Molten salt reactors are nothing new.

They’ve been around since the 1960s and date back to the days of the Molten Salt Reactor Experiment at Oak Ridge National Laboratory.

Now, almost 60 years later, several companies are starting to develop them as energy systems of the future—including TerraPower, backed by Bill Gates.

Southern Company, a leading energy company in the United States, is partnering with TerraPower to develop a molten chloride fast reactor (MCFR) that uses liquid salts as both a coolant and fuel.

The U.S. Department of Energy already invested more than $28 million in cost-shared funds for the project to further identify and test materials used in the reactor.

How It Works

Crosssection of the molten chloride fast reactor by Southern and TerraPower.

The MCFR will be optimized to operate as a commercial reactor that can produce up to 1,200 megawatts of electricity, with a test reactor demonstrating smaller-scale potential.

The design uses liquid chloride salts as a coolant and fuel that flow through the reactor core—allowing the fission to directly heat the salts. The mixture is then circulated through a heat exchanger in a second loop that can be used for process heat, thermal storage or electricity generation.

Because the reactor operates at a high temperature, the process is more efficient at producing electricity than light water reactors. The reactor would also produce less waste and allow the MCFR to even consume waste from other reactors.

MCFR Benefits

MCFRs can enable the transition to a flexible, robust and low-carbon energy infrastructure.

It is a major departure in terms of simplicity, fuel cycle and proliferation characteristics relative to other more-complex nuclear reactor concepts and offers significant safety, performance and economic benefits.

The MCFR has what the industry calls a “walk-away-safe” design that would shut down the reactor without any need for electric pumps to prevent fuel damage. If there is a loss of coolant flow, the fuel salt would expand through the reactor core to passively halt the process and naturally circulate to remove decay heat.

Other benefits include:

  • No fuel assemblies to fabricate, replace or store
  • Online refueling for continuous operation to increase profit margins and reliability
  • Ability to use multiple fuels for operation including depleted and natural uranium, or even spent fuel
  • Enrichment only needed at startup
  • Ability to load follow and support other energy sources on the grid.

What’s Next?

Artist rendition of the Integrated Effects Tests (IET) facility.
Artist rendition of the Integrated Effects Tests (IET) facility
Southern Company
Southern Company and TerraPower are in the final stages of the design phase for an integrated effects test in support of a MCFR program. They are working with Oak Ridge National Laboratory, Idaho National Laboratory, Vanderbilt University and the Electric Power Research Institute to accelerate the development and deployment of a commercial MCFR.
They expect to begin testing in a $20 million test facility starting in 2021. The team has successfully scaled up their salt manufacturing process to enable this testing. Data generated from the test facility will be used to validate thermal hydraulics and safety analysis codes for licensing of the reactor.
In parallel with testing at this facility, Southern Company and TerraPower plan to begin the design and licensing of a test reactor targeted for operation in the late 2020s.

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