Zn. Cu/Zn shows linear relationship (r = 0.92) with Cu whereas Fe and Mn exhibit inverse correlation (r = –0.89) in different brands. Hydro distillation of pipali yielded an essential oil whereby 10 organic constituents were identified by GC-MS. Also barbituric and tannic acids were isolated from the aqueous methanolic extract of pipali.

Biomonitoring of atmospheric trace element deposition around an industrial town in Ghana

Parmelia sulcata lichen species have been used to study the atmospheric deposition of heavy metals and other toxic elements around an industrial area in Ghana. Natural soil samples were collected at all the sampling points and analysed in order to investigate surface accumulation of the heavy metals. The sampling points used for the study were: Afienya, Doryemu Cemetery and Doryemu River. The surface accumulation of the heavy metals would be used to examine the correlation of the elements in the lichen and soil samples in order to separate contributions from atmospheric deposition and from that of soil minerals. Thermal neutron activation analysis techniques employing a 30 kW tank-in-pool research reactor operating at a thermal neutron flux of 5×10 11 s −1 cm −2 was used to determine Al, Cr, Mn, Fe, Ti, Th and V in both the lichen and soil samples. The level of contamination was quantified using the enrichment factor approach. This approach was adopted in order to ascertain whether these elements are enriched in the soil or in the atmosphere. The sampling points were enriched in the atmosphere with Cr, Mn, Fe, Ti, Th and V in the decreasing order of Afienya, Doryemu Cemetery and Doryemu River.

Determination of elemental composition of atmospheric aerosol in the urban area of Islamabad, Pakistan

This study provides useful information about the level and chemical composition of particulate matter and about the possible sources of the aerosol pollutant in Islamabad, the capital of Pakistan. Atmospheric aerosol samples were collected during winter (January and February) 1995, from two locations of Islamabad, namely of Sector F-7 and Sector I-9. Twenty-four elements were detected by using thermal neutron activation analysis (NAA) and atomic absorption spectrometry (AAS). The concentration of total suspended particulates (TSP) in the area around the industrial sector (I-9) was found to be more than twice higher (297 ∝g/m 3 ) than in the Sector F-7 (133 ∝g/m 3 ). The enrichment factor analysis revealed Zn, As, Br, Sb, I and Pb, originated mainly from anthropogenic sources. The elemental ratio analysis indicated that both Sectors I-9 and F-7 are under the influence of coal burning processes whereas transportation is responsible for the toxic pollutants Pb and Br. The present results were discussed and compared with those of the literature. The results may also serve as base line level as this work employed samples collected in 1995 and many of the air environmental change factors occurred after the sampling year.

Availability of essential elements in Indian and US tea brands

Fifteen different brands of Indian tea leaves and seven US brands of flavoured tea were analysed for Na, K, Mn, Cu and Br by thermal neutron activation analysis (TNAA). Mn was also analysed by spectrophotometric and atomic absorption spectrometry (AAS) methods. In Indian tea, Mn concentration was found to be in the range 371–758 μg/g with a mean concentration of 575 ± 96 μg/g whereas in US tea it was in the range 79–768 μg/g with a mean concentration of 329 ± 231 μg/g. Na and Cu contents were also widely different in tea leaves from India and the USA but K contents were similar in the two tea leaves. Bromine was absent in tea leaves from the USA. Several standard or certified reference materials (SRMs/CRMs), including two tea leaves standards, were also analysed for data validation.