Bill Gates sees nuclear energy as a potential solution to lowering carbon-dioxide emissions around the world, and he has spent the past decade funding new ways to produce the energy in a safe, affordable way.
About 10 years ago, Gates cofounded a company called TerraPower to build new kinds of nuclear reactors.
TerraPower is developing a line of reactors that use a molten-chloride coolant, drawing on a decades-old, but still unused, invention to lower costs and reduce waste.
The most common reactors use light (or regular) water as a coolant.
Following a US Department of Energy investment worth US$40 million and a partnership with energy provider Southern Company, TerraPower plans on opening a new laboratory next year.
Gates' company wants to develop a molten-chloride prototype by 2030, and the laboratory will be used to test reactor materials in the meantime.
John Gilleland, the company's chief technology officer, told Business Insider that molten chloride designs are the "ultimate green reactor".
"It not only would allow you to produce electricity without carbon emissions, but by shipping the heat directly to some process in an industrial facility, you can provide the necessary heat to cause reactions to occur in industrial processing, or whatever you want to use it for, without carbon emissions," Gilleland said.
How a molten-salt reactor works
Nuclear energy grew into prominence after 20th-century scientists figured out how to harness the atom's power, but high costs and safety concerns over dangerous radioactive waste have deterred many countries from investing in it.
Scientists at the Massachusetts Institute of Technology Energy Initiative wrote that within the electricity sector, nuclear energy would be the least expensive solution to reducing greenhouse-gas emissions in the next few decades.
But nuclear energy accounts for only 11 percent of the world's electricity, according to the World Nuclear Association.
Nuclear energy is produced when radioactive fuel is put into a reactor to trigger fission – a process in which the nucleus of an atom splits within a reactor core.
In light-water reactors, solid fuel sits within cladding, or corrosion-resistant metal that prevents radioactive pieces from contaminating the coolant. The water around the cladding helps turn a reaction's heat into steam for turbines, which generate electricity.
TerraPower's liquid-chloride design, however, puts uranium fuel and the coolant in the same molten salt, Gilleland said.
Fission can heat the salts directly as the mixture flows through the reactor core, and the mixture then goes through heat exchangers to generate heat or electricity, he said.
Light-water reactors can't sustain reactions at very high temperatures because the coolant evaporates. With molten chloride, though, TerraPower could operate reactors at much higher temperatures than before.
In addition to generating electricity, nuclear technology could be used in high-temperature processes like fertiliser production and oil refining.
The materials inside light-water reactors degrade quickly and need to be replaced roughly every 18 months, as it becomes more difficult to sustain fission with older fuel.
Molten-chloride reactors, meanwhile, produce little residual waste and could theoretically run for years without the need to add fuel or get rid of waste.
TerraPower's design is also less likely to be used in nuclear-weapon production because its radioactive fuel is not isolated.
TerraPower's new reactor was inspired by a 1960s experiment
Though TerraPower began working on its newest line of reactors just a few years ago, the design is based on Cold War-era molten-salt technology. (TerraPower has also spent the past decade developing a travelling-wave reactor, another advanced design.)
Researchers at the Oak Ridge National Laboratory in Tennessee developed a molten-salt reactor in the 1960s, but funding came to a halt several years later as scientists raised concerns about corrosion and safety problems associated with the reactor.
Now, with government funding and the support of billionaires like Gates, these reactors have another shot at hitting the market.
TerraPower and Southern Company are working on their design with scientists from Oak Ridge National Laboratory, Idaho National Laboratory, the Electric Power Research Institute, and Vanderbilt University.
Several other startups are competing with Gates' company to commercialize similar molten-salt reactors.
In April, Florida-based company ThorCon received US$400,000 from the US Department of Energy for a joint research project with Argonne National Laboratory.
ThorCon aims to begin testing a molten-salt-fuelled fission reactor by 2023.
Department of Energy officials have also given US$2.1 million to Alabama-based Flibe Energy, which is using thorium instead of uranium.
And in the UK, Moltex Energy is making a Stable Salt Reactor, which uses molten-salt fuel. Moltex plans on deploying its product at a nuclear-reactor site by 2030.
At the same time, some nuclear startups have struggled to make their designs commercially viable. MIT-affiliated Transatomic Power, for example, shut down in September after seven years of operation.
The company, founded just after the 2011 nuclear disaster in Japan's Fukushima Prefecture, had claimed its reactors would produce electricity 75 times more efficiently than light-water reactors.
In a blog post announcing the shutdown, Transatomic CEO Leslie Dewan acknowledged there had been errors in early analyses and said the company was unable to scale up fast enough.
Transatomic Power later open-sourced its intellectual property for other researchers to use.
Clean energy is in urgent demand, and Gates' startup is at least a decade away from a working prototype
Renewable energy use is growing too slowly to prevent dangerous climate change on its own.
If governments don't implement new policies that reduce carbon-dioxide emissions, the bulk of the world's energy will still come from fossil fuels, according to the International Energy Agency's 2018 World Energy Outlook.
Solar, wind, and nuclear-energy systems are not keeping up with global energy demands, the report said.
About 25 percent of the world's electricity comes from renewable energy sources, according to the World Energy Outlook.
The International Energy Agency predicts that the share will rise to 40 percent by 2040, and nuclear energy can prove to be a vital factor in any changes.
For Southern Company and TerraPower, the companies' ambitious plan could produce a new reactor well before 2040.
The partners are developing a prototype with the capacity to produce up to 1,100 megawatts of electricity – enough to power about 825,000 homes, according to the California Energy Commission.
TerraPower's US$20 million laboratory, set to open in the state of Washington next year, will help researchers ensure the reactor is safe to run.
Gilleland said TerraPower will run tests with depleted uranium, which is not used in fission, to determine which materials can hold molten salt without being damaged by corrosion.
Gates, who still serves as TerraPower's chairman, has emphasised that fewer people die in nuclear-plant disasters than in coal-mine or natural-gas accidents.
During a 2010 speech at MIT, he also praised nuclear energy for its potential to benefit countries where solar and wind energy are scarce.
"It is infinite. You can filter out of the sea very cheaply enough uranium to run this thing for as long as the sun will shine," Gates said. "I love nuclear."
This article was originally published by Business Insider.
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