Development and analyses of self-passivating tungsten alloys for DEMO accidental conditions

Wegener, Tobias; Linsmeier, Christian; Litnovsky, Andrey; Rasinski, Marcin; Klein, Felix; Koch, Freimut; Brinkmann, Jens

doi:10.1016/j.fusengdes.2017.03.072

Journal Article

FZJ-2017-05136

Development and analyses of self-passivating tungsten alloys for DEMO accidental conditions

Wegener, T. (Corresponding author)FZJ* ; Klein, F.FZJ* ; Litnovsky, A.FZJ* ; Rasinski, M.FZJ* ; Brinkmann, J. ; Koch, F. ; Linsmeier, C.FZJ*

2017
Elsevier New York, NY [u.a.]

Fusion engineering and design 124, 183-186 (2017) [10.1016/j.fusengdes.2017.03.072]

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Please use a persistent id in citations: http://hdl.handle.net/2128/15784 doi:10.1016/j.fusengdes.2017.03.072

Abstract: Tungsten is considered the main candidate material for the first-wall in DEMO due to its high melting point, low erosion yield and low tritium retention. Nevertheless, it can cause a substantial safety issue in a loss-of-coolant accident (LOCA) in combination with air ingress into the plasma vessel, due to the formation and sublimation of volatile neutron activated tungsten oxide. Self-passivating tungsten alloys introduce a passive safety mechanism by forming a stable chromic oxide scale on the surface acting as a diffusion barrier for oxygen and preventing the formation of tungsten oxide. Self-passivating tungsten alloys optimized for oxidation resistance containing ∼12 wt.% Cr and ∼0.6 wt.% Y are investigated under conditions of argon–oxygen, humid argon and humid air atmospheres at different partial pressures and temperatures ranging from 1073 to 1273 K. Thin films with ∼3.5 μm thickness produced by magnetron sputter deposition are used as a model system. The oxidation resistance of these films in an argon–20 vol.% oxygen atmosphere is sufficient to prevent formation and release of tungsten oxide at temperatures of from 1073 to 1273 K. The sublimation of Cr in nitrogen–oxygen–water atmosphere at T ≥ 1273 K is discussed. A deeper understanding of the governing processes for oxygen/Cr diffusion under different atmospheres is gained, supported by SEM/EDX in combination with FIB cross-section and TGA measurements.

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