Evolution of Chernobyl Corium in Water: Formation of Secondary Uranyl Phases

Abstract

Two crystalline phases, which are analogues of common secondary uranyl minerals, namely, becquerelite (Ca[(UO2)6O4 (OH)6]·8H2O) and phurcalite (Ca2[(UO2)3O2 (PO4)2]·7H2O) were identified on the surface of a Chernobyl corium-containing sample affected by hydrothermal alteration in distilled water at 150 °C for one year. Phases were characterized using Single-Crystal X-ray Diffraction Analysis (SCXRD) as well as optical and scanning electron microscopy. Features of the structural architecture of novel phases, which come from the specific chemical composition of the initial fragment of Chernobyl sample, are reported and discussed. Precise identification of these phases is important for modelling of severe nuclear accidents and their long-term consequences, including expected corium–water interaction processes at three damaged Units of the Nuclear Power Plant Fukushima Daiichi.

The key role of sample analysis in Fukushima Dai-Ichi decommissioning, debris management, and accident progression investigation

“…The surrounding environment is a key factor because fuel debris, degraded structure materials, and surrounding water have affected each other. The ionic composition of water may largely define the types of secondary phase formation (Gurzhiy et al, 2023). Samples taken from the surfaces of the accumulated materials that were immersed in water for more than 10 years may have already experienced significant chemical alteration.…”