Instrumental neutron activation analysis of silicon wafers using the silicon matrix as the comparator

For the instrumental neutron activation analysis of trace impurities in high purity silicon wafer, a modified single comparator method has been applied. The energy distribution of the neutrons at the irradiation position was measured using the two flux monitors, Au and Co, and elemental contents were calculated using the silicon matrix in the wafer as a comparator. This has advantage of reducing the cross contamination from an external monitor during sample preparation and irradiation, the uncertainties from the non-homogeneity of the neutron flux and the error on the weight of comparators. Determination limits for 49 elements were presented under the condition of 72 hours irradiation at a neutron flux of 3.7·10¹³ n·cm^-2·s^-1 and 4000 s measurement. The analytical results obtained by this method and the conventional single comparator method were compared and were found to agree well within 5%.     

Neutron activation analysis of impurities in thorium and zirconium matrices

A neutron activation method is described for the analysis of small concentrations of Cu, Cd, Mn, Co, Cr and Zn contaminants in thorium and zirconium compounds used for telecommunication and reactor techniques. The thorium matrix is separated from the contaminants by pre-irradiation paper chromatography and the²³³Pa is isolated after irradiation by extraction into methyl isobutyl ketone and precipitation with cupferron. For the analysis of the contaminant in zirconium compounds only precipitation with cupferron is used after irradiation. The individual impurities are determined by γ-spectrometry following separation.     

Neutron activation analysis for chlorine in Zr-2.5 wt% Nb coolant tube material

Zr-2.5 wt% Nb has been found to be better compared to Zircaloy-2 as coolant tube material in Canadu-PHW reactors but has a stringent specification of less than 0.5 mg/kg of chlorine. Instrumental neutron activation analysis (INAA) for the determination of chlorine in Zr-2.5 wt% Nb is not possible because of the high activity produced due to the determination of the matrix. Hence a radiochemical neutron activation analysis (RNAA) procedure has been developed for the determination of chlorine in this material. For the first time the chlorine determination at less than a ppm level by NAA is being reported in this paper, in a number of Zr-2.5 wt% Nb samples ranging from 0.1 to 2 mg/kg.     

Neutron activation analysis of high-purity selenium : Determination of phosphorus,sulfur and chlorine

Chlorine was determined in selenium by irradiation of 2-g samples for 37 min at a flux of 8·10¹⁰ n/cm²/sec. Chlorine was volatilised from hot concentrated nitric acid and precipitated as silver chloride. The isotope ³⁸Cl (T_{$\text{1}\text{2}$}=37.3 min) was counted by γ-spectrometry. Sulfur and phosphorus were determined by irradiating 50-mg samples with and without cadmium shielding for 4 days at a thermal flux of 6·10¹² n/cm²/sec and a fast flux of 4·10¹¹ n/cm²/sec. The matrix activities were separated by distillation from sulfuric acid-hydrobromic acid at 200–220°. The isotope ³²P (T_{$\text{1}\text{2}$}=14.3 d) was then precipitated, together with phosphate carrier, as ammonium phosphomolybdate, and counted with a G.M. tube. Amounts of 0.4–1 p.p.m. chlorine, 65–520 p.p.b. phosphorus and 1.5–4.6 p.p.m. sulfur were found in high-purity selenium samples.     

Neutron activation determination of uranium by coprecipitation of neptunium-239 on zirconium phosphate

A method is proposed for neutron activation determination of U via²³⁹Np. This is separated by coprecipitation of ZrO(H₂PO₄)₂ and its 106 keV γ-peak measured. The sensitivity of the determination is 10⁻⁹ g. The method is based on the well-known ability of Np(IV) to coprecipitate with zirconium phosphate, while Np(VI) does not form insoluble phosphates or fluorides. This permits elimination of elements interfering, with the determination of²³⁹Np via the 106 keV γ-peak: Sm, Nd, Yb, Lu, Pa (from Th) and Ta. The rare earths are eliminated by coprecipitation on LaF₃, and Pa and Ta as insoluble phosphates in an oxidizing medium. The method is suitable for phosphorus-containing samples: phosphorites, apatites and their industrial treatment products. The results obtained for the uranium content with the proposed method are in good agreement with the results of other methods and authors.     

Determination of niobium and tantalum in binary alloys and zirconium alloys

Recent developments in the metallurgy of niobium, tantalum and zirconium have necessitated provision of analytical procedures for determining niobium and tantalum in the presence of each other and in the presence of zirconium. For this purpose, absorptioinetric procedures based on the formation of yellow coloured complexes, between pyrogallol and niobium or tantalum, have been critically examined. Direct absorptiometric procedures are described, which are suitable for determining niobium or tantalum in the range 2 to 7%; when either of these metals exceeds 7%, differential absorptiometric procedures are recommended. Corrections must lie made for absorption due to the presence of other metals which form complexes with pyrogallol. In tlie determination of niobium or tantalum up to 5%, the precision of the method is about ±0.05%. About 12 determinations can be made in a day, by one analyst.     

The determination of zirconium and aluminium in alloys slags and fumes by 14-mev neutron activation analysis

Aluminium and zirconium have beendetermined in alloys, slags and fumes by 14-MeV neutron activation analysis. Nuclear reactions with zirconium have been investigated, and the radioisotopes produced by 14-MeV neutron activation have been determined. The results for alloys and slags agree well with those obtained by chemical methods; precisions of 1.8% were obtained in ideal cases. The neutron activation method is capable of analysing 10–12 samples, in duplicate, per man-day.     

Zirconium as a multi-isotopic flux ratio monitor and a single comparator in reactor-neutron activation analysis

Different methods for the determination of thermal-to-epithermal neutron flux ratio are reviewed and nuclear data for commonly used monitor materials and for Zr isotopes are tabulated. It is shown that the use of the⁹⁴Zr−⁹⁶Zr isotope pair gives significant improvement in precision while measuring Φ_th/Φ_e ratios in the 20<Φ_th/Φ_e<200 range. When the single comparator method is applied, the use of the⁹⁴Zr isotope is suggested as a comparator with the⁹⁴Zr−⁹⁶Zr isotope pair for simultaneous flux ratio determination. Theoretical calculations show that the Zr comparator-flux ratio monitor gives better precision and accuracy than does Ru for two-thirds of the isotopes used for analysis in well thermalized (Φ_th/Φ_e>100) channels. The I_o/σ_th-values for the mentioned Zr isotopes have been experimentally determined and compared with previously published data. Research associate of NFWO.     

Determination of zirconium in zirconium metal and zirconium powder by use of mandelic acid

An accurate gravimetric method is proposed for the determination of zirconium in zirconium metal and zirconium powder by use of mandelic acid. The sample is dissolved in a mixture of hydrofluoric, nitric, perchloric and sulfuric acids, the solution is evaporated to dryness, and the salts are dissolved in dilute hydrochloric acid. Zirconium mandelate is precipitated at 80°. The residual zirconium in the filtrate is recovered by heating at 80° overnight and the combined precipitates are ignited to Zirconium dioxide. An investigation was made of the factors involved in the dissolution of the sample, precipitation with mandelic acid, ignition of the precipitate, and size of sample. The effect of hafnium is discussed.     

Determination of soluble and insoluble zirconium in magnesium alloys

A method for the determination of soluble and insoluble zirconium is described. To differentiate between the two forms, two solutions are prepared, in one of which the insoluble zirconium remains in suspension ; in the other it is brought into solution with hydrofluoric acid. Zirconium is extracted by trioctyl phosphine oxide/petroleum ether and determined in the extract spectrophotometrically with pyridyl-azo-naphthol (PAN) as reagent.     

The use of the microtron for the activation analysis of pure metals and alloys

Oxygen and carbon concentrations up to 0.06 ppm and 0.03 ppm respectively were determined in high purity metals such as Fe, Cu, Nb, Mo, In and some others. Analytical procedures and results of the determination of alloying additives in a number of rare metal alloys are given. The relative standard deviation constitutes 0.02 to 0.04. Accuracy of the procedures used is confirmed by a comparison of experimental results with those of the other analytical methods. Experimental data on the sensitivity of determining 35 elements are reported on irradiating them with thermal neutrons and a bremsstahlung emitted by the microtron. For most elements (for radioactive isotopes having a half-life of above 2 min.) sensitivity of the analysis is 10⁻⁶ to 10⁻⁸, g, at the microtron current of 30 μA and irradiation time of less than 10 min.     

Neutron activation as a routine method for the determination of trace elements in water

By freeze-drying the following elements can be determined in natural water except sea water: Au, Ba, Br, Ca, Ce, Co, Cr, Eu, Fe, K, La, Mo, Na, Sb, Sc, Se, U, Zn. Some problems may arise with respect to As and Hg. Cu, Cd and Ni can only be determined if present in high concentrations. Separation by adsorption on charcoal in presence of complexing agents gives yields between 75 and 100% for the following elements in sea water: Ag, Au, Cd, Ce, Co, Cr, Eu, Fe, Hg, La, Mo, Sc, Se, U, Zn (As 67%, Sb 56%). Activation or use of labelled ions and study of exchange give information about mobility of trace elements in suspended matter.     

Investigations on the comparator technique used in epithermal neutron activation analysis

The possible extension of the comparator technique of reactor neutron activation analysis into the field of epithermal neutron activation has been investigated. Ruthenium was used for multi-isotopic comparator. Experiments show that conversion of the so-called reference k-factors—determined by irradiation with reactor neutrons—into k_epi-factors usable at activation under cadmium filter, can be evaluated with fair accuracy. Sources and extent of errors and their contribution to the final error of analysis are discussed. Based on the paper presented at the 2nd European Conference on Analytical Chemistry, 25–30 August, 1975, Budapest, Hungary.     

Spot tests for the identification of titanium alloys and their differentiation from zirconium and its alloys

During manufacture every precaution is taken to safeguard against inadvertent mixing of titanium and zirconium alloys. There arc, howcvcr, occasions when confirmation of identity is desirable, Simple spot tests are described for the rapid differentiation of a range of titanium alloys and fur distinguishing these materials from zirconium and its alloys After a preliminary attack of the abraded metal surface with either fluoboric or hydrofluoric acid, characteristic coloured reaction products arc formed with well known reagents. and these tests serve to classify the material.     

Determination of thorium in magnesium alloys that contain zirconium

Summary An indirect polarographic method for the determination of thorium in magnesium alloys that contain zirconium, zinc, and rare-earth elements is described. The method depends on the precipitation of thorium as the tetra (m-nitrobenzoate) and the polarographic determination of the m-nitrobenzoic acid that is equivalent to the amount of thorium that was so precipitated. The only interference, that of zirconium, is forestalled by the prior removal of the zirconium on an anion-exchange resin. The zirconium can easily be eluted quantitatively from the resin, for subsequent determination.The method avoids tedious separational procedures, and yields accurate and precise values for thorium in the alloys for which it was devised. It is also applicable to simpler substances.The authors gratefully acknowledge the grant from the Defence Research Board of Canada that made possible this investigation (Project D44-75-10-04).     

Separation and determination of zirconium and hafnium in uranium matrix

Hafnium and zirconium are separated from uranium using an anion exchange resin column. The two elements are then separated from each other using extraction chromatography and determined separately by precipitation as tetramandelate. The determination method was verfied by isotopic cilution technique. The method proved to be selective, quantitative (>99%) and gives an error of <±2%.     

Total body sodium and chlorine in normal adults as determined by neutron activation analysis

Total body neutron activation analysis (TBNAA) has used to determine the absolute levels of total body sodium (TBNa) and total body chlorine (TBCl) in 81 normal adults. For the age span studied (30–90 years), the mean values of TBNa and TBCl remained relatively constant for males, but decreased slightly for females beyond sixty years of age. In order to reduce the variability in this cross-sectional study, the TBNa and TBCl values were normalized for body dimensions (weight, height, body surface area) as well as age and sex. In addition, TBNa was related to skeletal mass (total body calcium) and lean body mass (total body potassium). The quantity of body sodium in excess of the chlorine space was determined. This value, defined as sodium excess, was significantly correlated with total body calcium. The values for total body sodium, total body chlorine, and sodium excess obtained in the present study were compared with values previously reported in the literature.