Steam oxidation of PFC materials for advanced tokamaks

Oxidative erosion of graphite in air between 600 and 1000K

“…Both accident scenarios may produce combustible gases (H 2 , CO) and release radioactive material (tritium, activated dust). Investigations on such accident analyses [20,[26][27][28][29][30] were carried out above 900 K, where the in-pore diffusion of the gases is the rate limiting process. At higher temperatures (>1200 K), the mass transfer to and away from the surface is the slowest step and, as a result, the erosion is only slightly temperature dependent [21,28,31,32].…”

“…For lower temperatures (<900 K) the chemical reaction between oxygen and carbon is the rate limiting process [27,28,33,34]. The transition temperatures between the different ranges depent on various parameters such as specimen porosity, microscopic structure, specimen shape and size, partial and total pressure, and the presence of water vapour [26,28]. The kinetic energy of molecular oxygen also affects the oxidation behaviour [14,31,32].…”

“…For Si-doped graphites, silicon does not reduce the oxidative erosion rates by heating in air up to 1000 K [26,35]. At higher temperatures the presence of Si improves the oxidation resistance of carbon fibre-reinforced composite materials (CFCs), especially the reaction with steam [26,36].…”

“…At higher temperatures the presence of Si improves the oxidation resistance of carbon fibre-reinforced composite materials (CFCs), especially the reaction with steam [26,36]. It has been suggested that a protective SiO 2 layer forms on the surface of the material under these conditions [30,36].…”

The Safety and Tritium Applied Research (STAR) Facility: Status-2004

“…Examples of recent work are found in References [8,9]. This room also houses an inert gas glovebox that is equipped with an experimental system to investigate chemical reactivity of PFC materials exposed to steam [10,11]. A BET (Brunauer, Emmett, Teller) system is also set up in Rm.…”