A radiochemical procedure is described for the sensitive determination of89Sr and90Sr activity concentrations in soil and sediment samples. After leaching the sample with hydrochloric acid, Sr is separated from most of the soluble matrix constituents and Ca by solvent extraction using dicylclohexano-18-crown-6 in trichloromethane. After backextraction with a EDTA-solution (ethylene diamine tetra acetate), Sr is purified by several precipitation steps from traces of matrix constituents and radionuclides which might interfere the beta measurements of89Sr,90Sr and90Y. The detection limits are about 0.2 Bq/kg and 0.4 Bq/kg for90Sr and89Sr respectively. The procedure can be applied to all kind of environmental samples with small modifications of the sample preparation steps prior to analysis.
A radiochemical procedure was developed and optimized which allows sensitive241Pu measurement in various sample materials. As a first step, Pu isotopes are separated from matrix elements, purified radiochemically, electroplated, and measured by -spectrometry. The electrodeposited Pu is then redissolved in nitric acid and extracted with trioctylphosphinic oxide/cyclohexane. The organic phase is mixed with scintillator cocktail (PPO/Xylene) and Pu is measured with a liquid scintillation counter. The detection limit of the optimized procedure for a counting time of 100 minutes is 50 mBq241Pu per sample at a 95% confidence level.
The determination of Am and Cm in a radiochemical procedure for the sequential analysis of Pu, Am, and Cm in soils was improved and optimized. This method uses only solvent extraction and extraction chromatography for the separation and cleaning of Am and Cm from soils up to 50 g sample weight. After leaching with 8M nitric acid, Pu is extracted with TOPO/cyclohexane. Am and Cm are extracted out of the remaining leaching solution at pH 1 with TOPO/cyclohexane, too. After backextraction with 2M nitric acid, Am and Cm are separated from traces of matrix elements, especially Fe, on a TRU-column, afterwards on a TEVA-column from lanthanides (TRU-resin and TEVA-resin of Eichrom Europe, SARL, Paris, France). The clean Am/Cm-fraction is electroplated and measured by alpha-spectrometry. The detection limit of this optimized procedure is 0.03 Bq/kg soil at a 95% confidence level.
A radiochemical procedure is described for the fast and sensitive measurement of uranium isotopes in gaseous and liquid effluents of nuclear facilities. Equally, this procedure is suitable to measure uranium isotopes in all kinds of environmental samples. Uranium is leached from ashed sample materials with HNO3, HF, and Al(NO3)3 solution and separated from matrix elements by extraction with trioctylphosphinic oxide and backextraction with NH4F. After radiochemical cleaning by coprecipitation with LaF3 and anion exchange, uranium isotopes are electroplated on stainless steel discs from HCl/oxalate solution. The preparation is measured by alpha-spectrometry using surface barrier detectors. The detection limit for 1000 minutes of counting time is 2 mBq per sample and nuclide, the chemical yield is in the range of 50 to 80%.
Authors:U. Hoeppener-Kramar, M. Pimpl, and F. Willmann
Materials from decommissioning of nuclear facilities can be re-used without restrictions, if their mass specific activities are in accordance to the guidelines for allowable concentrations. To determine the nuclide specific activity level of representative samples, a clearance laboratory was installed at the Research Center Karlsruhe. For the purpose of low level radionuclide analysis, procedures, developed for environmental monitoring, were successfully adapted to decommissioning materials. For radionuclides, for which adequate procedures were not available, new methods were developed. The procedures for the analysis of radionuclides of prior interest for decommissioning measures are outlined, together with the respective sample decomposition methods.
Authors:L. Bogoeva, I. Mishev, M. Radicheva, and M. Pimpl
The concentration of the plutonium isotopes238Pu and239+240Pu in the surroundings of the research reactor was measured by application of a very sensitive and selective radionalytical procedure for the determination of plutonium in soils and plants, including lichens and mosses as bioindicators. All measured concentrations are in the range of variation of the global contamination with plutonium caused by fallout of atmospheric nuclear weapon tests and burning of satellites in the atmosphere. An additional contamination by plutonium isotopes due to discharges from the reactor in the past is not detectable.