by -
Molten salt reactors were first built in the 1950s but have not been used in the US since the 1970s.
-
The US Nuclear Regulatory Commission recently issued a permit to build a molten salt nuclear plant.
-
Kairos Power is leading the project, which it hopes to complete by 2027.
The US has issued permission to build a different type of nuclear reactor.
Called a molten salt reactor, the future could lead to smaller, easier-to-build nuclear power plants that could eventually power ships and other off-grid locations.
What makes this reactor different is how it cools its core, using molten salt instead of water.
Water vs. salt
Almost all the nuclear reactors in operation today use water for cooling. Their hearts can reach a temperature of 572 degrees Fahrenheit, much hotter than the boiling point of water of 212 degrees.
To prevent the water from evaporating and keeping it liquid at such high temperatures requires a lot of pressure, which costs extra technology, space and money.
On the other hand, some salts have a much higher boiling point, so they would not require the same expensive, high-pressure environments.
“You can use it at these high temperatures, and it doesn’t boil,” Nicholas V. Smith, project director of the molten chloride reactor experiment at the Idaho National Laboratory, told Business Insider. “You don’t need to have big, thick pressure vessels to have refrigerants.”
The first molten salt reactor tested in the 1950s, for example, was small enough to fit on a plane but the part of the Diablo Canyon Nuclear Power Plant in California that generates energy takes up 12 acres of land, according to Berkeley Engineering.
That interest, and others, is why the US The Nuclear Regulatory Commission just after the first license to build a non-water-cooled nuclear plant was issued.
It will be the first since 1968, Mike Laufer, chief executive officer of Kairos Power, told Bloomberg.
Kairos Power is the company that plans to build a test plant they call Hermes, which will be cooled by molten fluoride salt in Oak Ridge, Tennessee by 2027.
The first version of the plant will not provide electricity, but the company hopes its successor, Hermes 2, by 2028.
Why is molten salt worth re-examining?
Molten salt reactors have been around since the 1950s but the US largely abandoned them in the 1970s in favor of water-cooled reactors, many of which had already been built.
Recently, however, companies, including Kairos, and laboratories have been looking at salt-cooled reactors again.
“Salt is a better coolant than water, once you get down to the engineering details,” Smith told BI.
Because molten salt reactors don’t need those thick pressure vessels to keep water liquid at high temperatures, there’s more design flexibility, Smith said.
Reactors can be smaller than water-cooled options and built in a wider range of locations, for example.
“Molted salt opens up a lot of design options that you can’t get without,” Smith said. “As you move into that low-pressure paradigm, manufacturing becomes much simpler.”
“I see molten salt reactors being deployed prolifically in all areas,” from remote locations to shipping vessels to large power plants, he said.
How will Hermes work
Hermes will be to work at temperatures up to 1,200 degrees Fahrenheit. But its molten salt coolants – made from a mixture of lithium fluoride and beryllium fluoride called FLiBe – boil at about 2,606 degrees Fahrenheit, well above the temperature of the core reactor.
Therefore, the FLiBe will remain liquid at those high temperatures without additional pressure. That should make the reactors easier and cheaper to build, Smith said.
Kairos Power’s proposed fuel is also different from a conventional nuclear reactor. The company plans to use TRISO, or TRi-structured ISOtropic particle fuel.
It can withstand extreme temperatures better than current fuels, making it less likely to release radioactive fission products, according to the US Office of Nuclear Energy.
Challenges remain
Some challenges include limiting erosion.
“Oxygen is kind of the driving force for corrosion in molten salt,” Smith said.
The challenge is to limit the salt’s exposure to oxygen. “The processes are not the same, but the principles are the same as any other refrigerants,” he said. “You have to control the chemistry.”
Molten salt reactors have disadvantages. For example, “they could produce several different waste streams, all of which would require extensive processing and present disposal challenges,” physicist MV Ramana write in the year 2022.
One study suggested that the reactors could produce more nuclear waste than current systems and will use “highly corrosive and pyrophoric fuels and coolants that become highly radioactive after irradiation.”
Read the original article on Business Insider
