Prospect  of  a  High  Performance,  High  Radia5on,  Steady-­‐State  Scenario  for  CFETR  

Vincent Chan1,2, Jiangang Li3, Yuanxi Wan1 and the CFETR Physics Team

1 USTC 2 General Atomics

3 ASIPP

Presented at the 4th IAEA Demo Workshop Karlsruhe, Germany Nov 15-18, 2016  

1  

-  Complementing ITER

-  Demonstration of fusion energy

production (50-200 MW for Phase I)

-  Demonstration of high duty factor, 0.3

– 0.5

-  Demonstration of tritium self-

sufficiency with TBR > 1

-  Exploring options for DEMO blanket

and divertor solution

-  Solution for easy remote

maintenance of in-vessel

components

CFETR Shares Many Characteristics with DEMO

2

Steady-State with High Duty Cycle is Key to Meeting CFETR Mission

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Metrics ITER CFETR Phase 1-2 DEMO

Neutron wall loading (MW/m

2)

~0.5 0.4 – 2.0 2.0 – 4.0

Life of plant fluence (MW-yr/m

2)

0.2 – 0.4 1.2 – 10 10 – 34

Qfus

5 – 10 3 – 15 10 – 40 Plasma performance βN

2-3 2-4 4-6

Longest plasma duration (s) 10

2 – 10

4 10

5 - 10

6 10

7

Total availability 2% – 5% 30% – 50% 50% – 85% Tritium breeding TBR << 1 TBR≥ 1 TBR > 1 P

Heat/A

wall MW/m2( ) ~ 0.2 0.2 – 0.4 0.8 - 1.0

!

0D System Code Used to Scope out CFETR Baseline and Advanced Scenarios

B.  Wan,  Plasma  Science  IEEE,  42  (2014)  V.  Chan,  NF  55  (2015)   4

Does  not  iden*fy  specific  steady-­‐state  scenario  

Paths to Steady-State Have Experimental Basis

5

Projec5ons  From  Experiments  

Reverse  Shear  

Hybrid  Mode  

 F.Turco,  POP  2015  

S.Y.  Ding,  APS  invited  talk  2016  

ELM  control  Radia5ve  divertor  

Challenge:  -­‐  High  fbs  -­‐  qmin  control  

Challenge  -­‐  Flux  pumping?  -­‐  Avoid  2/1  

•  0D system code has missing physics

-  Pedestal contribution

-  Physics-based transport i.e. only assumes H factor

-  Profile information and stability

-  Achievable βN  and  fbs

•  IM informs key engineering design requirements

-  H&CD, Divertor heat and particle fluxes

-  Plasma control

•  Critical to CFETR diagnostics design and operation

Integrated Modeling (IM) Used to Quantify Reverse Shear (RS) Scenario and Connect with Engineering Design

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•  Physics code suite -  TGYRO with NEO and TGLF transport; EPED -  ONETWO/NUBEAM/TORAY/GENRAY for sources and sinks;

Ip evolution -  EFIT for equilibrium; GATO, ELITE, BOUT++, NIMROD, Nova-

K for stability -  SOLPS and OEDGE/DIVIMP for SOL and divertor •  Evolving electron density, Te and Ti, and momentum -  D&T/He/impurity profiles same as ne and obey quasi-

neutrality -  Boundary conditions at pivot point ~ top of pedestal •  SOL solution matches core parameters at pivot point

Physics-Based Models and Modeling Assumptions

7

OMFIT Framework Facilitates Self-Consistent Integrated Scenario Development

O.  Meneghini,  POP  23  (2016)     8

Self-Consistent Transport, Equilibrium and Pedestal: Fully Non-Inductive RS Solution

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Characteris5cs:  -  Strong  reverse  

shear  -  qmin  >  2  -  Moderate  ITB  

forma*on  

Optimization of Electron Cyclotron Frequency and Launch Location

E.  Poly,  Nucl.  Fus.  53  (2013)     10

ECCD  for  controling  qmin  

Optimization of Neutral Beam Energy

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•  NB  has  reasonable  CD  efficiency  and  is  efficient  in  providing  plasma  rota*on  for  good  confinement    

•  NB  launch  angle  is  constrained  to  avoid  both  large  shine  through  and  edge  hea*ng.    

Use of a Two-NB Strategy

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•  Fixed  high  energy  NB  at  300  keV;  op*mize  low  energy  NB  •  50  keV  NB  yields  the  highest  Q  and  lowest  edge  hea*ng  

Confinement Factor Responsible for Differences between OD and 1.5D Predictions

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H98=1.3  is  not  achievable  even  with  NB  rota*on  for  baseline  case  

R=5.7m  BT=5T  

Pedestal Collisionality has Significant Impact on Fusion Gain

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•  Keeping  pedestal  pressure  fixed,  pedestal  density  is  varied  •  Density  increases,  DPF  unchanged  -­‐>  Q  increases  significantly  •  Higher  pedestal  collisionality  might  also  benefit  ELM  control  PDM=pedestal  density  mul*plier  DPF=density  peaking  factor  

Turbulence Responsible for Weak Density Profile Change with Pedestal Collisionality

15

TEM  and  ITG  turbulence  influence  par*cle  transport  in  opposite  direc*ons  resul*ng  in  weaker  profile  change  

RF Dominated Steady-State Scenario is Another Option

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NB  competes  with  Tri*um  Blanket  for  port  space  

Higher BT CFETR (R=6.7m, BT=6T) has Higher Fusion Gain

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•  Confinement  improves  with  larger  R  and  BT  ⇒ Lower  CD  power  and  higher  fusion  gain  

•  Higher  βP  =>  higher  bootstrap  fac*on  •  n/nGW  =  0.8  

Phase  I  

Agreement  of  TGYRO/TGLF/NEO  with  Experiment  Improves  with  Lower  q95

J.T.  McClenaghan,  APS-­‐DPP  2016  C.K.Pan,  APS-­‐DPP  2015   18

q95=9  

q95=6=qCFETR  

Ti  

CFETR can Operate Over a Range of βp  and  βN

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High  fbs  

ITER-­‐like  

High  βN  

CFETR Baseline Stable to Ideal MHD in the Core, Unstable to ELMs

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-  Unstable  modes  driven  by  strong  pedestal  gradient  

-  Low  n  modes  stabilized  by  wall  at  r/a=1.2  

Helium Fraction Cannot Exceed 0.2 in Order to Meet CFETR Pfus Target

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PNB  (MW)  

PRF  (MW)

Pa  (MW)

Pcyc,Pbres,Pline(MW) βN H98 Q τE

(s) Ne0,nDT0 Te0,Ti0  (KeV)

fHe=0.05 52.5 10.1 34.9 5.2,4.5,6.7 1.93 1.04 2.79 1.73 7.49,6.44 28.0,25.3

fHe=0.1   58.0 10.1 21.9 3.8,4,4,6.4 1.62 0.92 1.61 1.60 6.94,5.42 24.9,23.2

fHe=0.15 59.5 10.1 18.2 3.7,4.6,6.7 1.58 0.92 1.31 1.63 7.04,4.9 23.8,23.0

fHe=0.20 62.5 10.1 12.7 3.2,4.7,6.7 1.47 0.88 0.88 1.57 6.81,4.15 22.2,22.0

Impurity Transport Profile Determined Using TGYRO

B.  Grierson,  APS-­‐DPP  (2015)     22

Γ imp = −Dimpnimp

aa

Ln_ imp+Vimpnimp

Impurity  profile  obtained  from  TGYRO  assuming  no  impurity  source  in  core   nimp (r) = nimp (rpivot )exp(

Vimp (x)Dimp (x)rpivot

r

∫ dx)

Argon  impurity  profiles  with  different  effec*ve  charge  Zeff.  

Fusion Performance Improves before Dropping Off with Increasing Zeff

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PNB  (MW)  

PRF  (MW)

Pa  (MW)

Pcyc,Pbres,  Pline(MW)

PLOSS/PTOT

H98 Q fbs τE(s) Ne0,nDT0

Te0,Ti0  (KeV)

Zeff=1.52 53.7 10.1 19.5 3.1,3.2,4.3 12.7% 0.86 1.44 35.5% 1.48 6.99,5.58 22.1,20.2

Zeff=1.89 53.5 10.1 21.8 3.8,4,4,6.4 17.1% 0.92 1.61 37.2% 1.60 6.94,5.42 24.9,23.2

Zeff=2.11 54.0 10.1 24.1 4.3,5.1,7.9 19.6% 0.96 1.76 39.6% 1.66 7.09,5.48 25.8,24.4

Zeff=2.35 55.3 10.1 24.5 4.3,5.8,9.5 21.8%   0.98  1.75 40.3%    1.68 7.07,5.45    25.6,24.5

Zeff=2.78 56.1 10.1 25.2 4.5,7.0,12.0 25.7% 1.01 1.76 42.1% 1.76 7.10,5.32 26.8,26.3

Zeff=3.20 57.6 10.1 23.3 4.3,8.1,14.4 29.5% 1.00 1.58 42.3% 1.78 7.02,5.08 25.2,25.2

Zeff=3.67 59.9 10.1 23.1 4.9,10.0,17.1 34.4% 1.00 1.44 43.7% 1.78 6.99,4.88 25.9,25.6

Confinement Trend with Zeff is Consistent with Experimental Observation

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G.  Mckee,  PRL  (2000)  

R.  Dominguez,  NF  (1993)  

SOLPS Set Up to Couple Core-SOL-Divertor

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Divertor    plates  

Consistent Boundary Coupling Demonstrated

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Assumed  diffusion  coefficients  

Edge  hea5ng  not  included  

Heat  flux  decay  width  in  SOL  similar  to  scaling  law  

Heat Flux to Divertor Acceptable for Baseline Case

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A Steady-State, High Performance, High Radiation CFETR is Demonstrated

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Phase  I   Phase  II  Qfus   3.0   14.9  Pfus  (MW)   169   811  Ip  (MA)   7.6   10  Bootstrap  frac5on  fbs  (%)  

64   84  

βN 1.9   3.2  H98   1.3   1.3  NB/EC  Power  (MW)   36/20   35/20  

Neutron  wall  loading  (MW/m2)  

0.19   0.92  

Divertor  heat  load  Pdiv/R  (MW/m)  

10.4   25.8  

Ion  frac5on  nD/nT/nHe/nAr  

0.43/0.43/  0.05/0.003  

0.43/0.43/  0.05/0.003  

Ra5o  to  Greenwald  Limit  

.83   1.03  

-  R=6.6m,  BT=6T  -  2  NBs:  100/500  keV  -  Addi*onal  fueling  

needed  for  phase  II  

-  High   performance,   radia5ve   core   compa5ble   with   detached  divertor  

-  Performance  op5mized  using  NB  and  pedestal  control  -  Both  NB-­‐dominated  and  RF-­‐dominated  op5ons  are  available  

-  A  broad  opera5on  range  in  βN  and  βp,  stable  with  wall  at  r/a=1.2  -  Radia5on  in  the  core  acceptable  up  to  Zeff  ~  3.0  -  Helium  dilu5on  fHe  cannot  exceeds  0.2  to  meet  Pfus  target  

Future  work  will  focus  on  Phase  II  op5miza5on  of  the  R=6.7m  CFETR  consistent  with  steady-­‐state  and  a  radia5ve  divertor  solu5on  

Conclusion

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A reverse-shear, steady-state scenario with performance that meets the CFETR mission has been demonstrated

 

Acknowledgement

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Key  contributors:  J.L.  Chen,  X.  Jian,  D.  Zhao,  L.  Lao,  C.K.  Pan,  Z.Y.  Li,  N.  Shi,  X.J.  Liu,  Y.F.  Zhou,  S.F.  Mao,  G.Q.  Li,  P.  Zhu,  G.  Zhuang,  M.Y.  Ye    We  are  grateful  to  GA,  PPPL,  Wisconsin,  LLNL,  U.  York,  MPG-­‐IPP  and  U.  Toronto  for  the  use  of  their  physics  code  suites    

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BACK  UP  SLIDES  

•  Safety factor and q95

•  Rotation profile

•  Pedestal collisionality

•  Operational space in β    

•  Radiative core compatible with divertor

Control Aspects in Optimizing CFETR Performance for Reverse Shear Scenario

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TGYRO Flux Convergence Indicative of Transport Steady-State

J.  Candy,  POP  16  (2009)     33

All  transport  channels  are  evolved  to  steady-­‐state  

TGLF Physics-Based Transport Model Improving with Multi-scale GYRO Simulation

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Low-n ELM Stabilized by Wall at r/a=1.2

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Heat Flux to Divertor Consistent with Divertor Plate Angle

36