Numerical Analysis of Carbon Isotope Separation by Plasma Chemical Reactions in Carbon Monoxide Glow Discharge

Abstract

The separation of carbon isotopes in CO glow discharge has been studied, in which the formation of stable products enriched in 13 C is analyzed by the numerical simulation of kinetic model. Vibrational kinetics and vibrationally induced chemical reaction of CO molecules are considered in the kinetic model as well as electron impact reactions and isotope scrambling reactions of isotopically enriched products. The reaction yield and final isotope enrichment of the stable products are derived as a function of mean electron energy. When mean electron energy is 2.1 eV in the case of Maxwellian electron energy distribution and 3.3 eV in the case of Druyvesteyn one, the kinetic model can reproduce experimental isotope enrichment of precipitated carbon atoms in discharge reactor. The calculation suggests optimum mean electron energy of the plasma for isotope separation as 1.0 eV and, in this case, it is expected that 13 C enrichment coefficient for precipitated carbon atoms is about 10 and its reaction yield is about 0.5%.

The Recovery of Carbon-14 from the Graphite Moderator of a Dismantled Gas-Cooled Reactor through Plasma Chemical Reactions in CO Glow Discharge

“…In previous studies, 7,8) we performed carbon isotope separation through plasma chemical reactions in CO glow discharge; in this method, a carbon film enriched in 13 C is formed on the reactor walls through the disproportionation reaction of vibrationally excited CO molecules (CO(v)+ CO(w)!C+CO 2 ), because heavier isotopic CO molecules are preferentially excited due to the vibration-to-vibration (V-V) energy exchange among the vibrational states of the molecular gases. [9][10][11] In those studies, the maximum separation factor of 2.31 has been obtained for the 13 C in the carbon deposit on the discharge tube and the kinetic model was able to reproduce experimental isotope enrichment qualitatively.…”

The Recovery of Carbon-14 from the Graphite Moderator of a Dismantled Gas-Cooled Reactor through Plasma Chemical Reactions in CO Glow Discharge

“…On the other hand, products formed by the electron impact reactions R7, R8, R9 and R10 are not isotopically enriched; moreover, these reactions initiate the subsequent de-enriching processes by forming atomic oxygen. The improvements relative to the previous calculation model for the 12 C 16 O/ 13 C 16 O system 8) are explained below.…”

“…The kinetic model used in the present study is based on previous publications 8,10) and further developed to describe isotope enrichment in stable products by including more detailed atomic and molecular processes; the rate equations for the density of the vibrational quantum levels of 12 C 16 O and 13 C 16 O or 12 C 16 O and 14 C 16 O, the rate equations for the reaction products, and the Boltzmann equation for the electron velocity distribution were solved numerically as a function of discharge parameters such as the reduced electric field, the current density and the gas composition. The vibrational kinetic processes and chemical reactions considered in this model are listed in Tables 1 and 2.…”

“…In previous studies, 7,8) we performed carbon isotope separation through plasma chemical reactions in CO glow discharge; in this method, a carbon film enriched in 13 C is formed on the reactor walls through the disproportionation reaction of vibrationally excited CO molecules (CO(v)+ CO(w)!C+CO 2 ), because heavier isotopic CO molecules are preferentially excited due to the vibration-to-vibration (V-V) energy exchange among the vibrational states of the molecular gases. [9][10][11] In those studies, the maximum separation factor of 2.31 has been obtained for the 13 C in the carbon deposit on the discharge tube and the kinetic model was able to reproduce experimental isotope enrichment qualitatively.…”

“…[9][10][11] In those studies, the maximum separation factor of 2.31 has been obtained for the 13 C in the carbon deposit on the discharge tube and the kinetic model was able to reproduce experimental isotope enrichment qualitatively. 7,8) In this study, we developed a much more detailed kinetic model of 12 C 16 O, 13 C 16 O, and 14 C 16 O. Using this calculation model, we estimated the 14 C separation factor.…”