Warm Fusion

Lattice-confined fusion, LCF, may be the way we get to commercial fusion reactors.

 One promising alternative is lattice confinement fusion (LCF), a type of fusion in which the nuclear fuel is bound in a metal lattice. The confinement encourages positively charged nuclei to fuse because the high electron density of the conductive metal reduces the likelihood that two nuclei will repel each other as they get closer together.

LCF promises to be less expensive, smaller, and safer than other strategies for harnessing nuclear fusion. And as the technology matures, it could also find uses here on Earth, such as for small power plants for individual buildings, which would reduce fossil-fuel dependency and increase grid resiliency.

Inertial-confinement fusion devices can momentarily reach densities of 1026 deuterons per cubic centimeter. It turns out that metals like erbium can indefinitely hold deuterons at a density of nearly 1023 per cubic centimeter—far higher than the density that can be attained in a magnetic-confinement device, and only three orders of magnitude below that attained in an inertial-confinement device. Crucially, these metals can hold that many ions at room temperature.

The deuteron-saturated metal forms a plasma with neutral charge. The metal lattice confines and electron-screens the deuterons, keeping each of them from “seeing” adjacent deuterons (which are all positively charged). This screening increases the chances of more direct hits, which further promotes the fusion reaction. Without the electron screening, two deuterons would be much more likely to repel each other.

Electron screening makes it seem as though the deuterons are fusing at a temperature of 11 million °C. In reality, the metal lattice remains much cooler than that, although it heats up somewhat from room temperature as the deuterons fuse.

Overall, in LCF, most of the heating occurs in regions just tens of micrometers across. This is far more efficient than in magnetic- or inertial-confinement fusion reactors, which heat up the entire fuel amount to very high temperatures. LCF isn’t cold fusion—it still requires energetic deuterons and can use neutrons to heat them. However, LCF also removes many of the technologic and engineering barriers that have prevented other fusion schemes from being successful.