(republished from U. Wisconsin-Madison College of Engineering)
Several U.S. companies are developing microreactors that will be dramatically smaller than the large, centralized nuclear reactors operating today. Small enough to transport by truck, these compact reactors will generate power in the range of 1-10 megawatts—or, enough to power 1,000-10,000 homes for a year.
Because of their smaller size and technical features, microreactors could take on unique roles in future energy systems.
In the new study conducted by the Institute for Nuclear Energy Systems for the U.S. Department of Energy, the UW-Madison team set out to determine the potential role of microreactors in enhancing the energy resilience of federal government facilities. Resilience refers to the ability of a facility to continue operating when the external source of utility power becomes unavailable.
“The main finding of our study is that if microreactor vendors can reach their goals for total costs, and if they rely on low-interest government financing rather than private financing, then microreactors could be economically competitive against natural gas and increase the energy resilience of certain government facilities,” says Paul Wilson, the Grainger Professor of Nuclear Engineering at UW-Madison who led the study.
For the study, the researchers started with a list of approximately 1,800 U.S. government-owned facilities—which include hospitals, data centers, rocket launch facilities, biology laboratories and nuclear accelerators—around the country and narrowed it down to 211 facilities that consume an amount of energy large enough to make them good candidates for microreactors.
Currently, the utility power grid provides most of the electricity for those 211 facilities.
“Given the number of severe power outages that have occurred around the country over the past few years, from outages caused by wildfires in California to the winter storm in February 2021 that crippled the power grid in Texas and left millions without electricity, it’s important for these facilities to have robust on-site generators for backup in the event of a power grid failure,” Wilson says.
Currently, government facilities have on-site diesel or natural gas generators that are typically held in standby and used only for emergencies. In their analysis, the researchers examined whether a microreactor could effectively take over the role of these backup generators.
However, because even the much smaller microreactors are very expensive to build, using one merely as a backup generator wouldn’t be economically viable, Wilson says. So, the UW-Madison researchers developed an innovative dual-source configuration that leverages the strengths of microreactors—and, importantly, shifts the paradigm for backup power generation.
The approach involves placing microreactors at each of the government facilities, where they would run continuously and provide enough power to meet the facility’s critical power demand. In addition, each facility would buy electricity from the utility to meet its remaining power demand for non-critical uses. If the utility has an outage, the facility would only lose power for nonessential uses. Meanwhile, the microreactors would continue running uninterrupted, providing on-site “backup” power for critical needs.
Conversely, if the microreactor needs to refuel or if it shuts down, then power from the utility can serve as the backup. Wilson says a key assumption of the study is that facilities would implement this configuration, enabled by a microgrid to distribute this power around the facility.
Another benefit of microreactors is that they could run for months or even years before needing to refuel—which would provide the resilience required for operating during long-term power outages. On the other hand, relying on diesel or natural gas generators as backup could affect a facility’s resilience during major outages since the generators rely on a finite supply of readily available diesel or on a continuous supply of natural gas.
For comparison in their study, the researchers also modeled building a “green scenario,” a resilient, carbon-free energy system that excludes fossil fuels, including natural gas.
However, they found that relying entirely on renewable energy sources like wind and solar, coupled with battery storage, would require overbuilding the components of the renewable energy system to ensure adequate resilience—ultimately resulting in a more expensive system.
“To build a carbon-free energy system, our analysis shows that you’ll likely need something other than just wind, solar and batteries to make it cost effective. You need to include a source of clean energy that’s reliable and dispatchable—and we focused on microreactors as a solution,” Wilson says. “In our study, we showed that even using expensive microreactors is actually cheaper overall than a system that consisted of only solar and batteries—by about a factor of two, for the particular set of circumstances in our model. These results are similar to findings by other researchers.”
Because microreactors don’t emit greenhouse gases, they could also make a broader environmental contribution. “While an analysis of the potential climate impact of adopting microreactors was outside the scope of this study, it’s important to consider carbon emissions when making decisions about future energy systems,” Wilson says. “The Biden administration has recently announced plans to sharply reduce emissions, and this commitment could further tip the balance toward nuclear energy over natural gas.”
The study details opportunities for the federal government to be an early consumer for microreactors and offers several policy recommendations should the government decide to pursue a program to encourage the use of this emerging energy technology.
One of those policy ideas involves creating a program for the government to engage with industry vendors on microreactor research and development that’s modeled after the NASA Commercial Orbital Transfer System (COTS) program. That program, which financially rewards private industry for meeting key technology-development milestones, has played a major role in SpaceX’s successful development of spacecraft for transporting astronauts to the International Space Station.
Wilson hopes a similar program for microreactors could help kick-start the market. For example, the government could guarantee that it will purchase a set amount of microreactors if a vendor can demonstrate it can meet specific performance criteria.
As companies continue to develop their microreactor designs, they also will need to demonstrate that their reactors will operate safely, says Wilson.
“In order to unleash the full promise of microreactors, they will have to be designed to be safe enough to be located near population centers,” he says. “Their smaller size helps because there will simply be less radioactive material in the core at any time. This so-called ‘source term’ is a factor in siting reactors.”
Co-authors on the study include Wisconsin Distinguished Professor Emeritus of Engineering Physics Michael Corradini and Thomas M. Palmieri, a former U.S. Department of Energy official.
This work was supported by grants from the Department of Energy’s Office of Nuclear Energy via Idaho National Laboratory.
Author: Adam Malecek