Molten Salt Reactors (MSRs): What Are They?

There is a significant push to bring nuclear power back to the forefront of the clean energy sector. However, the same drawback with the clean energy source remains: radioactive solid waste. Standard reactors run on enriched uranium, which leaves behind the toxic waste. This radioactive waste must be stored for centuries. As a result, getting permits for new plants is incredibly difficult.

Because of this challenge, other options are becoming popularized. One of those options is molten salt reactors (MSRs). These advanced nuclear reactors use molten salts to cool the machine and can run on liquid fuel, making them inherently safer.

MSRs are Making a Comeback

Back in the 1960s, Oak Ridge National Laboratory (ORNL) ran a highly successful MSR program. This program solved most of the technical hurdles that come with traditional nuclear plants. The government, however, shut the program down in 1972 because leaders wanted breeder reactors instead, because those designs created materials like plutonium-239 for nuclear weapons.

Today, most plants use pressurized water reactors. The big fear with these is that if power and cooling both fail, a nuclear meltdown might be impossible to stop.

This is one of the most crucial challenges that MSRs can fix. If an MSR loses power, gravity drains the liquid fuel away safely causing no meltdown risk. Additionally, they are smaller, run at a lower pressure, and are far more efficient at generating electricity. The molten salt reactors also run on thorium, a cheap, abundant element leftover from mining rare earth metals.

Swapping Pressure for Corrosion

While the advanced reactors solve a lot of issues, they’re still not perfect. As a report The American Ceramic Society explained, “Essentially, you are swapping the challenge of high-pressure engineering for the challenge of high-corrosivity engineering.” Molten salt is highly corrosive, and it constantly eats away at the reactor’s parts.

That’s why engineers are turning to advanced ceramics, like silicon carbide, that can withstand extreme heat and corrosion. However, it isn’t a flawless fix yet because research shows that “the combined effects of radiation and corrosion cause eventual damage to the silicon carbide parts, too—hardening the ceramic and making it brittle.”

Despite these challenges, interest is growing fast. The U.S. Department of Energy is funding a test reactor in Tennessee.  Additionally, ORNL continues to push molten salt reactors towards deployment.