How nuclear batteries could speed the race to fusion power

Fusion power has always been a bit of a contradiction. The fusion part is actually kind of easy — an undergrad recently built a simple fusion device in his bedroom, for example — but getting electricity out of the reaction isn’t.

“A fusion reactor that makes power — and there’s plenty of those, they already exist,” Daniel Velásquez, materials science lead at Avalanche Energy, told TechCrunch. “A fusion reactor that makes electricity is better.” That’s where the nascent industry remains stuck.

Fusion reactions release tremendous amounts of energy by fusing two lighter atoms into a heavier one. But harvesting that energy has proven challenging. The most common approach is to heat water and spin a steam turbine, but that approach isn’t terribly efficient, harnessing at best around 60% of the power.

Avalanche Energy thinks it can capture more of that energy by developing new materials known as radiovoltaics. Radiovoltaics are similar to photovoltaics — traditional solar panels — in that they use semiconductors to transform radiation into electricity. They’ve been around for a while, but they’re not very effective. Existing radiovoltaics are easily damaged by the very radiation they harness and don’t produce that much electricity.

Today, Avalanche was awarded a $5.2 million contract from DARPA to develop new radiovoltaics, the company exclusively told TechCrunch. 

The Pentagon research agency is interested in using the materials in a new class of nuclear batteries, which use radioactive decay from materials like polonium to generate electricity. Such devices could help power spacecraft and satellites for several years. They could also be used in more energy intensive terrestrial military applications for days on end — “in particular for autonomous systems or missions where logistics are a little bit impermissible,” Velásquez said.

That’s not exactly what Avalanche is building toward as a company, but the DARPA award does overlap with its ambitions. 

For one, fusion reactions and nuclear batteries both produce alpha particles, a type of radiation that’s so energetic it can damage all kinds of equipment, including the wall of a nuclear reactor. Second, Avalanche is developing a desktop-scale fusion reactor that could replace diesel generators at remote military bases.

If the company can develop a new radiovoltaic for a nuclear battery, it could apply that knowledge to a new reactor part. Such a sheathing would help capture the alpha particles, protecting the reactor while boosting the amount of electricity it produces. Avalanche also won a $1.25 million award from the U.S. Air Force’s AFWERX research lab to use computational advances to speed materials discovery.

Fusion startups are all racing to achieve a milestone known as breakeven, which in the scientific world is known as Q>1, where Q is the ratio of power produced by the fusion reaction to the power required to sustain it. Putting those alpha particles to work generating electricity would potentially make commercial fusion power easier to attain.

Avalanche isn’t the only company with a reactor design that will produce alpha particles. If it succeeds, the company could find itself supplying other fusion companies with the technology, a trend that’s emerging within the industry.