[en] Full text: Gamma-ray spectrometry was used to detect the post-irradiation radionuclides in neutron irradiated nanocrystalline FINEMET and NANOPERM alloys. FeCuNbSiB and FeZrB nanocrystalline samples in the shape of ribbons were submitted to neutron irradiation in the range of fluence from 10¹⁶ up to 10¹⁹ n/cm². Conventional HPGe detector system with low-background chamber was used to record gamma-ray spectra on irradiated samples 6 and 24 months after irradiation. In the case of nanocrystalline FINEMET alloys the presence of ⁵⁴Mn, ⁵⁹Fe, ⁶⁰Co and ^l82Ta isotopes was identified from the gamma spectra recorded 6 months after irradiation. 18 months later, only ⁵⁴Mn and ⁶⁰Co isotopes were found. Gamma spectra of irradiated nanocrystalline NANOPERM samples showed peaks corresponding to the ⁵⁴Mn, ⁵⁹Fe, ⁶⁰Co, ⁹⁵Nb and ⁹⁵Zr isotopes. 24 months after irradiation only ⁵⁴Mn and ⁶⁰Co isotopes were found in the samples

[en] Full text of publication follows. Super Critical Water Reactors (SCWR) have been pre-selected as a one of the candidate concepts for the new generation of nuclear reactors in frame of Generation IV. Beside the design concept choice of construction materials is the most important question. Despite extensive research due to using various materials either in the conventional supercritical coal power plants or SCWO systems there is still missing knowledge about the properties of the materials in operational conditions of SCWR. That includes influence of irradiation and environment composition on chemistry of water especially process of radiolysis, mechanical properties of the materials and oxide films properties. The process of choice and testing of possible construction and fuel cladding materials are still under R and D (e.g. EU HPLWR project). Two types of tests were undertaken in SCW environment conditions (t = 600 deg C, p = 250 bar): U-bend specimens for constant displacement SCC tests and tensile specimens for SSRT tests. SSRT tests were carried out in SCW environment with different concentration of dissolved O₂: 1, 10, 100, 20 ppb (±5 ppb) and with different displacement rates: 0.1, 1, 10 μm/min. In SCC test with LI-bend specimens different time expositions were carried out in two concentrations of dissolved O₂: 0 and 200 ppb. Water chemistry was continually monitored by means of pH, conductivity and dissolved O₂ sensors. After the test the specimens were analysed by optical microscopy, SEM and XRD. (authors)

[en] The results are briefly presented of some measurements which were carried out with the aim to obtain an efficient and stable performance of a helium gas-flow CEMS detector. 4 tabs., 2 refs

[en] In the present paper, the measurement of Seebeck coefficient are discussed together with hardness measurements of the VVER1000 weld material irradiated to ∼10"2"4 m"-"2. The results were discussed in the light of the published literature in order to determine the key factors which affect the thermoelectric properties of the VVER materials and further the future nuclear structural materials. (authors)

[en] Transmission Moessbauer spectroscopy was used to study changes induced by irradiation of amorphous and nanocrystalline samples. In an as-cast sample, neutrons mostly affect the orientation of the net magnetic moment. The average hyperfine field decreases with increasing neutron fluencies. In the case of the nanocrystalline samples a new disordered structure is created in the amorphous remainder corresponding to boride phases as it is shown in the samples isothermally heated from 1 to 8 hours. The structural changes of the amorphous remainder depend on the stage of crystallization and total neutron fluencies. (author). 1 tab., 3 figs., 7 refs

[en] NANOPERM, HITPERM and FINEMET amorphous and nanocrystalline alloys were measured by Moessbauer spectrometry in the weak magnetic field of 0.5 T. It was shown that the most sensitive parameters of Moessbauer spectra are the intensities of 2^nd and 5^th lines. Rather small changes were observed also in the case of internal magnetic field values. The spectrum of nanocrystalline NANOPERM showed the increase of A23 parameter (ratio of line intensities) from 2.4 to 3.7 and decrease of internal magnetic field from 20 to 19 T for amorphous sub-spectrum under the influence of magnetic field. Spectrum of nanocrystaline FINEMET shown decrease of A23 from 3.5 to 2.6 almost without change of internal magnetic field value. In the case of amorphous NANOPERM and FINEMET samples the changes are almost negligible. HITPERM alloy shown the highest sensitivity to the weak magnetic field, when A23 increased from 0.4 to 2.5 in the external magnetic fields. The A23 of crystalline sub-spectrum increased from 2.7 to 3.8 and the value of internal magnetic field corresponding to amorphous sub-spectrum increased from 22 to 24 T. The behavior of nanocrystalline alloys under weak external magnetic field was analyzed within three-level relaxation model of magnetic dynamics in an assembly of single-domain particles. (authors)

[en] Meteorite Kosice fell down 28"t"h of February 2010 near the Kosice and represents an unique find, because the last fall of meteorite was observed in Slovakia at the year 1895. It supposes that for this kind of meteorite the orbit in cosmic space could be calculated. This is one of most important part because until now 13 places of meteorite find are known in the world of which cosmic orbit in space have been calculated. Slovakia is member of international bolide net, dealing with meteorite analysis in Middle Europe .Analysis of Kosice meteorite will also concern at the long live and short live nuclides. Results should be a contribution to determination of radiation and formative ages. From structural analysis of meteorite it will be possible to compare it with similar types of meteorites. In this work Moessbauer spectroscopy will be used for phase analysis from point of view iron contain components with the aim to identify magnetic and non magnetic fractions. From the analysis of magnetic part we can find that the first sextet with hyperfine magnetic field 33.5 T corresponds to bcc Fe-Ni alloy (kamacite) and second with field 31.5 T to FeS (triolite). Meteorites with mentioned composition belong to the mineral group of chondrites. Comparing our parameters with results of measurements at the similar meteorites we can conclude that Kosice meteorite contains the same components. According all Moessbauer parameters we can also include this meteorite in the mineral group of chondrites. (authors)

[en] The variability of the properties and the composition of the corrosion products of the stainless and mild steels in dependence on the conditions (temperature, acidity, etc.) is of such range that, in practice, it is impossible to determine the properties of the corrosion products for an actual case from the theoretical data only. Since the decontamination processes for the materials of the water-cooled reactor (VVER-440) secondary circuits are in the progress of development, it is necessary to draw the needed information by the measurement and analysis of the real specimens. After five year operation one feed water dispersion box and corresponding distributing pipelines were replaced by new ones in the steam generator (SG) 35 of NPP Bohunice with the aim to analyse their overall stage and corrosion products on the surface. Moessbauer spectroscopy can be useful tool in investigation of corrosion layers, therefore it was used in backscattering geometry to identify surface layers of the feed water dispersion box. Moessbauer spectroscopy in backscattering geometry was performed on two samples from the feed water dispersion box in order to analyse corrosion layers at its surface. In both samples the only form of identified corrosion product is magnetite, it forms 51% of the spectral area of sample 1, and 29% for sample 2. Rest of the spectral areas can be assigned as austenitic stainless steel, a base material of the feed water dispersion box.No traces of other types of magnetically ordered corrosion products were found. (authors)

[en] This study was focused on commercial oxide-dispersion strengthened steels - MA 956 (20 % Cr), PM 2000 (19 % Cr) and ODM 751 (16 % Cr) developed for construction of the Generation IV reactors. The ODS steels are investigated in order to compare their microstructure features and radiation resistance. Accumulation of vacancy defects due to alpha irradiation were observed by positron annihilation lifetime spectroscopy. The alpha particles were simulated by helium ion implantation performed in a linear accelerator with a cascade 1 MeV voltage source at Slovak University of Technology. The lowest presence of open volume defects was found in PM 2000 before and also after the radiation treatment. The lowest defect accumulation during implantation (radiation resistance) was demonstrated in ODM 751; although this steel contained the largest defects before and also after irradiation (vacancy clusters V5). (authors)

[en] Steels applied in nuclear facilities have to have very good resistance to corrosion, thus the investigation of the material degradation due to corrosion can be very useful even in condition of microstructural changes. This paper studies applicability of our positron annihilation lifetime spectroscopy as method sensitive to material corrosion and gives a review if it can be practically used for measurement of steels intended for nuclear power plants (NPPs) of 4"t"h generation (GEN IV). Our study was focused on investigation of commercial austenitic steel NF 709. This steel is candidate for construction of pipes, tubes and heat exchangers. (authors)