Pending legislation would allow small modular nuclear reactors in Illinois. What are they?

Legislation awaiting the governor's signature would lift Illinois' nuclear ban beginning in 2026 - but only for reactors that have an output of 300 megawatts or less.

That's compared to the large-scale, 1,000-megawatt reactors we're used to.

With not a single such small reactor in operation or production anywhere in the country, the technology is still in its early stages, but legislators say the state needs to prepare now to stay ahead of the game.

Though it will be years before a small reactor is seen in Illinois, experts say gears are in motion to change that, and the new generation of nuclear power, many argue, could cut costs, produce less waste and provide more flexibility when it comes to siting and cooling.

Reactors that produce between 100 and 300 megawatts of electricity are called small modular reactors, or SMRs. The modularity aspect of their design means they can be assembled in a factory and transported to operating locations via truck or rail. It also means additional reactor units could be added to a location as demand increases.

"Sometimes, one large reactor is cheaper than multiple small-sized reactors. That's why in the '70s, '80s and 1990s, people were focused on the larger size," said Taek Kim, the manager of nuclear systems analysis at Argonne National Laboratory. "But now people are saying if you build the large size, then your initial investment is huge. That's the big problem."

Despite its ability to provide instantaneous, carbon-free energy, construction of nuclear plants has been weighed down by time and money. For instance, Georgia's Vogtle plant's two new units - the first to be built in the U.S. in three decades - are coming online years behind schedule and billions over budget.

Small modular reactors could answer some of those concerns, potentially with a new business model in which the government has a smaller part.

"In the past in the U.S., reactors were generally very heavily subsidized by the government or in general the government had to play a big role," said Lorenzo Vergari, a nuclear engineering professor at the University of Illinois Urbana-Champaign. "Now, we're trying to go toward a more private business structure where smaller startups are working on their own to develop small prototypes, and then sell them to get a very economical price of electricity."

With new fuel and cooling technologies on the rise - such as reactors cooled by gas or molten salt instead of water - experts say small-scale nuclear power also has the potential to create more electricity with less waste. And in some cases, the waste could be easier to store.

At the same time, we know large-scale nuclear reactors best, and they're able to meet the high demand for electricity that the U.S. presents, Kim added.

"There are more than 400 reactors throughout the whole world in operation. That's a huge amount of experience," he said. "Some countries, for instance the United States, need a huge amount of electricity. In those cases, the large size is better in terms of economics, in terms of number of locations, in terms of number of reactors. There is a big benefit."

Though each reactor size has its pros and cons, the siting flexibility, factory model and promise of smaller initial investments have put a lot of momentum in place for small-scale nuclear to become a major energy player as the state and the country seek to decarbonize.

"Who will invest first and who will provide the first (small) reactor? That's the big question," Kim said.

As of 2022, there were three operational SMRs in the world, located in Russia, China and India.

The first SMR design to be certified by the U.S. Nuclear Regulatory Commission jumped that hurdle in January, but it was announced this month the company planning to build that operation in Utah - NuScale Power - terminated the project due to rising costs.

Now, eyes are on other companies that are well into the commission's review process like X-energy, Kairos Power and TerraPower, a startup co-founded by Bill Gates.

"Right now, the landscape is telling us that we have a few reactor companies that are ahead of others and are trying to get their reactors licensed," Vergari said. "The regulatory route in nuclear is always very, very long. When any reactor needs to be approved, it goes under review by the Nuclear Regulatory Commission, and these reviews take multiple years."

Vergari said Kairos Power, which went into review in 2021, is currently the closest to market. The company plans to construct a low-power demonstration reactor in the East Tennessee Technology Park in Oak Ridge, Tennessee, with an estimated operation date of 2026.

Meanwhile, Bill Gates' TerraPower is looking to build its first demonstration reactor in frontier-era coal town Kemmerer, Wyoming, by 2028.

"My expectation is that in the next five to seven years, we'll get some of these (demonstration) reactors built, and this will tell us which ones are the most economical to build," Vergari said. "In my opinion, at some point, one of these designs will become prevalent over the other ones, and that will be very convenient for states to actually try to secure one of these prototypes."

• Jenny Whidden,, is a climate change and environment writer working with the Daily Herald through a partnership with Report For America supported by The Nature Conservancy. To help support her work with a tax-deductible donation, see

Manufacturing company Westinghouse is aiming to have its new small modular reactor, called the AP300, available in 2027. The AP300 will generate about a third of the power of the company's flagship AP1000 reactor, two of which are being added to the Vogtle power plant in Georgia. Associated Press Photo
The AP300™ SMR features an ultracompact footprint. Experts say shrinking the size of the safety-related footprint can result in cost savings and reduced construction time. Business Wire Photo
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