Instrumental neutron activation analysis of sediment reference materials using the k0-standardization method

An instrumental neutron activation analysis technique has been developed for the determination of As, Au, Ba, Co, Cr, Fe, Hf, Sb, Ta, Th, U, W and Zn in large (10–15 g) geological samples using in-pool irradiation with a SLOWPOKE-2 reactor. The technique allows for the simultaneous irradiation of multiple samples using a neutron flux of between 4·10¹³ and 8·10¹³ n·m^–2·s^–1. The detection limits obtained using the analytical methodology described in this paper are acceptable for exploration geochemistry and the technique has been used to analyze samples collected as part of a metallic minerals survey of Jamaica.     

Multi-element determination in silicate rocks by instrumental neutron activation analysis

Instrumental neutron activation analysis technique was applied for the determination of 20 elements in 54 silicate rock samples which belong to three sedimentary geological formations located in the western desert of Iraq. The samples along with USGS standards were irradiated in an IRT-5000 reactor at a neutron flux of 3.7·10¹³ n·cm^–2·s^–1 The following minor and trace element constituents have been determined: Na, K, Ca, Fe, Sc, Cr, Co, Zr, Ce, La, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Th and U.     

Determination of thorium in human urine by neutron activation

A routine procedure for the determination of thorium in urine of workers has been developed by the neutron activation method. The technique suggested by Dang, et. al. has been modified in order to reduce the costs involved and the sample processing time. The samples were irradiated in the MIT (Massachusetts Institute of Technology-Boston) reactor, in a thermal neutron flux of 8×10¹²n.cm^–2.s^–1 for 31/2 hours. Thorium-232 was determined by counting²³³Pa.     

Ultratrace characterization of AlSiCu sputter targets for Th,U and 35 other elements by neutron activation analysis

Instrumental and radiochemical neutron activation analysis has been applied to a comprehensive trace characterization of AlSiCu sputter targets. By instrumental neutron activation analysis via long-lived indicator radionuclides, up to 33 elements were assayed with detection limits between 0.01 and 200 ng·g^–1. The high activity of⁶⁴Cu and²⁴Na produced from the matrix significantly limits the instrumental performance via short- and medium-lived indicator dionuclides. For this reason, a radiochemical separation was developed based on adsorption of²⁴Na on hydrated antimony pentoxide and extraction of⁶⁴Cu by diethylammonium diethyldithiocarbamate from HCl medium. By this radiochemical method, As, Ga, K, La, Mn, Mo, Re, Sb, U and W could be assayed via medium-lived radionuclides and the achievable limits of detection were between 0.1 and 25 ng·g^–1. Further improvement of detection limits for U and Th was achieved by a selective radiochemical separation of²³⁹Np and²³³Pa on a Dowex 1×8 column in HF and HF/NH₄F medium providing limits of detection for U and Th of 0.06 and 0.02 ng·g^–1, respectively. These techniques were applied to the analysis of two AlSiCu sputter target materials. Results are compared with those of glow discharge mass spectrometry.     

Flow-injection technique for determination of uranium and thorium isotopes in urine by inductively coupled plasma mass spectrometry

A sensitive and efficient flow-injection (FI) preconcentration and matrix-separation technique coupled to sector field ICP–mass spectrometry (SF-ICP–MS) has been developed and validated for simultaneous determination of ultra-low levels of uranium (U) and thorium (Th) in human urine. The method is based on selective retention of U and Th from a urine matrix, after microwave digestion, on an extraction chromatographic TRU resin, as an alternative to U/TEVA resin, and their subsequent elution with ammonium oxalate. Using a 10 mL sample, the limits of detection achieved for ²³⁸U and ²³²Th were 0.02 and 0.03 ng L^–1, respectively. The accuracy of the method was checked by spike-recovery measurements. Levels of U and Th in human urine were found to be in the ranges 1.86–5.50 and 0.176–2.35 ng L^–1, respectively, well in agreement with levels considered normal for non-occupationally exposed persons. The precision obtained for five replicate measurements of a urine sample was 2 and 3% for U and Th, respectively. The method also enables on-line measurements of the ²³⁵U/²³⁸U isotope ratios in urine. Precision of 0.82–1.04% (RSD) was obtained for ²³⁵U/²³⁸U at low ng L^–1 levels, using the FI transient signal approach.     

Instrumental neutron activation analysis of Al,V and Ti employing252Cf as a thermal neutron source

A rapid method for the determination of Al, V and Ti has been developed and is used for the analysis of these elements in different ores and alloys. An isotopic neutron source²⁵²Cf having a thermal neutron flux of the order of 8.5×10⁷ n·cm^–2 sec^–1 has been used for thermal neutron bombardment. Activity measurements were performed on a HPGe detector coupled to a PC based MCA unit. Depending on the half-life of the (n, ) product, different irradiation and cooling times were employed and thus the elements of interest were analyzed sequentially.     

Multielement determination in river water by neutron activation analysis

Concentrations of Al, Br, Ca, Ce, Co, Cr, Eu, Fe, Hf, La, Lu, Mg, Mn, Na, Rb, Sc, Sm, Sr, Tb, Th, Ti, V, Yb, Zn, and Zr have been measured in Tigris and Euphrates river water, using neutron activation analysis in combination with preconcentration technique. River water samples were preconcentrated by evaporation at 70°C under atmospheric pressure. The samples with standard reference materials were irradiated with a neutron flux of 2.3·10¹³ n·cm^–2·s^–1.     

Prompt gamma neutron activation analysis of boron with a 241Am-Be neutron source

A prompt gamma neutron activation analysis (PGAA) setup installed at ANRTC has been used to analyze boron. It consists of a 22.6% REGe detector and a 740 GBq ²⁴¹Am-Be neutron source moderated with water and paraffin. At the sample irradiation position, the thermal neutron fluence rate measured was 2.36·10⁴ n·m^–2· s^–1 and the corresponding Cd-ratio was 22 for gold monitor. The absolute detection efficiency in the range of 120–1500 keV was determined using ¹⁵²Eu standard solution. The sensitivity and detection limit for standard boric acid samples has been determined. The boron content in boric acid prepared from Turkish borate ores is measured to be 15.91±0.46% wt.     

Prompt gamma neutron activation analysis of boron with a 241Am-Be neutron source

A prompt gamma neutron activation analysis (PGAA) setup installed at ANRTC has been used to analyze boron. It consists of a 22.6% REGe detector and a 740 GBq ²⁴¹Am-Be neutron source moderated with water and paraffin. At the sample irradiation position, the thermal neutron fluence rate measured was 2.36·10⁴ n·m^–2· s^–1 and the corresponding Cd-ratio was 22 for gold monitor. The absolute detection efficiency in the range of 120–1500 keV was determined using ¹⁵²Eu standard solution. The sensitivity and detection limit for standard boric acid samples has been determined. The boron content in boric acid prepared from Turkish borate ores is measured to be 15.91±0.46% wt.     

Determination of Si,Al, Ti,Fe and Zr in glass sand samples by 14 MeV neutron activation analysis

Fast neutron activation analysis technique was applied for the determination of Si, Al, Ti, Fe and Zr in glass sand rock samples. The samples and standards were irradiated with a mono-energetic neutron flux of 10⁸n · cm^– · s^–1. Pneumatic facility was used. The gamma activities from samples and standards were counted using a 30 cm³ Ge(Li) detector, with FWHM of 2.9 keV at 1.332 MeV, coupled to an on-line computer facility.     

A borehole sonde using neutron activation technique

A simulated borehole sonde has been assembled, with an aluminium casing of 70 cm in length and 12 cm in inner diameter. It contains a 5 Ci Pu–Be source with a neutron yield of about 5.45·10⁶+10% n·cm^–2·s^–1, a shadow shield, and a Hp Ge detector of 15% efficiency and 2 keV FWHM for the 1.33 MeV line of⁶⁰Co. Evaluations of the assembly through the dependence of thermal neutron flux on water content, matrix composition and borehole configuration have been performed. Accordingly, thermal neutron flux distributions have been measured around the sonde and inside the ore in both the simulated dry and water filled borehole. From these measurements one could estimate that the effective moderating thickness of water is about 4 cm, while the volume matrix of the ore to be investigated by this assembly is a slab of about 8 cm width and a height of about 15 cm. It also follows that the uranium-thorium ore analysis method described in this work may become important as a field neutron activation technique.This work was financially supported by the IAEA under research project No. 3534/R.B.     

Epithermal instrumental neutron activation analysis of biological reference materials for iodine

Epithermal instrumental neutron activation analysis (EINAA) methods have been optimized and applied to several biological reference materials and selected food items for the determination of iodine. The method involves irradiation of the samples for different periods in epi-cadmium and/or epi-boron flux of the Dalhousie University SLOWPOKE-2 reactor and direct counting without any pre-treatment on a 25-cm³ hyperpure Ge detector. The 443 keV photopeak of ¹²⁸I is used for assaying the iodine content. Precision of measurements, expressed as the relative standard deviation, is 10–15% at 200–500 ppb and 3–12% at 500–6000 ppb levels of iodine. Accuracy of iodine measurements is within 5%. The detection limits for iodine in several biological materials with cadmium and boron, either alone or a combination of the two, as thermal neutron shields have been found to vary between 0.1 and 0.4 mg · kg^–1 for different periods of irradiation, decay and counting. The results suggest that the EINAA methods can be successfully applied to biological materials for routine analysis of iodine at levels higher than 200 ppb.     

Determination of uranium element concentration and235U isotope abundance by neutron activation analysis

A new neutron activation technique has been developed for the determination of uranium element concentration and²³⁵U isotope abundance in nuclear safeguards and reference material samples based on the activation of bare and cadmium-covered samples with different thermal to epithermal neutron flux ratios and on the combination of the two corre-sponding delayed-fission neutron measurements. The principle of the new technique can be applied also to improve multi-element neutron activation analysis.     

Determination of trace elements in Brazilian cigarette tobacco by neutron activation analysis

The determination of 14 trace elements /Ba, Ce, Co, Eu, Fe, Hf, La, Nd, Rb, Sb, Sc, Sm, Tb and Th/ has been carried out in three different brands of Brazilian cigarettes. The samples and standards were irradiated for 8 h at a thermal neutron flux of approx. 5×10¹² n cm^–2s^–1. After the irradiation, the -rays activity was measured on a Ge/Li/ detector coupled with a 4096-channel pulse height analyzer. The results were compared with those obtained for the tobacco from American, Iranian, Turkish, Pakistan and Yugoslavian cigarettes. The amount of each element transferred to the ashes was determined.     

Trace element analysis of some shaving powders commonly marketed in Nigeria using instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) technique has been employed viak ₀ approximation method to determine elemental composition of five shaving powders commonly marketed in Nigeria. Fe displayed the highest concentrations in the range 1000–2000 g·g^–1. Na and Zn concentrations were established in the range 200–400 g·g^–1. Heavy elements like Ga, La, Cr, Co, Ag, Ce and Nd concentrations were noted in the lower range of 1–10 g·g^–1 Br, As, Sb, Sm, Eu, W, Cs, Tb, Yb, Hf, Ta, Th and U concentrations were established in even lower traces in the <1 g·g^–1 range. Results obtained for a certified reference material, CANMET BL-1 and CERT (in house) Kaolin standard compared favourably with the literature values thus establishing the results presented for the shaving powders.     

Multielement determination in water by instrumental 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 with 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 determined in the water sample are Ca, Cl, Na, Mg, and K present in ppm-level 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 the rare-earth elements, Ag, As, Ba, Cu, Cd, Fe, Sr, W, Zn, seem to be present in the water sample.     

In vivo activation analysis of organ cadmium using the Tsing Hua Mobile Educational Reactor

This work describes a nuclear facility forin vivo prompt gamma activation analysis (IVPGAA) using a moderated neutron beam from a 0.1 W Tsing-Hua Mobile Educational Reactor (THMER). The IVPGAA measurement is a new technique for toxic cadmium determination in organs, which can efficiently be used in clinical diagnosis. The low-power nuclear reactor provides a total neutron flux of 3.3·10⁴ n·cm^–2·s^–1 on the surface of the central vertical neutron beam tube to which a liquid phantom is positioned. The capability of such partial-body irradiation facility is demonstrated. The detection limit of cadmium in the left kidney for a skin dose equivalent of 1.66 mSv (166 mrem) was 1.34 mg in a 500-s irradiation/counting period, and the sensitivity in the left kidney was 103 counts mg^–1·mSv^–1. The performance of IVPGAA system using the THMER nuclear facility therefore has the advantages of mobility and feasibility with high sensitivity under low neutron and gamma doses.     

Determination of uranium and thorium at the sub-ng/g-level in high-purity aluminium by radiochemical neutron activation analysis

Summary A radiochemical neutron activation analysis technique for the determination of uranium und thorium in highpurity aluminium via the indicator radionuclides ²³⁹Np and ²³³Pa, respectively, has been developed. The separation procedure is based on the removal of ²⁴Na on hydrated antimony pentoxide followed by ion-exchange on Dowex-1X8 from HCl/HF and HCl medium. The eluate fraction being of interest for the determination of uranium and thorium contains > 99% of ²³⁹Np and ²³³Pa and, in addition, 11±2% of hafnium and 29±5% of zirconium, and non-detectable fractions of other radionuclides. For a 3-day irradiation of a 100 mg sample at a thermal neutron flux of 10¹⁴cm^–2s^–1 and a decay time of 5 days, the attainable detection limit for both elements is 0.05 ng/g. The method was applied to the analysis of different high-purity aluminium samples, and the results are compared with those obtained in other laboratories.

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Bestimmung von Uran und Thorium in hochreinem Aluminium im sub-ng/g-Bereich durch radiochemische Neutronenaktivierungsanalyse

     

Non-destructive assay technique for the determination of <Superscript>238</Superscript>U/<Superscript>232</Superscript>Th ratio in the mixed oxides of uranium and thorium using prompt gamma-ray neutron activation

A non-destructive assay technique based on prompt gamma-ray neutron activation analysis for the determination of ²³⁸U to ²³²Th ratio in the mixed oxide fuel materials has been established. The method uses closely spaced high energy gamma-rays in the region of 4000 keV to 4150 keV enabling it to be applied for samples of any geometry and thickness without having any correction for gamma-ray attenuations and detection efficiencies.     

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.