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The application of secondary ion mass spectrometry (SIMS) analysis is described for the characterization of plutonium and highly enriched uranium (HEU) particles with a diameter to 10 μm. Applying a method previously described, particles of HEU could be detected in a scrap material, together with natural uranium. The isotopic composition of the particles was measured with a typical accuracy and precision of 0.5%. The spectrum of the trace elements in the uranium particles was also recorded. From the results it was possible to deduce that the uranium oxide, as UO2, was produced via a pyrochemical process. In a sample consisting of a mixture of three different species of particles, two of these were identified as plutonium particles. They were characterized according to their isotopic ratio 239/240 as well as to their dimension and shape. The results obtained by SIMS for the isotopic ratio were compared with those obtained analyzing the particles by Thermal Ionization Mass Spectrometry (TIMS). The shape and dimensions were confirmed by the analysis with Scanning Electron Microscopy (SEM). In both the cases the results obtained by SIMS were in good agreement with those from TIMS and SEM.

The analysis of seized nuclear material aims at identifying the origin of the material. Determination of the n(18O)/n(16O) ratio for the uranium oxide adds another characteristic property to the pattern which enables location of the production area of the material. A method has been developed for n(18O)/n(16O) ratio measurement which uses thermal ionization mass spectrometric (TIMS) analysis of the 238UO+ species. It has been shown that uranium oxides of different geographic origin have significantly different n(18O)/n(16O) ratios, whereas different samples of the same origin have constant oxygen isotopes ratios.

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Plutonium / Age determination / Secondary ion mass spectrometry / Particle analysisSummary. Age determination of plutonium particles is a highly important task in view of the pending cut-off treaty for nuclear weapons materials. By collecting particles from the vicinity or inside the nuclear facilities and determining their ages, it is possible to monitor the observance of the cut-off agreement.In this study, the age determination of Pu particles was demonstrated by Secondary Ion Mass Spectrometry (SIMS). To determine the ionisation efficiency difference of Pu and U, standard Pu materials with known ages were analysed. Finally, the age determination of two real Pu samples was demonstrated.

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Oberhalb = 700 K unterliegt c-TiS2 einer Phasenumwandlung zu hexagonalem TiS2 rnit den Gitterkonstanten a = 339.2 und c= 569.1 pm. Sowohl die Richtung der Symmetrieanderung als auch die Verringerung des Gittervolumens (3%) lassen erwarten, dab c-TiS2 metastabil ist. Diffe-. Mitteilung. Diese Arbeit wurde von der Deutschen Forschungsgemeinschaft und dem Fonds der Chemischen Industrie unterstiitzt. -89. Mitteilung: R Steudel in A. Miiller. B. Krebs: Sulphur-Its Significance for Chemistry. for the Geo-. Bio-and Cosmosphere and Technology, Elsevier, Amsterdam 1984. S. 3. 58 Q YCH Verlagsgesellschafi mbH. 0-6940 Weinheim. 1985