Untersuchungen zum Wechselwirkungsverhalten keramischer Schutzschichten und Betonen mit Hochtemperatur-Metallschmelzen
In consideration of economic interests as well as ecological aspects secured, world-wide power supply belongs to the largest challenges of our time. Regarding the CO2 global discussed problem (greenhouse effect), nuclear energy is continuously playing a major decisive role in the range of electrical energy production in future. A set of solutions is suggested and examined globally concerning security improvements of nuclear energy supply. Aim is to prevent the release of fission products under any circumstance. Furthermore, it is essential to limit consequences to the plant itself in case of hypothetical incidents. Exemplified at the European Pressurized Water Reactor (EPR) the requirements of controlling core melt-accidents are pointed out and a solution for melt retention (core- catcher) is described. Process knowledge of postulated core melt accidents is enhanced by understanding the behaviour of structural materials in combination with a core melt. Therefore, suitable measures to ensure the integrity of reactor containment can be developed. Explicitly the requirements of protective and sacrificial materials are identified. The stability of various refractory materials all based on zirconia (ZrO2) in contact with metallic phase of core melt has been investigated in large-scale experiments. These tests were characterised by high temperature metallic melts with melt temperature of about 2000°C and melt masses of up to 6 mg. They proved that zirconia could fulfil the task of a protective material against the metallic melt impact. Erosion effects have not been detected. The early sintering of the zirconia ramming mass led to high surface stability which could effectively prevent infiltration of the metallic melt into the zirconia ramming mass. Anyhow, loose ramming mass was still found below the stable layer. This is advantageous with respect to the prevention of crack formation due to thermal loads. Experiments investigating the behaviour of zirconia protective materials against high-temperature metallic melts showed a good long-term stability for the investigated zirconia compounds. Furthermore the MCCI (Molten Corium Concrete Interaction) behaviour of various structural and sacrificial concretes was characterised in experiments with high-temperature metal melts. The experimental goals are related to investigations of interactions between concrete and core melt in two-dimensional geometries, particularly in terms of ratio of horizontal and vertical erosion. In three transient experiments (without after-heating of melt) with high-temperature-melts six different types of concretes were investigated. These six tests were carried out with melt masses by 1 mg each and temperatures of about 2.000°C. In all attempts the rate of melt progression in the wall increases super proportional in comparison to the erosion at the bottom. The sacrificial concrete rich in iron oxide showed the highest erosion. The sacrificial concretes with portland cement showed a higher erosion than the sacrificial concretes with alumina cement. Due to largest integral erosion, iron oxide-rich concrete appears as sacrificial concrete most qualified. The results can be used both for the enhancement and validation of appropriate computer models and beyond that to meet a selection of suitable accident controlling measures. On the one hand the represented results are usable for answering questions to existing plants, on the other hand likewise also for future plants.
info:eu-repo/classification/ddc/620, Zirkoniumoxidkeramik, Beton, Hochtemperaturfestigkeit, Langzeitverhalten, Metallschmelze, Schutzschicht, Opferschicht, Kernschmelzen, Ingenieurwissenschaften, Leichtwasserreaktor, EPR, Corecatcher, chemische Wechselwirkung, Kernrückhaltung
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