Evolution of reactor plants with VVER-type reactors and basic principles of safety systems and normal systems application in accidents with core damage

The principal negative effect of beyond-design accidents, accidents of core damage included, is confined to a possibility of source term to the environment. The amount and nature of this process is determined by numerous parameters, including safety barriers resistance to radionuclides release. These barriers (natural structural boundaries) are: fuel matrix, fuel cladding, reactor vessel and primary circuit, concrete pit, reactor plant equipment compartments. On the basis of comparing safety systems for different reactor plants equipped with VVER reactors the article covers the main principles of using the former in accidents of core collapse as applied for the peculiarities of each stage of destruction. Methods of suppression and localization of beyond-design accidents taking into account the safety systems design features. 4 refs., 14 tabs