Mechanisms and Special Features of the Thermodeformational Behavior of a Channel Pipe and Graphite Elements in RBMK Reactors During Heating Due to an Accident

Two- and three-parameter quadratic fitting curves, characterizing the basic thermal and deformational parameters of the state of the structural components of a RBMK technological channel heated as a result of an accident, are constructed on the basis of numerical simulation. The parameters characterizing the accidental heating are assumed to be the heat flux density on the inner surface of the channel pipe, the pressure in the channel, and the thermal resistance on contact surfaces. The output functions are the temperature of the channel pipe at the moment it sets on the graphite, the rate of heating, the average rate of radial expansion of the pipe before and after it sets on the graphite, and the temperature of the surface of the opening in the block at the moment the pipe sets on the graphite. The fitting relations constructed can be used to obtain real-time estimates of the basic thermal and deformational characteristics of the heating process due to the accident and to develop new integral criteria for the integrity of a damaged RBMK channel.