Introduction Prediction of ITER loads and T retention A. Loarte

1. IntroductionPrediction of ITER loads and T retentionA. Loarte Alberto Loarte 10th ITPA Divertor and SOL Physics Group Avila – Spain 7/10 – 1 – 2007 1

2. Specification of ITER Loads • Specification of ITER loads has been reviewed during ITER Design Review  update to take into account present physics understanding • Particle/Power Fluxes to wall during diverted operation • Redefinition of divertor controlled ELM loads • Update of ELM divertor and wall power fluxes • Update of disruption and VDE thermal loads • Update of disruption and VDE EM loads • etc. Revised load specifications will be used to redesign details of ITER PFCs (main wall)  Advice from ITPA required Uncertainties in load specifications is considerable  judgment to specify reasonable and non-fluctuating values Alberto Loarte 10th ITPA Divertor and SOL Physics Group Avila – Spain 7/10 – 1 – 2007 2

3. Evaluation of T retention in ITER • T retention is one of the key drivers for plasma facing materials choice in ITER  PFM foreseen strategy based on present understanding of PWI in ITER Change of CFC to W divertor to minimise T retention • Prediction of T retention in ITER is a complex and uncertain • Uncertain plasma fluxes and conditions • ITER-specific issues (high Tsurf/Gplasma, n-irradiation, etc.) • Formation of mixed-materials • etc. Determination of fuel retention for ITER on present understanding, on-going R&D and Hydrogen phase results crucial to decide on best timing for change of divertor plasma materials in ITER programme Alberto Loarte 10th ITPA Divertor and SOL Physics Group Avila – Spain 7/10 – 1 – 2007 3

4. Lipschultz QDT = 10 steady plasma loads (I) • All divertor tomakaks measure plasma particle fluxes (II B) to the main wall • Extrapolated plasma flux to the main wall in ITER 1.0 - 5 .0 1023 s-1 (1-5 % of Gdiv) Lipschultz IAEA 2000 Alberto Loarte 10th ITPA Divertor and SOL Physics Group Avila – Spain 7/10 – 1 – 2007 4

5. LaBombard NF 2004 QDT = 10 steady plasma loads (II) • Plasma fluxes predominantly on outer side of first wall • Corresponding maximum IIB power densities up to : 5 MWm-2 (Upper X- point) to 1 MWm-2 near outer midplane and 0.4 MWm-2 near inner midplane Alberto Loarte 10th ITPA Divertor and SOL Physics Group Avila – Spain 7/10 – 1 – 2007 5

6. 0.5 1.0 1.5 energy density / MJm-2 significantPAN fibreerosionafter 50 shots PAN fibreerosion offlat surfacesafter 100 shot PAN fibreerosionafter 10 shots erosion startsat PFC corners negligibleerosion CFC divertor target lifetime  20000 ELMs Tolerable ELM size QSPA experiments on NB31 targets show Tolerable ELM energy density 0.5 MJm-2 + no broadening + 2:1 in/out asymmetry  DWELM ~ 1MJ fELM ~ 20-40 Hz  8000-16000 ELMs/QDT=10 shot Alberto Loarte 10th ITPA Divertor and SOL Physics Group Avila – Spain 7/10 – 1 – 2007 6

7. Wall ELM loads Wall ELM power/particle deposition starting to be characterised/understood  extrapolation to ITER uncertain Uncontrolled ELMs in ITER DWELM = 20 MJControlled ELMs in ITER  DWELM = 1.0 MJ Model by W. Fundamenski and R. Pitts Uncontrolled ELMs  DWELM,wall = 2-4 MJControlled ELMs  DWELM,wall = 0.05-0.1 MJ tELM,wall ~ ½ tELM,divertor • AIIELM < Afil ~ Nfildpoldr ~ 10 * 0.25 * 0.1 = 0.25 m-2 (A. Kirk) • Uncontrolled ELMs  EIIELM > 8-16 MJm-2 (<qII,ELM> ~ 8-32 MWm-2 ) & Ewall,ELM (4o) ~ 0.6- 1.1 MJm-2 • Controlled ELMs  EIIELM > 0.2-0.4 MJm-2 (<qII,ELM> ~ 4-16 MWm-2 ) & Ewall,ELM (4o) ~ 0.01-0.03 MJm-2 Alberto Loarte 10th ITPA Divertor and SOL Physics Group Avila – Spain 7/10 – 1 – 2007 7