[en] Studies on the fate and transport of radioactive contaminates in the environment are often constrained by a lack of knowledge on the elemental distribution and general behavior of particulate bound radionuclides contained in hot particles. A number of hot particles were previously isolated from soil samples collected at former U.S. nuclear test sites in the Marshall Islands and characterized using non-destructive techniques [1]. The present investigation at HASYLAB is a part of larger research program at ITU regarding the characterization of environmental radioactive particles different locations and source-terms. Radioactive particles in the environment are formed under a number of different release scenarios and, as such, their physicochemical properties may provide a basis for identifying source-term specific contamination regimes. Consequently, studies on hot particles are not only important in terms of studying the elemental composition and geochemical behavior of hot particles but may also lead to advances in assessing the long-term impacts of radioactive contamination on the environment. Six particles isolated from soil samples collected at the Marshall Islands were studied. The element distribution in the particles was determined by confocal (micro)-XRF analysis using the ANKA FLUO beam line. The CRL (compound refractive lens) was used to focus the exciting beam and the polycapillary half lens to collimate the detector. The dimensions of confocal spot were measured by 'knife edge scanning' method with thin gold structure placed at Si wafer. The values of 3.1 x 1.4 x 18.4 (micro)m were achieved if defined as FWHMs of measured L?intensity profiles and when the19.1 keV exciting radiation was used. The collected XRF spectra were analyzed offline with AXIL [2] software to obtain net intensities of element characteristic lines.Further data processing and reconstruction of element distribution was done with the software 'R' [3] dedicated for statistical calculations. In figure 1 the distributions of Pu, Fe and Ti obtained for one of the studied hot particles are presented. The strongest signal was recorded for plutonium; the signals from iron and titanium are respectively 14 and 38 times less. It means that Pu is the most abundant of the observed elements. However, since the light elements are not detectable with the applied measurement conditions, it cannot be definitely stated if plutonium is the main element present in the sample. The isosurfaces are calculated at 20 % of maximum intensity for each element. Please note that the isosurfaces on the drawing are transparent. Changes in the spatial distribution of Pu, Fe, and Ti within the particle are shown in Fig. 2a, 2b, and 2c. Distinct elemental patterns are clearly visible at the higher concentration levels. The distributions of Cr, Cu, and Pb were also reconstructed but the results are not presented here. As it is shown in Fig. 1, the correlation between elements is good at low concentrations but the maxima of concentrations are not strongly correlated (see Fig. 2.). In general, the particle is inhomogeneous in terms of its elemental composition. Similar inhomogeneities were found for other particles with Pu identified as a major element in three of the six particles examined

[en] A portable radiometric head for in situ X-ray fluorescence (XRF) soil analysis has been constructed. The head consist of AMPTEK Si-PIN X-ray detector and an annular ²³⁸Pu source. The collected X-ray spectra with the use a portable spectrometer are processed with QUAS software (AXIL). The performance of the radiometric head has been tested. Several effects and factors affecting the in situ measurements Like: the matrix effects, a roughness of the soil surface, the inhomogeneity of a relatively small sample , the grain size, the humidity, the unknown organic matter content and the difference of the soil composition in the neighbourhood of the sampling point have been investigated. The measurements have been performed in the simulated in situ conditions. Thin and thick samples have been used for the calibration. The calibration equations have been validated with the standard reference materials (SRM's). The limits of the detection (DL) have been estimated. The results of soil analysis may be interpreted as a volume or surface contamination. For each case a different quantification method should be used. In the latter case backscatter fundamental parameter (BFP) method have been used to calculate element concentrations. The content of the low Z matrix was evaluated by measuring the ratio of coherent to incoherent backscattered primary X-ray intensities. It has been shown that the constructed radiometric head is useful for in situ soil analysis. Fact contamination screening of polluted soil is possible for higher contamination levels with measuring time per point equal to about 100 s. The possibility of the use of this portable head for the thin samples analysis, and for in situ determination of the surface contamination level of soils presented, too. (author)

[en] The paper describes a portable XRF spectrometer based on radioisotope excitation and a Peltier cooled Si-PIN X ray detector as well as its analytical performance. The influence of major interfering effects on the analytical results and the relevant correction procedures are also presented. The portable XRF spectrometer was applied to study the volume and surface contamination of soil samples. Both the thin samples approach and the backscatter fundamental parameter method were used for quantification. (author)

[en] Radioactive substances are often released to the environment in the form of particles. The determination of their chemical composition is a key factor in the overall understanding of their environmental behaviour. The aim of this investigation was to identify the source of one single radioactive particle collected from the Irish Sea and to understand its fate in the environment and in human body fluids. As the particle was supposed to be analysed for its dissolution behaviour in humans after ingestion, it was necessary to gain as much information as possible beforehand on the chemical and isotopic composition by means of non-destructive analysis such as SEM, SIMS, μ-XRF and μ-XANES. In this paper, an overview of the different non-destructive methods applied for the analysis of this particle and the results obtained is given. Additionally, the dissolution behaviour in human digestive solutions is discussed. (author)

[en] XANES has been recently used for the determination of oxidation states of actinides in environmental samples. To obtain reliable results, however, a sufficiently long counting time at every probing energy and a large number of experimental points per XANES spectrum are required, due to the complex mathematical model used to fit the measured spectrum. This makes micro-mapping difficult, since the time required for data collection becomes unacceptably long. A simplified model for data collection and evaluation is presented. Its effectiveness has been tested by measuring the distribution of Pu oxidation states in a 'hot' particle coming from a nuclear weapon test site. (author)

[en] The XRF Group of the PCI Laboratory provided the instrumentation for performing the measurements at the synchrotron beam line. The micro-beam X-ray scanning spectrometer was moved out from the Instrumentation Unit?s XRF laboratory and was installed at the synchrotron beam line. The spectrometer was equipped with three X-ray detectors, namely: a large area silicon drift detector (active area of 50 mm², positioned in the synchrotron orbital plane at 90 degrees in relation to the primary beam; the detector was provided by the Atominstitut, Vienna), for collecting the X-ray fluorescence spectra during elemental mapping and tomographic scanning; small area silicon drift detector (active area 2 mm², positioned in the beam behind the sample), for collecting X-rays transmitted through the sample; and a silicon drift detector (active area of 10 mm²) fitted with a polycapillary half-lens and aligned in confocal geometry. The analyzed samples were mounted on a motorized stage. The synchrotron beam was monitored with an ionization chamber and Si-PIN diode detectors. Four groups of samples were analyzed by performing 2D/3D tomographic scanning in absorption/fluorescence mode and in a 3D confocal mode: Freeze-dried human-bone sections prepared at the Atominstitut, Vienna, Austria in collaboration with the Instrumentation Unit. U/Pu-rich particles provided by the Institute for Transuranium Elements, Karlsruhe, Germany. Stained organs of malaria mosquitoes obtained from the Entomology Unit of the IAEA Laboratories and prepared using different methodologies by the Instrumentation Unit. Mineral grain sample prepared by the Agency?s fellow. Several additional measurements on standard samples were performed in order to establish the geometry of the synchrotron beam and other analytical parameters. The Instrumentation Unit is collaborating with the other groups on elaborating the acquired data. We would like to emphasize that the use of advanced analytical techniques in combination with synchrotron radiation source provided essential information about the investigated samples, which could not be obtained by other means. In particular, the use of the polarized and monochromatized synchrotron radiation dramatically improved the detection limits enabling X-ray fluorescence tomographic measurements of trace element distribution in bone tissue, mosquito samples and 3D mapping of element distributions in individual radioactive particles. The tasks were performed in cooperation with other research groups addressing the needs of the Member States laboratories. It should be a recommended way of bringing the Agency?s support and expertise in applications of advanced nuclear analytical techniques directly to its Member States

[en] Runit Island on Enewetak Atoll was very heavily impacted by the U.S. nuclear testing campaign in the northern Marshall Islands (1946-58). The primary source of contamination on Runit Island was the 1958 Quince safety test where a large quantity of device plutonium (Pu) was scattered over the area near the GZ. A second low-yield device was detonated on the same site 10 days later, further disturbing the soil and leaving behind a very heterogeneous pattern of contamination including milligram-size particles of plutonium. A limited cleanup of the Fig-Quince zone was carried out in 1979. During this period, the effectiveness of the cleanup operations was primarily evaluated on the basis of bulk soil concentration data with little consideration given to the heterogeneity and long-term material-, biological-, and environmental-specific impacts of residual high activity (hot) particle contamination. The aim of the present study was twofold; (i) to characterize the levels and distribution of residual contamination in the Fig-Quince zone, and (ii) to develop pertinent data on the frequency distribution, elemental and isotopic composition, and physico-chemical properties of hot particles isolated from surface soils from Fig-Quince with a view towards providing recommendations on the future management and possible cleanup of the site. Today, Runit Island remains under an administrative quarantine. (author)