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[en] The present report is the first Technical Report within the research project ''Validation and interpretation of selected models and of the coupling of the system codes ATHLET-CD and COCOSYS'', funded by the German Federal Ministry for Economic Affairs and Energy (BMWi 1501465) and projected at the Reactor Simulation and Safety Group, Chair of Energy Systems and Energy Economics (LEE) at the Ruhr-Universitaet Bochum (RUB). This report deals with the simulation of spray phenomena with the containment code system COCOSYS, which is developed by the German Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH. First, post-test calculations of the OECD THAI-2 tests HD-30 and HD-31 are presented. The simulation results are compared to experimental values and thereby assessed. The analysis focuses an the assessment of the simultaneous use of the COCOSYS models IVO (spray model) and FRONT (combustion model) as well as a spray entrainment model developed at RUB regarding the simulation of the phenomena related to the interaction of spray and combustion processes. The simulation results show the necessity to consider the induced turbulences. The simulation of these turbulences is performed by modifying the FRONT input parameters leading to an improvement of the simulation results. The consideration of the entrainment positively influences the simulated flow pattern. Subsequently, the simulation of the entrainment of interacting sprays, as occurring in containment spray systems, is considered. The entrainment of interacting sprays is influenced by droplet collisions and changes of the drag between the droplets and the atmosphere. For the simulation an entrainment factor, which has to be determined externally, is implemented into COCOSYS. Exemplary simulations of the OECD SETH-2 ST3 tests show, that in general the use of entrainment factors enables the calculation of alternated gas distributions.
[en] The technical report includes a search and comparison of Cumulative Energy Demand (CED) and greenhouse gas emissions from the production, use and disposal of boilers in a power range from 50 kW to 500 kW. The basis for the comparison of the data is a comparison of assumptions and system boundaries of different life cycle assessment databases used.
[de]Der Fachbericht umfasst eine Recherche und Gegenueberstellung des Kumulierten Energieaufwands (KEA) und der Treibhausgas-Emissionen der Herstellung, Nutzung und Entsorgung von Heizkesseln in einem Leistungsbereich von 50 kW bis 500 kW. Grundlage fuer die Gegenueberstellung der Daten bildet ein Vergleich von Annahmen und Systemgrenzen unterschiedlicher verwendeter Oekobilanz-Datenbanken.
[en] This report provides an overview of the current data basis by comparing and thus harmonizing the existing and available information about the Fukushima-Daiichi accident. This task is carried out at the Chair for Energy Systems and Energy Economics (LEE) at Ruhr-Universitaet Bochum (RUB) in the frame of the research project SUBA (Simulation des Unfalls in Fukushima-Daiichi zur Bewertung des Stoerfallanalysecodes ATHLET-CD). SUBA is part of the BMBF sponsored collaborative project WASA-BOSS. Preparing a comprehensive and accurate data basis is necessarily required for future research activities associated with the Fukushima-Daiichi accident, particularly for simulations with severe accident analysis codes. At first, the designs of the boiling water reactors (BWR) of the affected units 1-3 of Fukushima-Daiichi are described in detail. Technical data are provided by the operator TEPCO. Lacking data can also be taken from generic General Electric (GE) BWR 3/4 plants with Mark-I Containments. First an overview of available data regarding the Fukushima-Daiichi accident is given, in which the information of different institutions are compared and harmonized. Main design data for the boiling water reactor (BWR) are taken from the plant operator TEPCO. The current knowledge regarding the description of the accident is provided by web portals, ran by TEPCO. Focusing the analyses of plant behavior during the accident, important boundary conditions are determined. However, according to current knowledge the degree of possible core degradation regarding the damaged plant site is highly uncertain. To evaluate and to analyze the system code ATHLET-CD as well as to assess the applicability for plant simulations, sequences of the accident in Unit 3 are simulated using the code versions ATHLED-CD Mod. 3.0A as well as Mod. 3.0B. An input deck describing Unit 3 is modelled on the basis of the harmonized data. To evaluate the results with respect to the quality, a code-to-code comparison with MELCOR 1.8.6 Rev. 3704 is discussed. Overall the thermohydraulic behavior is represented in a good accordance to the measured data. Further the core degradation phenomena leading to RPV failure are simulated in a reasonable way. By analyzing the results of the plant simulations, the need of extension of the models regarding melt relocation into the lower plenum is indicated. As a contribution a model for melt relocation through the lower core structures is developed. Regarding the TMI-2 accident the application of this model shows plausible results for melt relocation. Furthermore the applicability of this model for plant calculations is shown by simulation the Fukushima-Daiichi accident.
[en] The present report is the 2nd Technical Report of the research project ''Analysis and Evaluation of the ASTEC model basis'' funded by the Federal Ministry for Economic Affairs and Energy (BMWi 1501433) and conducted at the Reactor Simulation and Safety Group, Chair of Energy Systems and Energy Economics (LEE) at Ruhr-Universitaet Bochum. Within this report, the quality of a nuclear power plant simulation with ASTEC is investigated. Different parameters are varied to analyze the simulation stability within the dataset, which describes a generic German Konvoi power plant and is deposit in the program set of ASTEC. Firstly, plant specifications in the data set are checked for plausibility. In addition, the compliance of the data set with the nodalization rules is verified. After that, the stationary phase, in which no accident is calculated, is analyzed and parametric studies are performed in the transient phase, focusing on the primary and secondary circuit as well as on the containment behavior. The performed calculations focusing the primary and secondary circuit indicate a high dependency of the simulation results on the user's input in the data set. There are significant deviations between each simulations results, for example in the different calculated point of time of the reactor pressure vessel failure. Already changes in the stationary phase cause a significantly earlier reactor pressure vessel failure compared to the simulation with the original data. Beyond that, the location of the leakage of the reactor pressure vessel lower head varied and therefore cannot be clearly determined, although there have been no changes by the user on the accident course. A reliable indication of the plant behavior under severe accident conditions is therefore difficult using ASTEC. The results of the parametric studies within the Containment show the same significant influence of certain parameter changes on the simulation results. By using the Generic-Containment-Benchmark nodalization for the containment simulation in the original data set instead of the given one, the time interval for the failure of the reactor pressure vessel decreases strongly. Partly, this effect can be lead back on a stronger heat release in the reactor pressure vessel, which is caused by a higher zircon steam reaction rate in the Genaric-Containment simulation. Moreover, a significant influence on the formation of a flammable mixture in the Containment is recognized by the implementation of the recombiners and the applied model. A preliminary comparison between two Genaric-Containment simulations using COCOSYS and ASTEC shows good matching results.
[en] A new method for rapid and reliable modelling of research reactors for deterministic safety analysis is presented. A rule-based software system is being developed to support the modelling process in ATHLET for selected research reactor types in the light of limited available data. The fundamental elements of the input deck are generated automatically by few input data necessary.
[en] In this study, the economic efficiency of a concept for underground pumped storage (UPSW) in hard coal mining plants is investigated. The aim is to evaluate an investment decision for a UPSW. Two technical design variants are considered: Variant 1 (600 m drop height / 461,814 m3 storage volume) and variant 2 (1000 m drop height / 355,982 m3 storage volume). Variant 2 differs fundamentally from variant 1 in that an active line system is already available at an altitude of 1000 m below NHN as an underground storage facility. In contrast, it is assumed that in the case of variant 1, a complete underground storage system must be excavated at a depth of 600 m. The underground storage system must be installed at a depth of 600 m below the surface. The framework data are selected on the basis of the Prosper Haniel hard coal mine of RAG. In addition, variant 2 is equipped with two ternary machine sets, whereas variant 1 has only one pump turbine. A deterministic techno-economic model of the UPSW based on Matlab has been developed for the performance of the economic analysis, which simulates the participation of the UPSW in the spot and secondary control energy market. The technical and economic framework conditions for the model originate mainly from the project partner Institute of Hydraulic Engineering and Water Management at the University of Duisburg-Essen as well as from electricity price forecasts prepared at the Chair of Energy Systems and Energy Economics. The calculation methodology used in this study corresponds to that of the dynamic investment calculation. For the consideration of data uncertainties a parameter variation based on a best- and worst-case scenario analysis is applied. The results of the study show that under the boundary conditions described here, a UPSW with sole participation in the day-ahead market does not generate a profitable revenue situation. In this respect, the results are in line with the current statements of PSW operators. For the economic operation of a UPSW it is therefore indispensable to offer more profitable system services such as the provision of control energy in addition to conventional electricity marketing on the spot market. In this study, the revenues from participation in the secondary balancing energy and spot market are also determined. Due to technical restrictions, participation in the secondary balancing energy market is only possible for both variants in connection with a power plant network. Obliging contracts that cannot be fulfilled due to a lack of storage capacity are taken over from the pool in the modeling. Although no profitable revenue situation can be achieved with simultaneous participation in the balancing energy and spot market, both variants reduce the financial losses compared to sole participation in the day-ahead market. Due to the plans of RAG regarding the future mine water retention level (700 m below NHN), variant 1 is the preferred plant concept from the point of view of the project group. Based on the findings of this study, the minimum storage volume for Variant 1 is approximately 600,000 m3 to meet the pooling requirement. With regard to the mechanical design, it is advisable to consider several sets of machines for further investigations, such as variant 1+ (two Francis pump turbines), as this is advantageous in terms of flexibility and controllability when participating in the electricity market. Consequently, further investigations are recommendable and very promising. On the basis of the results obtained in this paper, an investment in a UPSW cannot be presented economically under current market conditions. However, this would also apply to new conventional pumped storage plants. It should be noted that almost all the pumped storage plants currently available on the market have been written off. They therefore offer electricity at variable costs and are therefore cheaper than new pumped storage plants that have not been depreciated. This economic efficiency calculation involves major uncertainties, as the evaluation of new systems in early development phases can only be carried out on the basis of inadequate cost data. In addition, electricity economic, political and social unpredictability (e.g. the effects of changes to the Renewable Energy Sources Act (EEG) on electricity prices) represent a high uncertainty potential when considering these long-term investments during the energy turnaround.
[de]In der vorliegenden Studie wird die Wirtschaftlichkeit eines Konzeptes fuer Untertage-Pumpspeicherwerke (UPSW) in Anlagen des Steinkohlebergbaus untersucht. Ziel ist es, eine Investitionsentscheidung fuer ein UPSW zu bewerten. Dabei werden zwei technische Auslegungsvarianten betrachtet: Variante 1 (600 m Fallhoehe / 461.814 m3 Speichervolumen) und Variante 2 (1000 m Fallhoehe/ 355.982 m3 Speichervolumen). Variante 2 unterscheidet sich von Variante 1 grundsaetzlich darin, dass bereits ein aktives Streckensystem auf einer Hoehe von 1000 m unter NHN als Untertagespeicher zur Verfuegung steht. Im Gegensatz dazu wird angenommen, dass im Fall von Variante 1 ein komplettes untertaegiges Speichersystem in einer Tiefe von 600 m aufgefahren werden muss. Die Rahmendaten werden in Anlehnung an das Steinkohlebergwerk Prosper Haniel der RAG gewaehlt. Darueber hinaus ist Variante 2 mit zwei ternaeren Maschinensaetzen ausgestattet, wohingegen Variante 1 nur ueber eine Pumpturbine verfuegt. Fuer die Durchfuehrung der Wirtschaftlichkeitsanalyse ist ein auf Matlab basierendes deterministisches techno-oekonomisches Modell des UPSW entwickelt worden, das die Teilnahme des UPSW am Spot- und Sekundaerregelenergiemarkt simuliert. Die technischen und oekonomischen Rahmenbedingungen fuer das Modell stammen groesstenteils vom Projektpartner Institut fuer Wasserbau und Wasserwirtschaft der Universitaet Duisburg-Essen sowie am Lehrstuhl Energiesysteme und Energiewirtschaft erstellten Strompreisprognosen. Die in dieser Studie eingesetzte Berechnungsmethodik entspricht der Methodik der dynamischen Investitionsrechnung. Zur Beruecksichtigung von Datenunsicherheiten wird eine Parametervariation anhand einer Best- und Worst-Case Szenario Analyse angewendet. Die Untersuchungsergebnisse ergeben, dass sich unter den hier getroffenen Randbedingungen bei einem UPSW mit alleiniger Teilnahme am Day-Ahead Markt keine gewinnbringende Erloessituation einstellt. Die Ergebnisse decken sich dahingehend mit den aktuellen Aussagen von PSW-Betreibern. Zur wirtschaftlichen Betriebsweise eines UPSW ist es daher unabdingbar, neben der konventionellen Stromvermarktung am Spotmarkt, ebenfalls ertragreichere Systemdienstleistungen wie etwa die Bereitstellung von Regelenergie anzubieten. In der vorliegenden Studie werden die Erloese aus der Teilnahme am Sekundaerregelenergie- und Spot-Markt ebenfalls ermittelt. Aufgrund technischer Restriktionen ist die Teilnahme am Sekundaerregelenergiemarkt fuer beide Varianten jeweils ausschliesslich in Verbindung mit einem Kraftwerksverbund moeglich. Verpflichtende Kontrakte, die mangels Speicherkapazitaeten nicht erfuellt werden koennen, werden in der Modellierung vom Pool uebernommen. Obwohl keine gewinnbringende Erloessituation bei gleichzeitiger Teilnahme an Regelenergie- und Spotmarkt erreichbar ist, verringern beide Varianten im Vergleich zur alleinigen Teilnahme am Day-Ahead Markt, die finanziellen Verluste. Auf Grund der Planungen der RAG bezueglich des zukuenftiges Grubenwasserhaltungsniveaus (700 m unter NHN), handelt es sich bei Variante 1 aus Sicht des Projektverbundes um das bevorzugte Anlagenkonzept. Aus Erkenntnissen dieser Studie ergeben sich als minimales Speichervolumen fuer Variante 1 circa 600.000 m3 um die Poolungsbedingung zu erfuellen. Im Hinblick auf die maschinentechnische Ausfuehrung, ist fuer weiterfuehrende Untersuchungen die Betrachtung von mehreren Maschinensaetzen, wie etwa bei Variante 1+ (zwei Francis-Pumpturbinen), zu empfehlen, da diese bei einer Strommarktteilnahme vorteilhaft in Bezug auf Flexibilitaet und Regelbarkeit ist. Demzufolge sind weitere Untersuchungen empfehlenswert und durchaus vielversprechend. Auf Grund der in dieser Arbeit ermittelten Resultate kann eine Investition in ein UPSW bei derzeitigen Marktbedingungen nicht wirtschaftlich dargestellt werden. Dies wuerde aber auch fuer neue konventionelle Pumpspeicherwerke gelten. Zu beruecksichtigen ist, dass die derzeit am Markt verfuegbaren Pumpspeicherwerke fast alle abgeschrieben sind. Sie bieten deshalb die Elektrizitaet zu variablen Kosten an und sind damit billiger als nicht abgeschriebene neue Pumpspeicherwerke. Diese Wirtschaftlichkeitsberechnung beinhaltet grosse Unsicherheiten, da die Bewertung neuer Systeme in fruehen Entwicklungsphasen nur auf einer unzureichenden Kostendatenbasis erfolgen kann. Daneben stellen elektrizitaetswirtschaftliche, politische sowie gesellschaftliche Unvorhersehbarkeiten (z. B. die Auswirkungen von Aenderungen an dem Erneuerbare-Energien-Gesetz (EEG) auf die Strompreisgestaltung) in Zeiten der Energiewende ein hohes Unsicherheitspotential bei der Betrachtung dieser langfristigen Investitionen dar.
[en] Ruhr-Universitaet Bochum performed in a German funded project validation of in-vessel and containment models of the integral code ASTEC V2, jointly developed by IRSN (France) and GRS (Germany). In this paper selected results of this validation are presented. In the in-vessel part, the main point of interest was the validation of the code capability concerning cladding oxidation and hydrogen generation. The ASTEC calculations of QUENCH experiments QUENCH-03 and QUENCH-11 show satisfactory results, despite of some necessary adjustments in the input deck. Furthermore, the oxidation models based on the Cathcart–Pawel and Urbanic–Heidrick correlations are not suitable for higher temperatures while the ASTEC model BEST-FIT based on the Prater–Courtright approach at high temperature gives reliable enough results. One part of the containment model validation was the assessment of three hydrogen combustion models of ASTEC against the experiment BMC Ix9. The simulation results of these models differ from each other and therefore the quality of the simulations depends on the characteristic of each model. Accordingly, the CPA FRONT model, corresponding to the simplest necessary input parameters, provides the best agreement to the experimental data
[en] The present report is the final report in frame of the research project ''Validation and interpretation of selected models and of the coupling of the system codes ATHLET-CD and COCOSYS (VAMKoS)'', which is funded by the Federal Ministry of Economic Affairs and Energy (BMWi 1501465) and projected in the Reactor Simulation and Safety Group at the Chair of Energy Systems and Energy Economics at Ruhr-Universitaet Bochum. Objective of the project is the analysis and validation of selected modules for the simulation of accident relevant in- and ex-vessel phenomena of the accident analysis codes COCOSYS (Containment Code System) and ATHLET-CD (Analysis of Thermal-hydraulics of Leaks and Transients - Core Degradation). These codes are developed by Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH for the simulation of all essential processes and conditions during the operation and in the frame of severe accidents in light water reactors. Topics of the investigated working points are occurring phenomena during spray system operation, wall-boiling phenomena, occurring phenomena during core degradation and the plant application of the considered severe accident management codes. Selected experiments are simulated and the results are compared to the experimental data and are assessed. Furthermore, performed model development is documented. In the frame of plant application postulated severe accident scenarios are simulated. A brief overview of participation in the TH27 code benchmark is also given. In the frame of investigation regarding spray system operation with COCOSYS it becomes obvious that the dynamic influence of the spray system neither on the gas atmosphere nor on the propagating flame front is simulated sufficiently. In the simulation of the considered tests with ATHLET-CD the simulation results of wallboiling phenome can be improved by consideration of the critical heat flux density. Investigations on core degradation phenomena show an improvement potential regarding the oxidation model for melt and cladding inner side oxidation due to steam after bursting of the cladding. In the frame of simulation of two postulated severe accident scenarios and comparison simulations with MELCOR the significant higher user-friendliness of ATHLET-CD becomes obvious. On the other hand, development potential regarding relocation of degraded (not molten) core material becomes also obvious for ATHLET-CD.
[en] In case of a postulated accident in a nuclear facility air can be in contact with the fuel rods mainly in the following three cases : 1. loss of coolant accident (late phase after reactor pressure vessel failure or in mid loop operation), 2. spent fuel pool accident or 3. spent fuel storage cask break. In these cases the two main components of the air - oxygen and nitrogen - can react with the cladding material zirconium to zirconia and zircon nitride. Both reactions are exothermal, but the heat by the reaction with oxygen is nearly three times higher than the heat from the nitride formation. The zirconia formation will be first by water or steam, because of the affinity of metals like zirconium to react with oxygen and this process was estimated as the leading process and is mainly understood for the current cladding material Zircaloy-4 right now. Only in cases of local or global oxygen starvation the nitride formation takes place. Because of the impact on the cladding material structure and its further behaviour in case of a severe accident, the consideration of the nitrogen is necessary to calculate the physical behaviour of the core correctly in severe accident system codes like ATHLET-CD . Therefore the knowledge of the physical process of the nitride formation has to be improved. Detailed analyses of the nitride formation show, that there are two main phenomena which have to be considered. On the one hand the reaction of pure nitrogen with zirconium is weak and mainly based on impurities of the metal in a binary system. On the other hand the nitride formation increases in case of a ternary system of Zr-O-N. In this case the existing ZrO2 layer on the metal has a dominant influence, because the nitrogen reacts with defects in the ZrO2-x layer or under oxygen starvation conditions at the phase boundary between Zr and ZrO2 . (orig.)
[en] An empirical correlation for the estimation of the droplet entrainment from boiling water pools is under development. The correlation is validated on the basis of experiments, taken from test facilities of different scale, which investigate the effect of several boundary conditions on the droplet entrainment. The calculated values for the droplet entrainment are in good agreement with the experimental data, indicating that relevant influences are considered in the developed correlation with an appropriate quantity. Nevertheless, the application of the correlation on scenarios with flashing pools and non-boiling pools with gas flows through the pool surface have to be investigated in the ongoing validation process. Furthermore, other experiments are needed, which consider pools containing surface-active substances to depict the influence of surface tension on the droplet entrainment.