UJV Rez

Husinec, Czech Republic
Husinec, Czech Republic
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Konecna Z.,Czech Technical University | Zavadil M.,UJV Rez
Proceedings of the 2017 18th International Scientific Conference on Electric Power Engineering, EPE 2017 | Year: 2017

During long-term operation of safety cables, it can happen quite easily that standard operation conditions are not fulfilled. This paper deals with the thermal shock and its impact on electrical parameters and sustainability of quality of coaxial cables. The aim of this paper is to compare thermo-chemical properties (measured by DSC) of dielectric material of tested coaxial cable and electrical measurement (attenuation of cable). Experiments were conducted on three types of coaxial cable, each with a different kind of dielectric material: Teflon (PTFE), polyethylene (PE) and cross-linked polyethylene (XLPE) dielectric. © 2017 IEEE.


Koloma K.,UJV Rez | Cervinka R.,UJV Rez
Geological Society Special Publication | Year: 2017

The present work is focused on the study of strontium transport through crushed granite in the presence of bentonite colloids under dynamic arrangement. The aim of the experiments was to investigate the effect of bentonite colloids on strontium migration in crushed granite. The tracer behaviour was studied in a column set-up under aerobic conditions with a continuous inlet of the liquid phase of a constant tracer concentration (activity) and flow rate. Defined volumes of liquid phase were sampled at periodic time intervals at the column outlet for the measurements of tracer concentrations (activity). The transport was described by breakthrough curves. The stepwise approach included these steps: (1) an evaluation of the hydrodynamic column properties by the non-sorbing tracer 3H; (2) a column experiment with bentonite colloids in deionized water was performed; (3) migration of 85Sr solution in two liquid phases (deionized and synthetic granitic water); and (4) the transport of a radiocolloid suspension in deionized water was studied. Results showed different behaviour of bentonite colloids and strontium in the column. Bentonite colloids behaved as a non-sorbing tracer: Conversely, strontium showed strong sorption on granitic material. The strontium transport in the presence of bentonite colloids differed from strontium transport itself. The strontium transport in the presence of colloids was faster than transport without the bentonite colloids. The observed retention of strontium on granite suggests a higher affinity of strontium towards granitic rock than towards bentonite colloids, and showed the reversibility of the sorption of strontium on bentonite colloids.


Malet J.,UJV Rez | Parduba Z.,PSN RES SCA
Atomization and Sprays | Year: 2016

This paper presents the experimental characterization of a spray produced by a VVER-440 nuclear reactor type nozzle. Several droplet size and velocity profiles have been obtained at different pressure supplies and different heights below the outlet of the spray nozzle. Repeatability and stability have been checked. A log-normal size distribution can be fitted on the experimental results. Correlations between droplet velocities and sizes at different locations are also given, showing that for small droplet sizes (below 300 μm) no clear size-velocity correlation exists below 0.7 m from nozzle outlet, but for larger droplets, a classical evolution of this correlation is observed. It is concluded that the experimental data obtained at 300 mm from the nozzle outlet can be used as spray boundary conditions for numerical calculations with CFD codes. The other experimental data (at 500 and 700 mm from the nozzle outlet) can serve for detailed code validation, if the correlations between sizes and velocities are considered in the validation procedure: indeed, the averaging of droplet sizes and velocities can mask some typical spray results on droplet sizes and velocities evolutions. If a good code validation of the size-velocity correlations is obtained at 500 and 700 mm from the nozzle outlet, the concerned code may then be used with good confidence to extrapolate the results at other distances (for example, 3 m, 5 m) which cannot be obtained easily experimentally. © 2016 by Begell House, Inc.


Andel J.,UJV Rez
International Conference on Nuclear Engineering, Proceedings, ICONE | Year: 2014

Accumulator batteries installed in electrical emergency power systems of NPPs are power storages that secure quality and continuity of power supply for safety important and other sensitive systems. Key important function and characteristic of batteries is discharging time for which are batteries able to supply consumers. Better knowledge and improvement (prolonging) of this capability has been accented as one of "Stress tests" measures. This paper deals with conceptual design considerations and limitations related to battery system, comparison of discharging capabilities of various types of batteries, identification of typical power and safety requirements of consumers supplied form batteries. Next part of paper is focused on calculation and simulation methods of complex discharging load profiles targeted to determine realistic limits of discharging times. Finally there are described and technically commented/evaluated various possibilities to prolong power supply of vital systems from batteries in really difficult accident situation of NPP. All above mentioned is based on ENERGOPROJEKT PRAHA design experience from NPPs in Czech Republic and Slovak Republic. Copyright © 2014 by ASME.


Hustak S.,UJV Rez
International Conference on Nuclear Engineering, Proceedings, ICONE | Year: 2014

PSA specialists in UJV Rez, a. s. maintain a Living Probabilistic Safety Assessment (Living PSA) program for Dukovany Nuclear Power Plant (NPP), a four-unit VVER-440 plant type, which is operated in the Czech Republic. This project has been established as a broad framework for all plant activities related to risk assessment and as a support for riskinformed decision making carried out at this plant. In addition to recommendations for design and operation measures in order to increase the plant safety, it provides a basis and platform for all PSA applications at Dukovany NPP. The Living PSA model for Dukovany NPP is an integrated model representing the complete scope of Level 1 and Level 2 PSA for all plant operational modes. It produces the unit specific outputs for any Dukovany NPP unit. The RiskSpectrum® PSA software has been used for development and quantification of the PSA model. It is continuously updated and extensively used for various PSA applications at Dukovany NPP (e.g. risk monitoring, evaluation of plant Technical Specification changes, support for procedure development and training process, event analysis, etc.). The paper focuses on the important features of the Living PSA project for Dukovany NPP. It also discusses the broad experience gained during model development and update as well as possible future enhancements. Copyright © 2014 by ASME.


Machek J.,UJV Rez
International Conference on Nuclear Engineering, Proceedings, ICONE | Year: 2014

Paper describes original methods of signal validation, specially developed for in-core measurements, namely for Self Powered Neutron Flux Detectors (SPND) and for core exit coolant temperature measurements (thermocouples measurements). Some interesting examples of NPP Temelin data validation (SPND) and NPP Dukovany (thermocouple measurements) are presented; precision and sensitivity of methods used are discussed. Copyright © 2014 by ASME.


Podlaha J.,UJV Rez
International Conference on Nuclear Engineering, Proceedings, ICONE | Year: 2014

After more than 50 years of operation of the research reactor operated by UJV Rez, a. s. (UJV) or the Research Centre Rez, as the case may be, a large amount of spent nuclear fuel (SNF) of Russian origin has accumulated. In 2005, UJV joined the Russian Research Reactor Fuel Return (RRRFR) program under the US-Russian Global Threat Reduction Initiative (GTRI) and started the process of SNF shipment from the LVR-15 research reactor back to the Russian Federation (RF) using the SKODA VPVR/M transport packaging system (TPS). Two SNF shipments from UJV were carried out in 2007 and 2013. After the shipments were completed, only low-enriched nuclear fuel with a maximum enrichment below 20% of 235U remained on the territory of the Czech Republic. UJV also participates in shipments of SNF from other countries. The services of UJV comprise mainly SKODA VPVR/M TPS leasing, technical oversight and expertise during cask handling, SNF loading and cask closing and sealing. Up to now, UJV has participated in thirteen shipments of SNF from eight countries; one shipment is currently being prepared. High-level radioactive waste (HLW) will be generated from SNF reprocessing. The vitrified HLW will be returned to the Czech Republic as stated in the Russian-Czech Intergovernmental Agreement on Co-operation in Nuclear Energy. The return of the waste represents very complex and complicated work, technically, legally and contractually.. Copyright © 2014 by ASME.


Zdarek J.,UJV Rez
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2013

After the Fukushima Accident there is a worldwide strategy to develop the Defense in Depth strategy to mitigate the Severe Accidents. This effort has long tradition for new designs of NPPs. However the existing NPPs are lacking such a systematic approach. For the VVER 440 type NPP family the concept of the IN Vessel Strategy was adopted many years ago for the Loviisa NPP in Finland. However the VVER 1000/320 Units are lacking final treatment with the Severe Accidents. Effort of our research is to prepare the analytical and experimental proof to justify this concept for higher power VVER type NPPs. Copyright © 2013 by ASME.


VERLIFE - "Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs during Operation" was developed within the 5th Framework Programme of the European Union in 2003 and later upgraded within the 6th Framework Programme "COVERS - Safety of WWER NPPs" of the European Union in 2008. This Procedure has to fill the gap in original Soviet/Russian Codes and Rules for WWER type NPPs, as these codes were developed only for design and manufacture and were not changed since their second edition in 1989. VERLIFE Procedure is based on these Russian codes but incorporates also new developments in research, mainly in fracture mechanics, and also some principal approaches used in PWR codes. To assure that VERLIFE Procedure will remain a living document, new 3-years IAEA project (in close co-operation with another project 6th Framework Programme of the European Union "NULIFE - Plant Life Management of NPPs") started in 2009. Within this project, upgrading/updating of the VERLIFE procedure is prepared together with the extension by (at least) following procedures: - Lifetime of reactor pressure vessel internals - Leak-before-break concept for WWER NPPs - No-break-zone for WWER NPPs - Probabilistic approach for failure and lifetime assessment of WWER reactor pressure vessels and primary piping (including Risk-informed ISI) - Qualification of NDT procedures - Thermal fatigue evaluation - Supports of components and piping Final document, after its approval by expert groups of the IAEA and NULIFE, will be issued in 2014 as "IAEA VERLIFE Guidelines for Integrity and Lifetime Assessment of Components and Piping in WWER NPPs". © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.


Morte M.,UJV Rez
Proceedings - 2016 17th International Scientific Conference on Electric Power Engineering, EPE 2016 | Year: 2016

From point of view of power engineering the successful commercial market with electric vehicles demands a completely new concept of their integration into contemporary electrical network. The electric vehicles have very limited range, so they have to be charged in short periods, that means for the grid problems with peaks in the daily load profile. The paper outlined one of the most promising-decentralization of the network with help of multiagent systems. Each agent collects and evaluates data about vehicles from small area, manages such area relative independently, so the main problem is to create an algorithm for optimal cooperation and communication with the other agents. The example of such cooperation is shown, firstly as the simple linear programming problem, the secondly more complex, with using the game theory which is the mathematical basis for multiagent systems. The system is connected with the smart grid, so the possibilities of altering the load profile are shown. The last chapter explores the necessity of the shift of such grid to artificial intelligence and the epistemic modal logic is presented as a possible solution. © 2016 IEEE.

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