Publication of an article regarding the phase composition of Chornobyl lava
The article “Phase composition of lava-like fuel-containing materials of Unit 4 of the Chornobyl NPP. Black ceramics) has been accepted for publication. The article was prepared by employees of the Institute for Safety Problems of Nuclear Power Plants of the NAS of Ukraine (S. V. Gabielkov, A. D. Skorbun, I. V. Zhyganiuk, V. G. Kudlai, P. Ye. Parkhomchuk, S. O. Chikolovets) and the Institute of Environmental Geochemistry of the NAS of Ukraine (V. V. Dolin, V. M. Slivinskyi). According to The SCImago Research Group’s 2021 ranking, this journal is ranked in the first quartile of Q1 in the field of nuclear physics, nuclear energy, and materials science.
The purpose of the study was to determine the phase composition of black ceramics of lava-like fuel-containing materials (LPVM) of Unit 4 of the Chornobyl NPP three and a half decades after the accident and to identify the physical and chemical processes responsible for the change of state and the formation of new crystalline phases in the black ceramics of LFCM during the period of time from the accident to the present.
It was established that 36 years after the accident, the uranium-containing crystalline phase Rameauit K2Ca[(UO2)3O3(OH)2]2·6H2O and crystalline phases that do not contain uranium were found in the black ceramics of the Chornobyl NPP 4th unit: magnesium oxide MgO, Katoite Ca2.916Al2(SiO4)1.104(O4H4)1.89, calcium-magnesium silicate CaMgSiO4, magnesium aluminate MgAl2O4 and magnesium silicates MgSiO3 and Mg2SiO4. The presence of uranium oxide UO2.338(U4O9), chornobylite Zr1-xUxSiO4 and possibly iron α-Fe was confirmed. Most of the uranium in the crystalline phases is in the form of Remeuite, not uranium oxide.
For the first time, the phases of black ceramics are divided into three groups, based on their “origin”: before, during and after the accident. Part of the uranium oxide and α-Fe iron “formed” before the accident. During the accident, another part of uranium oxide, magnesium oxide and chornobylite were synthesized. Calcium-magnesium silicate, magnesium aluminate, and magnesium silicates apparently began to form as lava crystallized as it cooled and continued this process after the accident. Remeuit and Katoit were obtained after the accident.
It is shown that for 36 years after the accident, the following physical and chemical processes took place and are taking place in the black LFCM ceramics: oxidation of uranium oxide, formation of Remeuite and Katoite, and crystallization of the glass phase.
The obtained results will be used to predict the behavior and develop methods and technologies for handling fuel-containing materials formed as a result of the accidents at the Chornobyl and Fukushima nuclear power plants.
The article is the first step in establishing the world priority of Ukrainian scientists in the field of handling highly active nuclear materials of the Chornobyl NPP.
The work was carried out within the framework of funding of the budget topic of the NAS of Ukraine (No. 0120U103480).
The authors are grateful to the reviewers for their high evaluation of the obtained results and to the editors of the Journal of Nuclear Materials for funding the publication of the article in Open access.
Online link to the article: https://www.doi.org/10.1016/j.jnucmat.2023.154392.
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