Thermodynamic Analysis of Radioactive Graphite Oxidation in NiO-NaCl-KCl-Na2CO3-K2CO3 Melt in the Atmosphere of Argon


Behavior of U, Pu radionuclides was investigated when heating radioactive graphite in NaCl – KCl – Na2CO3 – K2CO3 melt with NiO additives using the thermodynamic modeling method. Calculations were made by the TERRA software that is used for the determination of phase composition, thermodynamic and transport properties, taking into account chemical and phase changes in temperature range 373 – 3273 K. Calculation of equilibrium phase composition and parameters of equilibrium was carried out using reference information about properties of the individual substances (INVATERMO, HSC, etc.). This study demonstrates that at a temperature of 1273 K the condensed carbon burns down with the formation of CO and CO2. Increasing temperature to 1673 K causes the condensed compounds of uranium to evaporate. This study determined that uranium exists in the form of ionized UO−3 in temperature range from 1673 to 3273 K. Plutonium exists in the form of gaseous PuO2, PuO in temperature range 2373 – 3273 K.

Keywords: thermodynamic modeling, radionuclides, radioactive graphite

[1] Tsyganov, A. A., et al. (2007). Problem of Disposal of Reactor Graphite from Shutdown Industrial Uranium-Graphite Reactors. Bulletin of the Tomsk Polytechnic University, vol. 310, issue 2, pp. 94-98.

[2] Russian Atomic Society. Rosatom Retrieved March 4, 2019 from about industry/rosatom-otrabotaet-metodobezvrezhivaniya radioaktivnogo-grafita-iz-reaktorov/. Pub- lication date March 2017.

[3] Russian Atomic Society. Retrieved March 4, 2019 from 08/66585. Publication date June 2016.

[4] Linsley G. and Wickham A. J. Waste Technology Section International Atomic Energy Agency Vienna International Centre. IAEA-TECDOC-1647 (2010). Progress in Radioactive Graphite Waste Management. Vienna: IAEA.

[5] Belov, G. V. and Trusov, B. G. (2013). Thermodynamic Modeling of Chemically-Reacting Systems. Moscow: Bauman Moscow State Technical University.

[6] Vatolin, N. A., Moiseev, G. K. and Trusov, B. G. (1994). Thermodymic Modeling in High-Temperature Inorganic Systems. Moscow: Metallurgy.

[7] Barbin, N. M., et al. (2017). Termodynamic Modeling of Thermal Processes Involving Actinides (U, Am, Pu) in the Course of Heating Radioactive Graphite in Steam. Radiochemistry, vol. 59, issue 5, pp. 445-448.

[8] Barbin, N. M., et al. (2016). Behavior of Carbon and Uranium at Radioactive Graphite Heating in Water Vapor. Thermodynamic Modeling. Russian Journal of Chemistry and Chemical Technology, vol. 59, issue 9, pp. 16-20.

[9] Barbin, N. M., et al. ( June 2017). Сomputer Modeling Of Thermal Processes Involving Cs During Heating Of Radioactive Graphite In Water Vapor. Presented at MATEC Web of Conferences. 17, Avenue du Hoggar Parc d’Activités de Courtabœuf BP 112 F-91944 Les Ulis Cedex A France. EDP Sciences.

[10] Kobelev, A. M., et al. (November 2014). Calculation of Heat Physical Properties at Heating System Radioactive Graphite Water Vapor. Presented at XXXI All-Russia Conference «Sibirskiy heat-physical seminar». Novosibirsk (Russia): Institute of Thermal Physics UB RAS.

[11] Barbin, N. M., et al. (October 2015). Thermodynamic Modeling of the Behavior of Uranium, Plutonium, Americium and Europium in the Combustion of Radioactive Graphite in Water Vapor. Presented at Proceedings of the IX International Seminar of Universities on Thermal Physics and Energy. Kazan (Russia): Kazan State Power Engineering University.

[12] Romenkov, A. A., et al. (June 2010). Pilot Plant for Graphite RW Oxidation in Molten Salt: Experimental Results. Presented at Annual Report of JSC NIKIET. Moscow (Russia): JSK NIKIET.

[13] Shidlovskiy, V. V., et al. (June 2010). Radioactivity Danger Analysis of Graphite Stacks of Shutdown Industrial Uranium Graphite Reactors at Federal State Unitary Enterprise ”Mayak Production Association”. Presented at Annual Report of JSC NIKIET. Moscow (Russia): JSK NIKIET.