Experiments Start on a Meltdown-Proof Nuclear Reactor

Transatomic Power, a startup that’s developing a novel type of nuclear reactor, has begun a series of experiments that will either verify its design or send it back to the drawing board. The experiments were made possible by $2.5 million in new investments from Founders Fund, the venture capital firm cofounded by Peter Thiel, and two family funds.

The reactor would be smaller and safer than a conventional nuclear unit, potentially making it far cheaper. It would use molten salt as its coolant, making it meltdown-proof and thus requiring fewer costly safety systems. Transatomic’s design could also consume nuclear waste, and it could use nuclear material that couldn’t easily be used to make a weapon.

A few other companies, as well as a large project in China, are pushing forward their own molten-salt reactors (see “Resurrecting a Meltdown-Proof Reactor Design”). But Transatomic’s is more compact and potentially cheaper (see “Safer Nuclear Power at Half the Price” and “TR35: Leslie Dewan”).

Transatomic’s design is based on a reactor developed and tested in the 1960s at Oak Ridge National Laboratory in Tennessee. If a conventional reactor is damaged and its water pumps fail, as happened at Fukushima, the water coolant can evaporate, leading to a meltdown resulting in explosions and the release of radiation. Molten salt evaporates at a far higher temperature—even if a reactor is damaged and pumps fail, it won’t evaporate and will continue to cool the fuel, preventing the release of radiation. Transatomic’s design also introduces new materials that could make for an even cheaper and more compact nuclear reactor.

CEO and cofounder Leslie Dewan says the company will conduct experiments to determine whether these new materials will perform as expected under the radioactive, high-temperature, and highly corrosive conditions found in a reactor. Transatomic is paying to use facilities at MIT to conduct the experiments under a three-year agreement. The experiments are a key step in an ambitious goal of building a demonstration reactor in the United States by 2020, Dewan says.

The Oak Ridge design uses graphite for the part of a nuclear reactor that keeps nuclear reactions going by controlling the speed of neutrons emitted by the fission reactions. Transatomic’s design instead uses zirconium hydride, a more efficient material that should allow the reactor to be far smaller. But the new material has to be protected from the corrosive molten salts by silicon carbide. Among other things, the new experiments will determine whether that cladding will work as expected.

Transatomic is also using a new type of molten salt that should allow the reactor to burn nuclear waste, and also enable it to use nuclear material that couldn’t easily be repurposed to make a nuclear weapon. But the new salt works at a slightly higher temperature than the previous one, so Transatomic will run tests to confirm that other materials in the reactor can withstand these higher temperatures.