This story originally appeared on Grist and is part of the Climate Desk collaboration.

Back in 2009, Simon Irish, an investment manager in New York, found the kind of opportunity that he thought could transform the world while — in the process — transforming dollars into riches.

Irish saw that countries around the globe needed to build a boggling amount of clean-power projects to replace their fossil fuel infrastructure, while also providing enough energy for rising demand from China, India, and other rapidly growing countries. He realized that it would be very hard for renewables, which depend on the wind blowing and the sun shining, to do everything. And he knew that nuclear power, the only existing form of clean energy that could fill the gaps, was too expensive to compete with oil and gas.

But then, at a conference in 2011, he met an engineer with an innovative design for a nuclear reactor cooled by molten salt. If it worked, Irish figured, it could not only solve the problems with aging nuclear power, but also provide a realistic path to dropping fossil fuels.

“The question was, ‘Can we do better than the conventional reactors that were commercialized 60 years ago?” Irish recalled. “And the answer was, ‘Absolutely.’”

Irish was so convinced that this new reactor was a great investment that he bet his career on it. Nearly a decade later, Irish is the CEO of New York City-based Terrestrial Energy, a company that expects to have a molten-salt reactor online before 2030.

Terrestrial is far from alone. Dozens of nuclear startups are popping up around the country, aiming to solve the well-known problems with nuclear power — radioactive waste, meltdowns, weapons proliferation, and high costs.

There are reactors that burn nuclear waste. There are reactors designed to destroy isotopes that could be made into weapons. There are small reactors that could be built inexpensively in factories. So many ideas!

To former Secretary of Energy Ernest Moniz, an advisor to Terrestrial, it feels as if something new is underway. “I have never seen this kind of innovation in the sector,” he said. “It’s really exciting.”

Other reactors, like Terrestrial’s molten-salt-cooled design, automatically cool down if they get too hot. Water flows through conventional reactors to keep them from overheating, but if something halts this flow — like the earthquake and tsunami in Fukushima — the water boils off, leaving nothing to stop a meltdown.

Unlike water, salt wouldn’t boil off, so even if operators switched off safety systems and walked away, the salts would keep cooling the system, Irish said. Salts heat up and expand, pushing uranium atoms apart and slowing down the reaction (the farther apart the uranium atoms, the less likely a flying neutron will split them apart, triggering the next link in the chain reaction).

“It’s like your pot on the stove when you are boiling pasta,” Irish said. No matter how hot your stove, your pasta will never get hotter than 212 degrees Fahrenheit unless the water boils off. Until it’s gone, the water is just circulating and dissipating heat. When you replace water with liquid salt, however, you have to get to 2,500 degrees Fahrenheit before your coolant starts to evaporate.

This stuff can sound like science fiction — but it’s real. Russia has been producing electricity from an advanced reactor that burns up radioactive waste since 2016. China has built a “pebble bed” reactor that keeps radioactive elements locked inside cue ball-sized graphite spheres.

In 2015, to keep track of the startups and public-sector projects working on trying to provide low-carbon energy with safer, cheaper, and cleaner nuclear power, the centrist think tank, Third Way, started mapping all of the advanced nuke projects across the country. There were 48 dots on the first map, and now there are 75, spreading like a candy-colored case of measles.