recent results from usa magnetic fusion power...

RECENT RESULTS FROM USA MAGNETIC FUSION POWER PLANTS

Farrokh NajmabadiUniversity of California, San Diego, La Jolla, CA, United States of America

German Nuclear Society Annual Meeting on Nuclear Technology 2004

25-27 May 2004, Düsseldorf,

You can download a copy of this presentation fromARIES Web Site: http://aries.ucsd.edu/ARIES/

The ARIES Team Has Examined Several Magnetic Fusion Concept as Power Plants in the Past 15 Years

• 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)

• SPPS stellarator (1994)

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

• ARIES-RS reversed-shear tokamak (1996)

• ARIES-ST spherical torus (1999)

• Fusion neutron source study (2000)

• ARIES-AT advanced technology and advanced tokamak (2000)

• ARIES-IFE assessment of IFE chambers (2003)

• ARIES-CS Compact Stellarator Study (Current Research)

Analysis of Conceptual Fusion Power Plants Identifies Key R&D Issues and

Provides a Vision for Fusion ResearchScientific & Technical

AchievementsPeriodic Input from

Energy IndustryGoals and

Requirements

Evaluation Based on Customer Attributes

Attractiveness

Characterizationof Critical Issues

Feasibility

Projections andDesign Options

Balanced Assessment ofAttractiveness & Feasibility

R&D Needs andDevelopment Plan

No: Redesign Yes


Provides a Vision for Fusion ResearchPeriodic Input from


RequirementsScientific & Technical

Achievements


Attractiveness


Feasibility



No: Redesign R&D Needs andDevelopment Plan

Yes

Conceptual Design of Magnetic Fusion Power Systems Are DevelopedBased on a Reasonable Extrapolation of Physics & Technology

Plasma regimes of operation are optimized based on latest experimental achievements and theoretical predictions.

Engineering system is based on “evolution” of present-day technologies, i.e., they should be available at least in small samples now. Only learning-curve cost credits are assumed in costing the system components.

Conceptual Design of Magnetic Fusion Power Systems Are DevelopedBased on a Reasonable Extrapolation of Physics & Technology

Plasma regimes of operation are optimized based on latest experimental achievements and theoretical predictions.

Engineering system is based on “evolution” of present-day technologies, i.e., they should be available at least in small samples now. Only learning-curve cost credits are assumed in costing the system components.


Provides a Vision for Fusion ResearchPeriodic Input from


RequirementsScientific & Technical

Achievements


Attractiveness


Feasibility



R&D Needs andDevelopment Plan

No: Redesign Yes

Customer Requirements

Top-Level Requirements for Fusion Power Plants Was Developed in Consultation with US Industry

Public Acceptance:No public evacuation plan is required: total dose < 1 rem at site boundary;Generated waste can be returned to environment or recycled in less than a few hundred years (not geological time-scale);No disturbance of public’s day-to-day activities;No exposure of workers to a higher risk than other power plants;

Public Acceptance:No public evacuation plan is required: total dose < 1 rem at site boundary;Generated waste can be returned to environment or recycled in less than a few hundred years (not geological time-scale);No disturbance of public’s day-to-day activities;No exposure of workers to a higher risk than other power plants;

Reliable Power Source:Closed tritium fuel cycle on site;Ability to operate at partial load conditions (50% of full power);Ability to maintain power core (avilability > 80%);Ability to operate reliably with < 0.1 major unscheduled shut-down per year.

Reliable Power Source:Closed tritium fuel cycle on site;Ability to operate at partial load conditions (50% of full power);Ability to maintain power core (avilability > 80%);Ability to operate reliably with < 0.1 major unscheduled shut-down per year.

Economic Competitiveness: Above requirements must be achieved simultaneously and consistent with a competitive life-cycle cost of electricity.

Economic Competitiveness: Above requirements must be achieved simultaneously and consistent with a competitive life-cycle cost of electricity.

Top-Level Requirements Translate into Directions for System Optimization

Top –Level Requirements for Commercial Fusion Power

Have an economically competitive life-cycle cost of electricity:• Low recirculating power;• High power density;• High thermal conversion efficiency;• Less-expensive systems.

Gain Public acceptance by having excellent safety and environmental characteristics:• Use low-activation and low toxicity materials and care in design.

Have operational reliability and high availability: • Ease of maintenance, design margins, and extensive R&D.

Fusion Plasma

Portfolio of MFE Configurations

Externally Controlled Self Organized

Example: Stellarator• Confinement field generated by

mainly external coils• Toroidal field >> Poloidal field• Large aspect ratio• More stable, better confinement

Example: Field-reversed Configuration• Confinement field generated mainly by

currents in the plasma• Poloidal field >> Toroidal field• Small aspect ratio• Simpler geometry

Important Parameters of a Fusion PlasmaFusion power density, Pf ~ β2BT

4 and β ∝ βΝ (I/aB)High magnetic fieldHigher performance plasma (βΝ )

Recirculating power is dominated by the power to drive and maintain plasma current.

Maximize self-driven bootstrap current

Confinement is not a major issue for a power plant size plasma.

Important Parameters of a Fusion PlasmaFusion power density, Pf ~ β2BT

4 and β ∝ βΝ (I/aB)High magnetic fieldHigher performance plasma (βΝ )

Recirculating power is dominated by the power to drive and maintain plasma current.

Maximize self-driven bootstrap current

Confinement is not a major issue for a power plant size plasma.

Optimization involves trade-off among various parametersTrade-off between bootstrap current fraction and β⇒ Advanced Tokamak Regime

Trade-off between vertical stability and plasma shapeTrade-off between plasma edge condition and plasma facing components capabilities,…

Evolution of ARIES Designs

Approaching COE insensitive of current drive

Approaching COE insensitive of power density

1st Stability, Nb3Sn Tech.

ARIES-I’

Major radius (m) 8.0

β (βΝ) 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

ARIES-AT

5.2

9.2% (5.4)

11.5

3.3

36

0.14

0.59

5

Detailed Physics Modeling Has Been Performed for ARIES-AT

• High accuracy equilibria;• Large ideal MHD database over profiles, shape and aspect ratio;• RWM stable with wall/rotation or wall/feedback control;• NTM stable with LHCD;• Bootstrap current consistency using advanced bootstrap models;• External current drive;• Vertically stable and controllable with modest power (reactive);• Rough kinetic profile consistency with RS /ITB experiments, as

well GLF23 transport code;• Modest core radiation with radiative SOL/divertor;• Accessible fueling;• No ripple losses;• 0-D consistent startup;

Fusion Technologies

ARIES-AT Fusion Core

The ARIES-RS Utilizes An Efficient Superconducting Magnet Design

TF Coil Design• 4 grades of superconductor

using Nb3Sn and NbTi;• Structural Plates with

grooves for winding only the conductor.

TF Structure• Caps and straps support

loads without inter-coil structure;

• TF cross section is flattened from constant-tension shape to ease PF design.

Use of High-Temperature Superconductors Simplifies the Magnet Systems

Inconel strip

YBCO Superconductor Strip Packs (20 layers each)

8.5 430 mm

CeO2 + YSZ insulating coating(on slot & between YBCO layers)

HTS does not offer significant superconducting property advantages over low temperature superconductors due to the low field and low overall current density in ARIES-AT

HTS does offer operational advantages:∗ Higher temperature operation (even

77K), or dry magnets∗ Wide tapes deposited directly on

the structure (less chance of energy dissipating events)

∗ Reduced magnet protection concerns

and potential significant cost advantagesBecause of ease of fabrication using advanced manufacturing techniques

Advanced Brayton Cycle Parameters Based on Present or Near Term Technology Evolved with Expert Input from General Atomics*

Brayton Cycle He Inlet and Outlet Temperatures as a Function of Required Cycle Efficiency

500

600

700

800

900

1000

1100

1200

1300

0.53 0.54 0.55 0.56 0.57 0.58 0.59 0.6 0.61

Gross Efficiency

Tem

pera

ture

(°C

)

Key improvement is the development of cheap, high-efficiency recuperators.

Maximum He temp eratu re

Minimum He temp eratu re

Maximum LiPb temp eratu re

RecuperatorIntercooler 1Intercooler 2

Compressor 1

Compressor 2Compressor 3

HeatRejection

HX

Wnet

Turbine

Blanket

IntermediateHX

5'

1

22'

38

9

4

7'9'

10

6

T

S

1

2

3

4

5 6 7 8

9 10

Divertor

LiPbBlanketCoolant

He DivertorCoolant

11

11

ARIES-ST Features a High-Performance Ferritic Steel Blanket

• Typically, the coolant outlet temperature is limited to the max. operating temperature of structural material (550oC for ferritic steels).

• By using a coolant/breeder (LiPb), cooling the structure by He gas, and SiC insulators, a coolant outlet temperature of 700oC is achieved for ARIES-ST leading to 45% thermal conversion efficiency.

OB Blanket thickness 1.35 m OB Shield thickness 0.42 m Overall TBR 1.1

ARIES-AT2: SiC Composite Blankets

Outboard blanket & first wallSimple, low pressure design with SiC structure and LiPbcoolant and breeder.

Simple manufacturing technique.

Very low afterheat.

Class C waste by a wide margin.

LiPb-cooled SiC composite divertor is capable of 5 MW/m2 of heat load.

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%.

Innovative Design Results in 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

Tem

pera

ture

(°C

)

Radial distance (m)

Poloidaldistance(m)

SiC/SiCPb-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

The divertor is part of the replacement module, and consists of 3 plates, coolant and vacuum manifolds, and the strongback support structure

The divertor structures fulfill several essential functions:1) Mechanical attachment of the plates;2) Shielding of the magnets;3) Coolant routing paths for the plates and inboard blanket;

Attractiveness:Evaluation Based on

Customer Requirements

Our Vision of Magnetic Fusion Power Systems Has Improved Dramatically in the Last Decade, and Is Directly Tied to Advances in Fusion Science & Technology

Estimated Cost of Electricity (c/kWh)

02468

101214

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 EfficiencyHigh β is used to lower magnetic field

ARIES-AT is Competitive with Other Future Energy Sources

EPRI Electric Supply Roadmap (1/99):Business as usualImpact of $100/ton Carbon Tax.

01234567

Natural Gas Coal Nuclear Wind(Intermittent)

Fusion (ARIES-AT)

AT 1000 (1 GWe)AT 1500 (1.5 GWe)

Estimated range of COE (c/kWh) for 2020*

* Data from Snowmass Energy Working Group Summary.

Estimates from Energy Information AgencyAnnual Energy Outlook 1999(No Carbon tax).

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

ivity

(Ci/W

th)

Time Following Shutdown (s)

1 mo 1 y 100 y1 d

Radioactivity Levels in Fusion Power PlantsAre Very Low and Decay Rapidly after Shutdown

• Low afterheat results in excellent safety characteristics• Low specific activity leads to low-level waste that decays

away in a few hundreds years.

• Low afterheat results in excellent safety characteristics• Low specific activity leads to low-level waste that decays

away in a few hundreds years.

ARIES-RS: V Structure, Li Coolant;ARIES-ST: Ferritic Steel Structure,

He coolant, LiPb Breeder;Designs with SiC composites willhave even lower activation levels.

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

Multi-Dimensional Neutronics Analysis was Performed to Calculate TBR, activities, & Heat Generation Profiles

Very low activation and afterheat Lead to excellent safety and environmental characteristics.All components qualify for Class-C disposal under NRC and Fetter Limits. 90% of components qualify for Class-A waste.On-line removal of Po and Hg from LiPb coolant greatly improves the safety aspect of the system and is relatively straight forward.

ARIES-AT Also Uses A Full-Sector Maintenance Scheme

Feasibility:Fusion Development Path

The development path to realize fusion as a practical energy source includes:

Demonstration of high performance, steady-state burning plasmas.Demonstration of high performance, steady-state burning plasmas.

Fusion power technologies are a pace setting element of fusion development. Development of fusion power technologies requires:1) Strong base program including testing of components in

non-nuclear environment as well as fission reactors.2) Material program including an intense neutron source to

develop and qualify low-activation material.3) A Component Test Facility for integration and test of power

technologies in fusion environment.

Fusion power technologies are a pace setting element of fusion development. Development of fusion power technologies requires:1) Strong base program including testing of components in

non-nuclear environment as well as fission reactors.2) Material program including an intense neutron source to

develop and qualify low-activation material.3) A Component Test Facility for integration and test of power

technologies in fusion environment.

ITER-Based Development Path

Tokamak physics

ITER

Bas

e Pl

asm

a ph

ysic

s

ST, stellarator, RFP, other ICCs

Maj

or F

acili

ties

Bas

e T

echn

olog

ies

14-MeV neutron source

Fusion power technologies

Plasma support technologies

Decision pointDEMO

Component Test Facility

Theory & Simulation

ICC ETR DEMO

recent results from usa magnetic fusion power...

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