Brittle destruction of carbon based materials under off-normal ITER-FEAT conditions

A numerical simulation model for brittle destruction of carbon based materi als (CBMs) based on crack generation by thermal shocks was developed. Crack generation in heated graphite samples depends on the grain anisotropy, the grain size, the failure stress distribution of the bonds connecting adjace nt grains and on the temperature and the temperature gradient in the sample . A realistic value for the mean failure stress was obtained from a numeric al simulation of destructive compression tests and from a comparison of cal culated and measured onset of brittle destruction for volumetric heating. G raphite predamaging due to crack propagation into the depth of the sample o r due to volumetric heating might occur, resulting in an enhancement of bri ttle destruction under cyclic heat loads for typical ITER-FEAT off-normal e vents. Results of a consistent analysis of brittle destruction and of targe t screening by dust particles and of enhancement of brittle destruction und er cyclic heat loads are presented.