ITER as a Step to Fusion Power

1
ITER as a Step to Fusion Power

• Prof. Robert J. Goldston, Director
• Princeton Plasma Physics Laboratory
• Fusion Power Associates
• Annual Meeting and Symposium
• Forum on the Future of Fusion
• November 19, 2003

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Questions for Magnetic Fusion

• How is plasma pressure limited?
• ???Sets maximum fusion power
• ???Solar flares / magnetic substorms
• How do hot particles sustain plasmas?
• ? For plasma self-heating, current
  sustainment
• ???Coronal heating / cosmic rays
• What causes plasma transport?
• ? Must confine heat in 200M C plasma
• ? Astrophysical accretion disks
• How do plasmas interact with materials?
• ? Must handle high heat loads
• ? Materials processing / plasma thrusters
• How do fusion neutrons affect components?
• ? Long-life, low activation, tritium
  regeneration.
• ? Materials science / fission energy
• How can we make practical S/C magnets?
• ? Need large, high field, reliable, low-cost
  magnets.
• ? Accelerators / electric transmission

ITER Final Design
Todays Position ITERs Advances Requirements
for Fusion
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How is Plasma Pressure Limited?

• Plasma pressure limit determines fusion power in
  a sustainable configuration.
• Fast instability limits are understood.
• Slower instabilities are being controlled.
• New plasma configurations are under study that
  can operate at higher pressure, have less impact
  from disruption.
• ITER will extend the understanding of pressure
  limits to much larger plasmas.
• Data from ITER will contribute to understanding
  other configurations.
• For practical fusion energy, fusion plasmas need
  to produce 4x more power in an ITER-size system.

Toroidal rotation can stabilize a tokamak plasma
in the presence of an electrically conducting
shell.
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How do Hot Particles Sustain Plasmas?

• Plasma temperature and current must be sustained
  steadily.
• Modest plasma self-heating wasdemonstrated in
  TFTR JET.
• Hot particles have been usedto sustain plasma
  currents.
• Instability thresholds are generally understood,
  nonlinearconsequences are under study.
• New plasma configurations are under study which
  do not require external drive for sustainment of
  plasma current.
• ITER will study regimes with very strong heating
  by fusion products, in new regimes where multiple
  instabilities can overlap, with possibly new
  nonlinear consequences. ITER will study
  steady-state operation at moderate gain.
• ITER will contribute to the development of other
  plasma configurations.
• For practical fusion energy, need plasmas that
  can be efficiently sustained at high gain in full
  steady-state.

Fusion energy production has outpaced Moores law.
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What Causes Plasma Transport?

• Low heat loss is required for high plasma gain.
• A standard model has been developed
  forunderstanding ion heat loss.
• The mechanism of electron heat loss is under
  study.
• Plasma fusion gain 1 has been achieved.
• Advanced computing and detailed
  plasmadiagnostics are critical elements inthe
  advance of understanding.
• ITER will extend the study of turbulent plasma
  transport to much larger plasmas, providing a
  strong test of intensive vs. extensive turbulence
  scaling at Q gt 10 for long pulses, Q gt 5 in
  steady state.
• Other plasma configurations will benefit from
  studies in ITER.
• For practical fusion energy, need to be able to
  sustain plasmas efficiently, with low heat loss
  (Q 30).

Simulation of field-aligned turbulence in
Spherical Torus plasma.
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How do Plasmas Interact with Materials?

• Fusion plasmas generate intense steady heat
  loads, with high off-normal loads, which must be
  handled reliably.
• The mechanisms of heat flow along magnetic field
  lines to material surfaces are understood.
• Techniques have been developed to disperse heat
  as it flows to a material surface.
• Some magnetic configurations have more favorable
  exhaust geometries, and/or are less subject to
  off-normal events.
• Liquid lithium surfaces are under study as a
  potential revolutionary approach.
• ITER will extend the study of plasma-materials
  interactions to much higher power and much
  greater pulse length, but still well below power
  plant heat fluxes and durations.
• All other plasma configurations will benefit from
  ITERs practical experience with plasma facing
  components.
• For practical fusion energy, need to be able to
  support 3x higher heat flux, with multi-year
  component lifetimes.

Tungsten brush capable of handling 25 MW/m2
heat flux.
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How do Fusion Neutrons Affect Power Plant
Components?

• Fusion plasmas generate high-energy
  neutronswhich damage materials and must
  becaptured to regenerate tritium.
• New ferritic steels have improved
  propertiescompared with those developed for
  fission breeders, with much lower radioactivity.
• New blanket designs allow higher
  temperatureoperation, and so greater efficiency.
• Advanced computation is being used to optimize
  the design of fusion materials.
• ITER will allow the first break-in testing of
  blanket modules, but at 4x lower neutron flux
  and much lower fluence than practical fusion
  power systems.
• All other fusion plasma configurations will
  benefit from ITERs experience.
• For practical fusion energy, materials and
  components will need to be qualifiedat
  power-plant neutron flux and fluence.

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How Can We Make Practical, Large-scale
Superconducting Magents?

• Almost any magnetic fusion configuration will
  need large-scale, reliable, low-cost
  superconducting magnets.
• RD tests have been undertaken for ITER at very
  large scale.
• Fusion and high-energy physics have a track
  record of advancing the frontiers of
  superconducting magnet technology.
• ITER will test full-scale superconducting magnets
  in a practical fusion environment.
• Other magnetic fusion plasma configurations will
  benefit from ITERs experience.
• For practical fusion energy the cost of such
  magnets needs to be driven down through RD and
  experience.

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ITER will make Critical Contributions in Each Area

• Extend the understanding of pressure limits to
  much larger size plasmas.
• Study regimes with very strong heating by fusion
  products, in new regimes where multiple
  instabilities can overlap.
• Extend the study of turbulent plasma transport to
  much larger plasmas, providing a strong test of
  intensive vs. extensive turbulence scaling.
• Extend the study of plasma-materials interactions
  to much higher power and much greater pulse
  length.
• Provide the first break-in testing of blanket
  modules.
• Test full-scale superconducting magnets in a
  practical fusion environment.
• ITER is a major step to fusion power.

ITER Final Design