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  • Author or Editor: R. Gijbels x
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Abstract  

The analytical difficulties of the determination of very low concentrations of ruthenium in silicate rocks are discussed. A preseparation procedure is proposed which allows to determine ruthenium in rocks above 0.1 ppb concentration.

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Abstract  

Triple gamma coincidence counting of192Ir allowed the determination of Ir by instrumental neutron activation analysis down to 1 ppb in ultrabasic rocks and down to ca. 20 ppb in some high-furnace slags; the limiting factor for the latter matrix was the presence of124Sb. Radiochemical neutron activation analysis of the USGS standard rocks revealed that the Ir contents are up to three orders of magnitude lower than previously reported, except for the ultrabasic rocks. The factor of merit of several scintillation and semiconductor, gamma-ray detectors was determined for the neutron activation determination of Pd, Pt and Os. In the case of radiochemically pure sources, a NaI(Tl) wafer was preferred; in the presence of high-energy gamma-emitters, a Ge(Li) low-energy photon detector was superior.

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Abstract  

The determination of palladium, platinum and rhodium in industrial concentrates such as lead foam and raw lead by neutron activation analysis is described. The noble elements are separated from the matrix by spontaneous deposition on amalgamated copper powder prior to activation. After the determination of palladium and platinum, rhodium is coprecipitated on iron hydroxide, and the precipitate irradiated for the determination of rhodium. The results are compared with those obtained by fire assay.

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Abstract  

A systematic study has been made on the reducing power of amalgamated copper powder in hydrochloric acid solution for palladium, platinum, rhodium, iridium, gold and silver. In order to apply this method to the activation analysis of palladium, platinum and rhodium in industrial concentrates which contain a large amount of ‘base elements’, the behaviour of palladium, platinum and rhodium in the presence of the ‘base elements’ has also to be considered.

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Abstract  

Long-lived rhodium radionuclides were produced by the following reactions:103Rh(n, 2n)102(m)Rh;103Rh(γ,xn)100Rh,101Rh,102(m)Rh;104Pd(d, α)102(m)Rh; Ru(d, n)99Rh,101(m)Rh,102(m)Rh; and
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $${}^{104}Ru(n,\gamma )^{105} Ru\mathop \to \limits^{\beta - } {}^{105}Rh$$ \end{document}
. 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.
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Abstract  

The accuracy of the live-time circuit of a 400-channel analyzer was studied in detail, and was found to be unsatisfactory even for long-lived radionuclides. It was found that automatic live-time correction with the multi-channel analyzer gave rise to increasing positive errors with increasing count rate; this overall positive error was composed of a positive error due to the slowness of the electronic circuitry, and a smaller negative error due to the finite pulse-width. Adequate correction could be performed by feeding the information from the dead-time output of the multi-channel analyzer to an external live-time circuit with variable oscillator frequency and pulse-width. Four methods for dead-time correction were compared experimentally in the case of short-lived radionuclides (T as low as 7 sec): the method of Bartošek et al., the method of Schonfeld, the use of a sufficiently short counting time as compared to the half-life, and the live-time mode of counting without additional correction. These four methods were applied to the determination of oxygen and silicon in rocks by 14 MeV neutron activation analysis. Results are given for USGS standard rock G-2.

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Abstract  

Electrophoretic focussing of ions was applied to the separation of fission products present in solutions of nuclear uranium fuel irradiated in various European reactors. By combining two separation methods, all the long-lived fission products could be determined individually and quantitatively by counting with a NaI(T1) and a GM detector of known detection efficiency. Radiography and autoradiography were used for semi-quantitative purposes. The concentrations of235U and238U were determined from a short post-irradiation of the fuel solution and counting of140Ba−140La and239Np, respectively. An iterative calculus method is presented which allows calculation of the irradiation history of the fuel solution from the above analyses. without any a priori knowledge.

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Abstract  

To sulfide geothermal waters from the French Pyrenees region and bicarbonate and chloride waters from the French Vosges area, all of the following analysis techniques were applied in order to compose a broad inventory of trace elements: (1) for the dissolved material: neutron activation analysis after a freeze-drying step using a very short cycle (I), short cycle (II) or long cycle (III), neutron activation after co-crystallization on 1-(2-pyridylazo)-2-naphthol (PAN) using a short cycle (IV) or long cycle (V), X-ray fluorescence after co-crystallization on PAN (VI) and spark source mass spectrometry after evaporation on graphite (VII) or preconcentration on PAN, and, (2) for the filtered or suspended material: neutron activation using a very short (VIII), short (IX) or long cycle (X) and X-ray fluorescence (XI). Altogether, on the average some 30 elements could be determined above the detection limit in solution and 15 in suspension. It appeared, however, that for procedures (I), (II), (IV), (VI), (VIII) and (XI) the investment of time and cost had not been efficient enough. Invoking only procedures (III), (V), (IX), (X) and for low salinity geothermal waters only: (VII), the number of elements detected was almost as large.

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