Fusion Power Plants: Visions and Development Pathway

Farrokh NajmabadiUC San Diego

15th ICENESMay 15 – 19, 2011San Francisco, CA

You can download a copy of the paper and the presentation from the ARIES Web Site:

ARIES Web Site: http://aries.ucsd.edu/ARIES/

The ARIES Team Has Examined Many Fusion Concepts As Power Plants

Focus of the talk is on Tokamak studies: ARIES-I first-stability tokamak (1990)

ARIES-III D-3He-fueled tokamak (1991)

ARIES-II and -IV second-stability tokamaks (1992)

Pulsar pulsed-plasma tokamak (1993)

Starlite study (1995) (goals & technical requirements for power plants & Demo)

ARIES-RS reversed-shear tokamak (1996)

ARIES-AT advanced technology and advanced tokamak (2000)

Criteria for power plant attractiveness were developed in consultation with Electric Utilities and Industry

Nature of Power Plant Studies has evolved in time.

Concept Exploration (< 1990) Limited physics/engineering trade-offs due to lack of physic

understanding. The only credible vision was a large, expensive pulsed

tokamak with many engineering challenges (e.g., thermal energy storage).

Concept Definition ( ~ 1990-2005) Finding credible embodiments (Credible in a “global” sense). Better physics understanding allowed optimization of steady-

state plasma operation and physics/engineering trade-offs.

Concept Feasibility and Optimization (> 2010) Detailed analysis of subsystems to resolve feasibility issues. Trade-offs among extrapolation and attractiveness.

For the same physics and technology basis, steady-state devices outperform pulsed tokamaks

ARIES-I’Pulsar*

Medium (~ 8 m major radius)High (~ 9 m major radius)Size and Cost

Non-inductive driveExpensive & inefficient

PF SystemVery expensive but efficientCurrent-drive system

HighLowRecirculating Power

High Bootstrap, High A, Low IHigh Bootstrap, High A, Low IOptimum Plasma Regime

Yes, 65-%-75% bootstrap fraction, bN~ 3.3, ~ 1.9%b

No, 30%-40% bootstrap fractionbN~ 3, ~ 2.1%bCurrent profile Control

Higher (B ~ 16 T on coil) Lower because of interaction with PF (B ~ 14 T on coil)

Toroidal-Field Strength

MediumLowPower Density

* Many engineering challenges such as thermal energy storage,lower performance of fusion core due to thermal cycling, etc.

Improving Economic Competitiveness

Reducing life-cycle cost: 80s goals:

Low recirculating power; High power density;

Later Additions High thermal conversion

efficiency; Less-expensive systems.

Mass power density= net electric output / mass of fusion core

QE = net electric output / recirculating electric power

Directions for Improvement

Increase Power Density (1/Vp)What we pay for,VFPC

rD

r > D r ~ D r < D Improvement “saturates” at ~5 MW/m2 peak wall loading

(for a 1GWe plant). A steady-state, first stability device with Nb3Sn

technology has a power density about 1/3 of this goal.

Big Win Little

Gain

Decrease Recirculating Power Fraction Improvement “saturates” at plasma Q ~ 40. A steady-state, first stability device with Nb3Sn Tech.

has a recirculating fraction about 1/3 of this goal.

High-Field Magnets ARIES-I with 19 T at

the coil (cryogenic). Advanced SSTR-2

with 21 T at the coil (HTS).

High bootstrap, High b 2nd Stability: ARIES-II/IV Reverse-shear: ARIES-

RS, ARIES-AT, A-SSRT2

ARIES-AT

5.2

9.2% (5.4)

11.5

3.3

36

0.14

0.59

5

COE insensitive of current drive

COE insensitive of power density

Evolution of ARIES Tokamak Designs

1st Stability, Nb3Sn Tech.

ARIES-I’

Major radius (m) 8.0

(b bN) 2% (2.9)

Peak field (T) 16

Avg. Wall Load (MW/m2) 1.5

Current-driver power (MW) 237

Recirculating Power Fraction 0.29

Thermal efficiency 0.46

Cost of Electricity (c/kWh) 10

Reverse Shear Option

High-FieldOption

ARIES-I

6.75

2% (3.0)

19

2.5

202

0.28

0.49

8.2

ARIES-RS

5.5

5% (4.8)

16

4

81

0.17

0.46

7.5

A range of attractive tokamak power plants is available.

Estimated Cost of Electricity

(1992 c/kWh)

0

2

4

6

8

10

12

14

Mid 80'sPhysics

Early 90'sPhysics

Late 90's Physics

AdvancedTechnology

Major radius (m)

0

1

2

3

4

5

6

7

8

9

10

Mid 80's Pulsar

Early 90'sARIES-I

Late 90'sARIES-RS

2000 ARIES-AT

Approaching COE insensitive of power density High Thermal Efficiency

High b is used to lower magnetic field

Fusion Technologies Have a Dramatic Impact of Attractiveness of Fusion

ARIES-I Introduced SiC Composites as A High-Performance Structural Material for Fusion

SiC composites are attractive structural material for fusion Excellent safety & environmental

characteristics (very low activation and very low afterheat).

High performance due to high strength at high temperatures (>1000

oC).

Large world-wide program in SiC: New SiC composite fibers with proper

stoichiometry and small O content. New manufacturing techniques based on

polymer infiltration or CVI result in much improved performance and cheaper components.

Recent results show composite thermal conductivity (under irradiation) close to 15 W/mK which was used for ARIES-I.

SiC composites are attractive structural material for fusion Excellent safety & environmental

characteristics (very low activation and very low afterheat).

High performance due to high strength at high temperatures (>1000

oC).

Large world-wide program in SiC: New SiC composite fibers with proper

stoichiometry and small O content. New manufacturing techniques based on

polymer infiltration or CVI result in much improved performance and cheaper components.

Recent results show composite thermal conductivity (under irradiation) close to 15 W/mK which was used for ARIES-I.

Continuity of ARIES research has led to the progressive refinement of research

High efficiency with Brayton cycle at high temperature

Imp

rove

d B

lan

ket

Tech

no

log

y

ARIES-I: • SiC composite with solid breeders• Advanced Rankine cycle

ARIES-RS:• Li-cooled vanadium• Insulating coating

ARIES-ST: • Dual-cooled ferritic steel with SiC inserts• Advanced Brayton Cycle at 650 oC

ARIES-AT: • LiPb-cooled SiC composite • Advanced Brayton cycle with h = 59%

Many issues with solid breeders; Rankine cycle efficiency saturated at high temperature

Max. coolant temperature limited by maximum structure temperature

Outboard blanket & first wall

ARIES-AT features a high-performance blanket

Simple, low pressure design with SiC structure and LiPb coolant and breeder.

Innovative design leads to high LiPb outlet temperature (~1,100oC) while keeping SiC structure temperature below 1,000oC leading to a high thermal efficiency of ~ 60%.

Simple manufacturing technique.

Very low afterheat.

Class C waste by a wide margin.

Design leads to a LiPb Outlet Temperature of 1,100oC While Keeping SiC Temperature Below 1,000oC

• Two-pass PbLi flow, first pass to cool SiCf/SiC box second pass to superheat PbLi

q''plasma

Pb-17Li

q'''LiPb

Out

q''back

vback

vFW

Poloidal

Radial

Inner Channel

First Wall Channel

SiC/SiCFirst Wall SiC/SiC Inner Wall

700

800

900

1000

1100

1200800

900

1000

1100

1200

1

2

3

4

5

6

00.020.040.060.080.1

00.020.040.060.080.1

Radial distance (m)

Poloidaldistance(m)

SiC/SiC

Pb-17Li

Bottom

Top

PbLi Outlet Temp. = 1100 °C

Max. SiC/PbLi Interf. Temp. = 994 °C

Max. SiC/SiC Temp. = 996°C

PbLi Inlet Temp. = 764 °C

Modular sector maintenance enables high availability

Full sectors removed horizontally on rails Transport through maintenance corridors to hot

cells Estimated maintenance time < 4 weeks

ARIES-AT elevation view

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

104 105 106 107 108 109 1010 1011

ARIES-STARIES-RS

Act

ivit

y (C

i/W th

)

Time Following Shutdown (s)

1 mo 1 y 100 y1 d

After 100 years, only 10,000 Curies of radioactivity remain in the585 tonne ARIES-RS fusion core.

After 100 years, only 10,000 Curies of radioactivity remain in the585 tonne ARIES-RS fusion core.

SiC composites lead to a very low activation and afterheat.

All components of ARIES-AT qualify for Class-C disposal under NRC and Fetter Limits. 90% of components qualify for Class-A waste.

SiC composites lead to a very low activation and afterheat.

All components of ARIES-AT qualify for Class-C disposal under NRC and Fetter Limits. 90% of components qualify for Class-A waste.

Ferritic SteelVanadium

Radioactivity levels in fusion power plantsare very low and decay rapidly after shutdown

Level in Coal AshLevel in Coal Ash

Fusion Core Is Segmented to Minimize the Rad-Waste

Only “blanket-1” and divertors are replaced every 5 years

Only “blanket-1” and divertors are replaced every 5 years

Blanket 1 (replaceable)

Blanket 2 (lifetime)

Shield (lifetime)

Waste volume is not large

0

50

100

150

200

250

300

350

400

Blanket Shield VacuumVessel

Magnets Structure Cryostat

Cu

mu

lati

ve

Co

mp

ac

ted

Wa

ste

Vo

lum

e (

m3

)

1270 m3 of Waste is generated after 40 full-power year (FPY) of operation.Coolant is reused in other power plants 29 m3 every 4 years (component replacement), 993 m3 at end of service

Equivalent to ~ 30 m3 of waste per FPYEffective annual waste can be reduced by increasing plant service life.

1270 m3 of Waste is generated after 40 full-power year (FPY) of operation.Coolant is reused in other power plants 29 m3 every 4 years (component replacement), 993 m3 at end of service

Equivalent to ~ 30 m3 of waste per FPYEffective annual waste can be reduced by increasing plant service life.

0

200

400

600

800

1000

1200

1400

Class A Class C

Cumu

lative

Comp

acted

Was

te Vo

lume (

m3)

90% of waste qualifies for Class A disposal

90% of waste qualifies for Class A disposal

Some thoughts on Fusion Development

Nature of Power Plant Studies has evolved in time.

Concept Exploration (< 1990) Limited physics/engineering trade-offs due to lack of physic

understanding. The only credible vision was a large, expensive pulsed

tokamak with many engineering challenges (e.g., thermal energy storage).

Concept Definition ( ~ 1990-2005) Finding credible embodiments (Credible in a “global” sense). Better physics understanding allowed optimization of steady-

state plasma operation and physics/engineering trade-offs.

Concept Feasibility and Optimization (> 2010) Detailed analysis of subsystems to resolve feasibility issues. Trade-offs among extrapolation and attractiveness.

ITER has changed the magnetic fusion landscape

ITER has heightened understanding of many subsystem issues: New sets of physics information/correlations has been

developed to define design requirements for many subsystems (e.g., in-vessel components, transients).

Realities of designing practical systems to be built.

Increased interest in fusion nuclear engineering and material Realization that new material and technologies have to be

developed now.

New Paradigms for Power Plant Studies in the ITER area

Detailed design of subsystems in context of a power plant environment and constraints Can only be done one system at a time. Parametric surveys to understand physics/engineering trade-offs. Sophisticated computational tools are now widely available. Interaction with material and R&D community to indentify material

properties and R&D needs. Current ARIES project is focusing on detailed design of in-

vessel components.

System Tools to analyze trade-offs among R&D risks and benefits. A new System approach based on the survey of parameter

space as opposed to optimizing to a design point.

Thank you!