Heating and Retention of Corium
Development and Experiments at Large-Scale Installation for Heating and Retention of Corium
Tech Area / Field
- FIR-NSS/Nuclear Safety and Safeguarding/Fission Reactors
8 Project completed
Senior Project Manager
Tocheny L V
VNIIEF, Russia, N. Novgorod reg., Sarov
- Forschungszentrum Karlsruhe GmbH, Germany, Karlsruhe\nIRSN - Institut de Radioprotection et de Sûreté Nucléaire, France, Fontenay aux Roses\nEDF, France, Paris\nEuropean Commission / Joint Research Center / Institute for Transuranium Elements, Germany, Karlsruhe\nAREVA / Areva NP GmbH, Germany, Erlangen\nCEA / DEN, France, Gif-sur-Yvette Cedex\nGesellschaft für Anlagen und Reaktorsicherheit mbH, Germany, Köln
Project summaryThe main goal of the Project is the experimental and computational verification of the technology for the localization and retention of reactor core melt (corium) at a large-scale installation during a severe accident at a nuclear power plant (NPP).
To experimentally test melt behavior, melt interaction with concrete at a severe accident at NPP it is planned to develop a large-scale installation that is to heat and retain melt of materials of reactor core EPR along with the complex of diagnostic and measuring equipment. To obtain the adequate results of the research of the melt interaction with concrete, the installation should have the following characteristics: melt volume -150 L, melt mass ~1200-1300 kg, melt temperature –~2500-3000С, heat fluxes towards walls and a bottom of a catcher ~100 kw/m2 , melt retention time –1-2 hours. It is planned to manufacture a large-scale catcher with a concrete bottom and walls. The characteristics meet the requirements of a catcher designed for the melt localization and retention. The melt mass is about 200 tons, hence, we have chosen the installation with heating of the mass of ~1200-1300 kg reasoning on the necessity to model a real catcher rather adequately taking into account the scope of experiments.
The peculiarity of the Project is a new technology for the core melt heating and retention, which is similar to the nuclear reactor core melt. The technology has been developed by RFNC-VNIIEF. Special pyrotechnic substances will be used to heat the melt and reach the melt parameters required. To retain the necessary melt temperature in the process of experiment with the melt, some gas(-fired) burners will burn, which use a propane-butane mixture or hydrogen.
An urgent problem is to extend the results of model experiments to the real catchers. The role of a geometrical factor and melt dynamics along with the distribution of the components of the mixture of the melt can be analyzed by means of computational modeling of the processes of heat- and- mass transfer along with physical and chemical conversions in the catcher. Theoretical analysis will be based on the following scenario of accident development.
The reactor core melt at a given temperature pours entirely into the catcher. The homogenous (but stratified) or non-homogenous (in a random way) distribution of the metallic and oxidation components of the melt will be considered as the primary distribution of the melt material.
Then, as a result of volumetric energy release due to radioactive fuel decay, endo- and exothermal chemical reactions, melting and solution of concrete along with heat removal through the walls of the catcher, some temperature distribution sets in the melt. At the same time, melt components concentrations distribution takes place due to the processes of diffusion and convective mixing.
Within the framework of the Project it is necessary to conduct a lot of design-theoretical research work along with the performance of complex and expensive experimental research. RFNC-VNIIEF disposes high-skilled specialists in the field of the design-theoretical and computer simulation of fissile materials multi-component melts flows. RFNC-VNIIEF specialists have developed: the physical and mathematical and computer models of heat and mass transfer in various media, melts included; the models of melt interaction with different materials; the data base on the thermal and physical properties of melts and materials; 1D,2D, 3D computer programs to calculate heat and mass transfer for multi-component systems in complex geometries, thermal hydraulics taking into account phase transformations and chemical reactions.
Within the framework of the Project it is planned to develop the large-scale installation for core melt heating and retention, which is similar to the nuclear reactor core melt, with characteristics described above. It is planned to conduct experiments on the interaction of the melt with concrete at the large-scale experimental installation. It is planned to develop, perform calibration methodical tests and check measuring equipment complex capacity for work for diagnostics of melt temperatures, thermal fields in concrete. It is planned to use metallographic techniques and electron microscopy for analyzing an ingot of a sow melt. It is planned to develop computational models for calculating thermal fields in melt and concrete, melt parameters, interaction of melt with concrete.
The main specific feature of the suggested Projects in comparison with other works in this field is the larger mass of the melt (~1200-1300 kg) and pyrotechnic technology of melt heating and retention.
Reactor core melt materials similar to reactor core melt (EPR) are planned to contain (mass. %): 40-50% ZrO2; 50-60% Fe.
The results achieved during the Project implementation can be used to develop promising NPP safety systems for severe accidents conditions.
During the Project implementation, 84 developers of nuclear weapon will be partly involved into the activity unconnected with military programs.
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