F. A. Akopov

Behavior of plasma-sprayed zirconium dioxide ceramic under the thermochemical effect of components of the reactor core melt

ConclusionThe investigations have shown that, even though the zirconium dioxide layer sprayed on the metal interacts considerably with molten oxides of other metals (Fe, Ti, Ni), forming a porous loose structure, the saturation zone even with air cooling (not to mention water cooling) of the cold surface does not reach the metal, i.e., a considerable part of the zirconium dioxide remains integral and capable of transmitting large heat fluxes with no substantial damage. That attests to a promising outlook for the construction of a protection refractory layer of both an external and in-reactor core catcher by plasma-spraying ceramic onto a metal substrate.

Optimization of the Materials Composition in External Core Catchers for Nuclear Reactors

Existing schemes of core melt retention apparatus for water-cooled water-moderated nuclear reactors are analyzed. In-shaft variants of melt catchers at nuclear power plants with VVÉR-1000 reactors are proposed. It is shown that TiO2- and Nd2O3-based materials increase the operational reliability of the retention apparatus by modifying the processes occurring in the melt and by preserving the integrity of refractory coatings consisting of zirconium dioxide. TiO2-based material not only decreases the effect of the melt on the refractory but also confines some fission products in geologically similar matrices which are synthesized as the melt cools.

Thermal stability of the lining in a zirconium dioxide trap in a major accident

Test results are presented on the thermal stabilities of specimens and full-scale components (bricks) made of a new ceramic based on zirconium dioxide. The thermal resistance has been improved by using a certain ratio of coarse-grained and fine-grained fractions. The resistance has been determined by the use of single or repeated heating and cooling cycles. The data give a forecast of the resistance when these components are used in the coating of a trap subject to the action of molten core material in major nuclear power station accidents.

Interaction of Dioxyzirconium Ceramics with the Sacrificial Material of the European Reactor Trap

The present paper discusses the complications that can arise in using in the core melt trap of the European nuclear reactor being designed a sacrificial material of 40% FeOx–60% SiO2 composition. The investigation of the interaction of zirconium dioxide ceramics with the sacrificial material has permitted the conclusion that at a local baring of the refractory layer its destruction can occur. The addition of neodymium oxide to the melts lowers erosion and excludes regeneration of the ceramics structure.

Formation of mineral-like matrices for immobilization of fuel and fission products during a serious accident in a nuclear reactor

The results are discussed of experimental studies which confirm the formation of mineral-like matrices capable of incorporating UO2 and its fission products into their structure on the basis of isomorphic substitution during crystallization of core melt with based on titanium dioxide sacrificial material.

Some Problems on the Thermal State of the External Corium Catcher and on Selecting Its Optimum Structure

The thermal state of a molten corium and of the walls of the storage chamber of an EPR external corium catcher has been analyzed. It is shown that the strong nonuniformity of distribution of the heat‐flux density over the surface of the storage chamber of the catcher makes it impossible to coordinate with the required degree of accuracy the processes of melting of a taphole and the processes of dilution of the oxide component of the melt (required to ensure the inverse stratification of the corium) with sacrificial concrete. Additional technical measures are required to ensure the effectiveness of the catcher.

Estimate of the Thermal Regimes of a Flat Zirconium Dioxide Ceramic Trap during a Serious Reactor Accident

Physical and mathematical models are constructed and a medium-term forecast is made of the thermal state of a flat trap consisting of zirconium dioxide ceramic for a serious accident in a nuclear reactor.It is shown in the radiation-thermal conductivity approximation that radiation transfer strongly influences the dynamics of thermal processes developing in the trap.It is established that the time during which the temperature of the cold boundaries of the bottom and roof of the trap reaches the critical value is much shorter than the values predicted in models which neglect the role of radiation.The influence of partial permeation of melted iron oxides into the trap bottom on the quasistationary state is investigated.

High-temperature zirconium-dioxide binders for the Masonry of the outer trap of a reactor

Investigations were performed for the purpose of selecting the compositions of zirconium dioxide binding materials (mortars) with two types of binders: barium monoaluminate and zirconium dioxide binding suspension. The foundations of a technology for obtaining these materials and their applications were developed and the density, porosity, contraction, and behavior in contact with steel and iron oxide melts were described. The mortars developed were recommended for use in a refractory shielding of the outer trap based on zirconium dioxide heat-resisting materials, 2 figures, 1 table, 7 references.

Use of Refractory Coatings in Systems for Melt Containment in a Serious Accident at a Nuclear Power Plant with a VVÉR Reactor

A computational analysis is performed of the use of zirconium dioxide ceramic in melt containment systems with relatively thin heat-conducting structures. The results of an investigation of the physicochemical processes for the interaction of melt with zirconium dioxide ceramic are presented. It is shown that the use of zirconium dioxide ceramic together with a passive water source gives the required melt cooling parameters for 3 to 24 h depending on the cooling regime. 4 figures, 9 references.