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.     

Instrumental neutron activation determination of Pt,Ru, Ir,Sc, Cr,Fe, Co,La, Ce,Nd, Sm,Yb, Lu,Hf and Ta employing CIRUS reactor as a thermal neutron source

An accurate and simple method has been developed for the determination of Pt, Ru, Ir and other elements employing instrumental neutron activation analysis (INAA). Nondestructive analysis has been carried out for the determination of these elements in different rock samples such as Dolerite, Dyke Dolerite, Country Basalt, Hyaloclastite, Trachyte, Ijolite, Spillite, Diorite and Lamprophyre from various locations like Daman, Tapti, Murud, Talasari, Ranala and Bassein in Maharashtra state. High flux provided by the CIRUS reactor (1×10¹³ n cm^?2s^?1) has been used for thermal neutron bombardment followed by radioassaying of the (n,γ) products on a HPGe detector coupled to a PC-based MCA unit.     

Neutron scattering by hydrogen in cold neutron prompt gamma-activation analysis

The effects of neutron scattering by hydrogen within targets for cold neutron prompt -ray activation analysis (CNPGAA) have been characterized. For most targets studied, the probability for neutron absorption, and hence CNPGAA sensitivities (counts·s^–1·mg^–1), decrease with increasing H content and with target thickness. Comparisons with results from thermal neutron PGAA indicate that the effects of cold neutron scattering differ from those of thermal neutron scattering. CNPGAA sensitivities for l/v nuclides show similar sensitivity decreases, while Sm sensitivities show smaller decreases.     

The determination of boron in biological materials by neutron irradiation and prompt gamma-ray spectrometry

A prompt-gamma neutron activation technique has been developed using the (n, ) apparatus situated at the O degree through-tube of the Imperial College CONSORT II Reactor with a thermal neutron flux at the target position of approximately 2×10⁶ n cm^–2 sec^–1, and a Compton-suppression system involving a lithium-drifted germanium (Ge(Li)) detector and a sodium iodide anti-Compton shield. Boron levels of 1–5 g g^–1 (detection limit 0.05 g B for 10,000 sec period of measurement) can be attained using the Compton-suppression system with graphical inter-polation correction for the 472 keV sodium-ray peak contribution to the Doppler-broadened 478 keV boron gamma-ray peak resulting from the¹⁰B(n, )⁷Li reaction. Very good agreement is reached for boron levels compared using this system for various Standard Reference Materials and other published values. Measurement of the boron content of bone and tooth samples from rheumatoid arthritis individuals shows lower levels, (p<0.05); 16.13±7.53 g g^–1, when compared with a control population; 19.79±4.18 g g^–1. A positive correlation existed between the boron content of bone and tooth material for each study group. Results indicate that boron availability may be associated with rheumatoid arthritis.     

Analytical possibilities of the BOR 60 reactor

The analytical potential of a fast neutron reactor has been studied. The maximum density of the neutron flux is 2.5·10¹⁵ cm^–2·s^–1 at a maximum energy of 450 keV. The determining reaction for activation analysis at this reactor is an (n, n) reaction. The possibility of selectively determining Pb, Hg, Cd, Au, Ag and other elements at a level of 10^–5–10^–8% is demonstrated. This activation technique allows rapid determination of these elements.     

Thermal neutron activation analysis of Cu in its ores by using an241Am−Be neutron source

A thermal neutron activation method has been developed for the determination of Cu in Cu–Pb–Zn ores and chalcopyrite ore concentrates using the reaction⁶³Cu(N, )⁶⁴Cu. The samples were irradiated with thermal neutrons from an²⁴¹Am–Be neutron source and the annihilation -radiations of 0.511 MeV were counted on 3×3 NaI(T1) detector coupled with single channel pulse height analyzer. The method is nondestructive, economical and ideal for bulk analysis of ores with 1–16% Cu.     

Instrumental neutron activation analysis of blood serum

Instrumental neutron activation analysis has been used to determine 15 trace elements in twelve blood serum samples taken from healthy students at Bilkent University in Ankara. The method allowed the determination of Sc, Cr, Mn, Fe, Co, Zn, Se, Rb, Cs, Ce, Eu, Tb, Hf, Ta and Hg, which occur at the g.ml^–1 to ng.ml^–1 levels. There are no values reported for Tb, Hf, Ce, Eu and Ta before. The other results are compared with the values reported in the literature. Most are in the range of the reported values except for Fe, Zn, Se and Cs.     

Chlorine loss from polyvinylchloride under neutron irradiation

PVC samples were irradiated for 1 hour with a thermal neutron flux of _th =4.71·10¹¹n·cm^–2·s^–1 and the chlorine lost during irradiation was measured by -ray spectrometry. About 15% of loss of chlorine has been observed for untreated samples while samples heated to temperatures of 60 and 80°C for one minute before irradiation have been found to loose about 8% and 3%, respectively. The results indicate an influence of the polymer structure on the release of chlorine.     

Extraction-chromatographic system TBP-HBr in radiochemical neutron activation analysis of high-purity materials

The extraction and extraction-chromatographic behaviour of a variety of elements in the TBP-HBr system with concentrations from 0.1 to 7M HBr has been studied. The results allowed the development of simple procedures for radiochemical neutron activation determination of 22 impurity elements (Na, K, Sc, Cr, Mn, Fe, Co, Ni, Cu, Ga, As, Se, Rb, Sr, Zn, Mo, Ag, Sb, Te, Ba, La, Hf and W) in high-purity cadmium and indium samples with detection limits from 1 g g^–1 for Fe and Zr to 0.01 ng g^–1 for Na, Sc, Mn with relative standard deviations < 0.15. To increase the selectivity of the extraction-chromatographic separation, use was made of extraction suppression and co-extraction effects. The procedure for the extraction-chromatographic separation of scandium from a number of other elements is described as an example. The procedure can be used for simultaneous quantitative separation of impurity radionuclides from radiation produced long-life scandium radionuclides in the neutron activation analysis of titanium and vanadium.     

The in vivo neutron activation analysis of calcium in the skeleton of normal subjects,with hypokinesia and bone diseases

A facility developed for the in-vivo neutron activation analysis (IVNAA) of calcium in some parts of tubular limb bones, in the hand, foot and spine is described. The⁴⁸Ca(n, )⁴⁹Ca reaction is used, the gamma-rays of⁴⁹Ca (E=3.08 MeV, T_1/2=8.8 min) are measured. The irradiation is carried out with five of ten²³⁸Pu–Be neutron sources with a source stength of 5·10⁷ n s^–1 each arranged in a bath filled with water. NaI(T1) detectors (from 2 to 4 in number) of 150×100 mm size supplied with lead and shadow shielding are used in the counting unit. The construction of the facility started in 1972 and has been in operation since 1974. It has been used for the examination of patients suffering from limb bone tumors, of children with rickets-like and similar diseases and for studies in space medicine.     

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.     

Thermal neutron activation analysis of different varieties of mustard and sunflower seeds

Neutron activation analysis (NAA) technique has been used for the estimation of Mn, Na, and K in different varieties of oil seeds of mustard and sunflower in India. The samples were irradiated in a²⁵²Cf source with neutron flux of 10⁹ n s^–1 and the analysis was done using a multichannel analyzer (MCA) coupled to high purity germanium (HPGe) detector. Different varieties of seeds are found to have different concentrations of tracer elements when compared among themselves.     

Analysis of shape memory alloys by neutron activation

The transition temperatures and ageing of shape memory alloys (SMA) depend on the chemical composition and purity. Methods for the deterrnination of trace impurities, doping and major elements in NiTi, CuZnAl and CuNiAl were developed using neutron activation analysis and -spectroscopy. For traces in Zn containing alloys, a chemical separation based on anion exchange resins was developed. Multielement analysis leads to detection limits ranging from 0.0001 to 1 g·g^–1. For major elements, optimization of the irradiation and spectrometry parameters enables standard deviation better than 0.5%.     

Evaluation of the determination of iodine in drinking well water by neutron activation analysis and separation by isotope exchange

The determination of total iodine in drinking and well water by neutron activation analysis and separation of¹²⁸I (T=25.0 min) by isotope exchange has been examined at the 5–15 ng.ml^–1 level. Using the Lazy Suzan of a Triga Mark-II reactor, the capacity is 5 samples per hour at a precision of 15–20% per aliquot and no apparent systematic bias.     

Large-sample neutron activation analysis: Present status and prospects

Neutron activation analysis is attractive for trace-element determinations in large samples. Facilities for reactor irradiation and -ray spectrometry of kilogram-size cylindrical samples are described. The thermal neutron flux is ca. 5·10¹²m^–2·s^–1 with a _th/ _epi>10⁴, so neutron self-thermalization can be neglected. The correction for the neutron attenuation within the sample is derived from measurement of the neutron flux depression just outside the sample. Correction for -attenuation in the sample is performed via linear attenuation coefficients derived via transmission measurements. Also the natural radioactivity in the sample is taken into account. Examples are given of materials to which large sample INAA has been applied successfully, and further lines of development and exploration are indicated.     

Multielemental analysis of IAEA intercomparison standard Hay Powder,V-10 and some edible plant leaves by neutron activation

Instrumental Neutron Activation Analysis (INAA) has been employed for the multielemental determination of an IAEA intercomparison standard Hay Powder, V-10 and some edible plant leaves consumed in India. The samples were irradiated with thermal neutrons at a flux 10¹² n·cm^–2·s^–1 in a reactor for 5 minutes, 1, 2, 5, 10 and 15 hours and counted by high resolution -ray spectrometry. Nearly 18 elements have been determined. Good agreement is observed for most of the elements in several NBS standards and the proposed CRM V-10. Some edible vegetable plant leaves have also been analyzed.Partly presented at the 7th International Conference on Modern Trends in Activation Analysis, June 23–27, 1986, Copenhagen, Denmark, MTAA-7169.     

Fast non-destructive determination of iron and sulphur in coal by means of neutron radiative capture

The possibility of determination of iron and sulphur in large-scale samples of coal /20–50 kg/, based on process /n, /, was evaluated. The spectral lines of the doublet 7631 keV and 7645 keV were used for the determination of iron, while the line at 5421 keV was used for the determination of sulphur. The neutron source was²⁵²Cf /total neutron emission at 2.5×10⁷ s^–1/ located additionally in D₂O moderator. A Ge/Li/ detector was used for gamma radiation detection. The calibration dependencies of the analyzer were linear. In exposure times of up to 1 h, the detection limits of 0.34% and 0.64% and accuracies of 0.25% and 0.4% have been achieved in case of iron and sulphur, respectively.     

Non-destructive bone aluminum assay by neutron activation analysis

A non-destructive method based on instrumental neutron activation analysis (INAA) for the assay of aluminum in bone samples is described. The²⁸Al signal obtained upon neutron irradiation includes contributions from both the reaction²⁷Al(n,)²⁸Al and³¹P(n,)²⁸Al. The first reaction is with the thermal neutrons and the second one is with the fast neutrons. The contribution from the³¹P reaction is calculated from the fact that Ca/P ratio in bone mineral is constant and the amount of calcium can be measured from the thermal reaction⁴⁸Ca(n, )⁴⁹Ca. The aluminum values obtained by the INAA procedure agreed within 10% of those obtained by atomic absorption spectrophotometry. With this assay the levels of aluminum in normal bones (<70 g g^–1 apatite) cannot be determined reliably but higher aluminum levles in bone biopsies associated with Al toxicity, e.g. some patients with renal osteodystrophy, can be determined with a precision of ±10%.     

Instrumental neutron activation analysis of lanthanides and other elements employing CIRUS reactor as a thermal neutron source

The high thermal neutron flux provided by the CIRUS reactor (1×10¹³ n cm^–2s^–1) has been used to determine elements having long half-lives or poor thermal neutron crosssections. Selective cooling time and the use of a high resolution HPGe detector in conjunction with a PC based MCA unit have made it possible to analyze many elements in a single irradiation run. The method developed has been used for the analysis of ores such as Ilmenite, Rutile, Sillimanite, Garnet, Zircon and Monazite.     

Neutron activation analysis for the determination of contaminants in food contact materials

A neutron activation method has been developed for the analysis of high density polyethylene, low density polyethylene, polypropylene, polyethylene terephthalate and polystyrene. Samples weighing 2–5 g were irradiated in a thermal neutron flux of 10¹⁶ neutrons m^–2 s^–1 and measured with gamma ray spectrometry for 64 elements. With the method developed here over 50 elements can be detected at concentrations below 1 mg/kg. Correction factors were applied for neutron flux variation and counting geometry.The method was validated using reference material citrus leaves (NIST) for Na, Mg, Al, K, Ca, Mn, Cu, Sr and I, and a suite of in house standards doped with Al, Cr, Co, Mg, Zn and Sb confirmed repeatability of the method. The method was used to measure inorganic contaminants in the raw polymers and retail samples of plastic packaging used in contact with food.