Stuttgart 2012 – scientific programme

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P: Fachverband Plasmaphysik

P 26: Plasma-Wand-Wechselwirkung

P 26.5: Talk

Friday, March 16, 2012, 15:30–15:45, V57.02

Investigations of Porosity Enhanced Removal of Fuel Containing Carbon Codeposits by Thermo-Chemical Removal — •Sören Möller, Arkadi Kreter, Hans Günter Esser, and Ulrich Samm — Institute for Energy- and Climate Research - Plasma Physics, Forschungszentrum Jülich GmbH, Association EURATOM-FZJ, Partner in Trilateral Euregio Cluster, Jülich, Germany

Thermo-chemical removal (TC) of amorphous hydrogenated carbon layers (a-C:H,D,T) with reactive gases is a candidate to reduce tritium retention in fusion devices. A significant scatter of the removal rates at similar wall temperatures and pressures is observed. For a better understanding a model was developed here, showing that the scatter can be explained by layer properties. a-C:H layers can have a substantial amount of porosity, forming an open pore network. The diffusion of gas through this network will enable reactions of the removal gas in the whole layer volume. Based on this porosity and the Arrhenius temperature dependence of removal rates, a reaction-diffusion differential equation is formulated. According to the model, the absolute removal rates are proportional to the layer thickness up to a layer property dependent value. This understanding may contribute to the design of an integral scenario for the T-inventory control in fusion devices. To test the model experimentally, TC experiments with different layer thicknesses were performed in the labfacility PADOS. Other parameters, such as the wall temperature of 350°C, the total oxygen pressure of 10mbar and the initial layer texture were kept constant. The comparison of experiment and model will be presented in the contribution.