The engineering department is making substantial innovations in nuclear energy research by developing unique parts intended for pumping liquid metal.
Fort Lewis College is one of five U.S.-based academic institutions studying how to increase the efficiency of the next generation of nuclear power plants, which involves using metal as a coolant that could help minimize radioactive waste.
Because nuclear power involves blasting radioactive atoms apart, things get pretty hot— and just like a car’s engine that runs off of miniature explosions— it needs a coolant, Billy Nollet, associate professor of physics and engineering at FLC, said.
Right now, most nuclear power plants keep cool with water. FLC’s thermal hydraulics lab is studying how to safely use liquid sodium as a coolant instead, he said.
Some advantages to using this liquid metal in lieu of good old fashioned water involves how it can chill reactors at atmospheric pressure— the weight of air on Earth’s surface— along with how long spent waste stays radioactive, he said.
Nollet started the FLC thermal hydraulics lab in 2013 where he and engineering students have been studying the way corrosion happens inside nuclear power plants and how to keep liquid sodium flowing through the piping hot cycle of nuclear energy.
“So imagine your car,” Nollet said. “Your car has a radiator that has a water pump that flows the antifreeze around. It has a thermostat which controls the temperature at which all this happens. You can take that water out and replace it with alcohol or some other of your mineral oil or liquid sodium. We are just removing the fluid and switching it out with something better. So rather than water we use something else.”
What is Nuclear Energy
Nuclear power generates electricity in a significantly different way than coal and natural gas, and creates low to zero carbon emissions, Nollet said.
While nuclear power won’t contribute to greenhouse gases, it does create radioactive waste that is notably dangerous, he said.
This radioactive waste comes from uranium and plutonium. These natural and radioactive resources used for nuclear energy make for spectacular fission after their atoms split.
Fission is the heat energy flying out of a broken nucleus. This hot shrapnel travels through the reactor to make steam, which then spins a turbine that generates electricity, Nollet said.
Inside Nuclear Reactors
This is where FLC’s thermal hydraulics lab comes in. Thermal hydraulics is the study of how to use fluids to move energy around, Nollet said.
Their fluid of choice is liquid sodium— a liquid metal that looks similar to mercury, and can chill reactors more efficiently than water, he said.
It doesn’t have the same problems as a water coolant, which boils much more quickly than liquid sodium and thus loses its chilling ability, Andrew Napora, a sixth semester engineering student, said.
Another benefit of using liquid sodium is how it decreases the amount of spent fuel and its lifetime of radioactivity, Nollet said.
Spent fuel is what is left over after nuclear fission that can’t be used anymore.
“These things are dangerous when they're highly radioactive,” he said. “That's the part we need to make sure we keep away from the public.”
This radioactive waste is stored in rural areas at the bottom of water tanks until it becomes stable for dry storage, which can take decades to millennia, Nollet said.
A New Generation of Nuclear Power
“With a sodium cooled reactor we can solve that spent fuel problem,” Nollet said.
In new sodium reactors, the neutrons come in at a much higher speed, which means that it gives the particle it runs into a lot more energy, which is what it needs to blow itself apart, Napora said.
“Think of a neutron like a worker bee,” Nollet said. “If you have a lot of them in there, you can do a lot of things. In a water cooled reactor you have very few, but you need a lot of them keep the fission reaction going. In a sodium reactor, we have more workers which frees up more of them to do other things.”
Another task these neutrons can be assigned would be to transmute, he said.
Transmutation involves taking that spent fuel and beating it up with more neutrons during fission. This makes the spent fuel break down into material that doesn’t stay radioactive as long, Nollet said.
“So rather than having spent fuel that last for thousands of years, we can turn it into spent fuel that lasts a few decades,” he said.
Another advantage of sodium reactors is their ability to handle raw uranium, which comes right out of the Earth and into a reactor without being refined, Nollet said.
The more an element like uranium is enriched, the more it becomes a weapon grade material, so it’s advantageous to keep these resources less refined in terms of safety, Nollet said
Also, sodium reactors can allow the fuel— uranium or plutonium— to burn completely, so there is little to no waste left over, he said.
Sodium cooled reactors are getting close to a closed fuel cycle. As of late-2019, highly radioactive spent fuel is essentially contained forever, Nollet said.
“With a closed fuel cycle, that fuel— once it's burned up— could be more or less returned to the Earth,” he said.
FLC’s thermal hydraulics lab is researching corrosion in reactors, which is inevitable regardless of what kind of coolant is used, Nollet said.
The lab has also developed the unique design to pump the liquid sodium coolant through the reactor.
It’s a moving magnet pump, which picks up the molten metal and moves it through the reactor to cool down and maintain the explosions of fission, Nollet said.
“Basically, because sodium is volatile, because it's dangerous, we do everything we can without touching it,” he said. “So we can push the sodium without touching it, we don't have any propellers or shafts that have to go through and seal.”
This particular type of research for sodium cooled reactors could become the new, fourth generation of nuclear reactors, which are still being researched and developed, he said.
Right now, the world uses generation two and three reactors to contribute to energy production, and they use water, Nollet said.
According to the International Atomic Energy Agency, France generated 72 percent of its energy with nuclear power in 2018, while the U.S used 19 percent.
“We're always solving very specific problems in this huge puzzle piece that is a reactor,” he said. “And in particular, our puzzle piece is cooling systems. So the radiator in your car— that's basically what we do.”