Molten salt reactors, a scientific innovation previously passed over by the Department of Energy, are gaining momentum as the next "big thing" in clean energy production.

The Oak Ridge National Laboratory hosted a mix of researchers, regulators, venture capitalists and reactor developers at its third annual molten salt reactor workshop last week. There, vendors talked about design, fuel, safety and regulations that pertain to the pursuit of advanced reactor technology.

As far as advanced reactors go, molten-salt cooled reactors are nothing new to ORNL. The laboratory constructed the first experimental molten salt reactor in 1964. It reached nuclear criticality the next year.

The Department of Energy was looking into nuclear energy at the time, the laboratory built and studied 13 different kinds of reactors. The Energy Department ended up moving forward with reactors cooled by light water, which are widely used today.

So, the Oak Ridge National Laboratory decommissioned the experimental molten salt reactor just five years after it reached criticality.

"The molten salt reactor experiment was very successful in that it demonstrated that concept worked and successfully," said Alan Icenhour, associate director of the Nuclear Science and Engineering Directorate.

"As we move to the future, there's rekindled interest in what's called advanced reactor technology, and that's looking into how we can further improve and extract even more energy from that," he said.

The reactors work by pumping molten salt in a loop to cool off hot uranium fuel in a continuous reaction. The reactors are appealing because they operate at very low pressure and at high temperatures, which makes them more energy efficient than existing water-cooled reactors.

"They've become attractive not only in the United States, but in other countries as people investigate it and see that the characteristics of these reactors lend themselves to being beneficial as a power source," Icenhour said.

Nuclear reactors have lifespans, and reactors in the southeast are expected to start going offline in the 2030s. By the 2050s, none of the existing nuclear reactors in the southeast will be operational.

Many reactor developers at the conference hope to begin implementing molten salt reactors into the grid by the mid-2020s.

"We would like this technology to be ready to fill that void if it can be and if it makes sense," said Lou Qualls, ORNL's national technical director for molten salt reactors. "So we're studying it now to see if it's a technology that we could have ready in time."

Still, Qualls said, there are cynics of the technology.

"The real competition for the market is the status quo," Qualls said.

"What we're doing today isn't going to be what's going to work in the future, so we have to innovate and improve. When you just kind of explain to people that it's been done before we did this 50 years ago and it worked pretty well, that's the first thing they're surprised about. We've done this and it worked."