Process resulting in the destruction of the No. 4 unit reactor at the Chernobyl nuclear power plant

The results of an investigation of structural fragments of the core of the destroyed reactor in the No. 4 unit of the Chernobyl nuclear power plant are analyzed. It is shown on the basis of investigations of the fission product distribution over the cross-section of the graphite blocks and the determination of the physical properties of graphite that the temperature of the graphite blocks, including the reflector, at the moment they were ejected from the core exceeded 1000°C. The heat content of the fuel was estimated on the basis of an analysis of fragments of the dispersed uranium dioxide particles and an analysis of possible graphite dispersal mechanisms at the moment of the explosion. It is shown that energy sufficient for dispersing and partial vaporization of the fuel and for dispersing the graphite could have been introduced into the fuel during the accident process. Analysis confirms the possibility of a core destruction scenario with ejection from the shaft and ejection of part of the fuel in the form of vapor and dispersed particles into the atmosphere.