Vuje (Slovakia)

The paper is focused on broader considerations regarding the commissioning process of the 3rd Unit of nuclear power plant VVER-440 type in Mochovce (Slovakia). The new nuclear plant built in Europe is getting much more slowly than expected, declared or scheduled. Besides the nuclear power plant in Olkiluoto (Finland) and also Flamanville (France), the 3rd Mochovce Unit has finally been in full operation since 6 November 2024. Nevertheless, the more than 30 years of construction process, which was intermittently stopped and frozen, make this success story exceptional. Lessons learned from commissioning are every time specific for different countries but commissioning of nuclear power plant without presence of general designer, respecting all safety requirements and taking full responsibility for this process is unique. Still, in general, the actual Slovak experiences and knowledge could help optimise new buildings in Europe, including dreams about small modular reactor deployment or the building of other clean and sustainable use of advanced nuclear facilities in the future.

The microstructural evolution and mechanical properties of WWER 440 steam generator steel GOST 22K after long-term operation were thoroughly examined in this study. The samples were taken directly from a steam generator using the small punch test method. The uniqueness of these samples lies in the fact that they were real operating materials used in a nuclear power plant with different years of operation. The microstructure was characterized using optical microscopy and transmission electron microscopy supplemented by selective electron diffraction and semi-quantitative chemical microanalysis. It was found that with the prolongation of the operation time of the steam generator, the density of carbides increased slightly, which was reflected in a decrease in the mean distance between particles, but these differences were very small, which indicates the microstructural stability of GOST 22K steel. The stability of this steel was also confirmed by measuring its mechanical properties, which changed only minimally depending on the years of operation. The tensile strength values were in the range of 508 to 579 MPa. In the case of the ductile-to-brittle transition temperature (DBTT), a slight increase was found after 6 years of operation. The DBTT did not change significantly with subsequent operation.

Abstract In the past few years, miniature testing techniques to evaluate the mechanical properties of structural materials of nuclear reactors have gained interest due to the limited number of irradiated surveillance specimens and strict safety regulations. One of such miniature testing techniques is the Small Punch Testing (SPT) method, which uses tiny discs to estimate mechanical properties such as tensile properties, fracture toughness and the ductile-to-brittle transition temperature of the examined material. As described in the ASTM E3205 standard: Standard Test Method for Small Punch Testing of Metallic Materials, empirical relations are used to correlate the yield strength and the ultimate tensile strength to the SPT parameters determined from the investigated material. The validity of these empirical relations at high fluence irradiation needs to be further studied and understood to assess the potential applicability of the SPT technique for the evaluation of the effect of high-fluence irradiation in reactor pressure vessel (RPV) steels and for the implementation of this testing method in surveillance programs of existing nuclear power plants. In this current work, SPT tests have been performed on six RPV model steels in the as-received and highly neutron irradiated state. These alloys were part of the joint NRG-JRC irradiation campaign LYRA-10 and resemble VVER and PWR RPV steels with tailored chemical compositions to study the synergetic effect of Ni, Mn and Si in the high fluence regime. The tensile properties of these materials prior and after irradiation are correlated with the SPT results and the shifts in SPT fitting parameter βp0.2 as effect of irradiation and chemical composition are studied to evaluate the effectiveness of this technique for screening of irradiation-induced hardening.

Hyperspectral imaging has become an active area of research and development in the world. In the past, hyperspectral imaging was only available to selected research teams in specific areas such as space research. Nowadays, the use of hyperspectral imaging systems is increasingly entering commercial use. Given the current technical capabilities, hyperspectral imaging can be implemented in the performance of aerial surveys of outdoor power lines

Abstract The main degradation mechanism of NPP’s components is radiation damage, but these processes are situated only in the core region of the reactor pressure vessel (RPV). The main mechanical loading of all individual parts of NPP’s primary circuit are the influence of high pressure at elevated temperature till 300°C. These processes lead to the fatigue damage of structural materials, which is characterized as the thermal fatigue or thermal ageing. The decommissioning of two V1 units in Slovakia provides a great opportunity to preserve materials from equipment that was in conditions of real operation for decades (app. 28–29 campaigns). VUJE, in cooperation with other partners, prepared necessary steps to create a material archive and related database including all relevant information from the decommissioned units of WWER-440 reactors. The main goal is to evaluate the real influence of long-term operation (LTO) on the degradation of NPP parts, such as steam-generators (SGs). The Small Punch Test (SPT) methods are mainly used for evaluation of materials actual state. By the SPT technique it is possible to evaluate the basic tensile properties as the ultimate tensile strength and the yield stress of the tested materials from a very small amount of obtained material. The paper deals with description of special sampling from steam generators of operating units in Slovakia and subsequent testing of samples taken by the SPT method. All these results were compared with reference testing on materials taken from decommissioned V1 NPP.

The CONFIDENCE dissemination workshop “Coping with uncertainties for improved modelling and decision making in nuclear emergencies” was held in December 2–5, 2019 (Bratislava, Slovak Republic). About 90 scientists and decision makers attended the workshop. The dissemination workshop allowed the presentation of the CONFIDENCE project results, demonstration of the applicability of the developed methods and tools in interactive discussion sessions and the collection of feedback from the participants. The results were disseminated not only in the form of presentations and posters but also through interactive workshops where all participants were involved in round table working groups. A fictive accidental release scenario taking place at a nuclear power plant was developed and used by each work package in the workshop to provide the basis for interactive sessions and discussions.

This paper reports on the research of mental models of uncertainties management in an emergency situation which was carried out in the framework of the European CONFIDENCE (COping with uNcertainties For Improved modelling and DEcision making in Nuclear emergenCiEs) Project. The methodology included the mapping of mental models among several emergency preparedness and response experts and then performing interviews based on structured protocol with lay people in five countries: Germany, Greece, Slovak Republic, Slovenia and Spain. The aim of these investigations was to trace the concepts and understandings of emergency preparedness and response and to identify possible gaps between experts and lay people. The article presents the main results of this research and suggestions for the improvement of EP & R planning.

The project CONFIDENCE (COping with uNcertainties For Improved modelling and DEcision making in Nuclear emergenCiEs) final dissemination event attracted 88 participants to review and discuss the project results and provide ideas for future research work. The workshop highlighted progress in understanding uncertainties in all phases of an emergency. It was also demonstrated that consideration of uncertainties are important when developing countermeasure strategies. Stakeholder engagement as well as societal and ethical aspects in decision making have to be considered. Formal decision making tools were improved and tested. In addition, CONFIDENCE participants, representatives of international organisations and end users, provided their ideas on research needs and the way forward.

The submitted contribution is devoted to the issue of the existence of latent losses on the overhead lines. Quantification of latent losses of electricity is a very complicated task, which has been solved in practice for several years. In their assessment, however, often appear some inconsistencies which cause is often unknown. The magnitude of these losses in some cases cannot be negligible. From the point of view of maintaining an efficient and reliable operation of distribution and transmission systems in the future, attention will still need to be paid to the problem of latent loss analysis.