Transatomic Power co-founder and CEO Leslie Dewan. (Photo by Kyle Alspach for BostInno.)

A Cambridge startup that’s seeking to turn nuclear power into something most everyone will feel good about has taken the next key step in its long-term plan, raising $2.5 million in new funding from investors including Peter Thiel’s Founders Fund.

Transatomic Power, founded by MIT nuclear science graduates, has now raised $4.5 million since last summer.

The startup has designed a nuclear reactor that would aim to produce electricity using existing nuclear waste, helping rid us of one of the major issues associated with conventional nuclear plants. The Transatomic reactor design would also not be prone to melting down, according to the company.

And of course, the reactor would have the same environmental benefit of being carbon-free as existing nuclear power designs.

In a recent interview, Transatomic Power co-founder and CEO Leslie Dewan said the company is aiming to break ground on a demonstration facility within five years and have it operational a few years after that. “For the nuclear industry, it’s very fast-paced,” she said.

The company is aiming to have an operating demonstration facility within six years; “very fast-paced” for the nuclear industry.

Dewan, who holds a PhD in nuclear engineering from MIT, founded Transatomic Power with fellow MIT grad Mark Massie, who serves as CTO. Transatomic’s chairman is Ray Rothrock, an MIT-trained nuclear engineer and former longtime partner at Venrock.

The new funding will be used for lab testing of key components involved with the reactor design, and for refinement of the design for a prototype reactor. The company will be testing materials under a three-year research agreement with the Department of Nuclear Science and Engineering at MIT.

Along with Founders Fund, investors in the new round included Acadia Woods Partners and Daniel Aegerter of Armada Investment AG.

Transatomic’s previous $2 million fundraise—last July—came from FF Science, a unit inside Founders Fund that’s focused on moonshot-type technology bets.

The nitty gritty

Transatomic’s reactor uses nuclear fuel dissolved into a molten salt, instead of relying on the solid fuel of conventional nuclear reactors. The Transatomic reactor also wouldn’t have to use new nuclear fuel, but could actually operate using nuclear waste dissolved into molten salt. The reactor would use up nearly all of the potential energy in uranium, unlike traditional reactors, which use just 3 to 5 percent of the energy, according to Transatomic.

As for improving safety, Dewan said that the molten salt fuel doesn’t have the same cooling requirements as conventional nuclear reactor fuel. If it were to fail, it would fail while in a solid mode—and thus be far safer than typical nuclear fuels, which fail while in a liquid mode and produce radioactive steam.