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Micronuclear reactors offer a viable, clean energy alternative

June 13, 2023
Small-scale nuclear generators present big opportunities for affordable, carbon-free, and resilient energy production in a variety of building applications.

Technology has gotten progressively smaller, lighter, and more powerful over time. Supercomputers the size of several refrigerators that sent man to the moon can now fit in the palm of a hand.

The same downsizing trend is happening in nuclear technology today—and it’s opening significant possibilities for clean energy in the commercial buildings industry. The U.S. Department of Energy (DOE) is developing small-scale nuclear generators as an affordable, carbon-free, and resilient component of microgrids that could be ready within the next decade. These compact reactors would 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, according to the DOE.

Micronuclear reactors 101

As their name implies, micronuclear reactors are “small nuclear reactors producing a few megawatts of heat and electricity, thus much lower than traditional grid-scale reactors producing thousands of megawatts of power,” explains Jacopo Buongiorno, professor of nuclear science and engineering and director of the Center for Advanced Nuclear Energy Systems at the Massachusetts Institute of Technology (MIT).

Like conventional reactors, micronuclear reactors leverage the nuclear fission chain reaction to create energy, albeit on a much smaller scale, says Kathryn Huff, assistant secretary at DOE’s Office of Nuclear Energy (ONE): “Some of them are intended to be on a sufficiently small scale that they can be transported … [or be built] in a single location, but they would replace the kind of infrastructure that would usually rely on backup diesel generators or dedicated, small fossil fuel generators.”

According to ONE, microreactors are not defined by their fuel form or coolant, but by three main characteristics. First, they are factory fabricated. All components of a microreactor would be fully assembled in a factory and shipped to their destination. This eliminates difficulties associated with large-scale construction, reduces capital costs, and will help get the reactors online and operational quickly.

Second, they are portable, due to their smaller unit design. Vendors can easily ship the entire reactor by truck, shipping vessel, airplane, or rail car.

Third, they are self-regulating. Simple and responsive design concepts will allow microreactors to self-adjust. They do not require many specialized operators, and they utilize passive safety systems that limit the potential for overheating or reactor meltdown.

The compact powerhouses can produce up to 20 MW of energy within the size of standard ISO shipping containers towed by an 18-wheeler truck. Though microreactors are not commercially available yet, Huff says the DOE has built more than 50 small, experimental reactors in Idaho.

Critical applications abound

Primary use cases of micronuclear reactors span a range of building applications that require reliable clean energy. These include remote communities, transportation charging plazas, commercial and industrial facilities, space stations, and critical infrastructures such as defense installations and emergency-response facilities, such as hospitals and medical campuses.

“The whole HVAC system for buildings could be powered by such microreactors,” Buongiorno says. “Depending on the demand, multiple microreactors may be needed for large building complexes, or multiple users could share a single microreactor in small building clusters.”

Last year, Purdue University began a partnership with Duke Energy to explore the possibilities of using smaller, advanced nuclear energy to meet the long-term needs of its Indiana campus.

“Microreactors could support things like critical infrastructure, data centers—the kinds of things that we can’t allow to shut down in the event of grid disruption,” Huff says. The Department of Defense could deploy microreactors to displace traditional diesel generators that supply power on the front lines of conflict, ultimately saving lives, she adds. “Some of those conflict zones have resulted in the diesel transport lines being a source of real casualties for Americans.”

Microreactors hurdles and hazards

The topic of nuclear energy can be controversial, though information and education can mitigate public concerns. Buongiorno says the challenges with microreactors are “mostly around regulations/licensing and security, since microreactors would be co-located with the energy users”—for example, within factories or neighborhoods.

Huff is quick to point out that micronuclear reactor technology is safe and secure. “It will fit within the security and safety framework that the Nuclear Regulatory Commission already applies to existing nuclear reactors.”

Perhaps a bigger obstacle to the technology’s widespread commercial adoption is cost. “We don’t expect [microreactors] to compete with the costs of renewables, which are quite cheap,” Huff observes. However, for applications that require resilient, reliable power on demand with long duration energy storage, she says, “nuclear microreactors can present an excellent alternative at a cost that would be competitive.”

Unlike natural gas and diesel generators, microreactors can operate for five to 30 years without needing to be refueled—a huge upside for remote applications. Along with generating electricity, they also output energy in the form of heat, which could be used in applications such as district heating or industrial processes, Buongiorno says. The heat also could be used to produce hydrogen, thus boosting the economics of microreactors, according to the Idaho National Laboratory report Small Reactors in Microgrids.

Clean, complementary technology

Many scientific studies have found that the best path to rapid decarbonizing multiple sectors of the economy includes both renewables and nuclear. Buongiorno, for one, doesn’t see microreactors and renewables as competitors, but rather as “complementary technologies.”

“Nuclear and renewables are low-carbon energy sources, so replacing current systems which use natural gas, coal, or oil with nuclear and renewables will result in a decrease of emissions,” he explains. “The advantage of nuclear over renewables is its extreme compactness—100 times less land than renewables per unit energy generated; reliability—nuclear can be always on regardless of weather; and versatility—[its ability to produce] heat plus electricity.”

The DOE is working to accelerate clean energy technologies from the lab to market to achieve net-zero emissions by 2050, Huff says. The agency has produced a series of Liftoff Reports to provide a common knowledge base and a tool for ongoing dialogue with the private sector on the pathways to deploying clean, reliable sources of energy like microreactors.

“Our prediction for net zero is that we’re going to need hundreds of gigawatts of clean power, of which we expect about 200 new gigawatts will need to be from nuclear [sources],” Huff says.

That massive amount of energy will require many more large-scale nuclear reactors, she notes. However, replacing fossil fuels in applications needing resilient, clean, on-demand power, such as data centers and district heating, will benefit from smaller-scale solutions. “They don’t need hundreds of megawatts of nuclear power,” she says. “They need a couple of megawatts, and for those applications, microreactors will be perfect.”

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About the Author

Robert Nieminen | Chief Content Director

Robert Nieminen is the Chief Content Director of Architectural Products, BUILDINGS and i+s, sister publications of Smart Buildings Technology. He is an award-winning writer with more than 20 years of experience reporting on the architecture and design industry.

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