Synthesis and Spark Plasma Sintering of Microcrystalline Thorium Dioxide for Nuclear Fuel Products
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Synthesis and Spark Plasma Sintering of Microcrystalline Thorium Dioxide for Nuclear Fuel Products O. O. Shichalina, b, *, K. R. Frolovb, I. Yu. Buravleva, b, I. G. Tananayevb, c, d, V. V. Faizovab, S. A. Azona, b, N. I. Andreevac, and E. K. Papynova, b aInstitute
of Chemistry, Far East Branch of the Russian Academy of Sciences, Vladivostok, 690022 Russia b Far Eastern Federal University, Vladivostok, 690090 Russia c Ozersk Technological Institute, a filial of the MEPhI National Research Nuclear University, Ozersk, 456780 Russia d Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] Received March 4, 2020; revised March 20, 2020; accepted March 27, 2020
Abstract—Thorium dioxide represents a future of the world market of nuclear fuel for fourth generation nuclear reactors. In this regard, the problems of technologies for thorium separation from irradiated fuel, its conversion into fuel raw materials, and fabrication of required quality fuel products need effective solutions. In this work the synthesis of microcrystalline mesoporous ThO2 powders through the deposition of the oxalate complex from nitrate solutions, and its consolidation by spark plasma sintering (SPS) technology has been studied. The influence of the SPS temperature ranging within 1000–1600°С on the ThO2 powder shrinkage dynamics, phase composition, microstructure, and density of pelletized ceramic products has been studied. Vickers microhardness parameters of samples have been determined. The results show that highspeed (minutes-taking) SPS consolidation of powders at 1600°C and 80 MPa can provide ThO2 ceramics with 92.5% theoretical density. Microcrystalline powders with particle sizes averaging 3-4 μm can be used as raw materials instead of less accessible nanoscale materials. The study shows the expediency and prospects of further studies with the view of SPS technology adaptation for the needs of the nuclear industry. Keywords: nuclear fuel, thorium oxalate, thorium dioxide, spark plasma sintering, SPS DOI: 10.1134/S0036023620080148
INTRODUCTION Thorium dioxide (ThO2) is the basis of the nuclear fuel cycle implemented on the Th-232 isotope [1], which forms the fissile nuclide U-233 upon capture of thermal neutrons. The modern nuclear power industry pays special attention to thorium nuclear fuel and positions it as an alternative to replace U-235. This is due to the greater availability of thorium, its better thermophysical properties, high melting point, increased thermal conductivity, and low coefficient of thermal expansion. Relatively inert, ThO2 has higher oxidation stability and radiation resistance compared to uranium dioxide UO2 [2]. Fewer transuranic elements are formed when such fuel is generated, so the non-proliferation of nuclear weapons is observed when ThO2 is used in traditional light-water reactors [3]. Prospects for the use of ThO2 nuclear fuel have been experimentally studied in Chinese (HTR-10), Canadian (
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