Session 3.2: Material – PMI and High Heat Flux Testing

1. Session 3.2: Material – PMI and High Heat Flux Testing • R. Neu: Recent PMI Experience in Tokamaks • R. Doerner: PMI Issues beyond ITER • M. Roedig: High Heat Flux Testing of Different Armor • F. Escourbiac: Critical Heat Flux Testing in Support of ITER • S. Abdel-Khalik: Experimental Validation of He-Cooled Divertor Thermal Performance

2. R. Neu: Recent PMI Experience in Tokamaks • Flux dependence of chemical erosion is settled and it provides a firm basis for extrapolations • Erosion of high-Z materials is mainly caused by low-Z impurities • Destructive transients (large ELMs, disruptions) are not easily acceptable in present day machines • D-retention by co-deposition with C is quantitatively reproduced in dedicated tokamak experiments • D-retention in metals is low (lab experiments, Asdex Upgrade) • Dust investigations just started, sources are not well known • Conditioning by boronization / Be evaporation are helpful for O-reduction, but not helpful for long pulse operation • lab experiments and modelling are indispensible for extrapolations

3. R. Doerner: PMI Issues beyond ITER • Higher efficiency will lead to higher armor temperatures • Steady state operation: sufficient time to develop PMI at high temperatures • Almost all PMIs are temperature dependent • Very few data for DEMO relevant temperatures • High temperature work is needed • DEMO relevant fluence data is needed

4. M. Roedig: High Heat Flux Testing of Different Armor • PFCs – Thermal Fatigue • Technical solutions up to 20 MW/m2 are available • CFC and W monoblocks represent a very robust design solution • After n-irradiation: elevated surface temperatures (esp. Carbon) • PFMs – Thermal Shock Behavior • Tungsten: melting (tile edges) starts at 0.4 MJ/m2 • Deformed tugsten: dense crack pattern for low cycle numbers, cracks gow perpendicular to the surface • CFC: brittle destruction – PAN fibers parallel to the surface are heavily eroded • After n-irradiation: increased crack formation in W, increased erosion and crack formation in carbon

5. F. Escourbiac: Critical Heat Flux Testing in Support of ITER • CHF increases with twist ratio, tape thickness, water pressure, flow rate • CHF decreases with width of tube and inlet temperature • On the base of the TONC-75 correlation, a whole set of correlations was developed for heat transfer prediction • Predictive tools already used for Tore Supra and W7-X components and are now applied to ITER PFCs

6. S. Abdel-Khalik: Experimental Validation of He-CooledDivertor Thermal Performance • Approach • Test modules which match already the geometry of the proposed designs • Tests at prototypical non-dimensional parameters • Compare data against CFD model predictions • Outcome • Validated CFD codes can be used to optimize design and establish limits on manufaturing tolerances • Results • Code predictions match experimental data  predicted thermal performance data (10 MW/m2) values are reliable • Preferable to use simple one-equation turbulance models (Spalart Allmaras)