210 likes | 343 Views
CCIC-03 - A few excerpts from…. Edge Power Fluxes in ITER : Implications for TBM Alberto Loarte ITER Fusion Science and Technology Department with thanks to : M. Sugihara, R. Pitts, A. Kukushkin, M. Shimada, C. Lowry, R. Mitteau, M. Pick, C. Kessel, G. Saibene, A. Portone, …. Outline of Talk.
E N D
CCIC-03 - A few excerpts from… Edge Power Fluxes in ITER : Implications for TBMAlberto LoarteITER Fusion Science and Technology Departmentwith thanks to : M. Sugihara, R. Pitts, A. Kukushkin, M. Shimada, C. Lowry, R. Mitteau, M. Pick,C. Kessel, G. Saibene, A. Portone, ….
Outline of Talk • Introduction • Expected power fluxes to TBM frame and TBM during steady-state phases (H(He), D and DT phases) • Expected power fluxes to TBM frame and TBM during transient phases (H(He), D, and DT phases) • Conclusions
New ITER ramp-up/down plasma scenarios • Development of low li ramp-ups an control of VS during ramp down heating during current ramp-up/down • Full-bore ramp-up with divertor configuration from Ip ~ 3.5 MA • Maintaining divertor configuration as long as possible in ramp-down 5 MW (10-30 s), 10 MW (30-50 s), 15 MW (50-75 s), 20 MW (75-100s) Wb saving : 25 (ICRH), 34 (ECRH), 39 (LHCD) C. Kessel A. Portone
Assumptions for calculations of TBM power fluxes • Power fluxes to TBM depend on detailed first wall design and detailed specifications of plasmas in all phases of ITER scenarios not yet fully developed • Highest fluxes on TBMs when 2-port limiters are retracted estimates performed for this case (need for 2-port limiters being re-evaluated as part of FW design) • Plasma regimes considered during ITER operation phases • 7.5 MA/2.65T L-mode with <ne> = 0.4 nGW and Pinp < 50 MW (H) • 7.5 MA/2.65T L-mode with <ne> = 0.4 nGW and Pinp < 50 MW (He, D) • 7.5 MA/2.65T Type I ELMy H-mode with <ne> = 0.85 nGW and Pinp = 73 MW (He, D) • 15 MA/5.3T L-mode with <ne> = 0.4 nGW and Pinp < 73 MW (H, He, D) • 15 MA/5.3T Type I ELMy H-mode <ne> = 0.85 nGW and Pinp < 50 MW (DT) • 9MA/5.3T advanced scenario with and Pinp < 60 MW (DT) • Power fluxes to TBM and TBM frame in shadow of blanket modules evaluated • Plasma fluxes parallel to B fluxes on structures depend on geometry examples given for fluxes on TBM recessed 5 cm from separatrix & 3o impact angle • Radiation and charge-exchange fluxes perpendicular to TBM • Plasma fluxes versus local separatrix position at TBM port (separatrix deviation by ripple < 12 mm see J. Snipes’ presentation)
Power fluxes to main wall in limiter phases • Limiter phases during ramp-up (5 MA) and ramp-down (7.5 MA) in ohmic or with low level of heating (PSOL (MW) < Ip (MA)) for FW design • Power width scaling from divertor (~18 limiter) L-mode discharges (IPB) a) <ne>/nGW = 0.2, b) qlim ~ 3.45*(15/Ip(MA))0.7, c) Plim(MW) = Ip (MA), d) Zeff = 1.0+1.1/<ne>(1019m-3) Main SOL Limiter Shadow lp in limiter shadow ~ mm Positioning frame and TBM few cm in limiter shadow decreases plasma power to negligible values
Steady-state power fluxes to main wall during diverted phases (I) • Power fluxes to main wall between ELMs dominated by far-SOL turbulent transport and long tails in density profiles • Physics model to extrapolate far-SOL transport to ITER being developed empirical extrapolation of measurements + B2-Eirene modelling Parameters at line contacting the wall from B2-Eirene simulations for QDT = 10 • Te,w = 10-20 eV, Ti,w/Te,w ~ 2 • nw = 0.5-1.5 1019m-3 • VSOL < 100 ms-1 lq-far SOL ,mp = LcvSOL/cs,w< 0.17 m (for 15 MA H-mode)
Steady-state power fluxes to main wall during diverted phases (II) • Upper levels of power fluxes for other regimes based on empirical scalings of plasma parameters and from B2-Eirene results for QDT =10 further work is needed • Prad,bulk ~ <ne>2 • In far-SOL Te ~ 10 -20 eV (Ti/Te ~ 2) • ln,H-mode (QDT= 10) = 2.5 – 6.5 cm • ln,L-mode = 2 ln,H-mode • ln ~ Ip-1 • ne,sep ~ 1/3 <ne> • lq far-SOL,mp < vSOL*Lc/Lc(q=3)*(mxx/mDT)1/2 ASDEX Upgrade Neuhauser PPCF 2005 H-mode (Type I)
Steady-state power fluxes to main wall during diverted phases (III) • Plasma power parallel fluxes parallel to B near outer midplane wall in the range of 1-4 MWm-2 for all phases of operation (H DD & He DT) • Decay of power fluxes (IIB) in limiter shadow strongly dependent on dominant transport mechanism • lshadow < 1 cm for convective transport (lshadow ~ Llim/Lc) • lshadow ~ 2 - 5 cm for convective transport (lshadow ~ (Llim/Lc)1/2) Steady plasma power flux onto TBM negligible (5 cm, 3o) < 0.02 MWm-2 DRsep (1st field line conn to wall)
ELM power fluxes to main wall during diverted phases trise • Divertor damage avoidance during ELMs tolerable ELMs restricted in size • 15 MA QDT = 10 DWELM = 1 MJ & fELM = 20 - 40 Hz • 9 MA QDT = 5 DWELM = 2.4 MJ & fELM = 8 - 17 Hz • 7.5 MA H-mode DWELM = 2.4 MJ & fELM = 5 - 10 Hz • Occasional uncontrolled ELMs : ~ 20 MJ (15 MA & QDT =10), ~ 7 MJ (9 MA & QDT = 5), ~ 4 MJ (7.5 MA & H-mode) • Controlled ELM power flux on TBM negligible (5 cm, 3o) • < 0.01 MWm-2 • Uncontrolled ELM damage to TBM unlikely (5 cm, 3o) • < 0.005 MJm-2 Controlled ELMs
Power fluxes by charge-exchange • Charge-exchange fluxes estimated by B2-Eirene for QDT =10 and empirical scaling of total plasma outflux from nW and vSOL~ 1 order of magnitude uncertainty, with upper range in agreement with present experimental evidence • Charge-exchange power flux is maximum near the outer midplane • Charge-exchange atom flux ~ normal to wall receding TBM does not change loads much • For QDT = 10 typical C-X atom energy in the range 1 - 1.6 keV (Tped ~5 keV) beyond sputtering threshold (TBM erosion ?)
Power fluxes by radiation • Maximum radiative loads in main chamber limited by to 60% Pinp for L-mode and by L-H transition power for high confinement regimes (70 MW (QDT = 10) , 50 MW (QDT = 5), 30 MW (D), 40 (He)) • Highest radiation loads during steady-state Marfes (assuming performance is maintained which is unlikely) no any other additional power flux to the wall • Radiation peaking < 2 for normal conditions and < 3 for Marfes • Average radiation flux ~ normal to wall receding TBM does not change loads much
Power Fluxes during disruptions : Thermal quench (I) trise • Energy fluxes to first wall during disruption determined by : • Maximum plasma energy at thermal quench : 0.8 Wplasma for L-mode (typical 0.4), 0.5 Wplasma for H-mode (typical 0.25), Wplasma for advanced regimes • Broadening of the power flux footprint wrt full performance < 10 trise = 1.5 ms Maximum absolute fluxes Typical fluxes a factor of 2 lower for all regimes except 9MA advanced scenario high b disruptions Even worse case disruption loads are unlikely to damage TBM (5 cm, 3o) < 0.01 MJm-2
Power Fluxes during disruptions : Current quench • Power fluxes during current quench dominated by plasma radiation of the plasma poloidal magnetic energy ~ 550 MJ (15 MA), 190 MJ (9 MA), 140 MJ (7.5 MA) • Shortest time duration of current quench [Ip/(dIp/dt)] ~ 16 ms tEc.q. ~ 8 ms • Peaking of radiation during current quench < 3 • Average radiation flux ~ normal to wall receding TBM does not help much Even high Ip cases with high peaking at TBM (unlikely) are not expected to cause significant Be melting more detailed modelling for TBM could be done if needed
Conclusions • Studies carried out following ITER Design review have lead to re-specification of power fluxes to ITER PFCs • The design of the first wall has been modified for power fluxes IIB leading to higher power fluxes in some areas (upper X-point during diverted operation, outer side during ramp-up/down, etc.) • Power fluxes to TBM frame and TBM following same methodology as FW fluxes have been derived for steady and transient phases of ITER discharges • Present recession of ~ 5 cm beyond separatrix position at TBM is sufficient to maintain plasma fluxes to very low values (avoidance of edges on TBM face is advisable) both for steady-state and transients • Main power fluxes loads are radiative and C-X (erosion ?) • Typical values of ~ 0.3 MWm-2
SOL Profiles QDT = 10 B2-Eirene simulations for a large range of conditions B2-Eirene V. Kotov
ELM control and material damage J. Linke Control of ELM fluxes to divertor from material damage and experimental measurements in tokamaks • Material damage to CFC and avoidance of edge melting in macrobrushes for controlled ELMs Ediv < 0.5 MJm-2 • ELM experimental measurements Ediv < 0.5 MJm-2 DWELMcontrol < 1 MJ (x 20 smaller than uncontrolled) R. Dejarnac- PIC simulations 0.5 mm gap, T ~ 2.5 KeV A. Kukushkin et al.
ELM power fluxes to main wall during diverted phases (IV) • Basic design criteria EII,ELM(DRsep = 5 cm) < 0.1 EII,ELM(DRsep = 0 cm) A. Kirk Calculated with Fundamenski PPCF’06 Pcontrolled-ELMwall < 0.1 PELM < 4 MW
ELM power fluxes to main wall during diverted phases (V) • Filament impact leads to concentrated power deposition • Typical FWHM = 0.25-0.5 ELM filament spacing • Random impact reduces average ELM power flux by 1.7-3.1 ELM filament impact overlap leads higher heat flux than average JET- R. Pitts. PSI’08 • <q||,ELMupper-X>= 12-24 MWm-2 (Dt < 0.5 s with q||,ELMupper-X = 16-32 MWm-2)
ELM power fluxes to main wall during diverted phases (I) • Divertor damage avoidance during ELMs tolerable ELMs restricted in size • 15 MA QDT = 10 DWELM = 1 MJ & fELM = 20 - 40 Hz • 9 MA QDT = 5 DWELM = 2.4 MJ & fELM = 8 - 17 Hz • 7.5 MA H-mode DWELM = 2.4 MJ & fELM = 5 - 10 Hz • Occasional uncontrolled ELMs : ~ 20 MJ (15 MA & QDT =10), ~ 7 MJ (9 MA & QDT = 5), ~ 4 MJ (7.5 MA & H-mode) • Determination of ELM fluxes to main wall main wall by “validated” models but uncertainties remain allowance for these in specifications • Basic design criteria • EII,ELM(DRsep = 5 cm) < 0.1 EII,ELM(DRsep = 0 cm) • lELM = 2.5 – 9.0 cm
ELM power fluxes to main wall during diverted phases (II) • Filament impact leads to concentrated power deposition • Typical FWHM = 0.25-0.5 ELM filament spacing • Random impact reduces average ELM power flux by 1.7-3.1 ELM filament impact overlap leads to higher heat flux than average but for short periods (0.5 s for 40 Hz) JET- R. Pitts. PSI’08
ELM power fluxes to main wall during diverted phases (III) trise • ELM plasma power fluxes parallel to B near outer midplane wall ~ 6 MWm-2 for DT and ~ 2 MWm-2 for DD/He • Energy fluxes parallel to B for uncontrolled ELMs in limiter shadow can cause melting of exposed edges • Decay of ELM fluxes (parallel to B) in limiter shadow strongly dependent on dominant transport mechanism • lshadow < 2-5 mm for convective transport (lshadow ~ Llim/Lc) • lshadow ~ 1 - 2 cm for diffusive transport (lshadow ~ (Llim/Lc)1/2)