Features of high-temperature diffusion in concrete at the 4th block of the Chernobyl NPP

The element distribution and structural-phase changes in core samples taken from concrete wall in one of the rooms of the Chernobyl Nuclear Power Plant subjected to penetration of lava-like fuel-containing mass were studied by γ-ray activation and crystal-optical methods and IR spectrometry. High-temperature diffusion processes in concrete that occurred in the course of the Chernobyl accident (1986) were simulated using the developed numerical model describing concrete as a porous multiphase system occurring on the local level in the thermodynamic equilibrium with the matrix voids filled with water and gas. Comparison of theoretical results with profiles of the content of particular elements and with characteristics of newly formed minerals shows that the high-temperature fluid cloud saturated with aggressive reduction gases played the decisive role in the processes occurring during the first stage of the accident.