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Southern Company subsidiary and TerraPower complete installation of Integrated Effects Test, a key milestone in development of Molten Chloride Fast Reactor

Project continues pathway of U.S. Department of Energy Advanced Reactor Concepts (ARC-15) program to promote design, construction and operation of Generation-IV nuclear reactors

Southern Company, through its subsidiary Southern Company Services, and TerraPower have completed installation of the Integrated Effects Test, marking a crucial milestone in the development of TerraPower’s first-of-a-kind Molten Chloride Fast Reactor (MCFR). The test is the world’s largest chloride salt system developed by the nuclear sector. The project culminates years of separate effects testing and is expected to demonstrate how the MCFR technology will perform in delivering a commercial-scale, cost-effective, carbon-free molten salt reactor energy source by 2035.

“Southern Company’s research and development program is committed to advancing next-generation nuclear as part of a diverse technology portfolio supporting our goal of a net-zero future for customers,” said Dr. Mark S. Berry, Southern Company Services senior vice president of R&D. “We are honored to engage with TerraPower, the Department of Energy and the other team members to further this goal through the Integrated Effects Test. Collaborations of this kind are critical to making transformational change in our energy system a reality.”

TerraPower Integrated Effects Test

Located at TerraPower’s laboratory in Everett, Washington, the Integrated Effects Test is a nonnuclear, externally heated, up to 1-megawatt multiloop system to support future deployment of a fast-spectrum salt test reactor. The project continues work initiated in 2015 by Southern Company Services and TerraPower under the U.S. Department of Energy (DOE) Advanced Reactor Concepts (ARC-15) award, a multiyear effort to promote the design, construction and operation of Generation-IV nuclear reactors. The project team also includes CORE POWER, EPRI, Idaho National Laboratory, Oak Ridge National Laboratory and Vanderbilt University. The program represents a $76 million total project investment with a 60%-40% public-private cost share.

“The completion and installation of the Integrated Effects Test is an important step to advancing TerraPower’s Molten Chloride Fast Reactor technology,” said Jeff Latkowski, TerraPower’s senior vice president of innovation programs. “The MCFR will play a pivotal role in decarbonizing heavy industries, and we are proud to work with Southern Company, CORE POWER and other partners to develop the systems necessary to bring new reactors to market.”

The next-generation of nuclear reactors promise the same stable value to customers that is derived from the current operating nuclear fleet, can complement intermittent renewable resources on the grid, and hold the potential to provide zero-carbon, high-grade process heat and thermal storage for energy-intensive industrial markets and ocean transportation sectors that currently rely on fossil fuels. Nuclear energy will be central to a sustainable, clean-energy future – providing affordable, reliable, resilient and dispatchable carbon-free power that is available 24 hours a day, making the success of this project integral to achieving a net-zero economy by 2050.

The Integrated Effects Test signals important progress in the technology demonstration road map for TerraPower’s MCFR. Data from operation of the test will help validate thermal hydraulic and safety analyses needed for the MCFR. The system will also support development and operation of the Molten Chloride Reactor Experiment at Idaho National Laboratory, a less than 200-kilowatt reactor meant to provide experimental and operational data. Both the Integrated Effects Test and the Molten Chloride Reactor Experiment will inform the design, licensing and operation of an approximately 180-megawatt MCFR demonstration planned for the early 2030s time frame.

A Sept. 9 ribbon-cutting ceremony was attended by representatives from Southern Company, TerraPower, Idaho National Laboratory, the project and construction team, and technology partners. Construction of the Integrated Effects Test was completed by McAbee Construction Inc., and all electrical support was provided by Gulf Electric Company.

In a recorded message during the event, Dr. Kathryn Huff, assistant secretary for the U.S. Department of Energy’s Office of Nuclear Energy said, “The IET facility is a huge step forward in commercializing molten salt reactor technology that will help the U.S. transition to a new, clean-energy economy and help position the U.S. as a leader in the development of advanced reactor technologies.”

TerraPower’s MCFR is one of the most advanced Generation-IV nuclear technologies under development and is separate from TerraPower’s NatriumTM reactor and integrated energy storage technology. The MCFR is a liquid salt-fueled, salt-cooled fast reactor that will enable operation at low pressures and high temperatures. It offers superior performance, inherent benefits in safety and life-cycle sustainability, reduced capital investment and O&M costs, and has the ability to operate using a number of fuel sources – including depleted and natural uranium or even spent fuel from existing reactors.


About TerraPower
TerraPower is a leading nuclear innovation company that strives to improve the world through nuclear energy and science. Since it was founded by Bill Gates and a group of like-minded visionaries, TerraPower has emerged as an incubator and developer of ideas and technologies that offer energy independence, environmental sustainability, medical advancement and other cutting-edge opportunities. It accepts and tackles some of the world’s most difficult challenges. Behind each of its innovations and programs, TerraPower actively works to bring together the strengths and experiences of the world’s public and private sectors to answer pressing global needs. Learn more at