Page 32 - PEN eBook October 2025

SMART ENERGY SMART ENERGY

turn into amorphous phases over time. They looked helping mitigate tritium retention, a major safety
at how plasma conditions affect the buildup of silicon concern.
and carbon on surfaces, which can change how erosion
behaves. Additionally, because high-Z materials such as
tungsten emit intense radiation (X-rays) during
EROSION RISKS: SiC AS A FUSION plasma disruptions, they can rapidly cool the
SURFACE MATERIAL plasma, destabilize confinement, and increase the

Modeling with Wall Boundary Code (WBC) and Ion risk of damage to other components. In contrast,
Transport Monte Carlo with Dynamic (ITMC-DYN) silicon’s lower radiation emission in SiC helps
suggests that erosion risks for SiC in fusion reactors preserve plasma stability and reduces the severity of
may be overstated. While DIII-D (an advanced U.S. disruption-induced energy loss.
fusion research device in San Diego, designed to study
plasma behavior under magnetic confinement) tokamak While SiC isn’t yet a mainstream material in
experiments using the Divertor Materials Evaluation operational tokamaks, it’s on the radar as a
System show high localized erosion, simulations for plasma-facing material for future fusion reactor
carbon-free DEMO reactors with full SiC coverage designs. Integrated modeling using ITMC-DYN and
predict a near-complete redeposition of silicon WBC frameworks—validated by
and carbon across the divertor. Redeposition is the experiments—indicates that SiC surfaces, even
process by which eroded atoms from plasma-facing when amorphized under plasma conditions, retain
components return to the surface instead of escaping favorable erosion behavior due to high local
into the plasma. This dramatically reduces net erosion redeposition of sputtered particles. Compared
and plasma contamination. with graphite, SiC offers better stability, reduced
contamination, and improved durability, especially in
Tokamak schematic showing superconducting magnets in blue (Source: ITER) Carbon erosion from SiC is estimated to be 7× carbon-free tokamak environments.
lower than from pure carbon (e.g., graphite) surfaces,

fields—SiC stands out for its exceptional thermal from high-melting-point materials such as tungsten
stability and ability to withstand temperatures (atomic number Z = 74, melting point 3,422°C). In ITER,
exceeding 2,000°C. these plates endure heat fluxes of 20 MW/m (slow
2
transients).
In addition to its heat resistance, SiC offers low
neutron activation, which results in significantly less DIVERTOR MATERIALS
long-term radioactive waste than with conventional Tungsten has long been used in divertors, but issues
structural materials. It is also resilient to radiation such as plasma contamination, disruptions, and high
damage and mechanical stress. Furthermore, its radiation during transients have led researchers to
insulating properties make it valuable in magnets and explore alternatives.
current-drive systems.
SiC stands out thanks to its excellent thermal
Researchers are actively developing SiC-based performance, resistance to melting via sublimation,
composites, such as SiC/SiC, for integration into and much lower radiation than high-Z materials
critical reactor components, including blankets, such as tungsten. Because silicon (Z = 14) radiates
divertors, and load-bearing supports. less intensely, plasma retains more energy, improves
confinement, and operates more efficiently.
Among these, the divertor plays a vital role.
Positioned at the bottom of the vacuum chamber, EROSION PHENOMENA
it handles the heat and particles escaping from the Scientists are concerned about how materials in
plasma. Functionally, it extracts plasma byproducts, fusion reactors erode, move, and affect the plasma’s
shields reactor walls from thermal and neutron core. One experiment showed that crystalline SiC
damage, reduces plasma contamination, and erodes twice as slowly as amorphous SiC, where atoms
enhances overall plasma stability, especially in are in a random, disordered arrangement.
high-confinement operation.
More studies confirmed this trend and explored how
The divertor achieves this by shaping magnetic erosion changes under different plasma temperatures.
fields to guide escaping particles toward specially Researchers also investigated how atoms are removed
engineered divertor plates, where they can be safely (sputtered), transported, and redeposited and how
absorbed and cooled. Divertor plates are made surfaces evolve—especially how crystalline SiC might

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