Catcher for the Molten Core
Design of a Catcher for the Molten Reactor Core at an NPP on the Basis of Zirconia Concrete
Tech Area / Field
- FIR-MAT/Materials and Materials Conversion/Fission Reactors
3 Approved without Funding
Joint Institute for High Temperatures RAS, Russia, Moscow
- OGBET, Russia, Moscow\nOKB Gidropress, Russia, Moscow reg., Podolsk\nNuclear Safety Institute, Russia, Moscow\nResearch Institute of Technology, Russia, Leningrad reg., Sosnovy Bor
- Forschungszentrum Karlsruhe Technik und Umwelt, Germany, Karlsruhe
Project summaryIn the project P064-94 "Design of a catcher for the molten reactor core at the NPP on the basis of arconia concrete" (01.06.94-31.05.97, 528400 $) new protective material has been proposed and scientific fundamentals of the such catcher creation has been developed. These project executors are the same: HEDRC, INS, EDB "Gidropress", SRIT and INR FZK. A this working continuation is proposed in new project offered below.
The task of such catcher is to gather the melt, which may appear during the severe accident development, and to spread it over a large surface (more than 50-100 m2) and to provide heat release from the melt (by flooding of water).
The catcher normal operation is determined by the protective layer material resistance to thermal shock when the melt enters and by the further prolonged resistance to the influence of a chemically active corium melts.
An original solution of this task was offer in the ISTC project P064-94. This solution is based on the creation of special thermal shock resistant zirconia concrete of hydraulic hardening (ZHC). It is important that the use of a concrete technology increases the adaptability of catcher manufacture.
A given concrete is a polyfraction set of grains (0.01-5 mm) of mono- and polycrystalline ceramics of zirconia bound in monolith by crystallohydrates of barium monoaluminate (BaAl2O4) - which is the hydraulic binder. Water content in concrete is about 3 % mas. (~13 % vol.). When the temperature is higher than 1000-1300 K, concrete is a two-phase porous (P»20-25 %) grain ceramics with 94 % mas. zirconia stabilized by ittria.
The task of a new project will be:
1) development of cheaper variants of zirconia concrete with the account of its operating peculiarities consisting of a catcher;
2) development of an experiment.al-industrial technology of ZHC use;
3) investigation of a phase diagram of the main oxide components of molten corium UO2+ZrO2+FeOj,
4) investigation of molten zirconium interaction - the most corrosive ingredient of core melt - with its own and other oxides; investigation of melt jet influence on zirconia surface;
5) influence (directed correction) on corium composition in the catcher for guarantee of its separation into lighter oxide melt (placed from above) and more heave metallic melt (placed from below). That separation will provide essential increase of the resistance of zirconia material of catcher protective covering to core melt influence. It'll require installation of a precatcher, development of optimal methods of introduction of chemical additives into a melt and way of freezing of spread melt periphery;
6) on the basis of fulfillment experimental investigations development and testing of core melt chemical interaction with ZHC for it following introduction into catcher work model.
The Technical Approach
Technical approach and methodology are determinated by particular tasks of the investigations being planned, and they are usually known and traditional. The peculiarities are determined by the combination of material studies, thermophysical approaches, experimental methods, methods of mathematical modeling, peculiarities of comparatively new objects of study (barium monoaluminate as a binder, zirconia, the range of rather high temperatures for oxidizing atmosphere and etc.)
The Anticipated Results
The project fulfillment will allow to improve the designed project of a molten corium catcher providing its stationary retention with decrease the cost of catcher production and develop experimental - industrial technology of the works with ZHC.
Potential Role of Foreign Collaborators
Investigations of melt jet influence on zirconia surface, participation in discussion of project fulfillment and in the development of the catcher variants for NPP several types.
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