This Special Issue presents extended versions of selected top papers of the Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion (MEDPOWER), held in ...Dubrovnik in 2018. The 11th Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion (MEDPOWER 2018) was held in Cavtat, Dubrobnik, Croatia, from 12 to 15 November 2018. The conference gathered more than 200 scientists, researchers, and experts from all around the world. A total of 147 oral presentations were held during the conference, with an additional 50 papers presented in special sessions. The top 10 papers have been selected for this Special Issue in Energies, covering a variety of topics from end-user challenges, distribution and transmission network operation and planning, to generation planning and modeling.
This study describes an application of hybrid modelling for an atmospheric variable in the Krško basin. The hybrid model is a combination of a physics-based and data-driven model and has some ...properties of both modelling approaches. In the authors’ case, it is used for the modelling of an atmospheric variable, namely relative humidity in a particular location for the purpose of using the predictions of the model as an input to the air-pollution-dispersion model for radiation exposure. The presented hybrid model is a combination of a physics-based atmospherical model and a Gaussian-process (GP) regression model. The GP model is a probabilistic kernel method that also enables evaluation of prediction confidence. The problem of poor scalability of GP modelling was solved using sparse GP modelling; in particular, the fully independent training conditional method was used. Two different approaches to dataset selection for empirical model training were used and multiple-step-ahead predictions for different horizons were assessed. It is shown in this study that the accuracy of the predicted relative humidity in the Krško basin improved when using hybrid models over using the physics-based model alone and that predictions for a considerable length of horizon can be used.
The paper presents the MAAP 4.07 analysis of containment heat removal after reactor vessel failure resulting from the initial Station Blackout (SBO) accident. The accident is analysed considering ...mitigation measures for heat removal from the containment using alternative equipment (Alternative Residual Heat Removal (ARHR) pump and heat exchanger (ARHX) and, also, Alternative Safety Injection (ASI) pump). The mitigation actions are taken according to NEK Severe Accident Mitigation Guidelines (SAMG).
There are several possibilities to remove the heat from the containment once the reactor vessel fails and, for all of them, the necessary condition is to have the sufficient source of water (Residual Water Storage Tank (RWST), Alternative Boron Water Tank (ABWT) or other) and the appropriate heat exchanger available. Two options are presented within this paper:
1. Injection to the Reactor Coolant System (RCS) using ASI pump and recirculation (sump to RCS) through ARHR system via ARHX,
2. Spraying the containment through Containment Spray (CI) system using ARHR pump and, then, recirculation (sump to spray) through CI and ARHR systems via ARHX.
The results show that the containment heat removal can be done with either of analysed ways if the water is provided for recirculation (assumed containment level 3.9 m ~ 760 m3). However, with the fact that the reactor cavity is not flooded, the cooling using ASI will initially result in considerable containment pressure increase because the water is spilled through the RCS over the hot molten core debris. Therefore, it must be stated that the preferable way of containment pressure reduction, once the vessel has failed, is by using the containment spray. On the other hand, if RWST is not available, then the initial water delivery cannot be made from ABWT via CI system because this option does not exist. It shall also be pointed out that, if the active containment heat removal is started early enough, the Passive Containment Filtered Vent System (PCFVS) opening would be prevented and no fission products shall be released to environment.
Sludge removal is performed on two steam generators (SG’s) at the Krško Nuclear Power Plant (NEK) during every outage. SG’s are a meeting point of five major plant systems: Reactor Coolant System ...(RC) on the primary side and four systems on the secondary side – Auxiliary Feedwater System (AF), Blowdown System (BD), Main Feedwater System (FW), and Main Steam System (MS). Sludge removal activities take place on the secondary side of the SG’s on the top of the tube sheet. It always consists of classical Sludge Lancing (SL) which is done by spraying water at different angles (30°, 90°, 150°) between the tube gaps in the steam generator tube bundle with a pressure of around 220 bars. Another method is Inner Bundle Lancing (IBL) which means spraying water directly inside the tube bundle with a traveling lance tape with a spraying nozzle at the end. Water is sprayed at an angle or directly on the top of the tube sheet with a robot-guided manipulator which is placed inside a steam generator. The manipulator and therefore the spraying action is controlled by an operator and at times it is fully autonomous to provide the highest protection measures possible. Another method of sludge removal which was for the first time utilized in 2019 at the Krško site was Chemical Cleaning (CC) of both SG’s. During this process, a chemical was injected into the SG’s through the BD system and periodically pumped between the two SG’s to create a dynamic flow and maximize the cleaning effect. To achieve the best results, a constant temperature of the chemicals had to be maintained at all times. Upon completion of chemical cleaning, a rinsing phase was followed to remove any post-treatment chemicals. After all sludge removal activities, a televisual inspection (TVI) of the top of the tube sheet was performed to access the hard sludge area and to search for potential foreign objects in the SG’s. If for instance an object of importance during TV inspection is found, an attempt to retrieve it would usually take place. Other methods of sludge removal such as upper bundle flushing or ultrasonic cleaning have not been implemented in NEK thus far. Since the power plant uprate in May 2000, NEK conducted SL on both SG’s every outage also starting with IBL in 2013 and 2015, and the same method was used in the 2018 outage. During the outage in 2019, all three methods (SL, IBL, and CC) have been utilized with the main purpose to extend the full load operation of the plant, preventing and/or stopping denting processes in the SG’s from occurring, reducing and stopping the build-up of hard sludge area to increase/sustain efficiency and remove foreign objects found in the SG’s. SG’s U-tubes are a barrier between the primary side coolant and the secondary side of NEK and the environment. Therefore, it is crucial to keep the highest level of integrity of the U-tubes because any leak could potentially mean a release of radioactive material into the atmosphere. This paper describes the purpose and workflow of sludge removal activities in the outage of 2019 in NEK.
Polovicu teritorija Hrvatske karakterizira krš, izniman prirodni resurs koji se ujedno intenzivno gospodarstveno i turistički iskorištava. Daleko od ljudskih očiju, u krškim špiljama i jamama, krije ...se većina zaliha pitke vode, ali i jedna od najvećih prijetnji krškom podzemlju Hrvatske. Speleolozima je jedan od ciljeva zaštita krškog podzemlja koje desetljećima revno istražuju, a nedavno su ukazali na problem koji je bio vidljiv samo njima, a to su divlji deponiji otpada u speleološkim objektima. Trenutno ih Hrvatska broji više od 800, a rasprostiru se diljem našeg krškog područja. Kako bi se bolje razumjeli pojedinačni utjecaji onečišćenih lokacija na stanje okoliša, a time i usmjerili napori prilikom čišćenja speleoloških objekata, izrađena je primarna analiza podataka „Katastra onečišćenih speleoloških objekata“ te je razrađen okolišni kontekst onečišćenja.
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Predstavitev zdravstvene kartice - zobozdravniška ambulanta, čakalnica, nova kartica, zdravnica pregleduje otroka, bolniška sestra in mama, izjava dr. Stanislav Čuber, vodja projekta Kartice zdravstvenega zavarovanja.- Information:- After the Slovenian Institute for Health Insurance Assembly had adopted a decision to test the medical insurance cards in the Municipality of Krško, people already started to prepare for the project. The presentation of the medical card had already taken place in Ljubljana, now the detailed information was presented to reporters in the Posavje region.- Original language summary:
Potem, ko je skupščina Zavoda za zdravstvenega zavarovanja Slovenije junija letos sprejela sklep, da kartico zdravstvenega zavarovanja pilotsko preizkusijo v območni enoti Krško, so se tam že pričeli pripravljati na ta projekt. V Ljubljani so v javnosti kartico pred časom že predstavili, danes pa so podrobnostih o projektu izvedeli še novinarji v Posavju.- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
The paper presents the RELAP5/mod3.3 analysis of natural circulation cooldown with one inactive loop for Nuclear Power Plant Krško (NEK). The aim of the analysis is to determine the limiting cooldown ...rates during operator recovery actions to minimize the effect of flow stagnation in inactive loop. Since this is typical asymmetrical transient, the RELAP5/mod3.3 NEK model with split reactor vessel model was developed (models of the reactor vessel and core were axially divided in two parts) and used for this analysis. The several transients of cooldown, with one inactive loop, for different time after shutdown (different decay heat) were performed. The extreme conservative assumptions were applied for the analyses, i.e. the complete loss of feedwater (FW) and auxiliary feedwater (AF), including turbine driven (TD) AF pump, and the cooldown has started after the SG is completely dry (inactive). The analyses show that the cooldown rate shall be significantly reduced, and, based on the results the procedure ES-0.2 “Natural Circulation Cooldown” was modified.
Sinjsko polje je krško polje i nalazi se u središnjem dijelu rijeke Cetine. Obuhvaća 62 km2, a većim je dijelom meliorirano s povoljnim uvjetima za poljoprivredu. Za analizu suše u ovome radu ...primijenjeni su standarizirani indeks oborine (SPI) i standardizirani indeks protoka (SSI). Razmatrani su meterološki podaci sa stanice Sinj i hidrološki podaci sa postaja Han i Grab iz razdoblja 1981-2010. Pomoću vrijednosti SPI i SSI određena su sušna razdoblja koja su izražena pripadnim trajanjem, intenzitetom i magnitudom.
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