The determination of trace oxygen in lead by helium-3 and helium-4 activation analysis

The determination of oxygen in lead by³He and⁴He activation analysis was studied. Both methods were applied to the same material containing 0.9 μg·g^?1 of oxygen. The¹⁸F formed from oxygen was separated from matrix activities by extraction of Po with N-benzoyl-N-fenylhydroxylamine, followed by distillation of fluorosilicic acid and precipitation of lead fluorochloride (⁴He activation) or by distillation followed by precipitation (³He activation). The yield of the separation, which amounted on the average to 68%, was determined via the¹⁹F(n,⁴He)¹⁶N reaction. The coefficients of variation were 21 and 45% for⁴He and³He activation analysis, respectively, thus indicating a less homogeneous distribution of the oxygen. Nuclear interferences of sodium and fluorine were shown to be negligible.     

Non-destructive determination of trace elements in tungsten by helium-3 activation analysis

A non-destructive method is described for the determination of trace impurities at sub-p.p.m. levels in a tungsten matrix by 14-MeV ³He activation analysis. A Ge(Li) spectrometer and a multichannel analyzer were used to determine V, Fe, Ni, Zn and Mo impurities. Interfering reactions are discussed in detail.     

The determination of oxygen in silicon by alpha and helium-3 activation analysis

A non-destructive analytical method for oxygen in silicon by both helium-3 and α-particle activation analysis was applied to different samples, containing 0.05–10 p.p.m. of oxygen. The accuracy and precision of the method were studied. For concentrations above 1 p.p.m., the average coefficient of variation is about 6% for α-activation and 13% for helium-3 activation. For concentrations of about 60 p.p.b., the corresponding figure is about 20%. The results of both methods, which agree within 8%, are compared to infrared analysis. The determination limit of the method is 4 p.p.b. for helium-3 activation and 22 p.p.b. for α-activation.     

Trace determination of lead by helium-4 activation analysis

The determination of lead via 30 MeV⁴He bombardment to produce the long-lived radioisotope²¹⁰Po was studied. The validity of the technique was tested by the analysis of a series of NBS glass samples doped with 61 different trace elements at nominal 500 to 1 ppm level concentrations. The measurement sensitivity of alpha counting with surface barrier detectors was evaluated. The detection limit was estimated at 0.1 ppm. The⁴He-activation technique coupled with -counting features a unique combination of sensitivity and accuracy for the trace determination of lead.     

The simultaneous determination of carbon and oxygen in semiconductor silicon by helium-3 activation analysis

A non-destructive method for the simultaneous determination of carbon and oxygen in silicon by helium-3 activation analysis is described. The determination is based on a simplified standardization method. The method was applied to samples containing 0.05–3 p.p.m. of carbon and 0.05–10 p.p.m. of oxygen. The determination limit of carbon varies from 30 to 300 p.p.b. depending on the oxygen concentration.     

The determination of carbon in aluminium by deuteron activation analysis

Carbon can be determined in aluminium by deuteron activation analysis via the ¹²C(d, n)¹³N reaction. ¹³N is separated from other activities by steam distillation. A carbon concentration of 0.25 μgg^-1 with a standard deviation of 0.05 μg g^-1 was obtained for aluminium of 99.5% purity.     

Oxygen determination in calcium fluoride by deuteron activation analysis

Oxygen at trace level in calcium fluoride was determined by instrumental deuteron activation analysis based on the ¹⁶O(d,n)¹⁷F reaction. The irradiations were performed with 2.5 MeV deuterons for 60 s at currents ranging from 300 to 500 nA. The results obtained for powders and single crystals were compared. Received: 25 October 1999 / Revised: 23 November 1999 / Accepted: 23 November 1999     

Oxygen determination in calcium fluoride by deuteron activation analysis

Oxygen at trace level in calcium fluoride was determined by instrumental deuteron activation analysis based on the 16O(d,n)17F reaction. The irradiations were performed with 2.5 MeV deuterons for 60 s at currents ranging from 300 to 500 nA. The results obtained for powders and single crystals were compared.     

Trace analysis of heavy metals in high purity materials by helium-3 activation analysis

A method is described to determine traces of V, Fe, Ni, Zn, Nb and Mo in high purity matrices of niobium, tantalum and tungsten by non-destructive 14 MeV³He activation analysis. The influence of nuclear and γ-ray interferences in the determination of these elements is discussed.     

Simultaneous determination of aluminium and phosphorus by neutron activation analysis

With the use of the pneumatic tube system of the BER II reactor, the irradiation position of which is equipped with a movable cadmium shield, the aluminium and phosphorus levels in bone powder and in human bone biopsies were determined. The contribution of aluminium and phosphorus to the²⁸Al activity could be separated mathematically after the samples had been irradiated with and without cadmium shielding. The sensitivity and limit of quantitative determination of the analytical procedure were determined using the addition method and the fact that the levels of each element measured was independent of the amount of the other element was proved.     

Oxygen determination by fast neutron activation

A method for the determination of oxygen based on the reaction¹⁶O(n, p)¹⁶N is suggested. The samples are irradiated in stainless steel capsules with fast neutrons. The total neutron flux passing through the sample is proportional to the flux passing through the wall of the capsule. Therefore, the activity induced in the capsule according to the reaction⁵⁶Fe(n, p)⁵⁶Mn can be used to monitor the neutron flux through the sample. Thus, the necessity of maintaining the sample in an exact position during the irradiation is eliminated.     

The determination of sulphur in copper,nickel and aluminium alloys by proton activation analysis

The ³⁴S(p, n)^34mCl reaction induced by 13-MeV protons is used for the determination of sulphur in copper, nickel and aluminium alloys. The ^34mCl is separated by repeated precipitation as silver chloride. The results obtained were 3.08 ± 0.47, 1.47 ± 0.17 and <1μg g^-1 for copper, nickel and aluminium alloys, respectively.     

Non-destructive determination of aluminium,silicon and oxygen in steel by 14 MeV neutron activation analysis

Analysis of steel for aluminium, silicon and oxygen is presented. The use of a Ge(Li) detector and the technique of precise photopeak integration enabled to attain a detection limit of 0.04% for Al. A method of the evaluation of the iron interference in silicon determinations is proposed.     

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.     

Determination of aluminium in lutetium by instrumental neutron activation analysis

In lutetium metal 45 ppm aluminium have been determined by instrumental neutron activation analysis. Interference from the very intensive γ-radiation of^176mLu was eliminated by application of lead filters. The determination limit of the method was estimated to be 0.7 μg or 3 ppm Al.     

Yield determination in activation analysis by radiotracers

Radiotracers for yield determination in activation analysis can be used as isotopic radiotracers by labelling of the carrier solution or as non-isotopic radiotracers for precipitation reactions with a labelled reagent as last separation step or for extraction processes with a labelled organic complexing agent. These possibilities are demonstrated by selected examples concerning determinations by neutron and also by photon activation (W, Cu, F, I, Sn). Suitable tracer nuclides (isotopic or non-isotopic) and ways to increase their number are given. Advantages and disadvantages of the different radiotracer methods for yield determination are discussed.     

Determination of silicon in aluminium by 14 MeV neutron activation analysis

A method has been developed for determining silicon in aluminium by fast neutron activation. It is based on the separation of two gamma lines by a Ge(Li) detector: the 1.73 MeV line from the product of²⁷Al(n, α)²⁴Na and the 1.78 MeV line from the²⁸Si(n, p)²⁸Al reaction. In the case of aluminium-silicon alloys 100 μg silicon can be determined, with an error of 10% in an aluminium sample of 1 g. This work was supported in part by the International Atomic Energy Agency.     

Determination of aluminium in bulk coal samples by neutron activation analysis

The determination of Al₂O₃, in bulk coal samples to an accuracy of about 0.2% Al₂O₃ has been achieved by means of a thermal-neutron activation technique based on the reaction ²⁷Al(n,γ)²⁸Al. In the analysed samples, which had widely different compositions, the Al₂O₃ concentrations ranged from 1 to 11% and the ash contents from 7 to 40%. Al₂O₃ concentrations measured by x-ray fluorescence showed a linear relationship with both the 1.78-MeV γ-ray count following the decay of ²⁸Al and the thermal-neutron count near the samples during irradiation. The linear relationship, which was obtained by regression analysis of the experimental data, determined the Al₂O₃concentrations with a standard deviation of 0.24% Al₂O₃. The particle sizes in the samples ranged from —0.5 to —40 mm, the moisture contents ranged from 1 to 6%, and the sample weights ranged from 8 to 11 kg. However, inclusion of these parameters in the regression analysis did not significantly improve the results for Al₂O₃.     

Determination of aluminium and sodium in tungsten by non-destructive activation analysis

The sodium and aluminium content of tungsten has been measured by thermal neutron activation analysis. The concentration of aluminium was evaluated from the 1.78 MeV, and that of sodium from the 2.76 MeV full energy peaks. The minimum detectable concentrations of impurities were 0.04 microg of aluminium and 0.07 microg of sodium per 100 mg of tungsten.