Abstract
The GRS program package AC2 with its codes ATHLET/ATHLET-CD and COCOSYS aims for the reliable computational simulation of significant phenomena occurring during normal operation, design basis accidents, and severe accidents in the cooling circuit and containment of a nuclear power plant. To keep the modelling at the state-of-the-art, continuous development and validation is required. This is accomplished through participation in several national and international experimental research programs, where AC2 or one of its codes are assessed against both separate effect tests and integral tests. This paper exemplifies the status of validation and application of COCOSYS by means of calculations of iodine chemistry and molten corium/concrete interaction after reactor pressure vessel rupture. Further, calculations using the external 3D module CoPool coupled to COCOSYS on thermal stratification in large water pools are discussed. The examples given demonstrate the progress of the COCOSYS development and the capability to simulate phenomena in the containment during incidents and accidents with good results. Future applications comprise the entire spectrum of incidents and accidents for Generation III/III+ systems with just one program package.
Kurzfassung
Das Programmpacket AC2 der GRS mit den Einzelprogrammen ATHLET/ATHLET-CD und COCOSYS strebt die zuverlässige Computersimulation wesentlicher Phänomene, die während Normalbetrieb, Auslegungsstörfällen und Ereignissen mit Kernzerstörung (Unfälle) in Kühlkreislauf und Containment eines Kernkraftwerks auftreten können, an. Um die Modellqualität auf dem Stand von Wissenschaft und Technik zu halten, ist eine kontinuierliche qualitätsgesicherte Weiterentwicklung und Validierung notwendig. Dies wird durch eine Beteiligung an einer Vielzahl von nationalen und internationalen Experimentalprogrammen sichergestellt. Dabei werden AC2 oder eines seiner Programme anhand eines Vergleichs der Rechnungsergebnisse mit den entsprechenden experimentellen Daten sowohl von Einzeleffekt- als auch von Integralexperimenten bewertet. Im vorliegenden Beitrag wird der Stand der Validierung von COCOSYS beispielhaft für die Modellierung der Iodchemie und der Schmelze-Beton-Wechselwirkung dargestellt. Darüber hinaus werden Ergebnisse der Anwendung des an COCOSYS gekoppelten externen 3D Moduls CoPool für die thermische Schichtung in großen Wasservorlagen im Containment dargestellt. Die aufgeführten Beispiele zeigen den Entwicklungsfortschritt sowie die Fähigkeit von COCOSYS auf, Phänomene während Stör- und Unfällen mit guter Genauigkeit abzubilden. Zukünftige Anwendungen zielen darauf ab mit nur einem Programmpaket das gesamte Unfallspektrum für Anlagen der Generation III/III+ abzudecken.
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