The passive core catcher increases the safety barrier and confinement by preventing radioactive material releases from the primary circuit and the reactor vessel. The passive core catcher provides receiving and subsequent cooling of liquid and hard corium fractions released from the damaged reactor vessel. It is installed in a concrete pit below the reactor vessel. This device comprises four variable parts located (top-to-bottom) in the direction of corium movement from the reactor vessel to the concrete pit basement. The variable parts are the lower plate, vent header, barrel with the filler, and heat exchanger.

The lower plate is designed as a guiding structure, similar to a funnel, in which the corium from damaged reactor vessel flows into the passive core catcher.

The vent header is installed under the lower plate and is designed as a thermal shield protecting the thermal insulating structures. It also protects the reactor vessel from corium outflow installed on the concrete cantilever and in the foundation of lower plate at the stage of corium outflow from the reactor vessel.

This allows to increase operating period of the specially installed thermal shields and to lower the intensity of their damage in the course of radiation heat exchange with corium and aerosol atmosphere in the concrete pit sub-reactor room.

The vent header increases the operating time and reduces the radiation intensity to the thermal shields.

The barrel with filler functions as a corium diluent and thermal absorber for the surrounding peripheral structures (the core catcher). The optimum content of ferric, aluminium oxides, and structural steel in sacrifice material allows to lower volumetric power density in the corium melt, release of gas and radionuclide masses into the confinement, melt temperature.

The evaporation of water causes a period of corium direct cooling through a heat exchanger. The heat exchanger is gravity fed from the inspection well and begins after the corium chemical reaction with the filler and melting of barrel steel structures. Heat exchanger passive make-up and corium direct cooling by the water supplied through concrete cantilever pipelines allows us to avoid human intervention for 24 hours (the moment of reactor vessel damage with corium).