9.3 Structural Materials for Fusion Reactors

Fusion reactors require specialized materials to withstand extreme conditions. From the first wall facing plasma to superconducting magnets, each component demands unique properties. Materials must endure high temperatures, neutron bombardment, and intense magnetic fields while maintaining structural integrity.

Neutron irradiation poses significant challenges, causing displacement damage, transmutation, and activation. These effects lead to material degradation and radioactivity. Developing advanced materials like nanostructured alloys and ceramic composites is crucial for overcoming these hurdles and realizing practical fusion energy.

Structural Materials in Fusion Reactors

Components of fusion reactors

Top images from around the web for Components of fusion reactors

• 

  The Oil Drum: Europe | Will Nuclear Fusion Fill the Gap Left by Peak Oil? View original

  Is this image relevant?

• 

  fusion reactor Archives - Universe Today View original

  Is this image relevant?

• 

  fusion reactor Archives - Universe Today View original

  Is this image relevant?

• 

  The Oil Drum: Europe | Will Nuclear Fusion Fill the Gap Left by Peak Oil? View original

  Is this image relevant?

• 

  fusion reactor Archives - Universe Today View original

  Is this image relevant?

1 of 3

Top images from around the web for Components of fusion reactors

• 

  The Oil Drum: Europe | Will Nuclear Fusion Fill the Gap Left by Peak Oil? View original

  Is this image relevant?

• 

  fusion reactor Archives - Universe Today View original

  Is this image relevant?

• 

  fusion reactor Archives - Universe Today View original

  Is this image relevant?

• 

  The Oil Drum: Europe | Will Nuclear Fusion Fill the Gap Left by Peak Oil? View original

  Is this image relevant?

• 

  fusion reactor Archives - Universe Today View original

  Is this image relevant?

1 of 3

• First wall directly faces the plasma requires high thermal conductivity, low activation, and resistance to erosion and neutron damage
• Blanket surrounds the plasma chamber breeds tritium and extracts heat requires compatibility with coolant and breeding materials, as well as resistance to neutron damage
• Divertor extracts heat and ash from the plasma requires high thermal conductivity, resistance to erosion and neutron damage, and compatibility with coolant
• Vacuum vessel provides vacuum environment for plasma confinement requires structural integrity, vacuum tightness, and compatibility with other components
• Superconducting magnets generate strong magnetic fields for plasma confinement require high critical current density, mechanical strength, and radiation resistance
• Cryostat provides thermal insulation for the superconducting magnets requires structural integrity, low thermal conductivity, and compatibility with the vacuum vessel
• Tritium breeding blanket generates tritium fuel through interactions with neutrons requires compatibility with breeding materials (lithium), high tritium permeability, and resistance to neutron damage
• Shield protects superconducting magnets and other components from neutron and gamma radiation requires high neutron absorption cross-section, structural integrity, and compatibility with the vacuum vessel

Performance of structural materials

• Austenitic stainless steels (316L) widely used due to good mechanical properties and compatibility with coolants limited by low thermal conductivity and susceptibility to neutron-induced swelling and embrittlement
• Ferritic/martensitic steels (Eurofer97) improved resistance to swelling and thermal stress compared to austenitic steels limited by lower creep strength at high temperatures
• Vanadium alloys have high thermal conductivity and low activation challenges include compatibility with coolants and susceptibility to oxidation
• Tungsten has high melting point, thermal conductivity, and resistance to erosion brittle nature and high ductile-to-brittle transition temperature pose challenges
• Reduced activation ferritic/martensitic (RAFM) steels developed specifically for fusion applications to minimize long-term radioactivity improved resistance to swelling and embrittlement compared to conventional ferritic/martensitic steels
• Copper alloys (CuCrZr) used in high heat flux components like divertors and first wall have high thermal conductivity and strength, but limited by low melting point and radiation-induced softening
• Ceramic composites (SiC/SiC) have excellent high-temperature strength, low activation, and inherent radiation resistance challenges include brittle nature, joining, and compatibility with coolants
• Refractory metals (molybdenum, tantalum) have high melting points, thermal conductivity, and strength limited by poor ductility, oxidation resistance, and radiation-induced embrittlement

Effects of neutron irradiation

• Displacement damage occurs when neutron collisions displace atoms from their lattice positions, creating defects leads to hardening, embrittlement, and dimensional changes (swelling)
• Transmutation occurs when neutron capture reactions produce new elements, altering material composition can lead to the formation of embrittling phases or gases (helium)
• Activation is the process of neutron-induced radioactivity in materials affects safety, maintenance, and waste management
• Irradiation creep is time-dependent deformation under constant stress due to neutron damage can lead to dimensional instability and component failure
• Radiation-induced segregation is the preferential migration of alloying elements to grain boundaries or free surfaces can lead to localized changes in composition and properties, such as embrittlement or corrosion susceptibility
• Void swelling is the formation and growth of nanoscale voids due to the accumulation of vacancy defects results in significant volume increase and dimensional instability
• Radiation-enhanced diffusion is the accelerated diffusion of atoms due to the presence of irradiation-induced defects can promote phase transformations, segregation, and precipitation
• Radiation-induced precipitation is the formation of new phases or precipitates due to irradiation-enhanced diffusion and segregation can lead to changes in mechanical properties, such as hardening or embrittlement

Challenges in material development

• Challenges include simultaneous requirements for high-temperature strength, neutron resistance, and compatibility with aggressive environments long lead times and high costs associated with material development and qualification limited availability of fusion-relevant testing facilities
• Opportunities in material development include:
  1. Nanostructured materials: Engineered grain boundaries and interfaces can improve strength and radiation resistance
  2. Oxide dispersion strengthened (ODS) alloys: Nanoscale oxide particles enhance high-temperature strength and creep resistance
  3. High-entropy alloys: Multi-principal element alloys with unique properties, such as high strength and thermal stability
  4. Additive manufacturing: Enables rapid prototyping and optimization of complex geometries and functionally graded materials
• Multiscale modeling links atomistic, mesoscale, and continuum models to predict material behavior under fusion conditions opportunities to guide material design and reduce experimental testing
• In-situ characterization techniques enable real-time monitoring of material evolution under irradiation and high-temperature conditions enables better understanding of damage mechanisms and validation of models
• Ion irradiation experiments use accelerated testing with ion beams to simulate neutron damage allows for rapid screening of materials and investigation of specific damage mechanisms
• International collaborations pool resources and expertise to address common challenges in fusion material development opportunities for standardization of testing methods and data sharing