Nuclear power is leveling up, with plans for an entire floating power plant fueled by something you’d least expect to find in a reactor—table salt.
By the mid-2030s, a fleet of smaller floating nuclear power plants (FNPPs) that use “molten salt reactors” could form the largest floating power plant in the U.S. Nuclear innovation company Core Power, based in the U.K., dreamed up the design, and its Liberty program will oversee construction of the plant. A central shipyard will manage the build, keeping up with tasks such as maintenance and refueling. Some of the FNPPs in the fleet can be stationed near the coast, while others will be further out in the ocean. A definite location for the FNPP has not yet been announced.
Rather than the typical fuel powering a nuclear reactor, uranium-235 rods, these reactors will be using salt and powdered uranium oxide melted together. Instead of the water used in traditional generators, salt will also be used as a coolant, virtually eliminating the risk of evaporation.
The Liberty Project’s network of mass-produced FNPPs is expected to generate around 175 GWh of clean electricity per year. That is an enormous shift from fossil fuels, which have been warming the planet and wreaking havoc with the climate worldwide over the last 150 years. While efforts in more eco-friendly energy sources like wind and solar have been gaining momentum, energy production still makes up about three-quarters of total greenhouse gas emissions globally, according to the International Energy Agency.
“We have an opportunity to use energy differently,” said Core Power CEO Mikal Bøe at a recent summit in London. “The output [of fossil fuels] is exhaust gases, and those are the heart of the decarbonization debate. In a sense, the challenge here is if we’re going to solve decarbonization.”
Molten salt reactors were first conceived in the 1960s by scientists at Oak Ridge National Laboratory who came up with the Molten Salt Reactor Experiment. The brainchild of nuclear physicist Alvin Weinberg, it was the first nuclear reactor to use molten salt as both a coolant for fuel and a component of the fuel itself. It was also the first reactor ever to run on uranium-233 or U-233. Though it ran at full power for more than 13,000 hours from 1965 through 1969, the Department of Energy eventually lost interest in the project and shut down operations. Then things were pretty much silent until research resumed in the early 2000s.
“It wasn’t until the 2010s or so when there started to be interest on the industry side, with people thinking this might be a viable technology for smaller reactors,” Oak Ridge lab physicist Ted Besmann, Ph.D., told Popular Mechanics. “There began to arise small companies inspired by the MSRE that began to take an interest in molten salt reactors.”
The original Oak Ridge lab’s nuclear salt reactor used U-233 atoms that experienced nuclear fission when bombarded with neutrons. The U-235 that Core Power is planning to use in its reactors is slightly more powerful at 200 MeV—or 200 million electron volts—which releases 1.8 million more times the energy of the same mass of diesel. Besmann sees more advantages than just more energy output. The problem with water as a coolant is its volatility, or evaporation at high temperatures. Pressure in these types of reactors needs to be so high that the water would evaporate without thick-walled steel vessels to keep it contained. If that pressure is lost, so is the water, and without a coolant, the reactor fuel will overheat and radioactive sludge could ooze out, causing a highly dangerous situation.
Molten salt reactors that use salt as a coolant have an advantage because the boiling point of salt is much higher. Even at extreme temperatures, the molten salt will still be far below its boiling point, so it only needs a thin vessel to contain it. If things do overheat, coolant salt circulating around the reactor will expand and stop the fission reaction inside.
“There are also potential advantages in that you can refuel the reactor while it’s operating,” said Besmann. “You can reprocess the fuel and continue to run the reactor. These are potential advantages nobody has ever demonstrated, but it’s one of the possibilities that add to the attractiveness of this kind of reactor.”
three parts of floating nuclear power plants to generate fuel
Core Power
This illustration depicts the offshore production of energy using a floating nuclear power plant.
Core Power’s concept of a floating nuclear power plant has advantages of its own. Putting FNPPs on industrial barges instead of building them on land not only makes them more mobile, but less problematic, because the construction and imposing presence of the plant won’t take over an entire neighborhood. Nobody really wants to live next to a nuclear power plant. It’s also possible for a floating network of power plants to generate more power than at just one site on land, and with an immense amount of power comes a huge amount of transmission. A single FNPP on a grid can deliver power to any point on that grid.
Future applications for molten salt reactors could extend to portable versions that supply energy to remote sites or military bases, as Besmann sees it. Trucking fuel to bases has been one of the largest sources of casualties for the military, but a small nuclear plant could solve that issue. For now, he thinks the Core technology looks promising.
“I think their broad thinking about providing large-scale amounts of power from sea-based systems has a lot to recommend it,” he said. “Success will probably hinge less on the sea-based concept and more on the ability for reactor vendors to supply plants that can deliver electricity at a competitive price.”
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