On décrit la détermination de traces dans le germanium, le silicium et le sélénium. En appliquant des techniques gamma spectrométriques,
précédées ou non de séparations chimiques il est possible de doser les éléments suivants dans (1) germanium: As, Cu, Au, Ga,
Zn, Hg, Cr, Sn, Sb, Co, In, Ni, Ir, Se, Sc, Ag, Ta, Hf et U; (2) silicium: P, Au, Sb, Ga, Fe, K, Cr, Mo, Sn, As, Co, In, Zn,
Cu, W, Ta, Na, Eu, Sm, La, Sc et T1; (3) sélénium: Cl, Br, I, P, S, Te, Na, K, Cr, Fe, Co, Cu, Zn, Ga, Sc, Ag, Cd, La, W,
Au et Tl. Les concentrations et ou limites de détections varient de quelques parties par million à 10−3 parties par milliard.
Several modifications are proposed of the established methods of iodine determination in serum. Prior to the actual analysis,
the serum is lyophilized. This preliminary treatment permits the use of large samples. Through lyophilization human blood
serum samples can easily be reduced to one-tenth of the original weight. Reduction is even more dramatic with materials from
other than human origin. After irradiation the samples are subjected to chemical treatment in the presence of an iodine carrier
and131I-labelled thyoxine. This procedure has been adopted for the determination of the iodine content and the chemical yield in
one and the same radioactive measurement. The analysis technique itself consists of an open system Schöniger combustion. The
open combustion allows the use of large samples; the gases evolved are absorbed upon their subsequent passage through potassium
hydroxide and hydrochloric acid; the mineralization requires less than two minutes. After the addition of a substochiometric
amount of silver nitrate, silver iodide is precipitated from an ammoniacal solution as a flat sample, which has been found
ideally suited for high efficiency counting with a Ge(Li) detector. The spectrum gives evidence of an excellent decontamination
from the38Cl,80Br and82Br activities. The iodine content can be calculated from the ratio of the photopeak areas at 364.5 keV and 442.7 keV corresponding
to131I and128I, respectively. The chemical procedure requires a mere 15 min, and the recording of the γ-ray spectrum takes no longer than
30 min. The technique is not limited to serum only. It proved well suited for the analysis of many other types of biological
material, e.g. human skin tissues.
The determination of boron, carbon, nitrogen and oxygen in metals and semiconductors by charged particle activation analysis (CPAA) is reviewed. It is shown that CPAA is a sensitive and accurate method suitable for the analysis of reference materials.
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.
The double irradiation technique, which is used to detect the production of a given nuclide from different chemical elements,
by two different reactions in a polyenergetic neutron flux, cannot be generally applied. The application limits have been
defined and calculated, based on the statistical fluctuation of the measured activities. The experimental verification and
the practical applications of the calculated limits for activation analysis, and transmutation reaction cross section studies
. The average cross-section of the103Rh(n, 2n)102Rh reaction in a fission neutron spectrum is about 0.75 mb. Irradiation of rhodium in the bremsstrahlung spectrum of 50 MeV
electrons yielded a102Rh activity of 0.11 μCi/g after 3 days at a power of 2 kW. The thick target yield of the reaction104Pd(d, α)102Rh was 0.002 μCi/μAh for 12 MeV deuterons. The thick target yield of the reaction Ru(d,xn)102Rh was 0.05 μCi/μAh for 12 MeV deuterons and 4.8 μCi/μAh for 18 MeV deuterons. The best yield was obtained by deuteron bombardment
of ruthenium. The chemical separation of carrier-free Rh radionuclides from deuteron-irradiated ruthenium is described, with
a chemical yield better than 90%. The same procedure has also been applied for the isolation of105Rh from neutron-irradiated ruthenium. γ-Ray spectra of99Rh,101(m)Rh and102(m)Rh from deuteron-irradiated ruthenium and of105Rh from neutron-irradiated ruthenium, taken with a Ge(Li) detector, are shown; a number of γ-rays, not reported in the literature,
were observed. The γ-ray energies were determined with a precision of ca. 0.3–0.4 keV.
The effects of inaccurate sample sizes and sample positioning on 14 MeV neutron activation analysis results are estimated
for 30, 20 and 10 mm diameter targets. It appears that axial positioning is the most critical parameter and that using a larger
tritium target will yield an overall improvement of the reproducibility.
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: