DoE digs up molten salt nuclear reactor tech, taps Los Alamos to lead the way back

The collaborative effort pits supercomputers against the agency's corrosive reactor research

After more than 50 years, molten salt nuclear reactors might be making a comeback. The US Department of Energy (DoE) has tapped Los Alamos National Laboratory (LANL) to lead a $9.25 million study into the structural properties and materials necessary to build them at scale.

"The US needs projects like this one to advance nuclear technologies and help us achieve the Biden-Harris administration's goals of clean energy by 2035 and a net-zero economy by 2050," said Asmeret Asefaw Berhe, director of the office of science, in a statement.

The study, conducted as part of the Scientific Discovery though Advanced Computing (SciDAC) program, seeks to gain a better understanding of the relationship between corrosion and irradiation effects at the atomic scale in metals exposed to molten salt reactors through simulation.

Unlike conventional fission reactors, which rely on large quantities of water for cooling and power generation, molten salt reactors – as their name suggests – utilize metallic fluoride salts for the nuclear fuel and coolant. In these reactors water is only used to generate power.

This isn't the first time the DoE has explored this reactor tech. In the middle of last century, Oak Ridge National Laboratory (ORNL) took the lessons learned from the Aircraft Reactor experiment to build a functional nuclear aircraft power source and began construction of a molten salt test reactor.

The experiments, conducted between 1957 and 1969, utilized a mixture of lithium, beryllium, zirconium, and uranium fluoride salts. Cooling was also achieved using a fluoride salt mixture, but it lacked the uranium and zirconium found in the fuel.

The experiments proved promising, as molten salt reactors were generally smaller and considered safer compared to the pressurized water reactors still used today. But both proved too heavy for powered flight or materials design.

Because cooling was achieved by circulating molten salt through a heat exchanger as opposed to water, the risk of a steam explosion is effectively nonexistent. However, as the Oak Ridge National Laboratory found during the Molten Salt Reactor Experiment, fluoride salts are incredibly corrosive and required hardened materials to safely contain them.

ORNL's Molten Salt Reactor Experiment utilized specialized materials fabricated from Hastelloy-N – a nickel-molybdenum alloy developed by the lab with a high resistance to corrosion even at high temperatures. The research program announced this week will revisit the material choices and examine a variety of metals using higher-performance compute resources to simulate how they'll perform at scale in these reactors.

"These partnerships promise to advance our understanding of material phenomena essential to designing and demonstrating safe and efficient advanced nuclear reactors," Kathryn Huff, assistant secretary for nuclear energy, said in a statement.

While LANL will lead the project, the program will also see contributions from Idaho National Laboratory, Lawrence Berkeley National Laboratory, Sandia National Laboratories, as well as Carnegie Mellon University. Curiously, ORNL, which pioneered the reactor tech and Hastelloy-N, wasn't listed as a contributor on the project.

"These collaborations bring together cutting-edge scientific techniques with real-world applications and enable the deployment of new reactor designs in timeframes not otherwise possible," Berhe said. ®

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