Status and Prospects of Nuclear Fusion Using Magnetic Confinement Hartmut Zohm Max-Planck-Institut...

Status and Prospects of Nuclear Fusion Using Magnetic Confinement

Hartmut Zohm

Max-Planck-Institut für Plasmaphysik, Garching, Germany

Invited Talk given at DPG Frühjahrstagung, AKE, Berlin, 17.03.2014

• Nuclear Fusion using Magnetic Confinement

• Fusion Roadmap and Roadmap Elements

• The German Contribution

• Summary and Conclusions

A simplistic view on a Fusion Power Plant

The ‚amplifier‘ is a thermonuclear plasma burning hydrogen to helium

Centre of the sun: T ~ 15 Mio K, n 1032 m-3, p ~ 2.5 x 1011 bar

Pin = 50 MW

(initiate and control burn)

Pout = 2-3 GWth

(aiming at 1 GWe)

A bit closer look…

Fusion reactor: magnetically confined plasma, D + T → He + n + 17.6 MeV

Centre of reactor: T = 250 Mio K, n = 1020 m-3, p = 8 bar

3.5 MeV 14.1 MeV-heating wall loading

Pin = 50 MW

(initiate and control burn)

Pout = 2-3 GWth

(aiming at 1 GWe)

Schematic layout of a Fusion Power Plant

The goal is to generate and sustain a plasma of 25 keV and 1020 m-3

This can be done in a toroidal system to avoid end losses

helical magnetic field lines to compensate particle drifts

Magnetic confinement

'Stellarator': magnetic field exclusively produced by coils

Example: Wendelstein 7-X (IPP Greifswald)

Plasma can be confined in a magnetic field

'Tokamak': poloidal field component from current on plasma

Simple concept, but not inherently stationary!

Example: ASDEX Upgrade (IPP Garching)

Plasma can be confined in a magnetic field

The promise of fusion power plants

Supply of base load electricity (not dependent on externals)

• complementary to stochastic sources like wind or solar

Sustainable energy source (fusion fuel available for many 1000s of years)

• Deuterium e.g. from sea water

• T will be bred from Li in the innermost part of the reactor Fusion energy will be environmentally friendly

• no CO2 emission

• no uncontrolled chain reaction

• radioactive waste (= structural materials) relatively short-lived

The road to Fusion Energy holds many challenges

Fusion plasma physics

• heat insulation of the confined plasma

• exhaust of heat and particles

• magnetohydrodynamic (MHD) stability of configuration

• self-heating of the plasma by fusion born -particles

Fusion specific technology

• plasma heating

• fuel cycle including internal T-breeding from Li

• development of suitable materials in contact with plasma

The road to Fusion Energy holds many challenges

Fusion plasma physics

• heat insulation of the confined plasma

• exhaust of heat and particles

• magnetohydrodynamic (MHD) stability of configuration

• self-heating of the plasma by fusion born -particles

Fusion specific technology

• plasma heating

• fuel cycle including internal T-breeding from Li

• development of suitable structural and first wall materials

The European Roadmap to Fusion Electricity

JET (EU)3 m

80 m3

~ 16 MWth

(D-T)

ITER6.2 m

800 m3

~ 400 MWth

(D-T)

Major Radius

Volume

Fusion Power

ASDEX Upgrade (IPP)1.65 m

14 m3

1.5 MW

(D-T equivalent)

A step-ladder of fusion experiments to ITER

The machine has to be big in order to have sufficient heat insulation (E)

ITER = proof of principle for dominantly -heated plasmas

DEMO = proof of principle for reliable large scale electricity production

DEMO must be larger: 6.2 m 8.5 m, 400 MW ~ 2 GW

This brings new challenges for physics (and technology)

• higher density, higher pressure (stability!)

• higher power density (Pfus~R3, Atarget~ R)

• need for long pulse or steady state (tokamak presently a pulsed system)

We will not run out of work in near future!

• also alternative magnetic confinement concepts must be studied

The step from ITER to DEMO

Tokamak (ASDEX Upgrade, JET, ITER)

ITER = proof of principle for dominantly -heated plasmas

DEMO = proof of principle for reliable large scale electricity production

DEMO must be larger: 6.2 m 7.5 m, 400 MW ~ 2 GW

This brings new challenges for physics (and technology)

• higher density, higher pressure (stability!)

• higher power density (Pfus~R3, Atarget~ R)

• need for long pulse or steady state (tokamak presently a pulse system)

We will not run out of work in near future!

• also alternative magnetic confinement concepts must be studied

Example: W7-X stellarator (IPP Greifswald)

The step from ITER to DEMO

Stellarator (W7-X)

The Role of Stellarators in the EU Roadmap

Using technology developed on a tokamak DEMO, stellarator can be candidate for a Fusion Power Plant in the 2050s

German Fusion Programme: Combined Expertise

Unique combination of physics and technology

Coordinated effort through ‚German DEMO Working Group‘

Stellarator Physics and Technology

Plasma WallInteractions

Fusion Tokamak Technology Physics and

Technology

German DEMO Working Group: Roadmap Elements

7 Roadmap Elements that need to be tackled in any Roadmap have been identified

RE1: Consistent Tokamak Scenarios

RE2: Consistent Stellarator Scenarios

RE3: Enduring Exhaust of Power and Particles

RE4: Safety – Public Accpetance and Licensing

RE5: Sustainability – Tritium Self-sufficiency & Low Activation

RE6: Economic Viability – Efficiency / Reliability / Availability

RE7: Stellarator Specific Technology

The following examples highlight how these Roadmap Elements bring together the expertise of Fusion Research in Germany

Tokamak Scenarios (RE1) / Economic Viability (RE6)

Realistic fully noninductive scenario may require substantial PCD

Sets the goals for future gyrotron development at f > 200 GHz Issues of controllability must be incorporated from the start

KIT, 1MW, 105 – 165 GHzSP prototype

Mode for 237 GHz coax gyrotron

Brewster-angle technology (CVD Diamond window)

TE49,29Simulation of fullynoninductive DEMO scenario

Exhaust of Power and Particles (RE3)

Combined physics / technology requirements: P/Rsep 15 MW/m, Ptarget 5 MW/m2, Te,div 5 eV

Optimised technology solution may be He-cooled divertor

W-divertor in ITER

He-cooled divertor for DEMO

Stellarator Scenarios (RE2) & Technology (RE7)

• Stellarator specifics are incorporated into tokamak systems codes

• Critical elements in physics and technology will be assessed

Plasma geometry described by Fourier coefficients of LCFS obtained from VMEC.

Existing coil design of Helias 5-B builds model basis which is scaled as input.

Model relates power crossing separatrix to effective wetted area to estimate heat load.

Plasma GeometryModular

Coils / BlanketIsland Divertor

effm

m

n

nnnm

m

m

n

nnnm

rAVNnvmuszvusz

NnvmusRvusR

,,)sin()(),,(

)cos()(),,(

max max

max

max max

max

0,

0,

Plasma geometry described by Fourier coefficients of LCFS obtained from VMEC.

Existing coil design of Helias 5-B builds model basis which is scaled as input.

Model relates power crossing separatrix to effective wetted area to estimate heat load.

Plasma GeometryModular

Coils / BlanketIsland Divertor

effm

m

n

nnnm

m

m

n

nnnm

rAVNnvmuszvusz

NnvmusRvusR

,,)sin()(),,(

)cos()(),,(

max max

max

max max

max

0,

0,

Stellarator Scenarios (RE2) & Technology (RE7)

• Stellarator specifics are incorporated into tokamak systems codes

• Critical elements in physics and technology will be assessed

Significant progress of understanding in all basic areas of Nuclear Fusion research by developing plasma physics and technology base

• core plasma parameters sufficient for generation of fusion energy

• technical systems mature for controlling thermonuclear plasma

Nuclear Fusion research is ready for the next step

• ITER will be built in an international effort

• will allow qualitatitvely new studies: exploring plasmas with dominant -heating

The step to DEMO and a Fusion Power Plant builds on ITER but must be prepared in due time

•adress physics and technology in an integrated way

•bring in the stellarator line in a consistent manner

Conclusions

Status and Prospects of Nuclear Fusion Using Magnetic Confinement Hartmut Zohm Max-Planck-Institut...

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