Reactor neutron activation analysis of antimony, indium and cadmium in high-purity tin is interfered with by nuclear reactions
on the tin matrix. For a number of interfering reactions the cross-sections were determined. The following results were obtained:122Sn(n,γ)123mSn:σth=0.145 barn, I=0.79 barn;122Sn(n,γ)113Sn:σth=0.52, I=25.4 barn;112Sn(n, 2n)111Sn:
Neutron activation analysis for bismuth in lead was performed through the separation and measurement of210Po, using two different extraction procedures. The reproducibility of the results was good for lead containing bismuth in
higher concentrations. For high purity lead, variations in the bismuth content have been found by different analyses of the
same sample, owing to inhomogeneity in the distribution of the Bi metal traces. An independent analysis of the same lead samples
gave comparable Bi concentrations.
Fast neutrons are produced by irradiation of a thick beryllium target with deuterons from a cyclotron. The spatial neutron flux distribution was studied. Ge(Li) gamma-ray spectrometry was used to measure the radionuclides produced. Detection limits are tabulated along with the nuclear interferences.
A critical evaluation of different comparator methods is given. The method based on experimentally-determined and convertible
comparison factors (k) is considered to be the most suitable for general use. An alternative method is proposed, introducing
generalized k0 factors which are independent of irradiation and measuring conditions. This approach combines the simplicity of the absolute
methods with nearly the same accuracy attained by the relative ones. It is suggested that k0 factors be compiled in all cases when using single-comparator methods, to allow a continuous re-evaluation.
Arsenic, selenium and antimony were determined in four different tin samples. After distillation from HBr−H2SO4 medium arsenic and selenium were precipitated with thioacetamide, and antimony was subsequently separated by deposition on
iron powder. The separated samples were counted on a high-resolution Ge(Li) γ-spectrometer. The sensitivity of the method
is highly satisfactory.
Authors:F. Adams, J. Hoste, J. Bartosek, and J. Mašek
New circuits are presented to determine precisely the counting losses suffered in the entire gamma-ray spectrometer and to
allow automatic correction for them even in the case of time-dependent counting rates as encountered in the measurement of
short-lived radioisotopes. Experimental proof is given that the proposed circuitry allows accurate quantitative measurements
in gamma-ray spectrometry. With counting rates up to 20,000 cps losses amount to less than 1.5%.
Authors:R. Mortier, C. Vandecasteele, J. Hertogen, and J. Hoste
The determination of boron in rocks by charged particle activation using the10B(d, n)11C reaction is studied. A sample holder that allows reproducible irradiation of powdered samples is developed.11C is separated as11CO2. For boron concentrations between 2.35 and 25.2 μg·g−1, the standard deviations ranges from 7.1 to 22.8%. The results for USGS reference silicate rocks and Moroccan phosphate rock
are compared to those obtained by other techniques.
Authors:R. Cornelis, J. Versieck, L. Mees, J. Hoste, and F. Barbier
Vanadium in serum has been investigated by the aid of neutron activation analysis (8 min irradiation at 8·1013 n·cm−2·s−1 in the reactor FR-II of the Kernforschungszentrum in Karlsruhe). The lyophilized samples were dry-ashed before irradiation
and the52V activity extracted after irradiation. The values for V in the sera of 22 healthy males ranged from 0.029–0.939 ng V·ml−1. There is a real assumption that some of the high figures are due to persons being contaminated with V. The 18 healthy females
yielded a mean value of 0.033±0.012 ng V·ml−1 for 17 of them and one additional value of 0.139 ng V·ml−1. These V-data are the lowest ever reported in the literature. The analyses of two packed blood cell samples yielded 0.031
and 0.020 ng·g−1, indicating that about 68% of the total V in blood is present in serum. There was no correlation between the V-content and
age, nor between the V-content and the cholesterol, triglycerides or the lipoprotein fractions in serum.
A method has been developed for routine determination of cadmium in zinc ores by thermal neutron absorption analysis, based
on the attenuation of a thermal neutron flux passing through a neutron absorbing material. The thermal neutron flux is related
to the52V-activity induced in a vanadium detector, surrounded by pellets pressed from a mixture of powdered material with graphite.
Besides cadmium, also the major constitutents zinc, iron and sulfur contribute significantly to the total attenuation of the
thermal neutron flux. Calibration lines for these elements are worked out. All irradiations are carried out for 200 s in the
partially thermalized neutron flux of a 5 Ci227Ac—Be isotope neutron source. After a decay of 30 s, the52V-activity of the vanadium detector is measured for 400 s with a NaI(T1) scintillation detector. The analysis sequence, including
the computation of the results from the counting data, is automated by means of a LSI—11 microprocessor with 12K×16 bit memory.
Zinc ores, containing 0.02 to 1.45% cadmium, have been analyzed with a precision ranging from 12.6% to 0.54% relative. As
a test for the reliability of the method, two NBS standard reference materials were analyzed in the same way as the zinc ore
A Compton suppression gamma-ray spectrometry system has been evaluated for its use as a low level radioactivity counting facility.
The system consists of a premium quality Ge(Li) detector surrounded by a shield of NaI(T1) detector material. Compton suppression
is obtained by operating the two detector systems in anti-coincidence. Spectrum collection hardware consists of a NP11-A (DEC)
interface for two ADC's and a PDP 11/T 10 minicomputer with 64 K byte core memory. Software development and system operation
modes are described. System performance as a function of physical characteristics of the sample, scattering angle and gamma-photon
energy, is discussed. Continum reduction for cascaded gamma-transitions and natural backgorund are considered separately.