Characterisation of radioactive particles by SIMS

Secondary ion mass spectrometry (SIMS) was optimised for characterisation o f uranium- and plutonium-containing particles in soils, swipes and forensic samples, This was done by analysing in-house produced spherical UO2-partic les. Screening techniques as alpha-autoradiography together with SIMS analy sis were employed to detect UO2-particles in a soil sample from Chernobyl. The use of SIMS was exploited for the identification of uranium- and pluton ium-containing particles and for the determination of their isotopic compos ition. The particles collected on swipe samples were transferred to a speci al adhesive support for the analysis by SIMS, Particles containing highly e nriched uranium with diameters up to 10 mu m were also detected in a forens ic sample. For the measurements of the isotopic ratios a mass resolution of 1000 was used. At this resolution flat-top peaks were obtained which great ly improve the accuracy of the measurement. The isotopic composition of the particles was measured with a typical accuracy and precision of 0.5%. Stat istically meaningful results can be obtained, for instance, from a specimen containing as few as 10(10) atoms/mu m(3) of uranium in particles of UO2 w eighing a few picograms.