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The main objective of this numerical study is to investigate how to minimise the tritium content in the first wall of a tokamak reactor. Mainly pulsed tokamak operation with 100s cycle durations, 75s duty times, and outgassing phases with durations between 500 and 3000 s is envisaged. These outgassing phases are started after every N(p) cycle (20<N(p)<70). For modelling, a multicode is applied that describes the surface and volume processes determining the tritium inventory in and the permeation through the first wall, the neutral gas background due to the recycling of the plasma, and the transport processes governing the parameters of a three-species burning plasma. The calculations show that control of the wall temperature, determined by the heat transfer to the coolant and the radiation loading by the plasma, is decisive for the tritium buildup. Cooling is achieved by pressurized water or helium. The coolant channels are assumed to be composed of a corrugated steel sheet and the first wall, both connected in a panel-type construction. The main results are as follows. In long outgassing phases at elevated temperatures the tritium content after 1400 pulses is about 2.5 times lower than in continuous irradiation with time-averaged intensity. Shorter but more frequent outgassing phases are less efficient. Good outgassing efficiency at elevated temperatures is obtained at the expense of an enhanced tritium permeation to the outside. An oxide layer, acting as an ideal diffusion barrier at the outside of the vessel, prevents permeation but effects a tritium content 30% higher than in long outgassing phases.

Additional information

Authors: NICOLAI A, Institut für Plasmaphysik der Kernforschungsanlage Jülich GmbH (DE);BÖRNER P, Institut für Plasmaphysik der Kernforschungsanlage Jülich GmbH (DE);BORNER P, Institut fur Plasmaphysik der Kernforschungsanlage Julich GmbH (DE)
Bibliographic Reference: Article: Fusion Technology, Vol. 12 (1987), pp.119-136
Record Number: 198910227 / Last updated on: 1994-12-01
Original language: en
Available languages: en