Transfer of lithium-7 salt accelerates molten salt reactor deployment

More than 60 years after the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL) pioneered molten salt reactor technology, material from that historic effort are being prepared to support the next generation of advanced nuclear reactors.

Through a competitive award issued by Idaho National Laboratory and the DOE's Office of Nuclear Energy (DOE-NE), ORNL has shipped more more than two tons of solid lithium floride and beryllium floride, known as FLiBe salt to Natura Resources. Originally used as the secondary-system coolant in ORNL's Molten Salt Reactor Experiment (MSRE), the salt contains 99.99 percent enriched lithium-7, a rare but essential element in the efficacy of molten salt reactors. Natura will use the FLiBe salt for its research reactor at Abilene Christian University (ACU) in Abilene, Texas.

"ORNL has the only significant supply of lithium-7 enriched FLiBe salt currently available in the United States," said Kevin Robb, who is leading ORNL's effort to transport the salt and serves as head of ORNL's Energy Systems Development Group. "This transfer is helping accelerate the deployment of the next generation of molten salt reactors while commercial suppliers develop lithium-7 production capacity in the U.S."

"Few materials in the nuclear industry carry the history and significance of this FLiBe inventory. We are honored to build upon the foundation established by Oak Ridge National Laboratory and grateful to the Department of Energy for enabling its continued use in advancing molten salt reactor technology," said Jordan Robison, chief executive officer of Natura Resources. "This milestone connects one of the nation's most important reactor experiments with the next generation of nuclear innovation."

How FLiBe works

Molten salt reactors get their name from the salt mixtures used to cool their systems. Where conventional reactors use water to cool solid uranium fuel, a molten salt reactor uses salt, heated to a liquid, to move heat through the system. Natura's salt-fueled design uses uranium fuel dissolved in the liquid FLiBe to power the reactor and transfer heat.

FLiBe's unique properties enable molten salt reactors to operate at higher temperatures while remaining at low pressure, enabling greater efficiency in energy production and passive safety features.

The transfer of MSRE FLiBe salt contains lithium-7 enriched to 99.99 percent - a rare concentration not currently produced in the U.S. in large quantities. Enriched lithium-7 has a low neutron cross section, meaning it is less likely to absorb neutrons needed to sustain reactor operation. It also reduces the production of tritium, a radioactive form of hydrogen.

Historic reactor salt begins a new chapter

The MSRE FLiBe inventory has been stored at ORNL since the reactor ceased operation in 1969. ORNL transferred the salt from the original MSRE coolant tank into five large canisters in 1999. In 2012, salt from one of the large canisters was transferred into several smaller canisters for research use.

Now, the remaining inventory is poised for another research milestone. The shipment will travel more than 1,000 miles from ORNL to the site of Natura Resources' Molten Salt Research Reactor (MSR-1) at ACU. The project is on track to become the first salt-fueled molten salt reactor to operate in the U.S. since the MSRE.

In coordination with INL and DOE, ORNL has supported administrative transfer of the material from DOE's Office of Science to the Office of Nuclear Energy and collaborated with Natura on a transportation plan. ORNL also supported surveying, packing and loading of the salt ahead of the shipment.

At room temperature, the FLiBe is effectively a large salt rock contained in sealed metal vessels. This shipment will include the four remaining large canisters of the MSRE FLiBE, as well as two smaller canisters.

"This transfer connects ORNL's history with our continued leadership in advancing the next generation of molten salt reactors," said Robb. "By transferring this rare salt inventory, ORNL is helping ensure that a material created for one pioneering reactor experiment can contribute to another."

60 years of molten salt leadership

The laboratory's Molten Salt Reactor Experiment remains an important demonstration of molten salt reactor technology. ORNL has continued that work by providing scientific tools, facilities and expertise to help modern developers mature the technology for commercial use.

ORNL supports a broad range of research, from fundamental salt property measurements to applied engineering data that can inform design, licensing and eventual operation. The laboratory is home to several test facilities supporting molten salt reactor development, including the Facility to Alleviate Salt Technology Risks, a Liquid Salt Test Loop, and the Salt Pot Instrumentation and Components Evaluation Experiment. In partnership with the University of South Carolina, ORNL oversees DOE's Molten Salt Database, a comprehensive resource used by developers to develop models and accurately inform reactor design.

"ORNL's facilities and expertise have become increasingly significant as commercial interest in molten salt technologies has grown," said Robb. "We've been a trusted partner in the broader MSR community for more than 60 years, reducing risk, strengthening confidence and moving molten salt technologies closer to commercial reality."

ORNL is committed to supporting U.S. energy needs by pursuing strategic research that advances a wide variety of affordable, abundant and competitive nuclear technologies, and strengthens national security. The lab's scientific expertise and world-class facilities are often the first step in advancing nuclear energy innovations.

UT-Battelle manages ORNL for the DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science -Liz McCrory