TerraPower and SCS install test facility to advance molten chloride fast reactor

Article by Kerry Hebden

A schematic of TerraPower's molten chloride fast reactor (MCFR) technology

NUCLEAR reactor developer TerraPower, and US utility Southern Company have completed the installation of the Integrated Effects Test (IET), a system to learn how TerraPower’s molten chloride fast reactor (MCFR) technology will scale and behave at commercial size. 

Backed by a US$76m investment with a 60%-40% public-private cost share, TerraPower has been working on its IET concept for around five years.  

Now installed at the firm’s laboratory in Everett, Washington, the IET is essentially a large molten salt machine designed to test thermal hydraulics, such as the system’s temperature and flow.  

The IET is non-nuclear meaning it is not an actual reactor as it doesn’t use uranium, but it will give its designers an idea of how the real MCFR – a liquid salt-fuelled, salt-cooled fast reactor that operates with higher-energy neutrons – will respond when it is operational, as data from this real-world test will help validate scientific computational models needed for the MCFR. 

“The IET is really all about learning as much as we can, as quickly as we can, and as early in the development process as we can,” said Lauren Lathem, Principal Research Engineer at Southern Company.  

Although a demonstration of the reactor is not planned until the early 2030s, data from the test will also support the development and operation of the so-called Molten Chloride Reactor Experiment (MCRE) at Idaho National Laboratory, another TerraPower and Southern Company joint venture.  

According to Terrapower, which was founded by Bill Gates in 2006, the MCRE is “the world’s first fast-spectrum, salt-fuelled nuclear fission reactor to go critical”, meaning that it is operating on a self-sustaining nuclear chain reaction. 

The MCRE project will not generate electricity, say the firm, but it will operate at a power of up to 500 KW and demonstrate key physics performance important to the broader MCFR programme. 

Molten salt reactors were initially developed in the 1950s, and as they designed to operate at low pressures and high temperatures, they have a number of benefits over traditional nuclear reactors such as higher efficiencies, lower waste generation and smaller containment. They can also use a number of fuel sources, including depleted and natural uranium or even spent fuel from existing reactors, making them an attractive alternative to conventional fission reactors. 

However, they also have their disadvantages such as material degradation due to the corrosive nature of the salts present in the fluid, and the production of radioactive tritium if lithium is used as a carrier salt. Furthermore, as tritium is so small it is capable of escaping into the environment.  

But despite these drawbacks, molten salt reactors are now witnessing a revival due to their potential as pivotal players in decarbonising heavy industries, and the IET facility is seen as a huge step forward for the US in commercialising the technology. 

“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 Mark Berry, Southern Company Services Senior Vice President of R&D.  


Article by Kerry Hebden

Staff reporter, The Chemical Engineer

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