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  • Author or Editor: M. Geisler x
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Abstract  

Lunar soil samples of the Luna 16 Luna 20 missions were analysed by neutron activation in a neutron generator and a nuclear reactor, respectively, and following gammaspectrometry by NaI(T1) and Ge(Li) detectors. By 14 MeV neutron activation there were determined the abundances of 5 major elements (O, Mg, Al, Si, Fe) and by reactor activation the abundances of 18 major and trace elements (Na, K, Sc, Cr, Mn, Fe, Co, Mo, La, Ce, Sm, Eu, Tb, Yb, Lu, Hf, W, Th) and the detection limits of 4 additional elements (As, Rb, Sb, Cs). The standard rocks BM and GM of the ZGI were used as standards in the reactor activation analysis.

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Abstract  

Dy content has been determined by INAA in the Bulgarian standard rocks BV, GV, DM, MrA, OgG, OZnO and in the IAEA standard reference materials SL-1, SOIL-5, and SOIL-7. Results are compared with Dy values obtained by interpolation of the chondrite-normalized contents of other REE in these samples.

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Abstract  

Sensitive radiochemical procedures for the determination of arsenic in biological samples and silver in geological samples have been developed using77As and111Ag as yield tracers. In connection with this, the yield determination method by means of a radiotracer is discussed, its advantages are demonstrated, suitable tracer nuclides are listed and possibilities to increase their number are proposed.

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Abstract  

A method for the determination of nickel in ion exchange resins has been elaborated. It is based on the58Ni(n, p)58Co reaction. Samples of 500 mg are irradiated for 90 h in a fission neutron flux of 1013 n·cm−2·s−1. After decomposing by HNO3/HClO4 mixture the radiochemical separation is carried out by extraction of the Co-DDTC-complex in chloroform. Measuring by a 23 cm3 Ge(Li) detector for 15 h provides a detection limit of 10 ppb. Radiochemical yield is determined by57Co as radioactive indicator. Limitations by60Co are reduced by Cd-screened activation and by anticoincidence measuring technique.

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Abstract  

A very convenient method for yield determination in NAA is the use of isotopic radiotracers. But for the majority of elements determinable by NAA no suitable isotopic radiotracers exist. For some of these elements the radioreagent methodoffers afvourable opportunity to use also non-isotopic radiotracers. An activation analytical copper determination method is described using a radioactively labelled reagent for correction of separation losses. Results of copper determinations in 8 international standard reference materials are given.

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Abstract  

IAEA standard reference material SOIL-7 has been analyzed by both instrumental NAA and radiochemical NAA using epithermal neutron activation. These analyses confirm the NAA value of Ag in the intercomparison SOIL-7 which disagrees with some AAS values. Further geostandards were included and compared with literature data.

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Abstract  

A neutron activation analysis procedure was developed for the determination of osmium in geological materials. The method consists in the measurement of the 129.4 keV γ-rays of191Os after radiochemical separation of osmium. The sample decomposition, the chemical separation process and the optimal measuring conditions are described and discussed.

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Abstract  

Neutron activation analysis was used to determine the elements Cu, Mn, As, Cd, Fe, Mo, Zn, Co, Cr, and Se in biological materials. Three different activation analytical techniques were tested by analysing one and the same sample: (1) the instrumental determination, (2) the determination after removal of the major contaminants24Na and32P, and (3) the determination after radiochemical separation. These three techniques are described and the results obtained are discussed. The detection limits determined for each technique are compared.

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Abstract  

In the last years Cf-252 neutron sources will be incresingly used for nuclear analytical purposes. In the Central Institute of Isotope and Radiation Research, Leipzig, an irradiation equipment with a 3mg252Cf neutron source was constructed. It reaches thermal neutron fluxes of about 107 n·cm–2·s–1. The construction of this equipment and the different moderation geometries are described. Possibilities of the application for neutron induced autoradiography, neutron radiography and neutron activation analysis are demonstrated on examples.

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Abstract  

In the bremsstrahlung field of the Microtron MT 22, copper foils (0.035 mm thick) positioned along beam direction and also perpendicular to the beam at different distances from the bremsstrahlung target were irradiated. From these activated copper foils autorodiograms were prepared. By means of a densitron and a microdensitometer, the autoradiograms were measured. The densitron pictures give a qualitative impression of the geometry of the bremsstrahlung field, whereas the curves of optical density yield quantitative values. From optical density curves, conclusions have been drawn about optimal geometry for irradiation positions of samples in this bremsstrahlung field. A sample rotating device applicable for photon activation analysis by means of the MT 22 is described.

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