About the Nature of the course of BN Reactor beyond Design Accidents under post-accident Core Materials Relocation
In the safety analysis of BN reactor accepted division of beyond design accident into four stages: initial, transitional, post-accident material relocation and post-accident heat removal. Formed in transitional stage as a result of the molten cladding relocation and solidification initial steel blockages of channels for a while impede the flow down of liquid fuel and form a solid foundation for the pool. To move the fuel in channels it is required at first a melting of blockages. After reactor shutdown it is possible in the case of insufficient heat to the surrounding fuel assemblies. Under melt-through of blockage the melt will be flow into the channels between the yet solid parts of the fuel rods at some length, it hardens there and again forms a layer of blockages. As a result, the process of heat-generating mass moving will be not smooth, and the intermittent nature and will consist of repeating phases: melt-through of blockages layer, leaking of melt at some length and solidification, the melting of the next layer, etc.