2 research outputs found
3D effects on hydrogen transport in divertor monoblocks: influence of thickness and recombination on poloidal side
International audienceBombardment by high energy hydrogen particles (deuterium and tritium) of the tungsten divertor surfaces will lead to a build-up of hydrogen inventory, which can induce material embrittlement and so reduce the lifetime of plasma-facing components. Because tritium can be retained in the material and permeate to the coolant, it also represents radioactive issue.Hydrogen transport in ITER monoblocks has already been modelled numerically with 1D and 2D simulations for large sets of irradiation conditions, assuming there is no effect of the monoblock axial thickness (poloidal direction) due to its large size defined for ITER design (12 mm). Since the conceptual design for DEMO monoblock can still change, the aim for this study is to explore the impact of the monoblock axial thickness on the retention and permeation during plasma operation. Desorption from both, toroidal and poloidal gaps, is also studied during the baking phase. A 3D FESTIM [1] model is first built and transient simulations up to 1e6 s of continuous exposure are run with or without instantaneous recombination on poloidal side surfaces.In the case of instantaneous recombination, the poloidal gaps act as a strong sink for hydrogen leading to a decrease of the monoblock inventory. The total desorption flux on poloidal surfaces is greater than on poroidal surfaces but remains orders of magnitude lower than the retro-desorbed flux at the plasma-facing surface. For a monoblock thickness of 4 mm, the relative difference in the hydrogen inventory per unit thickness between the two cases (with and without recombination on poloidal sides) is ~200%. As the thickness of the monoblock increases, this difference decreases (~30% at 14 mm). The monoblock’s response to baking is then studied at different baking temperatures. For example, at 600 K almost all the hydrogen content in the monoblock is removed after 15 days of baking (mostly outgassing ~70% from poloidal side surfaces). Finally, it is shown that assuming a non-instantaneous recombination on the tungsten surfaces according to the literature data [2] would not have a major impact for baking temperatures above 600 K.[1] R. Delaporte-Mathurin et al., Nuclear Materials and Energy 21, p. 100709 (2019) [2] D. F. Anderl et al., Fusion Technology 21(2P2), pp. 745–752 (1992
3D effects on hydrogen transport in divertor monoblocks: influence of thickness and recombination on poloidal side
International audienceBombardment by high energy hydrogen particles (deuterium and tritium) of the tungsten divertor surfaces will lead to a build-up of hydrogen inventory, which can induce material embrittlement and so reduce the lifetime of plasma-facing components. Because tritium can be retained in the material and permeate to the coolant, it also represents radioactive issue.Hydrogen transport in ITER monoblocks has already been modelled numerically with 1D and 2D simulations for large sets of irradiation conditions, assuming there is no effect of the monoblock axial thickness (poloidal direction) due to its large size defined for ITER design (12 mm). Since the conceptual design for DEMO monoblock can still change, the aim for this study is to explore the impact of the monoblock axial thickness on the retention and permeation during plasma operation. Desorption from both, toroidal and poloidal gaps, is also studied during the baking phase. A 3D FESTIM [1] model is first built and transient simulations up to 1e6 s of continuous exposure are run with or without instantaneous recombination on poloidal side surfaces.In the case of instantaneous recombination, the poloidal gaps act as a strong sink for hydrogen leading to a decrease of the monoblock inventory. The total desorption flux on poloidal surfaces is greater than on poroidal surfaces but remains orders of magnitude lower than the retro-desorbed flux at the plasma-facing surface. For a monoblock thickness of 4 mm, the relative difference in the hydrogen inventory per unit thickness between the two cases (with and without recombination on poloidal sides) is ~200%. As the thickness of the monoblock increases, this difference decreases (~30% at 14 mm). The monoblock’s response to baking is then studied at different baking temperatures. For example, at 600 K almost all the hydrogen content in the monoblock is removed after 15 days of baking (mostly outgassing ~70% from poloidal side surfaces). Finally, it is shown that assuming a non-instantaneous recombination on the tungsten surfaces according to the literature data [2] would not have a major impact for baking temperatures above 600 K.[1] R. Delaporte-Mathurin et al., Nuclear Materials and Energy 21, p. 100709 (2019) [2] D. F. Anderl et al., Fusion Technology 21(2P2), pp. 745–752 (1992