[en] The radioactive tracers methods presently in use in hydrology are based on ''in situ'' low resolution gamma-ray spectrometry measurements. However sometimes the information obtained in this way is not conclusive and the need for better spectrometry systems is evident. Therefore the authors present a method for measuring in laboratory conditions samples of radioactive tracers collected ''in situ'' and concentrated on ions exchange resins, sing low level gamma-ray spectrometry with Ge(Li) detector. The advantages of this method in comparison with the methods based on Na(Tl) detectors are also presented in the paper. (authors)

[en] Neutron activation analysis combined with chemical preconcentration of the elements in water samples can give a high sensitivity in the determination of concentrations for In-EDTA, I^- and Br^- used as active tracers in hydrological studies. The authors have developed an improved method of analysis which is sensitive, selective and applicable to a wide range of underground and surface water samples including those having a high concentration of manganese ions. (author) 6 refs.; 2 figs.; 1 tab

[en] Two experiments are presented, on the possibilities of the use of indium in the form of the In-EDTA complex, as an activable tracer for hydrogeological studies. The determination of indium concentrations in the sampled water has been carried out by using the coprecipitation of indium with bismuth hydroxide, the neutron activation at the VVR-S reactor of the Institute for Nuclear Physics and Engineering - Bucharest and the measurement on the 417.0 keV line of sup(116m)In with the Ge(Li) spectrometric device. The advantages of the utilization of In-EDTA as a tracer for marking large volumes of water and of some long transit waters (of the order of months) have resulted. (authors)

[en] The authors present the main temporal marks of the history of a nuclear waste disposal site designed on multi-barrier principle, considering a 'time cut-off' of 10,000 years. Collective dose is considered as a representative parameter of the radiological impact assessment and its calculation can be done using an impact scenario elaboration procedure like the one described in this work. It is considered that a more realistic radiological impact assessment can be done only by a permanent comparison between experiment and the mathematical modelling of the radionuclide transport phenomena from repository to the biosphere. (Author)

[en] A preirradiation separation technique of the rare earth elements group in phosphate residues followed by neutron activation analysis is described. By the proposed work technique La, Ce, Eu, Dy, Yb, Lu, Sc and Y are separated on ion exchange resins like Dower 2 x 10(200-400 mesh, Cl- form) with a chemical yield of 90-95%. Finally, the variation of the pH-values, made possible the concentration of Sc at pH = 6.2, of rare earth elements at pH = 7 and of Y at pH = 8. The high sensitivity of the neutron activation analysis method allows a detection limit of 0.02 - 0.3 ppm and the individual determination of these elements. (author)

[en] The last years improvements in gamma-ray spectrometry instrumentation and methods, and increase of accuracy of nuclear data made possible the use of the absolute method of NAA as a series quantitative multielemental analysis method, competitive with the comparative one. The authors present results of NAA absolute method application on SL-1 (IAEA) and EOP (Radiological Institute Kovice) reference samples. It was used irradiation at a thermal neutron flux of 2.3 x 10¹⁹ n/cm² s and measurement with a Hp Ge Canberra detector coupled to a S100 multichannel system. Computer program SAMPO-90 for processing gamma-ray spectra was used. (Author)

[en] An instrumental neutron activation technique has been developed for the determination of concentration levels of Se, Br, Co, K, Mn, Na and Sc in dry pharmaceutical products like ORGASEL-50 and HUMANAFORT and biological samples. A precision of 5-10% was achieved. The detection limit for Se was 20-50 ppb. The method is relatively simple, accurate and suitable for simultaneous multielemental analysis of various samples. Especially for Se determination in pharmaceutical products it may be a routine analysis method and an indispensable tool for quality control in the fabrication process. At the same time, NAA was utilized for blood-plasma sample analysis obtained from 145 patients treated with the studied pharmaceutical products. (author)

[en] In this paper the authors present the use of a portable high resolution gamma spectrometer in the measurement of the surrounding area of a former repository for radioactive wastes, decommissioned more than 15 years ago. In the spectra recording this work the presence of Co-60 was evidenced. (Author) 2 Figs., 1 Tab., 6 Refs

[en] Tracer experiments supply thorough knowledge of the karst, facilitate confirmation or rejection of hydraulic connections between sinkholes and water emergences, and provide for the discovery of new connections. They are an ideal means of studying the vulnerability of the karst to pollutants. Tracer labelling also permits verification of the flow patterns of hydrokarstic structures and the performance of methodological and comparative studies concerning the behaviour of the karst between low flow and flood; important quantities of the tracer may remain in its auxiliary systems for a long period of time. Consequently, investigation of hydrokarstic structures should be performed through simultaneous or repeated labelling using different 'conservative' tracers. Multitracing experiments are employed to shorten the duration of research work by avoiding repeated trials and the necessity of performing investigations under analogue hydraulic conditions. 4 refs, 1 fig., 1 tab

[en] The application of a semiempirical method to determine the photopeak efficiency and the γ - γ coincidence correction factor, necessary in the case of the high efficiency (relative efficiency greater than 10 %) HPGe detectors, is presented in this work. The described method implies the successive determination of the following parameters: - the photopeak efficiency for a reference position, using standard point sources; - the photopeak efficiency for geometries of interest, using a semiempirical relation based on the effective solid angle calculation; - the total gamma efficiency, based on the peak/total values determination with laboratory-made single-gamma sources; - the γ -γ coincidence factor for gamma rays of interest. Tables with the values obtained for a specific case (HPGe detector with relative efficiency of 30.1% and point sources) are presented. (author)