The federal Department of Energy (DOE) is studying small nuclear generators as a carbon-free, resilient and potentially affordable component of microgrids, but some microgrid industry members say it’s unlikely their nonmilitary customers will soon embrace the technology because of safety concerns.
The DOE recently released a report that looked at a number of scenarios for siting a small nuclear reactor at a military facility in Southern California and found that under certain circumstances — especially if there is a carbon tax — the nuclear generator, along with distributed energy resources (DER) is more cost-effective and cleaner than natural gas.
Small nuclear generators are modular units sized 100 kW to 20 MW that can operate 24/7 and produce no carbon, said the report, Small Reactors in Microgrids: Technoeconomic Analysis. Unlike natural gas and diesel generators, the small reactors can operate for five to 30 years without needing to be refueled. Another benefit is their ability to produce heat along with electricity, which boosts their economics and could be used to produce hydrogen, according to the report authors.
The small reactors are expected to be safer than larger nuclear power plants because of simpler designs, passive coolant circulation, containment, shutdown systems and underwater and underground configurations, said the report.
According to Rick Bolton, CEO at Compass Energy Platform, which develops and finances energy infrastructure, “It does seem that we will need to include nuclear as a generating option to meet load demands, reduce carbon and achieve climate goals.” The military is likely the best industry to start siting the units to provide 100% on-site generation, rather than worrying about the insecurity of the gas transmission system, Bolton said.
“But it is most unlikely that we will see a proliferation of small nuclear reactors fueling microgrids. Safety will inevitably be an issue, as will security, particularly in the crowded urban areas where microgrids are useful,” he said.
No one has solved the problem of how to dispose of nuclear waste, he added.
Mike Byrnes, senior vice president of facilities and building services at Veolia North America, agreed that siting microgrids with nuclear reactors would be challenging.
“I don’t have any argument with the technology or the economics. I’m sure as a society we could get there if we wanted to,” Byrnes said. He added that by definition microgrids are located close to the load. “Who’s going to want a nuclear reactor where they live?”
Researchers addressing this topic understand that there will and should be hesitancy on the part of the public, said Tim McJunkin, distinguished researcher at Idaho National Laboratory, which published the report. There’s a need to prove that small “advanced” reactors are safe and secure. That’s why the DOE is investing in research and development, he said.
Who will test them?
The technoeconomic study focused on a military base on the premise that the military might be willing to test the technology. After all, naval bases and their communities accept nuclear powered ships close by.
Remote communities dependent on diesel fuel, especially those with military bases, might also be candidates for microgrids that include DERs and compact, modular nuclear reactors, according to McJunkin.
A separate report from Idaho National Laboratory pointed out that a number of factors need to be addressed when siting a nuclear power reactor. Cooling water must be available and environmental concerns must be addressed.
Designers should plan and design microgrids with small reactors with a goal of addressing sensitive safety issues and public concerns, said the report.
Idaho National Laboratory is building a 100-kW small nuclear reactor called “Marvel” at its Transient Reactor Test Facility. It’s expected to be operational in about three years.
Xendee models economics
As for the economics of small nuclear reactors, the technoeconomic analysis from Idaho National Laboratory modeled a number of scenarios using Xendee, a microgrid design platform.
The researchers used the Xendee platform to model the possible market penetration of small reactors and how they compete with or complement other DERs, said Michael Stadler, chief technology officer at Xendee.
Xendee modeled small reactors in combination with other DERs — photovoltaics (PV), storage and natural gas engines.
Under the first scenario, or base case, all energy was purchased from the utility. Other scenarios included PV, battery and natural gas engines, along with small reactors at different price assumptions.
“With carbon pricing the small reactors become attractive and save money against the base case,” said Stadler.
In the carbon pricing model, small reactors were attractive for base load operation, augmented by small gas generators for load following, batteries and some solar PV, he said.
Without carbon pricing, the Xendee model chose traditional DERs — PV, battery and gas engines. But these models didn’t assume economies of scale that are attained when the reactors are larger or when multiple reactors are included in a microgrid, said Stadler.
“When considering economies of scale, small reactors become attractive fast,” said Stadler.
The models did not include the long-term societal costs for storing burned fuel, he said.
Achieving economies of scale
Bikash Poudel, a postdoctoral research associate at Idaho National Laboratory, explained that the small reactors are cost competitive in larger microgrids that have a peak load of 14 MW or 15 MW.
That’s because of the economies of scale that can be realized by hosting larger reactors. Achieving economies of scale could include deploying a larger single-unit configuration because the manufacturing cost per MW lowers as the size of the reactor unit increases, Poudel said. The microgrid could also include multiple nuclear generators. Hosting multiple reactor units in the same plant setup reduces the total installation costs, Poudel said.
Coupling small nuclear generators and hydrogen
Poudel noted that small reactors produce heat that can be used for hydrogen production. While the lab’s studies have only looked at using small reactors to create electricity, Idaho National Laboratory also wants to investigate how producing the heat affects the economics of nuclear-driven microgrids.
Under the scenarios considered by the Idaho Lab researchers, reactors are sized between 0.1 MW and 20 MW and are manufactured in factory settings and transported to and assembled at the plant location, Poudel said.
With the US aiming to cut carbon emissions, now is the time to study the feasibility of using small reactors, said Idaho National Laboratory’s McJunkin. But, understanding that the public may object, the researchers plan to tread carefully.
“We look to be sober in our approach to reaching the climate, environmental and resilience needs of society without breaking the bank,” he said.
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