Nuclear power provides the promise of carbon-free electricity, but there are just too many “buts” for many people to accept. No one wants another Fukushima and the United States still doesn’t know what to do with more than 60,000 tons of radioactive waste that has accumulated at its reactor sites. Then there’s the issue of nuclear weapons proliferation and national security to worry about, not to mention the environmental toll of mining for uranium.

A startup–itself a rare concept in the nuclear industry–is working on designs for a new reactor that could address many of these concerns. Transatomic Power’s molten salt reactor design could run on either spent nuclear waste (for countries like the U.S. that have a lot of it) or fresh fuel enriched to lower, cheaper, and safer levels of uranium compared to traditional reactors.





“We have a type of nuclear reactor that environmentalists can really get behind,” says CEO Leslie Dewan, a 30-year-old graduate of MIT’s nuclear engineering PhD program and co-founder of the company.

Molten salt reactors aren’t new; designs for them have been around since the 1950s. They have advantages over the light water reactors in use today because they can be operated at normal pressures and shutdown safely even during a power failure. However, previous designs have required very highly enriched uranium to operate. Transatomic’s new design would require much lower-level uranium enrichment or could simply operate on radioactive waste. The reactor core would also be smaller and able to burn up to 96% of the energy from the fuel over long periods of time–a far higher efficiency than reactors today.

Dewan and her co-founder, Mark Massie, met at MIT in 2010 and decided to look for a project to work on together after they finished their grueling qualifying exams. With their hearts in their throat, they presented their concept for the first time to an audience at TEDxBoston. It was 2011, just after the Fukushima disaster had occurred, and they didn’t know how the audience would react. They received a standing ovation.





When they began, they were the first startup to ever come out of MIT’s nuclear engineering program. But since, there have been several others out of MIT alone. Along with companies like Helion Energy, General Fusion, and the Bill Gates-backed Terrapower, nuclear power startups having a renaissance in the last few years. Transatomic Power has raised money from investors including Peter Thiel’s Founders Fund and Acadia Woods Partners.

However, developing a new nuclear reactor is not a quick thing. They’ve finished the design and are starting a three-year program of experimental testing for key components of the design. That will answer questions about a lot of practical issues that affect cost, such as how long the parts will last under radiation and corrosive salts. Then, they’ll create more detailed blueprints. By 2020, their aim is to break ground on a prototype facility.