Thermal Neutron Activation Analysis Research Articles

The determination of selenium in biological material by thermal neutron activation analysis and atomic absorption spectrometry

Neutron activation analysis and atomic absorption spectrometry (graphite furnace) methods for the analysis of selenium in human tissue are described. The sensitivity (10–30 ng/sample), accuracy and precision are of the same order for both techniques and the choice can only be made on grounds of urgency or convenience. AAS should be chosen for the analysis of wet tissue or the urgent analysis of small numbers of dry tissue. NAA should be chosen for the analysis of large numbers of dry tissue samples where time is not important. The selenium concentration of human liver is shown to be in the region of 1 to 2 ppm (dry weight). Selenium may be lost from tissue during freeze drying if the samples are not maintained at −35°C.

Determination of trace elements in various organs of rats by thermal neutron activation analysis

The trace element levels in various organs of normal rats have been determined by means of thermal neutron activation followed by high-resolution gamma-spectroscopy. Abundances for 11 elements (Cu, Mn, Fe, Zn, Rb, Sb, Se, Cr, Co, Cs and Sc) were evaluated in the individual subjects. The present results were generally found within the ranges of the literature values, except for ultra-trace elements. Reliability of the method was assessed by analyzing NBS standard reference materials, Orchard Leaves and Bovine Liver. The trace element contents of the rat diet have also been measured, and comparison of them with those of the rat organs was given.

Thermal neutron activation analysis of hafnium in zircaloy with a Van de Graaff accelerator

Thermal neutron activation analysis of hafnium in zircaloy was investigated with a Van de Graaff accelerator. Thermal neutrons were obtained by moderating Be−D fast neutrons with paraffin blocks.179mHf isotope with a half-life of 18.6 s, produced by178Hf(n, γ)179mHf reaction, was utilized in the present analysis. This method made it possible to analyze hafnium rapidly and non-destructively by using scandium as an internal standard material. Several tens to hundreds of ppm of hafnium in zircaloy samples were determined within 2 minutes with a precision of about ±1%.

Electroinitiated polymerization coatings through packed and fluidized bed electrodes

Our previous studies on electroinitiated polymerization for formation of coatings on metal surfaces have all been in stationary cell systems. The feasibility of using either a packed bed or a fluidized bed cell in electroinitiated polymerization is now demonstrated, the objective being to form polymeric coatings on metallic and metal-coated nonmetallic particles. The metallic particles that have been used are aluminum and stainless steel and the monomer-electrolyte system used is DAA-sulfuric acid. A comparison of current densities under various cathode potentials for the packed and fluidized bed systems is presented. The coatings obtained are analyzed through IR to establish the polymer functional groups. Additionally, both elemental analyses and thermal neutron activation analyses have been carried out to establish the compositions of the polymer coatings.

Use of stable 48Ca in the clinical measurement of intestinal calcium absorption.

Measurements of intestinal-calcium-absorption efficiency are fundamental for understanding calcium homeostasis in health and disease. Stable calcium isotopes are attractive tracers for such measurements, to avoid excessive radiation exposure to the subject and permit serial studies at short intervals. To realize this, we found it necessary to improve the sensitivity and precision of existing thermal neutron activation analyses for 48Ca. This report describes the details, sensitivity, precision, and accuracy of the improved method, and gives the results of studies in which intravenous 48Ca was used in conjunction with oral 47Ca to measure intestinal-calcium-absorption efficiency in patients.

ChemInform Abstract: NON‐REACTOR ACTIVATION ANALYSIS‐ RECENT ADVANCES AND PRACTICAL SIGNIFICANCE

For several reasons, thermal-neutron activation analysis using nuclear reactions of (n,γ) type has been the predominantly utilized activation analytical technique. However, increasing use is now being made of other techniques. It has been the purpose of this paper to review recent basic and technical developments and new applications of the non-reactor activation techniques and to provide a picture of their power, their practical significance and their limitations. The activation by using neutrons from isotopic sources, 14-MeV neutrons, cyclotron-produced neutrons, charged particles and photons is considered.

Helium-4 and neutron activation analysis for phosphorus in aluminium—silicon alloys

An instrumental determination of phosphorus in aluminium-silicon alloys by activation with 20-MeV helium-4 particles can be based on the 31P(α , n) 34m Cl reaction. A mixture of aluminium powder and disodium hydrogenphosphate is used as a standard. For concentrations ranging from 1.7 to 25 μg g -1, the experimental standard deviation ranges from 1 to 24% with an average of 8%. The method was compared with thermal neutron activation analysis based on the 31P(n, γ) 32P reaction. 32P was chemically separated by precipitation as ammonium molybdophosphate. This technique yielded results with a standard deviation between 0.3 and 7.5% with an average of 2%. The agreement between the two methods was satisfactory. The results were also compared with photometry and atomic absorption spectrometry.

Activation analysis of alkaline rocks. A comparison between destructive and non-destructive methods

The United States Geological Survey reference sample AGV-1 andesite, and three alkaline rocks from the apatite mine of Jacupiranga, Brasil, were analyzed by thermal neutron activation analysis using destructive and non-destructive methods, and high resolution Ge(Li) gamma-ray detectors. One of the rocks, a carbonatite, was also analyzed by instrumental activation analysis with epithermal neutrons. A greater number of elements can be determined using the radiochemical separation, but the precision and accuracy attained by INAA and RNAA were of the same order for most of the elements analyzed. Epithermal activation was more advantageous for tantalum, terbium and holmium. Comparison of the analytical results for USGS reference sample (AGV-1) with the data published by others gave good agreement. Statistical tests used for comparison of the results of destructive and non-destructive methods, as well as other results are presented.

The estimation of barium in biological material by neutron activation analysis

Barium is estimated in biological material by thermal neutron activation analysis and measurement of139Ba by γ-counting. The biological material is digested with nitric acid and scavenged with ferric hydroxide. A special fluoride precipitation removes calcium and strontium and the barium is recovered as the chromate. The method allows the analysis of up to 40 samples per day and the sensitivity is 0.1 μg after irradiation for 85 mins at 4·1012n·cm−2·sec−1.

Determination of trace elements in carbonates by instrumental neutron activation analysis

A systematic non-destructive determination of eighteen trace elements (F, Na, Cl, Sc, Mn, Zn, Br, Sr, I, Ba, La, Ce, Sm, Eu, Tb, Yb, Th and U) in carbonate samples by thermal neutron activation analysis was developed. Three 0.2–0.5g samples were irradiated for 15 sec (in the case of determination of F), for 3 min (in the case of Na, Cl, Mn, Sr and I) and for 60 hrs (in the case of Sc, Zn, Br, Ba, La, Ce, Sm, Eu, Tb, Yb, Th and U) in the TRIGA MARK II Reactor at a thermal neutron flux of 5·1011 n·cm−2·sec−1 (15 sec and 3 min irradiation) and 1.5·1012n·cm−2·sec−1 (60 hrs irradiation), respectively. According to the half life of the nuclides formed, the activities were measured with a Ge(Li) spectrometer as follows,20F∶15 sec counting after 20–25 sec cooling,24Na,38Cl,56Mn,87mSr and128I∶600 sec couting after 30–120 min cooling,82Br,140La,153Sm,175Yb and239Np (daughter of239U)∶3000 sec counting after 1 week cooling,46Sc,65Zn,131Ba,141Ce,152Eu,160Tb and233Pa (daughter of233Th)∶5000 sec counting after 1 month cooling. The errors due to the fluctuation of the neutron flux and the counting geometry were minimized by the use of calcium determined previously with EDTA-titration as an internal standard. The interferences from24Mg(n, p)24Na and235U(n, fission) reactions were corrected by the activities produced by the reactions in unit weight of magnesium and uranium, and their concentrations in samples measured experimentally. The data of Na, Mn, Zn and Sr were compared with the results obtained by atomic absorption analysis.

Application of selective evaporation in the determination of arsenic and bromine in dry biological material by thermal neutron activation analysis

The application of selective evaporation in an air-flow to the determination of arsenic and bromine in neutron-activated freeze-dried biological material is reported. Bromine is evaporated as Br2 during oxidative mineralisation. After addition of 48% HBr, arsenic is removed as AsBr3. The evaporated elements are collected in 7M NaOH;82Br (T=35.3 h) and76As (T=26.4 h) are used for quantitative assay. The chemical yield is (98±2)% for arsenic, irrespective of the amount of arsenic carrier. For bromine it varies from (70±10)% for carrier-free evaporation to (98±2)% if sufficient carrier is added. This addition is not permitted if arsenic has to be determined. The limits of determination are 5 ng·g−1 and 2 ng·g−1 respectively. The precision is ≤10% for both elements. The procedure is performed in a standardised apparatus. It was applied to the analysis of standard kale, orchard leaves and animal blood. Bromine was determined instrumentally for purpose of comparison.

Neutron activation analysis of Bawachi seeds

Seeds of (the plant) P. Corylifolia Linn (Bawachi) known for their therepeutic value in indigenous medicine have been analysed for Cu, As, Sb and Se by thermal neutron activation analysis involving substoichiometric extraction and precipitation technique. The amounts of Cu, As, Sb and Se per gram of seeds dried at 80°C are 16.0±1.1 μg, 0.90±0.4 μg, 12.1±0.6 μg and 4.0±0.2 μg respectively.

Simultaneous determination of nitrogen and lithium by thermal neutron activation analysis

The determination of lithium and nitrogen in a variety of materials by thermal neutron activation is described. The nuclear reactions used are 14N(n,p) 14C and 6 Li(n,α) 3H. Radionuclides. 14C and 3H for counting are isolated by fusion of the irradiated sample in a vacuum system. Data are presented on lithium and nitrogen concentrations in several terrestrial standards. The new method allows reliable measurements on 10–50-mg samples.

Non-reactor activation analysis: Recent advances and practical significance

For several reasons, thermal-neutron activation analysis using nuclear reactions of (n,γ) type has been the predominantly utilized activation analytical technique. However, increasing use is now being made of other techniques. It has been the purpose of this paper to review recent basic and technical developments and new applications of the non-reactor activation techniques and to provide a picture of their power, their practical significance and their limitations. The activation by using neutrons from isotopic sources, 14-MeV neutrons, cyclotron-produced neutrons, charged particles and photons is considered.

Ident—a radioisotope-identification subroutine for use with the gamma-ray spectrum analysis program sampo

A radioisotope-identification and mass-determination subroutine has been added to the gamma-ray spectrum analysis program SAMPO. The subroutine IDENT contains a nuclear data library of 750 gamma-rays that are likely to be encountered in thermal-neutron activation analysis. Peaks found by SAMPO are compared with the library peaks and possible isotope identifications are made. To maximize the degree of confidence in the isotope identification, the subroutine carries out a half-life check and also confirms that the most prominent gamma-ray of the isotope concerned is present. Using the library data, together with information on the neutron flux, duration of the irradiation, subsequent decay time, and gamma-detection efficiency, the subroutine calculates the masses of elements identified in the sample, and can handle spectra acquired during either simple or cyclic irradiation. As well as the calculated masses the output contains information on identifications rejected by certain criteria. The nuclear data library used by the subroutine is presented in this paper in a simplified tabular form, and, as such, may be used for direct isotope identification and elemental mass determination.

Determination of certain selected bulk and trace elements in the bovine liver matrix using neutron activation analysis

Effective utilisation of neutron activation analysis (NAA) for the elemental analysis of biomedical samples with or without a radiochemical separation, especially when optimal Ge(Li) well type detectors are employed for the acquisition of complex spectra, is demonstrated by determining normal values for 25 elements in bovine liver. Optimal conditions for the determination of Ag, Br, Cl, Co, Cs, Fe, I. K, Mn, Na, P, Rb, Sb, Sc, Se and Zn with the aid of instrumental thermal neutron activation analysis (INAA) by varying the irradiation and decay time are presented. Where INAA was inadequate, simple post irradiation separation based on ion-exchange has been used to determine such elements as Au, Ca, Cd, Ce, Cr, Cu, La, Mo and W.

A Simple Pretreatment of Samples for Thermal Neutron Activation Analysis

A Simple Pretreatment of Samples for Thermal Neutron Activation Analysis

Fast-neutron sputtering of niobium

Neutron sputtering yield measurements of niobium are reported for 14.8-MeV (d,t) neutrons and for fast neutrons in the forward direction produced by 40-MeV deuteron bombardment of a thick Be target. Six irradiations were performed with 23 niobium targets with a range of 1.7×1015 to 6.1×1016 (d,t) neutrons. One irradiation was performed with five niobium targets irradiated with a range of 4.7×1016 to 4.5×1017 (d,Be) neutrons. Sputtering targets included single crystals and annealed and cold-worked material with various surface preparations. Target preparation overlapped or was identical, in several cases, to that used by another research group which has reported the observation of fast-neutron-induced ’’chunk’’ or micrometer particle emission. Several cm2 of collector which faced Nb targets irradiated to fluences of (0.4–1.1) ×1016 (d,t) neutrons/cm2 were carefully examined by scanning electron microscopy, but no evidence for neutron-produced chunk emission ?0.5 μm was found. Thermal neutron activation analysis was used to determine absolute yield on most of the silicon collectors which faced the front and back surfaces of the Nb targets. These determinations indicate that the yield in atoms/neutron for a wide variety of Nb target preparations, including those which are reputed to be high-probability chunk emitters, are likely to be less than several times 10−5. The experimental procedures are presented in detail. The present results for fast-neutron sputtering yields are discussed in relation to other recent results for niobium and theoretical estimates. Limitations in our experiments and others are also discussed. The present results, as well as other recent results for niobium, indicate that neutron sputtering will not be a significant factor in the erosion of the first wall or in plasma contamination in future fusion reactors.

A molybdenum-containing (2Fe, 2S) protein from desulphovibrio gigas, a sulphate reducer

An acidic protein that contains molybdenum, iron and labile sulphide has been isolated from Desulphovibrio gigas, a sulphate reducer. The protein was purified by Chromatographic procedures over DEAE-cellulose, Sephadex and alumina. The molecular weight, determined by polyacrylamide gel electrophoresis, is about 120 000. The amino acid composition is typical of the (2Fe, 2S) ferredoxins with a high proportion of acidic residues and about two cysteine residues per iron atom. It has twenty atoms of iron and twenty atoms of labile sulphide. One atom of molybdenum per molecule was determined by thermal neutron activation analysis. Optical absorption spectra indicate that the iron-sulphur chromophores are of the (2Fe, 2S) type.

Some practical procedures in computerized thermal neutron activation analysis with Ge(Li) gamma-ray spectrometry

The practical use of a correction procedure for random coincidence losses, the determination of the detection limit and the standardization of measuring conditions are described. Special correction methods for the interference of the Cu analysis by24Na, the burn-up of the radioactive nuclide formed and the interference of the Pt determination by Au are also given.