Developing Materials for Fusion Power

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Developing Materials for Fusion Power

• May 10, 2007
• Shreya Dave
• Christopher Whitfield
• 22.012 Fusion and Plasma Physics
• Professor Molvig

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Outline

• Why Materials?
• What are their applications?
• What conditions must they have the ability to
  withstand?
• What current research exists?
• Pros/cons of each
• Future outlook of each project
• What is the development strategy?
• How do we test these materials?
• International Fusion Materials Irradiation
  Facility (IFMIF)
• What are the concerns for unsafe materials?

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Why all this Materials Talk?

• The development of materials for use in nuclear
  fusion is perhaps the most critical component of
  the further development of fusion technology.
• Also, however, one of the biggest barriers.
• The research and development of these materials
  has been based on international collaboration
  from the beginning, like much of fusion
  development, so its a good slice of fusion
  development to look at
• Personal motivations.

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Areas of Application

• Plasma facing components absorb the thermal
  radiation and maintain the vacuum
• First wall
• Diverters
• Limiters
• Breeding Blanket where neutrons are absorbed to
  breed tritium.

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ConditionsDetails

• The Materials must, in general, withstand extreme
  energies, such as
• 14 MeV neutrons
• Neutral and Charged Plasma Particles
• High surface heat fluxes
• These materials must also possess
• Sufficient lifetime of plasma facing components
  or breeding blanket
• The ability to withstand expected surface heat
  and neutron wall load
• Ability to withstand the inherent displacement
  rate and transmutations reaction rates

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ConditionsEhrlich Said It
In the long term development, materials which
can withstand high neutron wall loads under
temperature and coolant pressure conditions
necessary to drive efficient thermodynamic
working cycles must be developed (Ehrlich 80).
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Material Possibilities

• Ferritic-martensitic steels
• Vanadium Alloys
• SiC/SiC ceramics
• Tungsten Alloys

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Ferritic Martensitic Steels Ehrlich Said It

• Furthest along the development path in that
  there exists a well developed technology and a
  broad industrial experience with such alloys in
  fossil and nuclear energy technology (Ehrlich
  82).

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Ferritic Martensitic Steels Positives

• Thermophysical and mechanical properties
• Compatibility with major cooling and breeding
  materials
• Low sensitivity to swelling and helium
  embrittlement

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Ferritic Martensitic Steels Drawbacks and
Clarifications

• Observed radiation-induced degradation of flow
  and fracture properties below about 350 Celsius
• Influence of ferromagnetism on plasma stability
  and Lorenz forces

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Ferritic Martensitic Steels Future Work

• Use of nano-scaled oxide dispersions and
  precipitates to expand application to higher T
• Need to develop a broad database to qualify
  material for use in breeding blankets
• Need to look at both structural and functional
  qualities of the material

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Vanadium Alloys Ehrlich Said It
Have a favorable combination of physical
properties and high creep strength and hence the
greatest potential of the three material groups
for high temperature operation in liquid lithium
(Ehrlich 82).
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Vanadium Alloys Positives

• Fastest decay of radioactivity in addition to
  long decay times
• Positive swelling and high temperature
  embrittlement results.

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Vanadium Alloys Drawbacks

• High solubility and permeability of tritium and
  solubility of interstitial elements (like O, C,
  N).

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Vanadium Alloys Future Work

• Development of self-heating, insulating, AND
  corrosion-protective material.
• This is the approach to help overcome
  magnetohydrodynamic effects in the breeding
  blanket

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SiC/SiC Ceramics Ehrlich Said It

• Potentially the most difficult challenge of
  the three groups of materials. They have
  potentially high payoffs in terms of very low
  radioactivity and decay heat at short and
  intermediate decay times and offer high operating
  temperatures (Ehrlich 82).

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SiC/SiC Ceramics Positives

• Low radioactivity
• Decay heat quickly
• High operating temperatures

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SiC/SiC Ceramics Drawbacks

• Lack of understanding of effects of neutron
  irradiation on the structure
• Limited production technology
• Insufficient heremtic sealing capabilities

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SiC/SiC Ceramics Future Work

• Must develop radiation-resistant materials
• Also, develop appropriate design rules for use of
  materials in structural parts.

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Development Process

• Phase I Initial experimentation
• Effectively everything that has taken place thus
  far
• Phase II Concept Exploration Phase
• Data base development, some tests
• Phase III Concept Confirmation
• More tests, ITER applications

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Development CommentsEhrlich Said It

• Phase II Questions on compatibility,
  corrosion, mechanical interaction,
  radiation-induced swelling, creep and dimensional
  instabilities in steep thermal and neutron
  gradients and the effective tritium release
  mechanisms have to be resolved (Ehrlich 83).
• Wow.
• Phase III A final concept confirmation of the
  selected design needs, however, the testing under
  real fusion neutron irradiation in a follow-on
  development phase III. This very late
  confirmation of a concept reveals the weak point
  in the presently adapted RD strategy (Ehrlich
  83).
• This is not ideal!

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Whats Next?We really cant figure out we did
this wrong 20 years from now.

• We must figure out a way to test these materials
  that does not require a fully developed fusion
  reactor.
• Otherwise, we might find that twenty years from
  now, much of our work was in vain.

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Materials TestingOutline

• The materials of a fusion reactor, especially
  those in the first wall and breeder components,
  are exposed to harsh environments.
• There has to be a feasible method to test these
  materials for their response to the severe
  conditions. This has evolved to be the
  International Fusion Materials Irradiation
  Facility (IFMIF).
• The severe conditions of a reactor result in many
  environmental and safety concerns. We will offer
  a brief introduction to the safety issues
  associated with the materials used in fusion
  reactors.

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IFMIF An Overview

• Currently there is no reliable source of
  high-flux neutrons that can be used for research
  of structural materials.
• It is an accelerator-based neutron source used to
  test specimen miniaturization technology as well
  as irradiation damage theory and modeling.
• Working together, the European, Japan, the United
  States and the Russian Federation (as an
  associated member) an IEA and IFMIF Conceptual
  Design Activity (CDA) was established in 1995.
• The construction of IFMIF is expected to commence
  in 2017. This means that it is unlikely to be
  useful to the design and implementation of ITER.
  A location has yet to be decided, but the
  facility will consist of the IFMIF buildings, the
  accelerator and power supply building, and the
  target and test operation building.

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IFMIF Goals

• Contribute to the understanding of the behavior
  of materials.
• Develop materials by controlling composition and
  microstructure
• Provide material technology for fabrication of
  reactors.

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IFMIFTechnicalities

• Capable of producing 14.6 MeV peak generation!
• This takes 40MeV of neutron particles.
• The footprint of the beam is 20 centimeters long
  by 5 centimeters, with a distribution of flux
  across the area.
• Radiation beams at 20 degree angle.

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IFMIF Facility Requirements

• Neutron flux to volume ratio 2 MW/m2 per volume.
  
• Neutron spectrum must meet First Wall neutron
  spectrum as closely as possible.
• Neutron fluence accumulation of 150 dpa in a few
  years
• Neutron flux gradient less than 10.
• Machine availability.
• Time structure.

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IFMIFWhat Might Kill Us

• Decay Heat
• Inventory-Based Activation Hazard
• Oxidation Driven Activation Product Mobilization
• Tritium Inventory
• Chemical Reactivity with water
• Disruption Tolerance
• Activation
• Reactivity
• On that happy note

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Research at MIT

• Ronald G. Ballinger, Course 3 and 22
• As a result of our research, new materials have
  been developed that allow either the mass of the
  magnet to be reduced for the same field strength
  as previous designs or higher fields to be
  developed for the same size of previous designs.
  Cost savings on the order of 25-40 can be
  achieved. These developments have placed our
  laboratory in the forefront of materials
  development for superconducting magnets.

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Research at MIT

• Linn W. Hobbs, Course 3 and 22
• We are investigating why some crystals are
  stable against amorphization, while others
  amorphize easily, and involved in designing
  crystal structures and compositions (such as
  zirconate pyrochlores and oxide spinels) that are
  especially resistant to amorphization. We are
  also studying the atomic structure of
  radiation-amorphized crystals using diffraction
  techniques and molecular dynamics modeling and
  the atomic rearrangements in counterpart glasses
  in displacive radiation fields.

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Developing Materials for Fusion Power, A Summary

• Why?
• Applications
• Current Research
• Development Strategies
• Testing
• Concerns
• Research at MIT

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References

• Ehrlich, K., Bloom, E.E., Kondo, T.
  International strategy for fusion materials
  development. J. Nucl. Mater. 79-88 (2000).
• Ehrilich, Karl, Mosland, Anton. IFMIF An
  international fusion materials irradiation
  facility. Elsevier Science B.V. (1998)
• IFMIF, Facilities. lthttp//www.frascati.enea.it/if
  mif/gt. (2007)
• Petti, D.A., McCarthy, K.A., Gulden, W.,Piet,
  S.J., Seki, Y., Kolbasov, B.. An overview of
  safety and environmental considerations in the
  selection of materials for fusion facilities.
  Elservier Science B.V. (1996)

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Questions??