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Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 1
Report on ITER Design Review Sub-group on : Heat and Particle Loads to
in-vessel components associated with limiter and X-point operation, TF
ripple, H&CD systems, ELMs, disruptions, VDEs, Marfes and runaway
electrons in ITER
Alberto LoarteEuropean Fusion Development Agreement
Close Support Unit – Garching
Acknowledgements: A. Grosman, P. Stangeby, G. Saibene, R. Sartori, M. Sugihara,
W. Fundamenski, T. Eich, P. Snyder, V. Riccardo, G. Counsell, R. Pitts, B. Lipschultz,
P. Andrew, G. Pautasso, A. Leonard, G. Strohmayer, G. Federici, A. Kirk, J. Paley,
M. Lehnen, B. Alper, C. Ingesson, etc.
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 2
ITER PID only specifies Pmaxlimiters = 15 MW (max 9 MW on one limiter)
Fluxes to limiter during Ramp-up/down (I)
Reference ITER ramp-up(/down) has long limiter phases up to Ip = 7 MA (10 MA) in which
plasma is limited by two limiters 180o apart (power loads & erosion)
2 limiter configuration and qlim = 5 lead to long
connection lengths in SOL (>> 200 m)
Magnetic shear + perpendicular transport simple “single exponential” power decay length (Kobayashi, NF 2007)Main Uncertainties
PSOL for all ITER reference scenarios (ramp up/down with heating)
Scaling of SOL transport with Ip and R (JET extrapolation for Kobayashi NF 2007)
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 3
ITER power and power fluxes estimated with B2-Eirene for a range of burn conditions (mainly QDT = 10) to maintain detachment but weak physics basis
for SOL transport and main chamber fluxes
Fluxes to main wall and divertor during diverted operation (I)
near SOL transport p = 5 mm (close to most pessimistic scalings 4 mm) for Ip = 15
MA (6 mm for scenario 3 (hybrid) and 8 mm for scenario 4 (ITB) if p ~ Ip-1)
qII = 570 – 760 MWm-2 for PSOL = 100 MW (typical for scenarios 1 & 2)
H-mode scenarios 1 & 2 wall = 5–20 cm qIIwall < 0.04 MWm-2 lIB
L-mode scenarios 1& 2 (PSOL=35 MW, L=2 H) & wall=5–20 cm qIIwall < 1.0 MWm-2 IIB
0.5o < < 15o FW load < 0.5 MWm-2 fulfilled but loads on edges ? (2mm steps) and edges of ports ?
Main uncertainties : In/out divertor power asymmetry (ballooning transport) Far SOL transport (wall fluxes) Scaling of p
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 4
Particle flux to ITER main wall expected to be > 1023 s-1 (> 1% of div)
Fluxes to main wall and divertor during diverted operation (II)
Lipschultz
0.00 0.05 0.10 0.15
105
106
L = 60 m, TSOL
= 10-20 eV, VSOL
= 30 - 100 m
qup
II qlow
II
qup
perp qlow
perp
Distance to Separatrix (m)
q II (W
/m2 )
104
105
qperp (W
/m2)
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.140.0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
Distance to active separatrix at midplane (m)
An
gle
of
inci
de
nce
(o )“Scarce” data & ITER B2-Eirene modelling : n (sep ~ 5 cm) = 0.4 - 1.0 1019 m-3
vSOL = 30 – 100 ms-1
TSOL = 10 – 20 eV SOL = 4.5 – 21 cm
qII < few MW II B on (outer) first wall local particle & power fluxes on edges and edges of ports ?
qperp < 0.3 MW m-2 < OK for FW panels
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 5
w/o convection
with convection
P//=94kW (/20MW)P//=88kW
Q//=0.4|VRF|necs
•Integrated losses : typically 100kW for 20MW injected (low density case)
•Localised peak at 10MW/m2 ; average
~2.5MW/m2
•These results depend crucially on the density value in the first cm in front of the wall (far-SOL transport ?) • Sheath rectification may reach 2-3 kV
Sputtering of surfaces!
Fluxes associated with heating systems and steady-state non-toroidal asymmetries
NBI shine-through limit ne > 3.7 1019 m-3 (30% nGW) for 0.5 MWm-2 (edges ?) but no
local ionisation or first orbit losses included Ripple losses expected to to lead to less than 0.3 MWm-2 (3-D effects ?) Effect of ELM RMP coils on power deposition assymetries ? ICRH (and LH) can lead to large power fluxes on PFCs near and far field (not included
in PID) EFDA Task TW6-TPHI-ICFS2 (L. Colas, CEA)
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 6
In transient events 1 cm SOL field line touches first wall for 1 s
Plasma Position and Shape Control
If plasma in H-mode then depending on location of contact plasma stays in H-mode or H L transition
H-mode H L350 MJ 175 MJ
qIIcontact-wall 77 – 102 MWm-2
pcontact-wall 0.5 cm
tcontact-wall 1 s
qIIL-H contact-wall > 105 - 140 MWm-2
pL-H 1.0 cm
pL-H < 1.7 s
sin = 1-8 10-2
sin = 1.5-2.5 10-1
in “minor disruptions” separatrix can touch dome for ~ 1 sqII in,dome ~ 380 - 570 MWm-2
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 7
PID estimates of ELM loads for ITER carried out on simplified experimental basis
Fluxes to main wall and divertor during ELMs (I)
Specified loads are of the right magnitude but can be improved to include ELM physics understanding (time dependence, in/out asymmetries, relation “” vs WELM/Wped
Sugihara, ITER_D_22JYYU, 2005
700-950 MWm-2 3.5-4.7 GWm-2
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 8
Fluxes to divertor during ELMs (II)
222
exp1)(ttt
tqELM
WELM < 30 MJ
Adiv,ELM = 4 m-2
Broadening < 1.5
rise,ELM = 200-500 s
down,ELM = 1-2 rise,ELM
Loarte, PPCF’03
Eich, PIPB’07
Eich application of
Fundamenski PPCF’06
Eich, PIPB’07
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 9
Fluxes to divertor during ELMs (III)
TPFdiv,ELM < 1.5
Ein,ELM/Eout,ELM = 1-2
Divertor ELM load near separatrix ~ toroidally symmetric but strong in/out asymmetries
Eich, PRL’4
Loarte, PPCF’03 from Leonard JNM’97
DIII-D
Eich, JNM’07
Eich, JNM’07
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 10
Fluxes to divertor during ELMs (III)
Wdiv,ELM 5 MJ 30 MJ
Einmax (MJ) < 3.3 < 20
Eoutmax (MJ) < 2.5 < 15
Einmin (MJ) < 2.5 < 15
Eoutmin (MJ) < 1.7 < 10
qinmax (GWm-2) < 6.2 < 37.5
qinmin (GWm-2) < 1.9 < 11.3
qoutmax (GWm-2) < 4.7 < 28.1
qoutmin (GWm-2) < 1.3 < 7.6
risemax (s) 500 500
risemin (s) 200 200
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 11
Part of WELM is reaches the main wall PFCs formation and ejection of filaments
Fluxes to main wall during ELMs (I)
0.05 0.10 0.15 0.200.0
0.2
0.4
0.6
0.8
1.0
1.2DOC-L = 0.27 1.2MA q
95 = 3.1
2MA q95
= 3.7
2MA q95
= 4.6
3MA q95
= 3.1
WE
LM
IR/
WE
LM
WELM
/Wped
Model of qII(t) for detached filaments developed by Fundamenski (PPCF’06) and validated with JET data (Pitts NF’06) Application to ITER
JET-Eich, PIPB’07
MAST- Kirk, EPS’06
AUG- Herrmann –PPCF’06
?
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 12
qII in filament estimated with model by Fundamenski required input to model : nfil, Tfil, <vELM/cs,ped> & distance from sep @ filament detachment
Fluxes to main wall during ELMs (II)
ELM fluxes to main wall (beyond second sep) only on outer wall Power reaches the wall in filamentary structures (for ITER Snyder results in NF’04) :
distance between filaments (m) = 15/n (if no break-up and all become unstable) filament poloidal width (m) = 3/n (rough estimate) Decay length of filaments in “limiter” shadow ~ Llim/LSOL ?
Outstanding issues : Relation VELM & WELM vELM/cs,ped = 10-2 WELM/Wped or 1.5 10-3 (WELM/Wped)0.5
nfil, Tfil Rfil at instant of detachment & ELMWall (~ ELM
div ?) wall
ELM sputtering
0.0000 0.0005 0.0010 0.0015 0.0020
0.1
1
10
From modelling by W. Fundamenski
5 cm from sep 10 cm from sep 15 cm from sep
VELM
/CS
q II (G
Wm
-2)
nfil = 7.5 1019 m-3, T
fil = 5 keV, detachment from R
ped = - 5cm
0
200
400
600
800
1000
qII upper-B
e-walllow
er-Be-w
all (MW
m-2)
Herrmann-AUG
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 13
PID specifications generally in line with current evidence from disruption loads but need to be refined to incorporate latest findings on divertor/wall
loads
Fluxes to main wall and divertor during Disruption thermal quench (I)
Classification of loads per disruption type (ideal MHD limits, etc.) and scenario Disruptions in limiter phase are absent in specifications Toroidal and in/out asymmetries ? Radiation during thermal quench ?
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 14
Fluxes to main wall and divertor during Disruption thermal quench (II)
Plasma energy at t.q. typically less than 40% expected from H98 = 1 (Size scaling ?)
Dedicated experiments at JET in 2006/2007 show that Wt.q. < 0.4 W (Type I H-mode) for density
limits, radiative limits and NTM driven disruption
JET-Riccardo NF’05
MAST-Counsell
t.q. timescale has large scatter associated with MHD activity but similar to ELMs large amount of energy
reaches PFCs after qmax
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 15
Fluxes to main wall and divertor during Disruption thermal quench (IV)
Broadening of power width causes energy deposition IIB everywhere on PFCs (TPF < 2) significant amount of energy deposited outside divertor
Disruptions in divertor conditions triggered by ideal MHD limits and in limiter seem completely different many aspects
(P. Andrew, PSI’06, Riccardo NF’05, Finken NF’92, Janos JNM’92, TFR JNM’82)
JET-Paley-PhD Thesis ‘07
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 16
Fluxes to main wall and divertor during Disruption thermal quench (V)
Ideal MHD limit disruptions can lead to large interactions with inner-wall or outer wall not seen in other disruption types Not included in PID for scenario
4 (ITB) implications for ITER ?
PNBI (X 10 MW) PICRH (X 10 MW)
Prad (X 100 MW)
JET Pulse No. 69816 ITB grad-P disruption
Wdia (MJ)
Ip (MA)
Mode-lock (a.u.)
n = 2 (a.u.)
n = 1 (a.u.)
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 17
Disruptions in limiter phase
Not considered in PID but potentially serious because of lack of broadening of power footprint for limiter disruptions (t.q. < 1.5 s.s.)
EOL-ramp-up : Ip = 7 MA, if Pinp = 5 MW Wplasma (ITER-89) = 15 MJ
BOL-ramp-down : Ip = 10 MA, if Pinp = 7 MW Wplasma (ITER-89) = 24 MJ
TEXTOR-Finken NF 1992
For p > 2 cm Aeff,limiters = 2.5 m2 (H. Pacher)
Disruptions during limiter phases may cause loads > 6 – 10 MJm-2 with t.q. ~ 1 msMajor issue for power fluxes during VDEs needs to be confirmed
Janos-TFTR-JNM 1992
Normal discharge
Disruptive-normal discharge
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 18
Large discrepancy between PID specifications and new proposed specifications in Sugihara NF ‘07
Energy Fluxes to main wall and divertor PFCs during VDEs (I)
~ 134 MJm-2s-1/2
Possible Realistic scenario Plasma drifts towards wall in H-mode At some point L-mode transition (H-modes
with X-point behind target at JET) Wplasma (30-50 % of Wplasma) deposited on wall in
t < L-mode with p ~ 1 cm Plasma is in contact with wall in limiter L-mode
PSOL = 100 MW + dW/dt Plasma disrupts in limiters configuration when
q ~ 1.5-2 with Wplasma > 100 MJ
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 19
PID specifications for Marfe loads in ITER (physics model ?)
Energy Fluxes to main wall and divertor PFCs during Marfes (I)
Three types of “Marfes” expected in ITER (L-mode Plasma) :
Inner-wall Marfe Potentially steady-state Prad < PSOL (100 MW) (<0.15MWm-2>)
X-point Marfe Potentially steady-state Prad < PSOL (100 MW) (<0.15MWm-2>)
Pre-thermal quench divertor Marfe short-lived (< 0.1 s in JET and AUG) period in
which ~ 0.25 of Wplasma (H98 = 1) can be radiated Prad ~ 900 MW (<1.3 MWm-2>)
Pre-thermal quench limiter Marfe short-lived (< 0.1 s in JET) period in which a
fraction (?) of Wplasma (H89 =1) can be radiated Prad < 240 MW (<0.35 MWm-2>)
For all cases radiation peaks near X-point region or inner-wall
Main issue is to determine realistic timescales and peaking factors of radiation on wall
due to Marfe for ITER
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 20
Examples of Marfes at JET
Energy Fluxes to main wall and divertor PFCs during Marfes (II)
Steady-state limiter MarfeA. Loarte Memo to RI-mode working group’99
Transient limiter MarfeJ. Wesson-Science of JET’99
~ Steady-state X-point MarfeA. Huber-PSI’06
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 21
Conclusions
Many of the PID specifications for PFC loads in ITER are not far
from expectations from latest experimental/model results Other are in disagreement with present evidence and/or absent A detailed review and update of PID specifications is needed &
will be carried out as part of the design review Contributions from ITPA groups and collaboration with ITER-IT
will be essential to do this review
Expected loads in ITER will determine fine details of PFC
construction (edge shadowing, etc. ), overall PFC configuration &
will have implications for the use of diiferent PFM in various areas
of the device
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 22
Other transients following plasma disturbances and noise in feedback/measurement system
Plasma Position and Shape Control (II)
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 23
Even if position control is recovered in 10s there are ~ 1s phases in which separatrix gets dangerously close to areas designed for low power loads
Plasma Position and Shape Control (I)
SOB Minor disruptionAppendix E
qII in,dome ~ 380 - 570 MWm-2 for ~ 1 s
Control of plasma in ITER can lead to fluxes IIB on PFCs > 100 MWm-2 for timescales ~ 1s and possibly fast H-L transitions
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 24
Most tokamaks find that close to 100 % of magnetic energy at t.q. is radiated with the exception of Alcator C-mod (< 25%)
Energy Fluxes to main wall and divertor PFCs during current quench
Wmag = ½ Lp Ip2
After t.q. p= 0 (0.2-pre), li~ 0.5 (0.85-pre), Ip <18 MA (15 MA-pre) Wmag < 1.85 GJ
a
Most of Wmag V.V. and in-vessel conducting structures Wc.q.PFCs < 315 MJ
For fastest timescale of c.q. in ITER ~ 16 ms (exponential) 36 ms (linear)
qradmax < 80 MWm-2
critical assumptions : Wc.q.PFCs < 315 MJ, 100% radiation & peaking factor < 1.4
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 25
Mitigation of disruptions by massive gas injection is a promising scheme but may lead to large fluxes on PFCs specification of
wall loads for ITER not yet in PID
Energy Fluxes to main wall and divertor PFCs during mitigated disruptions
Sugihara NF’07 assumes qrad = 0.5 – 1.0 GWm-2 in 1 ms
Estimates from Whyte for ITER predict <qrad> ~ 4 GW/m2 for trad < 200 s
Whyte PRL’02
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 26
Runaway generation mechanisms for ITER like disruptions conditions studied in detail but runaway losses and dynamics
are worse known specification of local loads for ITER ?
Runaway electron fluxes on PFCs (I)
Alberto Loarte 9th ITPA Divertor and SOL Physics Meeting IPP-Garching 7-10/5/2007 27
Runaway electron fluxes on PFCs (II)
Runaway electrons are not generated if q95 < 2-2.5 before current
quench (no r.e. in full VDEs but likely in disruptions) Runaway electrons are lost to PFCs by MHD turbulence when qedge =
3, 2 touches the wall Runaway beam has a peaked current profile ar.e. ~ 0.25 aplasma and is
vertically unstable Runaway impact point determined by vertical instability of column and
narrow e-folding length (~ few mm) Aeff ~ 0.5 m2 (if toroidally
symmetric) Runaways are lost in bursts of ~ 100 s over ~ 5-10 ms timescales
(JET and JT-60U)
Unclear whether all these facts are taken into account in present PID
specifications or not