Fast methods for determination of antropogenic actinides and U/Th-series isotopes in aqueous samples.

Rapid and simple methods are applied at the PSI radioanalytical laboratory for determining anthropogenic actinides in waste and nuclear reactor waters (U, Pu, Am, Cm) as well as for analysis of naturally occurring alpha-emitters in continental river and ground water. Anion exchange chromatography followed by alpha-spectrometry as well as alpha/beta-LSC is applied for the reactor coolant waters. To avoid alpha-spectrum interference between 238Pu and 241Am at 5.5 MeV, the Pu-fraction is purified using anion exchange resin. Prior to the separation of the Pu-fraction, all actinides (U, Pu, Am, Cm) are adsorbed batch-wise under stirring onto Actinide Resin and subsequent decomposition of the reagent. The residue is then re-dissolved in a sulfate buffer solution for electrolytic deposition. In tabular water samples isotopes of Ra and Po are analyzed additionally via sorption onto manganese coated discs (Ra) and deposition on silver discs (Po). For counting times of 1 day and use of 0.1-1l sample aliquots, detection limits of a few mBql(-1) can be obtained easily.

Gross alpha determination in drinking water using a highly specific resin and LSC.

Some results of experiments concerning a new highly specific resin for the extraction of alpha-emitting nuclides from drinking water samples are presented. The product used during these experiments is a new extraction chromatographic resin which consists of a combination of several reagents and extractants supported on inert polymeric substrates, called "Resin" hereafter. It shows strong affinity for Actinides in the tri-, tetra- and hexavalent oxidation state, as well as for radium, even in presence of large amounts of calcium. Gross-alpha activities were determined using alpha-/beta-discrimination liquid scintillation counting (alpha-/beta-LSC) by direct measurement of the dried resin after extraction. Counting conditions were optimised accordingly. A method for the determination of alpha-emitting nuclides in drinking water was developed and tested using intercomparison and spiked drinking water samples.

Improvement in 90Sr measurements at very low levels in environmental samples

Various anthropogenic sources contribute to the inventory of long lived beta emitters in the environment. Studies have been carried out to obtain the 90Sr distribution in environment in order to estimate its impact in terms of radiation exposure to humans. Various environmental samples were collected and analysed for 90Sr activity concentrations. As natural beta emitters are present in all matrices, an incomplete radiochemical separation leads to over evaluation of the results. An accurate and reliable method has been routinely implemented to extract, purify, and analyse 90Sr in all types of environmental matrices by the Laboratory of Radioactive Measurement in Environment. The radiochemical procedure is combined with a proportional counting for 90Sr detection. After leaching the 20 g aliquot, different protocols have been tested. The effectiveness of Sr-spec resin for Sr isolation has been demonstrated and chosen for the protocol selected. Radiochemical procedure was tested using IAEA reference materials. Results are discussed in terms of recovery, purification efficiency and limit of detection. The influence of a filtrated atmosphere on proportional counting is also discussed.