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

To the Computation of Equilibrium States of Hydrocarbon Combustion Products under the Lack of Oxygen

In this paper, we propose a unified approach to the computation of equilibrium states of hydrocarbon combustion products under the lack of oxygen when both gaseous and condensed carbon phases can appear simultaneously among the components of chemical reaction. One of the principles forming the basis of the approach is that the particles of a condensed substance are “large molecules” consisting of a great number of normal molecules. To illustrate the feasibility of the formulated approach, the problem of explosion of reacting gas mixture in a volume has been numerically solved. The computations have been performed for oxy-acetylene and air-acetylene mixtures.