Assessment of the Importance of Different Factors for the Delay in Reaching a Serious RBMK Core State with Complete Loss of Power to the Power Unit

The computational results obtained for different scenarios of an accident caused by the loss of all power to a power-generating unit with RBMK and no possibility of restoring power from backup sources (dieselgenerators and others) are presented. The main problem is to determine the effect of different factors on the time to failure of physical safety barriers for the RBMK core. It is shown that passive water reserves in water tanks in the reactor’s emergency cooling system and deaerators as well as means for lower the pressure in the circulation loop make it possible to slow down seal-failure onset to fuel elements and channel tubes to 20–24 h after an accident starts. The diagnostics indicators making it possible to judge the state of reactor facilities are analyzed.