Phase composition of brown ceramics of lava-like fuel-containing materials of the object “Shelter” ChNPP

• Main Authors: S. V. Gabielkov, I. V. Zhyganiuk, V. G. Kudlai, A. V. Nosovsky, P. E. Parkhomchuk, S. O. Chikolovets, V. M. Shcherbin
• Format: Article
• Language: English
• Published: Institute for Nuclear Research, National Academy of Sciences of Ukraine 2019-12-01
• Series: Âderna Fìzika ta Energetika
• Subjects: lava-like fuel-containing materials; brown ceramics; crystallization; oxidation; x-ray phase analysis; phase composition; compression; inclusions of uranium oxide; inclusions of zirconium oxides; silicon oxides; silicates of uranium; zirconium; aluminum; and calcium.
• Online Access: http://jnpae.kinr.kiev.ua/20.4/html/20.4.0388.html

Using the X-ray diffraction method, the phase content of brown ceramics of lava-like fuel-containing materials of the “New Safe Confinement – Shelter Object” Complex was investigated. Their type was identified and crystalline phase composition was estimated. Characterization of the silicate glass phase was also carried out. Uranium oxide is a derivative of “initial” reactor materials before the Chornobyl accident, cubic and tetragonal zirconium oxide and silicate zirconium were produced during the accident, and some silicium oxides, uranium, aluminum, and calcium silicates were formed during the glass matrix crystallization in the course of 33 years after the accident. Uranium oxide in the inclusions oxidized to UO2.34, it has cubic lattice, which is metastable under such oxygen content. These inclusions exist due to their compaction in the glass matrix. Their increased volume, due to oxidation of uranium oxide, is the cause of cracks in the material. Under degradation of brown ceramics, 20 - 25 % of uranium oxide from inclusions transfer into U3O8 oxide with grain degradation to micron and submicron levels. Currently, the crystallization of the glass matrix is at the stable development stage. A range of silicium oxides and uranium, aluminum and calcium silicates were formed during crystallization. There are typical and non-typical phases in the viewpoint of crystallization of industrial silicate glass.