Reaction of Unirradiated and Irradiated Nuclear Graphites with Water Vapor in Helium

摘要

Nuclear graphites more than 10 brands were oxidized with water vapor in helium and then some selected graphites were irradiated with fast neutron in the Japan Materials Testing Reactor to clarify the effect of radiation damage of graphite on their reaction behaviors. The reaction was carried out under a well defined condition in the temperature range 800 to 1000 exp 0 C at concentrations of water vapor 0.38 to 1.30 vol % in helium flow of total pressure of 1 atm. The chemical reactivity of graphite irradiated at 1000 +- 50 exp 0 C increased linearly with neutron fluence until irradiation of 3.2 x 10 exp 21 n/cm exp 2 . The activation energy for the reaction was found to decrease with neutron fluence for almost all the graphites, except for a few ones. The order of reaction increased from 0.5 for the unirradiated graphite to 1.0 for the graphite irradiated up to 6.0 x 10 exp 20 n/cm exp 2 . Experiment was also performed to study a superposed effect between the influence of radiation damage of graphite and the catalytic action of barium on the reaction rate, as well as the effect of catalyser of barium. It was shown that these effects were not superposed upon each other, although barium had a strong catalytic action on the reaction. (Atomindex citation 12:624534)