Overview of Pilot Plant Studies and contributions to FNSTand contributions to FNST

Jon Menard,Rich Hawryluk, Hutch Neilson,Stewart Prager, Mike Zarnstorffg ,

Princeton Plasma Physics Laboratory

Fusion Nuclear Science and Technology Annual MeetingUCLA

August 2-4, 2010August 2 4, 2010

Motivation for Pilot Plant studies

• Understand parameter space of FNS-capable facilities

– Provide context/choices for missions and designs of FNSF

– Identify remaining gaps necessary R&DIdentify remaining gaps, necessary R&D

– Is high neutron wall loading + small net electric possible?

• Assess requirements for net electricity from MFE

Required physics and technology performance design– Required physics and technology performance, design

– How large would pilot plant devices be?

• Have a plan to put electricity on the grid using MFE

– Demonstrate fusion’s viability and utility2

FNSF-P Definition• FNSF-P = Fusion Nuclear Science Facility – Pilot

• A member of the FNSF family:

– Steady-state plasma operating scenariosSteady state plasma operating scenarios

– Neutron wall loading ≥ 1MW/m2

– Tritium self-sufficiency

Ultimatel capable of higher ne tron all loading for– Ultimately capable of higher neutron wall loading for component testing

Si d t b bl f d i h f i• Sized to be capable of producing enough fusion power for (small) net electricity - a “pilot plant”

• Assume S&T basis between ITER and ARIES3

Key pilot metric is overall electrical efficiency Qeng

Qeng =ηth (MnPn + Pα + Paux + Ppump )

Paux + P + P b + P l + P lηaux

+ Ppump + Psub + Pcoils + Pcontrol

)/5/514( fuspumpnauxth PPQMQQ

ηη +++

η h = thermal conversion efficiency

)/1(5)(

fusextraaux

fuspumpnauxtheng PQP

QQQ

ηηη

+=

ηth thermal conversion efficiencyηaux = injected power wall plug efficiencyQ = fusion power / auxiliary powerMn = neutron energy multiplierBlanket and auxiliary heating n gy pPn = neutron power from fusionPα = alpha power from fusionPaux = injected power (heat + CD + control)Ppump = coolant pumping power

Blanket and auxiliary heating and current-drive efficiency + fusion gain largely determine electrical efficiency Q pump p p g p

Psub = subsystems powerPcoils = power lost in coils (Cu)Pcontrol = power used in plasma or plant control

that is not included in Pinj

electrical efficiency Qeng

Pumping, sub-systems power assumed to be proportional to inj

Pextra = Ppump + Psub + Pcoils + Pcontrolassumed to be proportional to Pthermal – needs further research

4

ARIES and EU studies have explored range of technologies for blanket and divertor

Pl t t ffi i 0 31/0 33 0 35 0 37 0 42 0 60

• Higher temperature enables increased thermal efficiency

Plant net efficiency 0.31/0.33 0.35 0.37 0.42 0.60

– Plant net efficiency is defined as ratio between the net electrical power output and the fusion power 5

FNSF-P study exploring 3 configurations:

• Advanced Tokamak (AT)– Most mature physics and technology data base

• Spherical Tokamak (ST)Spherical Tokamak (ST)– Most compact radially, vertical maintenance

• Compact Stellarator (CS)– Low re-circulating power, greatly reduced disruptivity

6

Initial Qeng ≥ 1 design points identified for AT, ST, CS

• Thermal conversion efficiencies compared: ηth = 0.3 and 0.45AT d CS il t h f i 0 3 0 5GW ST i 2 hi h

Fixed ηaux = 0.4, Mn=1.1, AT/CS inboard shield + blanket thickness = 1m, ST inboard shield thickness = 15cm

– AT and CS pilots have fusion power = 0.3-0.5GW – ST is ~ 2× higher– ST pilot has highest neutron wall loading, smallest radial build– CS has highest Qeng due to small power for heating and current drive g

– Approximate, preliminary pilot size: 2/3 linear dimension of ARIES-AT, ST, CS

• Ongoing analysis priorities for FNSF-P size and availabilityOngoing analysis priorities for FNSF P size and availability– Blanket radial build, pumping power– Magnet current density

Maintenance schemes

• Technology advances offer the most benefit.

– Maintenance schemes– Divertor and first wall heat flux limits

7• What advances should be

assumed in the design?

Advanced TokamakAdvanced TokamakFNSF-P Analyses

8

AT size depends on achievable TF current density

ARIES TF coil algorithm allows about 45 MA/m2 average currentabout 45 MA/m average current density over the TF coil, while ITER design allows about 15 MA/m2

Variation of the allowed jTF from ARIES to ITER shows that larger major radii are required as the ITER

l i h dvalue is approached.

Using the ITER jTF the radial build of ITER b i t lITER can be approximately reproduced, when ITER operating point is input.

Working with MIT to develop a better understanding of what should be requirement for a pilot plant

9

requirement for a pilot plant.

Systems studies have identified additional important parameters that influence size and fusion power

4000

3500Shield Thickness = 1.25)

4000

3500 Fdiv rad = 0.70W])

3500

3000

2500

Shield Thickness = 1.00Shield Thickness = 0.75

P fus

= [M

W] 3500

3000

2500

Fdiv,rad 0.70Fdiv,rad = 0.80Fdiv,rad = 0.90

(Pfu

s =

[MW

2000

1500

n P

ower

(P

2000

1500

ion

Pow

er

1000

500

Fusi

on

2.0 3.0 4.0 5.0 6.0 7.0 8.0

1000

500

Fusi

Major Radius (R = [m])0 0

2.0 3.0 4.0 5.0 6.0 7.0 8.0

Major Radius (R = [m])

Increasing the allowable heat flux to the divertor or the radiated heat fraction increases the maximum

Inboard “shield thickness” is a consideration for the radial build

10

fraction increases the maximum fusion powers accessible.and affects machine size.

Comparison of AT Pilot, ITER, ARIES

AT Pilot has smaller size higher field compared to ITER AT

11

AT Pilot has smaller size, higher field compared to ITER-ATNOTE: tradeoff between pilot plant thermal efficiency (0.3/0.45) and physics aggressiveness.Further work underway to benchmark pilot plant calculations vs. ITER, ARIES

Spherical TokamakSpherical TokamakFNSF-P Analyses

12

ST Pilot Plant study parameters, assumptions

Aspect ratio 1.7Plasma elongation 3.3Plasma triangularity 0.6Toroidal field at R0 2.4TE 0 5M VENBI 0.5MeVNon-inductive fraction 100% (BS+NBI)

• Scan major radius and density (Greenwald fraction)• Typically choose Pfusion, PNBI , QDT to be independent of ne

• Vary IP and H98 to achieve QENG=1, fNI=1

• Offset cost of increased R0 by reducing physics risk in QDT:• Choose ΔQDT º -5 for ΔR0 = +0.25m, q* > 2 limits maximum IP at low ne

• Solutions become more conservative as R0 is increased• Thermal conversion η=0 45 0 3 ΔIB hi ld=15cm SC PF coilsThermal conversion η 0.45, 0.3, ΔIB-shield 15cm, SC PF coils

13

Increased ne / nG reduces H98, βN, fast ion fractionIncreased R0 reduces H98, βN, bootstrap fraction

But one disadvantage of increased density is increase in required fBS

14NOTE: R=2.25m* case is same as R=2.25m case but with PNBI = 40 60MW

Now focusing on ST Pilots intermediate between ST-FNSF and ARIES-ST in size, β, fusion performance

15Possible ST progression: DD, PMI validate, FNS, component test, QENG 1

Compact StellaratorCompact StellaratorFNSF-P Analyses

16

Stellarator Pilot builds on ARIES-CS studyReference parameters for baseline: 

NCSX lik 3 i dNCSX‐like: 3 periods

⟨R⟩ = 7.75 m 

⟨a⟩ = 1 72 m⟨a⟩ = 1.72 m 

⟨n⟩ = 4.0 x 1020 m–3

⟨T⟩ = 6.6 keV ⟨ ⟩

⟨B⟩axis = 5.7 T

⟨β⟩ = 6.4%

H(ISS04) = 1.1

Iplasma = 3.5 MA                                                                           (b t t ) U Q i i t t t t k k lik fi t(bootstrap)

P(fusion) = 2.364 GW

P(electric) = 1 GW

• Use Quasi‐axisymmetry to get tokamak‐like confinement • 3D shaping for stability & sustainment

i h d i l d k kP(electric) = 1 GW

Ignited, no external heating• High density, low temperature compared to tokamaks• Only needs  ~ “L‐mode” confinement

17

High QEng > 1 accessible in stellarator pilot6

4

5

6

• External heating can be b t ti ll d d d t

2

3

B (

T) substantially reduced due to no-need for CD

0

1

3 4 5 6

Qeng=1.1Qeng=2Qeng=4

HISS04 < 2, βmax < 6%• Qeng=4.4 is maximum possible with assumed efficiencies: ηth=0.3,  plant load is 7% of 3 4 5 6

Major Radius (m)

5

6

ηth , pthermal power

• All cases have Pdi < 10 MW / m2

3

4

B (

T)

Qeng = 1.1All cases have Pdiv < 10 MW / m

1

2

H-ISS04=2H-ISS04=1.5H ISS04 1 25

• Required confinement enhancement modest, sub‐H‐

d03 4 5 6

Major Radius (m)

H-ISS04=1.25 mode

18

Neutron wall loading ≥ 1 MW/m2 for FNS testing possible in smaller major radius, higher Qeng CS Pilots

1 4

1.6m

2 )

p j , g Qeng

1.0

1.2

1.4Lo

ad (M

W/m • HISS04 < 2, βmax < 6%

0.6

0.8

utro

n W

all L

0.2

0.4

Peak

Neu

Qeng=1.1Qeng=2Qeng=4

0.03 4 5 6

Major Radius (m)

Qeng 4

• Higher wall loading possible at higher fusion power• Pfus = 475 MW, with HISS04 =2, β=6%, Pneut>2 MW/m2Pfus  475 MW,  with HISS04 2, β 6%, Pneut>2 MW/m• R/<a> = 4.5m/1m, B0 = 5.7T 19

Summary

• There is a range of FNSF missions, varying in their b fit d i kbenefits and risks.

• Net-electricity mission places high value onNet electricity mission places high value on technology advances to reduce device size and power consumption – useful for any FNSFpower consumption useful for any FNSF

• Push for smallest possible FNSF should be weighed i b fi f d i i iagainst benefits of modest increase in size:

– Increased physics margin (lower H98, βN, fBS, …)y g ( 98 βN BS )

– Increased space for magnets, blankets, divertors

Ability to access physics and technology closer to reactor– Ability to access physics and technology closer to reactor20