Masahiro Kotaka

Burn-off and Production of CO and CO2 in the Oxidation of Nuclear Reactor-Grade Graphites in a Flow System

The oxidation behaviors of IG-110 and PGX graphites were experimentally investigated in the temperature range from 500 to 1,500°C for the oxygen concentration of 10 and 30 wt% (1.37 and 5.09 mol%) and the reacting gas velocities of 6.63 and 19.9 m/s (estimated at 900°C). The graphite specimens were prepared to simulate the annular coolant channel in the core of the HTGR. It has been found that the upstream surface is more oxidized for both IG-110 and PGX graphites, and that the oxidized surface of PGX is rougher than that of IG-110. The oxidation of IG-110 starts at about 700°C and reaches the maximum above 800 to 900°C accompanied by the maximum production of CO2 around 850°C and a monotonic increase in CO with increasing temperature. The oxidation behavior of PGX is similar to that for IG-110, except that the oxidation starts at lower temperature and produces more CO2 over 750 to 950°C while the concentration of CO becomes lower in this temperature range. The present result for the product ratio of CO t...

Indo study of 1,2-fluorine atom migration in 1,1,2,2-tetrafluoroethyl radical, cation and anion

Abstract INDO molecular orbital calculations have been carried out to estimate the energy barrier heights of the 1,2-migration of a fluorine atom in 1,1,2,2-tetrafluoroethyl radical, cation, and anion. In addition, the 1,2-hydrogen atom migration in these chemical species has been studied. The results suggest that (1) the 1,2-fluorine atom migration through a fluorine atom bridging intermediate will occur more readily than the 1,2-hydrogen atom migration through a hydrogen atom bridging intermediate in the 1,1,2,2-tetrafluoroethyl radical, (2) on the contrary, the 1,1,2,2-tetrafluoroethyl cation will undergo the 1,2-migration of a hydrogen atom more readily than that of a fluorine atom, and (3) it will be difficult for the 1,1,2,2,-tetrafluoroethyl anion to undergo the 1,2-migration of a fluorine and a hydrogen atom. The enthalpy change associated with the 1,2-fluorine atom migration in the radical was estimated to be 2.5 kcal/mol, which was 1.5 times larger than the corresponding change in the trifluoroethyl radical.

INDO study of 1,2-fluorine atom migration in 1,2-difluoroethyl and 1,1,2-trifluoroethyl radicals

Abstract INDO molecular orbital calculations have been carried out to estimate the barrier heights to the 1,2-migration of fluorine and hydrogen atoms in 1,2-difluoroethyl and 1,1,2-trifluoroethyl radicals. The calculated results suggest that (1) the 1,2-fluorine atom migration through a fluorine atom bridging intermediate will occur more readily than the 1,2-hydrogen atom migration through a hydrogen atom bridging intermediate in both radicals, (2) a fluorine atom will undergo 1,2-migration in 1,1,2-trifluoroethyl radical more readily than in 1,2-difluoroethyl radical. The enthalpy change accompanied by the 1,2-fluorine atom migration in 1,1,2-trifluoroethyl radical was estimated to be 1.7 kcal/mol, which was in good agreement with the value(1.6 kcal/mol) obtained experimentally.

Notizen: Experimental Evidence for 1,2-Fluorine Atom Migration in Tritiated 1,1,2-Trifluoroethyl Radical

Tritiated compounds containing 2,2,2-trifluoroethyl groups were formed by the reaction of tritium atoms with trifluoroethylene. The result can be accepted as definitive evidence for a 1,2-fluorine atom migration occurring in the reaction intermediate, tritiated 1,1,2-trifluoroethyl radical.

1,2-Fluorine atom migration in the 1,1,2-trifluoroethyl radical

The reactions of energetic tritium (T) with 1,1,2-trifluoroethylene suggest that the excited ·CF2CHTF radical formed by tritium addition undergoes 1,2-fluorine migration, and eventually gives CF2CHT as the major product.