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  • Author or Editor: P. Roos x
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Abstract  

The program ROMOS and the assisting program RECAL are presented. These programs were designed to facilitate nuclide identification and concentration calculation in NAA using the k0-concept. For nuclide identification classical tests (energy match, decay factor) are complemented with a test of the saturation factor including the sensitivity of neutron acctivation analysis for the candidate nuclide. For nuclides emitting more than one gamma-energy the intensity of the observed peaks in the spectrum are compared. Thereby full account is taken of relative detection efficiency and true coincidence effects. Practical experience in using the interactive code shows that it is a convenient and time-saving working aid for an experienced experimenter.

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Abstract  

Activity concentrations of 237Np in peat and lichen samples in Finland were determined and contributions from nuclear weapons testing in 1950–1960s and the Chernobyl accident were estimated. 237Np was determined with ICP-MS using 235Np as a tracer. Activity concentrations of 237Np in peat samples varied between 1.98 ± 0.05 and 14.1 ± 0.3 mBq/m2. The contribution from the Chernobyl accident to the total 237Np deposition in peat was 0.1–13%, the Chernobyl-derived fraction of total 237Np in peat being much lower than the previously determined corresponding Chernobyl-derived fractions of 239+240Pu, 241Pu, 241Am and 244Cm.

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Abstract  

Fresh water from Lake Svartsjön, Sweden, was collected and four fractions were prepared: (1) adsorption on DEAE, (2) flocculation with Ca2+, (3) co-precipitation with Fe hydrous oxide and (4) co-precipitation with Mn hydrous oxide. The plutonium level in the lake is 65 fg/l (222 μBq/l), measured by ICP-QMS and ICP-SFMS. Pronounced accumulation in fractions (1) (34%) and (2) (66%), combined with observed levels of organic matter indicate that plutonium is predominantly associated with organic matter. Measurements of isotopic ratios indicate that 77% of the plutonium originates from weapons testing and the remaining appears to originate from the Chernobyl accident.

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Abstract  

This paper presents the activity concentrations of Pu isotopes in surface marine sediments collected from the Sudanese coast of the Red Sea. The following concentration ranges were determined: 238Pu, 4.7–28.6 mBq/kg; 239+240Pu, 53–343 mBq/kg dry weight. The average activity ratios of 238Pu/239+240Pu (0.075±0.045 mBqk/kg) and 239+240Pu/137Cs (0.026±0.025 mBq/kg) are appropriately comparable to the literature values that are characteristic of the global fallout from the atmospheric nuclear weapon tests. However, 239+240Pu/137Cs ratio in sediments collected from the biologically rich fringing reef is an order of magnitude higher compared to other sampling locations.

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Abstract  

In nuclear reactors plutonium and transplutonium isotopes are produced by multiple neutron capture of uranium and plutonium and are important for the energy production and their composition reflects the core burnout. Under normal operation these elements are not released to the environment in significant amounts. There are accordingly very few areas or source terms where exotic transplutonium elements, such as curium isotopes, can be studied in the environment. The Chernobyl accident provided a complex spectrum of fission and activation products in fallout while the relative amounts, compared to the core inventory, of refractory elements such as transuranium and transplutonium elements were small. The major alpha-activity consisted of 242Cm (T 1/2 = 163 d) that would have decayed after a few years. In this study we have demonstrated the presence of so called supported 242Cm from the long-lived 242Amm (T 1/2 = 141 a) in environmental samples, following fallout from the Chernobyl accident. It has also been possible to assess the core burn up by using the data obtained for the Cm isotopes. The curium isotopes 243Cm (T 1/2 = 29.1 a) and 244Cm (T 1/2 = 18.1 a) cannot be resolved by conventional alpha-spectrometry. The assessment of these isotopes in environmental samples contaminated from the Chernobyl accident has been made by studying the effective half-life of the mixture of the isotopes. The data are compared with those previously obtained by high-resolution alpha-spectrometry and spectral deconvolution.

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Abstract  

Trace element concentration patterns can be used for the identification of objects or materials. Early applications were related to the elucidation of identity or origin of objects. Recently, a number of applications have been reported of the use of trace element concentration patterns to recognize and identify components of mixtures of materials, mainly of environmental interest. In the present paper two examples are discussed of application of Target Transformation Factor Analysis to trace element concentration patterns, to identify sources of heavy metal air pollution. The materials studied are air particulate matter and epiphytic lichens used as biological accumulator.

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Abstract  

In 94 marble samples from 4 quarry districts in Italy (Carrara) and Turkey (Proconnesus, Dokimeion, Usak), minor and trace elements were determined by instrumental neutron activation analysis (INAA) and atomic absorption spectrometry (AAS). The maximum size of the calcite grains (MGS) of the rocks was measured in thin section. For 16 elements considered in this work, the concentration ranges show important inter-district overlaps; this also applies to the maximum grain size. However, the application of cluster analysis, using selected attributes, allows one to discriminate every pair of districts; 90 samples are classified correctly in all classification dendrograms.

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