[en] An irradiation facility was developed by means of which samples can be irradiated near the core edge of the reactor BER II in liquid nitrogen at a thermal neutron flux of 1.5.10¹³ n.cm_-2.s^-1 for a maximum of 14 days. The technique of neutron activation analysis is presented in which biological samples enclosed in thin-walled quartz ampoules are irradiated and measured directly without pretreatment. Using this method, losses of iron, zinc and selenium during pretreatment procedures (freeze-drying at 30, 60 and 90 deg C) for the analysis of plasma, erythrocytes and liver were studied. (author) 8 refs., 9 figs

[en] Epithermal neutron activation analysis (ENAA) was applied to the analysis of foods for iodine. The procedure involves irradiation of wet foods in a boron nitride vessel, followed by direct counting of the 442.9 keV gamma ray of ¹²⁸I without any processing of the sample. Three research reactors were evaluated for use in determining iodine by ENAA. The University of Virginia reactor at Charlottesville was chosen for this study because the reactor facilities minimized thermal heating of the boron nitride vessel, enabling irradiation of larger, more representative analytical portions. Iodine concentrations ranging from 0.003 to 0.74 μg/g are reported for 17 different food matrices. (author) 13 refs

[en] At Interuniversity Reactor Institute, a fast rabbit system was installed consisting of polyethylene tubing and a carbonfiber end point at the core position. Carbonfiber combines a good mechanical stability under in-core conditions with a very high purity. It can be expected that as a result of the use of this material, contamination by the rabbit will become negligible, so that samples can be counted directly without unpacking. Results obtained with this new system are presented, and compared with results obtained with an aluminium rabbit system used until now. (author); 6 refs.; 5 figs

[en] A simple radiochemical machine incorporating ion-exchange procedures is described. The system was tested repeatedly for the determination of Cd, Co, Cr, Cu, Mn and Mo at ultra trace concentration levels in a variety of biological samples such as reference materials, human blood serum, human milk, hair and certain dietary materials, thereby demonstrating its suitability for practical use. The procedure can also yield results for Ag, Au and W, without any further chemical manipulations. Results are tabulated. This scheme has been applied to process large number of samples from single investigations such as those arising from dietary studies, obtaining quick and reliable data for routine use. (author) 20 refs.; 11 tables

[en] Thermal decomposition of natural siderite and goethite was studied using Moessbauer spectroscopy and x-ray diffraction. Hematite and magnetite were the principal compounds formed during high temperature treatment of siderite. Natural goethite transformed to hematite at high temperatures. The crystal structures, stoichiometry and the nuclear magnetic properties of Fe-oxides formed are discussed. (author)

[en] The experiment SROK-3 proved the method of isotope dilution with alpha-spectrometric end to be suitable for determining the concentration of Pu in solutions of the spent WWER fuel. The participating laboratories manifested their capability to determine Pu at the μg/g solution level with an error of 0.20-2.9 relative %. To increase the precision of results, attention is to be paid to the preparation of sources of α-radiation and to the computer programs for processing the α-spectra. (author)

[en] The techniques employed to measure Th concentrations in acrylic (PMMA) samples at a level of a few tens of ppt are described. Measurements on eleven different acrylic samples yielded a mean Th concentration of 40+-20 ppt. (author)

[en] A method is described that allows the simultaneous determination of the self-absorption factors of the alpha particles from ²²⁶Ra and its daughter products in the final precipitate. For BaSO₄ they are 0.360+-0.037 and 5.67+-0.13. This second value corresponds to the ratio between the self-absorption factors of ²²²Rn, ²¹⁸Po and ²¹⁴Po and ²²⁶Ra. Four aliquots of the IAEA Low Grade Uranium Ore S-13 with 0.039% U₃O₈ were analyzed by gross alpha counting using the determined values for these parameters in the ²²⁶Ra activity calculations. The mean value of (0.040+-0.002)% U₃O₈ shows the validity of the results. (author)

[en] In order to study instrumental charged-particle activation analysis using the internal standard method, simultaneous determinations of several selected elements such as Ca, Ti, V, Fe, Zn, As, Sr, Zr and Mo, in oyster tissue, brewer's yeast and mussel were carried out by using the respective (p, n) reactions and a personal computer-based gamma-ray spectrometer equipped with a micro-robot for sample changing. In the determination constant amounts of Y and La were added to the sample and comparative standard as exotic internal standards. As a result, it was demonstrated that concentrations of the above elements could be determined accurately and precisely. (author)

[en] The substoichiometric separation of Yb(III) can be achieved by the extraction of a substoichiometric amount of thenoyltrifluoroacetone and an excess amount of phenanthroline in benzene. The appropriate pH range for the substoichiometric extraction is 6-8. The reproducibility of the substoichiometric extraction of Yb(III) is very good (RSD 1%). As an example, Yb in a manganese nodule is determined by the substoichiometry combined with the radioactivation analysis. The content of Yb is 17.63+-0.23 μg/g. The present procedure can be applied to the determination of other rare erath elements. (author)