Office of Nuclear Energy

What is a Nuclear Micro-reactor?

October 23, 2018

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A small reactor to bring power to remote locations

Nuclear is getting smaller… and it’s opening up some big opportunities for the industry.

A handful of micro-reactor designs are under development in the United States and they could be ready to roll out within the next decade.

These plug-and-play reactors will be small enough to transport by truck and could help solve energy challenges in a number of areas, ranging from remote commercial or residential locations to military bases.

Infographic that explains the features and benefits of micro-reactors.
Graphic by Sarah Harman | U.S. Department of Energy


Micro-reactors are not defined by their fuel form or coolant. Instead, they have three main features:

1.Factory fabricated: All components of a micro-reactor would be fully assembled in a factory and shipped out to location. This eliminates difficulties associated with large-scale construction, reduces capital costs and would help get the reactor up and running quickly.

2.Transportable: Smaller unit designs will make micro-reactors very transportable. This would make it easy for vendors to ship the entire reactor by truck, shipping vessel, airplane or railcar.

3.Self-regulating: Simple and responsive design concepts will allow micro-reactors to self-regulate. They won’t require a large number of specialized operators and would utilize passive safety systems that prevent any potential for overheating or reactor meltdown.

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Micro-reactor designs vary, but most would be able to produce 1-20 megawatts of thermal energy that could be used directly as heat or converted to electric power. They can be used to generate clean and reliable electricity for commercial use or for non-electric applications such as district heating, water desalination and hydrogen fuel production.

Other benefits include:

  • Seamless integration with renewables within microgrids
  • Can be used for emergency response to help restore power to areas hit by natural disasters
  • A longer core life, operating for up to 10 years without refueling
  • Can be quickly removed from sites and exchanged for new ones.

Most designs will require fuel with a higher concentration of uranium-235 that’s not currently used in today’s reactors, although some may benefit from use of high temperature moderating materials that would reduce fuel enrichment requirements while maintaining the small system size.

The U.S. Department of Energy supports a variety of advanced reactor designs, including gas, liquid metal, molten salt and heat pipe-cooled concepts. American micro-reactor developers are currently focused on gas and heat pipe-cooled designs that could debut as early as the mid-2020s.

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