[en] The positron annihilation lifetime spectroscopy (PALS) can be very suitable complement to many experiments on the RPV steels. The most interesting examples of such applications published in the scientific papers in last decade as well as our recent experiments are summarized in this paper. (authors)

[en] This CD contains three chapters about perspectives of development of nuclear energetics. It contains the following chapters: (1) Development of nuclear energetics and its reception by public; (2) Nuclear energetics - irreplaceable constituent of energetic sources; (3) Advanced types of nuclear reactors and their comparison from different aspects

[en] Non-destructive method, positron annihilation lifetime spectroscopy (PALS) was applied as an evaluation tool for microstructure study of the four different Fe-Cr alloys. This paper describes ion implantation technique as a tool for creating microstructure defect in structural materials, similar to radiation damage in nuclear facilities. In present state of the research non implanted specimens were measured using PALS, TEM and XRD. The results show the dependency of positron lifetime in defects on the Cr content. These results are necessary in further PALS spectra analysis of the implanted specimens. (authors)

[en] In this book new matters with arguments for support of use of nuclear energy as a unavoidable pool of energetic source are reviewed. Reactors of the fourth generation are described with accent on their safety and quality exploitation as well as their use in the future. The book is dedicated for body of NPP for relations with public and other workers of nuclear energetics. Arguments for advancement of development of nuclear energetics are presented

[en] Non-destructive methods as Positron annihilation spectroscopy (PAS) and Moessbauer spectroscopy (MS) were applied in the evaluation of the microstructure parameters and degradation processes of nuclear reactor pressure vessel (RPV) steel surveillance specimens. Study was oriented to the material investigation of Russian WWER-1000 steels (15Kh2MNFAA and 12Kh2N2MAA) with higher Ni content (1,26 wt.% in base metal and 1,7 wt.% in weld). For comparison, the WWER-440 weld metal (Sv10KhMFT) without Ni was measured, too. Specimens were studied in as received stage, after irradiation in LVR-15 experimental reactor to the neutron fluence F_(E>0.5MeV) = 4x10²³ m^-2s^-1 and after annealing in vacuum at 475 ⁰C/2h. Changes due to different chemical composition and due to irradiation were registered using MS. Post-irradiation thermal treatment and annealing of defects was well detected by different PAS techniques. It was observed that the sensitivity of PAS and MS parameters to defined irradiation treatment decreases with Ni-content increase. Results confirm the hypothesis that Ni affects size (decrease) and distribution (more homogeneous) of the Cu- and P-rich clusters and M_xC_x carbides. (author)

[en] Fission gas behavior within the fuel structure plays a major role for the safety of nuclear fuels during operation in a nuclear power plant. Fission gas distribution and retention is determined by both, micro- and lattice-structure of the fuel matrix. The ADOPT (Advanced Doped Pellet Technology) fuel, containing chromium and aluminum additives, shows larger grain sizes than standard (undoped) UO_2 fuel, enhancing the fission gas retention properties of the matrix. However, the additions of such trivalent cations shall also induce defects in the lattice. In this study, we investigated the microstructure of such doped fuels as well as a reference standard UO_2 by positron annihilation spectroscopy (PAS). Although this technique is particularly sensitive to lattice point defects in materials, a wider application in the UO_2 research is still missing. The PAS-lifetime components were measured in the hot lab facility of PSI using a "2"2Na source sandwiched between two 500-mm thin sample discs. The values of lifetime at the center and the rim of both samples, examined to check at the radial homogeneity of the pellets, are not significantly different. The mean lifetimes were found to be longer in the ADOPT material, 220 ps, than in standard UO_2, 190 ps, which indicates a larger presence of additional defects, presumably generated by the dopants. While two-component decomposition (bulk + one defect component) could be performed for the standard material, only one lifetime component was found in the doped material. The absence of the bulk component in the ADOPT sample refers to a saturated positron trapping (i.e., all positrons are trapped at defects). In order to associate a type of lattice defect to each PAS component, interpretation of the PAS experimental observations was conducted with respect to existing experimental and modeling studies. This work has shown the efficiency of PAS to detect lattice point defects in UO_2 produced by Cr and Al oxides. These additives create lattice irregularities, which are acting as sinks for fission products on one hand and trapping positrons on the other hand. Fitting of the obtained experimental data with a suitable theoretical model can provide a valuable qualitative assessment of these defects. At this stage of the research, some of the existing models were used for this purpose. (authors)

[en] In this work the determination of weighting factors and functions for WWER-440 ex-core neutron detectors using MCNP5 is presented. Precise and complex whole-core model of the WWER-440 was developed in MCNP5 and applied for solution of various reactor-physical problems (NPP Bohunice and Mochovce). Determination of weighting factors and weighting functions was performed for the source range ex-core detector CPNB44 (NPP Bohunice). At present, database of spatial weighting factors is generated.

[en] An accelerated monitoring system designed for the Slovak wet interim spent fuel storage facility in NPP Bohunice bases on the new designed 'cesium detectors' is presented in the paper. Since 1999, leak tests of WWER-440 fuel assemblies are provided by special leak tightness detection system 'Sipping in Pool' delivered by Framatome-anp with external heating for the precise defects determination. Although, this system seems to be very effective, the detection time of all fuel assemblies in one storage pool is too long. Therefore, a new 'on-line' detection system, based on new sorbent NIFSIL for effective ¹³⁴Cs and ¹³⁷Cs activity was developed. Design of this detection system and its application possibility in Slovak wet interim spent fuel storage facility as well as the first results are presented (Authors)

[en] This report discusses the application of various non-destructive testing methods on the microstructural characterization of the oxide dispersion strengthened steels with possible nuclear applications. Emphasis is put on a multi-technique approach and mutual correlation of results as well as on the validation and interpretation of the results obtained by destructive mechanical tests. The results of positron lifetime spectroscopy (PALS), Small angle neutron scattering (SANS) and thermoelectric power measurements (TEP) on the thermally aged ODS steels are discussed. Interpretation of the results was based on previously published papers on nuclear structural materials as well as on the preliminary TEM and XRD experiments performed in the collaboration with Nuclear Research Centre Negev, Israel. (author)

[en] Monitoring of WWER fuel assemblies condition in Slovakia is presented in the paper. The leak tightness results of fuel assemblies used in Slovak WWER units in last 20 years are analyzed. Good experiences with the 'Sipping system' are described. The Slovak wet interim spent fuel storage facility in NPP Jaslovske Bohunice was build and put in operation in 1986. Since 1999, leak tests of WWER-440 fuel assemblies are provided by special leak tightness detection system 'Sipping in Pool' delivered by Framatome-ANP facility with external heating for the precise detection of active specimens. Another system for monitoring of fuel assemblies condition was implemented in December 2006 under the name 'SVYPP-440'. First non-active tests started at February 2007 and are described in the paper. Although those systems seems to be very effective, the detection time of all fuel assemblies in one storage pool is too long (several months). Therefore, a new 'on-line' detection system, based on new sorbent KNiFC-PAN for effective ¹³⁴Cs and ¹³⁷Cs activity was developed. This sorbent was compared with another type of sorbent NIFSIL and results are presented. The design of this detection system and its possible application in the Slovak wet spent fuel storage facility is discussed. For completeness, the initial results of the new system are also presented. (authors)