US perfects lithium vapor cave, breaks nuclear fusion reactor heat barrier

“PPPL’s expertise in using liquid metals, particularly liquid lithium, for enhanced fusion performance is helping refine ideas about how it can best be deployed inside a tokamak,” emphasized Rajesh Maingi, who leads tokamak experimental science at PPPL and co-authored a recent paper in Nuclear Fusion on the proposed placement of lithium.

A strategic placement

Through extensive computer simulations, the researchers have pinpointed the optimal location for the lithium vapor cave: near the bottom of the tokamak, adjacent to the center stack.

“The idea behind a lithium vapor cave is to keep the lithium in the boundary layer away from the hot, fusing core plasma but near the excess heat,” said PPPL in its press release.

This strategic placement allows the lithium vapor to efficiently dissipate heat from the private flux region, an area distinct from the core plasma, without disrupting the plasma’s high temperature.

“The lithium evaporator really does not work unless it is placed in the private flux region,” highlighted Eric Emdee, an associate research physicist at PPPL and lead author of the new paper.

By capturing and neutralizing excess heat before it reaches the tokamak’s walls, the lithium vapor cave acts as a crucial safeguard.

Simple solution and targeted cooling

Initially envisioned as a “metal box,” the researchers discovered that a simpler “cave” configuration, akin to half a box, is sufficient to contain the lithium vapor.

“For years, we thought we needed a full, four-sided box, but now we know we can make something much simpler,” emphasized Emdee.

Notably, this new streamlined design not only optimizes the path for the evaporating lithium, enhancing its heat absorption capabilities, but also simplifies the device’s construction, making it more practical and cost-effective.

In addition to the lithium vapor cave, PPPL scientists have proposed an alternative heat management solution: a porous, plasma-facing wall.

This innovative wall allows liquid lithium to flow directly onto the surface exposed to the plasma, providing targeted cooling precisely where it is most needed.

“The advantage of the porous plasma-facing wall is that you don’t need to change the shape of the confinement vessel. You can just change the tile,” remarked PPPL Principal Engineering Analyst Andrei Khodak.

Paving way for fusion future

The path to commercial fusion energy is fraught with challenges, but the innovative solutions being developed at PPPL offer hope.

By tackling the critical challenge of heat management within fusion reactors, scientists are laying the groundwork for a future where fusion power becomes a viable and sustainable energy source.

The lithium vapor cave and the porous plasma-facing wall represent just two examples of the groundbreaking work being done at PPPL.

These ongoing efforts bring us closer to a world powered by clean and abundant fusion energy, a significant step towards addressing global energy challenges and mitigating climate change.