Characterization of household plastics for heavy metals using neutron activation analysis

Highly enriched concentrations of several heavy metals have been found in municipal solid waste incinerator (MSWI) ash. In an effort to identify possible sources of these metals in MSWI ash, a variety of disposable household plastic products was examined for heavy metal content. Using both thermal and epithermal neutron activation analysis (NAA) along with Compton suppression techniques, concentrations of several trace and heavy metals including Ag, As, Au, Ba, Br, Cd, Cr, Cu, Fe, Mn, Ni, Sb, Se, Sn, Sr, V, W and Zn were determined. Results indicate a wide range of concentrations for these elements, with large variations in plastics of similar color and intended use. As limits dealing with heavy metal content of consumer products are lowered, NAA techniques will provide a useful method for verification of product compliance.     

Determination of impurities in nuclear fuel element components by neutron activation analysis

Neutron activation analysis methods for the determination of impurities in zirconium cladding material and uranium oxide are described. Detection limits for the elements Al, Cd, Cr, Co, Cu, Hf, Fe, Mn, Ni, W and U in zirconium are below that required by the ASTM B 352-79 standard. The method has been tested on the NIST SRM 360a Zircaloy-2 from which the elements Na, Mg, Al, Ca, V, Cr, Fe, Co, Ni, Cu, Eu and U have been detected. The values for Cr, Fe, Ni and Cu are compared with the certified values. A method for the pre-irradiation separation of the elements Mg, Na, Al, K, Sc, Ca, V, Mn, Cr, Fe, Co, Cu, Zn, Rb, Zr, Cd, Cs, REE and Hf from uranium has been developed. A neutron activation analysis method for the determination of those elements in uranium is described. The method is tested by the analysis of the IAEA reference sample SR-54/64. The elements Al, Mn, V, Cu, Cr, Co, Ni and Fe have been detected and the results compared with the certified values.     

Characterization of a nuclear reactor for neutron activation analysis

Résumé Ouelques caractéristiques du réacteur nucléaire NBSR utilisé pour l'analyse par activation neutronique ont été évaluées; les techniques de mesure développées sont décrites. La discussion porte sur les caractéristiques suivantes: (1) le flux de neutrons thermiques absorbés par le cadmium, (2) la distribution énergétique des neutrons mesurée grace aux rapports cadmium et à des détecteurs à seuil. L'excès de pression dans les échantillons engendre l'irradiation.      

Evaluation of stray neutron distribution in medical cyclotron vault room by neutron activation analysis approach

Stray neutron distribution in a medical cyclotron vault room was evaluated by neutron activation analysis (NAA). Neutrons were generated in the production of radioactive nuclides, such as ¹⁸F, ¹¹C, ¹³N and ¹⁵O, for diagnostic usage. Indium foil was adopted to evaluate the stray fast and thermal neutron intensity based on ¹¹⁵In(n_f, n′)^115mIn and ¹¹⁵In(n_th, γ)^116m1In reactions, respectively. The indium foils were weighed, sealed and placed at 62 points around the 6.7×8.2 m² cyclotron room. Additionally, each indium foil was exposed for over 80 minutes during cyclotron operation and γ-peaks were analyzed using an HPGe detector to evaluate the number of stray fast (Φ _f) or thermal (Φ _th) neutrons. The minimum to maximum numbers of fast and thermal neutrons were (3.47±0.11)×10³ to (1.06±0.21)×10⁴ n·cm⁻²·s⁻¹ and 9 to 965 n·cm⁻²·s⁻¹, respectively. The minimum detectable limit for stray neutrons was included herein to demonstrate the reliability. Accordingly, 60 and two points, respectively, the confidence level associated with the reported intensities of fast and thermal neutrons reached 95%. The low qualified ratio in the evaluation of stray thermal neutrons might have been caused by either the high Compton scattering plateau or the low intensity of the gamma-ray peak in the relevant spectrum.     

Ocean-sediment analysis by neutron activation

Neutron activation analysis (NAA) techniques have been developed and applied to the analysis of marine sediments. More than 150 core sites have been sampled in the northwestern Gulf of Mexico. More than 500 surface and subsurface sediment samples have been analyzed for Ba, Cr, Fe, and various other elements of interest. Typical concentrations at various locations are given. An extensive half-life study was performed to verify that gamma lines, used for quantitation exhibited the decay parameters expected to the parent radionuclide. Suggested gamma lines are presented for a few elements of particular interest to ocean-sediment analysis.     

Interference by neutron induced second order nuclear reaction in activation analysis of rare earths

In determining the trace impurities existing in high-purity rare earth samples by the neutron activation analysis, there are much interference due to nuclides induced from neutron induced second order nuclear reaction. This paper presents the degree of interference calculated over the ranges of irradiation time from 10⁵ to 10⁷ sec and of thermal-neutron flux from 1·10¹² to 1·10¹⁵ n·cm⁻²·sec⁻¹. According to the results of these calculations, degree of interference under the neutron irradiation condition for 288 hrs in the thermal-neutron flux of 3·10¹³n·cm⁻²·sec⁻¹ is concluded to be 6.4·10⁶ ppm Gd in Eu, 2.2·10⁴ ppm Sm in Eu, 1.9·10⁴ ppm Ho in Dy, 1.1·10³ ppm Eu in Sm, 1.1·10² ppm Ce in La and 1.1·10 ppm Tb in Gd, respectively. Especially, the Gd determination in the Eu target is extremely affected by¹⁵³Gd formed from the¹⁵¹Eu (n, γ) reaction. On the contrary, this reaction is effective in producing¹⁵³Gd activity.     

Current status of neutron activation analysis and aplied nuclear chemistry

A review of recent scientometric studies of citations and publication data shows the present state of NAA and applied nuclear chemistry as compared to other analytical techniques.Research sponsored by the Office of Energy Research, U. S. Department of Energy, under Contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc.     

Determination of thorium and uranium at the nanogram per gram level in semiconductor potting plastics by neutron activation analysis

A method was developed to determine thorium and uranium in semiconductor potting plastics. The method is based on neutron activation and subsequent radiochemical separation to isolate and permit measurement of the daughter products²³³Pa and²³⁹Np of the induced²³³Th and²³⁹U. These plastics typically contain macro amounts of silicon, bromine and antimony and nanogram per gram amounts of thorium and uranium. The radiochemical method provides the necessary sensitivity and makes it possible to easily attain adequate decontamination of the tiny amounts of²³³Pa and²³⁹Np from the high levels of radioactive bromine and antimony.Deceased     

Determination of characteristic neutron flux parameters of nuclear reactors for thermal neutron activation analysis

The characteristic neutron spectrum parameters for thermal neutron activation analysis have been determined for the most important irradiation positions of the reactors BR1 and BR2 at Mol (Belgium), HFR at Petten (Netherlands) and FRJ2 at Jülich (Federal Republic of Germany). The method of determination is described.     

Cadmium by in vivo neutron activation analysis

Conclusions The neutron activation method is capable of indicating the presence of cadmium in man in vivo and quantitative determinations may be possible in the future. The sensitivity of the method is such that the detection threshold lies within the accepted ‘normal’ concentrations and is significantly below the encountered toxic levels. The method can be used for screening cadmium poisoning suspects as the radiation dose necessary for this purpose can be made as low as 0.5 rem. Another possible application of the technique is in the study of the role of cadmium in renal disorders, bone disease and hypertension. The measurement takes less than 0.5 hour with the minimum of discomfort to the patient.

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Résumé On peut déterminer la présence de cadmium chez l'homme à l'aide de technique de l'analyse par activation neutronique in vivo. La capture des neutrons thermiques par¹¹³Cd conduit à une émission γ prompt qui peut être détectée au moyen d'un semi-conducteur convenable. On a réalisé une installation à l'Université de Birmingham pour produire au moyen d'un cyclotron un faisceau de neutrons pulsés. Une série d'expérience a été faites sur des cadavres; ces expériences ont prouvé qu'il est possible de détecter le cadmium à une concentration de 2,0 ppm dans le volume d'un foie humain pour une dose de 1 rem. On discute des résultats et des applications possibles de cette étude.

     

Evaluation of trace-element pollution in Barada River environment by instrumental neutron activation analysis

The impact of tanning and electroplating industry on the eastern part of Barada River environment has been evaluated. Sediment, soil and plant samples were collected from nine sites at the river near the eastern industrial complex during 1999. Results of instrumental neutron activation analysis have shown high levels of Cr in sediment collected near the tanning factories; the highest value obtained being 2692 ppm. In addition, relatively high levels of Cr were also found in the agriculture soil collected near the riverbank in the industrial complex; Cr concentrations varied between 77 ppm and 327 ppm. However, Cr concentrations in plant leaves grown at riverbank were found low and this due to strong bounding of Cr to soil. Other trace metals such as copper and nickel were also high in sediment samples. The highest concentration of copper was about 4000 ppm, which is much higher than the natural levels; electroplating shops are the main source of this element in the area. Furthermore, concentrations of the studied trace metals have decreased as the sampling site distance became far from the industrial complex. In general, other trace elements were found to be at low concentrations, but the obtained data can be used as a baseline for future monitoring.     

Thorium ore analysis by X-rays in neutron activation analysis

The possibility of using characteristic X-rays from radioactive elements in activatio analysis was investigated during this work with particular emphasis on (n, ) products. The detection sensitivities for some elements are determined by X-rays employing a²³⁵Pu-Be neutron source. The technique has been applied to the analysis of thorium ores from the Anatolia Region, with great accuracy.     

Evaluation of minimum detectable amounts of iodine in biological samples by neutron activation analysis

Evaluation of minimal detectable amounts (MDA) of iodine in various or specified irradiation and measurement conditions is described. Interfering contributions due to Na and Cl to the spectral background as well as the dead time of detection system were calculated in details based on an experimental approach. The MDA of iodine for some important biological samples with various Na and Cl concentrations can be evaluated and predicted according to the specified irradiation and measurement arrangements to meet the requirement of analytical purposes.     

Evaluation of 40K in food by determining total potassium using neutron activation analysis

Summary Potassium is an extremely important major element to the human body. Potassium is made up of three isotopes with abundances of ³⁹K at 93.1%, ⁴⁰K at 0.0118% and ⁴¹K at 6.88%. It is also very well known that ⁴⁰K with its 1.3 ^. 10⁹ years half-life is a major naturally occurring isotope in the body and food. The usual way to determine total ⁴⁰K is to measure the single 1460.8 keV photon from beta-decay. However, this procedure requires a significant amount of sample and typical counting periods of at least a day in well-shielded germanium counting system. Another approach is to determine total potassium via neutron activation analysis using the well known ⁴¹K(n,g)⁴²K (T_1/2 = 12.8 h) reaction and then evaluate ⁴⁰K using the usual activity equation A = lN. In our laboratory we have effectively used epithermal neutron activation analysis and Compton suppression to determine potassium in air filters and other geological material. Upwards to 10-15 samples can be analyzed in one day using only gram quantities of material. In such way one can increase the output of determining ⁴⁰K by at least one order of magnitude. Results of a detailed investigation optimization of the methodology, quality control and detection limits will be presented for reference material and various food samples.     

Low level mercury analysis by neutron activation analysis

During the years 1974–77 about 200 low level mercury analyses on samples with less than 1000 ng Hg/kg were made at the Danish Isotope Centre. This paper describes our method of neutron activation analysis for low level mercury analysis. The accuracy of the mercury analyses is shown by the results of the determinations on NBS standard, SRM 1642, and on intercalibration analyses. The accuracy found is better than 10% for samples with about 100–300 ng Hg/kg and better than 10 ng Hg/kg for samples with less than 100 ng Hg/kg. The limit of detection for the analyses is about 1–5 ng Hg/kg, depending on the sample and the exact method of analysis. The lowest standard deviations on duplicate analyses are about 1 ng Hg/kg. The general level found in sea water is about 10 ng Hg/kg, in ground water about 50 ng Hg/kg, and in rain water about 100 ng Hg/kg.     

Multielemental determination in water by neutron activation analysis

Instrumental neutron activation analysis (INAA) technique has been applied to a water sample to determine the elemental concentrations. The sample was irradiated at a neutron flux of 1.2·10¹² n·cm^–2·s^–1 for two different periods followed by counting at three different decay times, using two coaxial type high-resolution Ge(Li) detectors. The dominant elements detected in the water sample are Ca, Cl, Na, Mg, and K present in levels while Co, I, Mn, Sm, and Sb are present in smaller amounts approximately on the average 0.01 ppm. Only traces of other elements such as rare-earth elements, Ag, As, Ba, Cu, Cd, Fe, Sr, W, Zn, seem to be present in the water samples.     

Measurement of the neutron flux distribution in a research reactor by neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry - The neutron flux distribution in the core region of the JRTR was measured through the neutron activation analysis method. Sample mount and a tool...     

Multielemental analysis of soils by instrumental neutron activation analysis

The results of an instrumental neutron activation analysis of some elemental concentrations in different soil samples near the industrial areas at Tirupati, India, are reported. Altogether 14 elements, Sm, La, Cr, Co, Zn, Cs, Ce, Th, Rb, Na, K, Sr, Fe and Eu were determined. The samples were irradiated with neutrons at the 100 kW Triga - Mainz research reactor and the induced activities were measured by gamma-ray spectrometry using an efficiency calibrated high resolution high purity germanium (HPGe) detector in connection with a multichannel analyzer. The results are discussed.     

Development of irradiation conditions for neutron activation analysis of inorganic trace impurities in plastics for microelectronic applications

The difficulties of analyzing plastics of high purity by chemical analysis methods have led to the application of neutron activation analysis. Because literature quotes pressure build-up in the irradiation containers as the reason for limited activation intensity the behavior of the six plastics PVI, PMMA, PVDF, PE, FEP and Silicone had to be investigated. The investigations showed, that pressure build-up was not the limiting factor. Furthermore hydrogen generation under irradiation seems to be the reason for explosions of ampoules by an oxyhydrogen reaction. The question of the ignition source could not be answered yet. To prevent oxyhydrogen reaction, the ampoules have to be filled with nitrogen. The experiments have shown, that if suitable sample masses and ampoule volumes are selected, even high neutron fluences can be applicated. After determining the permissible irradiation conditions, the impurity content of 30 elements in the six plastics were determined using destructive and nondestructive NAA.