“Think big” has been the U.S. nuclear-energy industry’s motto for most of the 60-plus years since the Shippingport Atomic Power Station went online in 1957 in Beaver County, Pa. Now, though, with electricity sources shifting to lower-cost natural gas and renewables, thinking small—or at least, smaller—is beginning to take hold. A new generation of nuclear power plants is on the drawing boards—many with much lower power outputs—that offer flexibility for future growth, along with potentially safer operation and less waste. Proponents say these plants are the industry’s best bet for capitalizing on the technology’s carbon-free advantages in our changing energy marketplace. One such design recently received final approval from the U.S. Nuclear Regulatory Commission (NRC), allowing it to proceed with development plans.

The ability to generate large amounts of energy on a 24/7 basis from a central plant was nuclear energy’s biggest selling point for decades. The nation’s largest facility, the three-unit Palo Verde Generating Station near Tonopah, Ariz., has a capacity of nearly 4 gigawatts (GW). Grand Gulf Nuclear Station in Port Gibson, Miss., is the nation’s largest single-unit station, with an output of 1.4 GW.

Even with a number of plants shutting down between 2013–2018 and only one new plant coming online, the nation’s nuclear fleet set a production record in 2018, generating more than 80.7 gigawatt-hours (GWh). In total, nuclear power meets 20% of U.S. electricity demand.

More important, as many states aim for ambitious greenhouse gas reductions, today’s nuclear plants also represent 55% of U.S. carbon-free generation. This fact is raising concern, as many of these facilities are more than 40 years old. Only one new plant, Watts Bar Unit 2, located in Spring City, Tenn. and operated by the Tennessee Valley Authority since 2016, has come into service since 1996. Two other plants, Georgia Power’s Plant Vogtle units 3 and 4 in Waynesboro, Ga., are under construction. Those stations were supposed to be in commercial operation in 2016 and 2017, respectively. However, planners now anticipate startups in 2021 and 2022, and the billions of dollars in cost overruns will result in rate increases for the utility’s customers.

Thinking small

Problems like these have led some to theorize the future of nuclear power lies in dreaming smaller.

“The current nuclear industry is facing a perfect storm of challenges,” said Alex Gilbert, a project manager with the Nuclear Innovation Alliance, a nonprofit think tank focused on furthering nuclear power as a carbon-free energy source. “We have exceedingly low load growth in the United States. So, over time, you don’t need to build new power plants. The overall pie is not growing, and you have natural gas and renewables” taking larger slices of the pie.

However, the low growth in U.S. demand for electricity is not expected to continue indefinitely. As renewably sourced electricity grows, many states and municipalities are boosting efforts to adopt electric heat pumps for heating and cooling and to increase the number of electric vehicles on the roads. These moves to curb fossil fuel use could contribute to substantial load growth over the next several decades.

The U.S. Department of Energy predicts such efforts could raise demand by as much as 38% by 2050. While carbon-free nuclear energy could play a significant role in meeting this need, it likely won’t be through new gigawatt-scale plants like those built in decades past.

“The challenges are that we don’t have a cost-effective option because our supply chain has atrophied,” Gilbert said.

The lack of a market for nuclear engineering talent and manufacturing expertise means the United States would be starting from scratch in replacing existing large generating stations. For example, a recent report commissioned by Georgia’s state utility regulators on the Plant Vogtle construction project found an 80% failure rate for new components installed at the plant. Such experiences create a lack of trust among regulators and utility customers that cost estimates will accurately reflect actual construction expenses.

“The No. 1 barrier is construction cost overruns,” Gilbert said, noting the competition nuclear faces from other generating technologies that are both more predictable and less expensive on a first-cost basis. “If you can’t guarantee what your plant is going to cost, you’re going to lose to renewables and natural gas every time.”

These challenges open a niche, Gilbert added, for the new plant designs that several startups have been developing for the last decade or so. These new designs are called advanced nuclear reactors (ANRs), with their primary “advance” being that most have moved away from the light-water design adopted by Plant Vogtle developers and China’s national utility. According to Gilbert, ANRs feature passive cooling systems for significantly increased safety and more efficient operations, so they are able to squeeze more electrons out of each unit of fuel.

Nuclear building blocks

The leading ANR candidate is called a small modular reactor (SMR), which, in late August, became the first to complete the NRC’s Phase 6 review process. This approval gives developer NuScale Power of Portland, Ore., the green light to develop a proposed installation on the grounds of the Idaho National Laboratory in Idaho Falls, with output being sold to Utah Associated Municipal Power Systems, Salt Lake City.

NuScale Power’s approach can essentially be boiled down to a nuclear plant in a box. The base unit is called a NuScale Power Module, each with an output of 60 MW. Modules include a reactor vessel, steam generators, pressurizer and containment in a factory-built unit that can be delivered to the customer site by truck. Up to 12 of the modules can be networked together for a total output of up to 720 MW.

NuScale’s technology complements intermittent generating periods of renewables.

“This makes it possible for regions with smaller electrical grids and limited infrastructure to add new electrical capacity in appropriate increments and consider siting plants at a broader range of distributed locations.” said Diane Hughes, the company’s marketing and communications vice president.

NuScale, backed primarily by the multinational engineering and construction leader Fluor Corp., Irving, Texas, has also explored cogeneration opportunities in oil refineries, hydrogen production and water desalination.

A larger option

Microsoft founder Bill Gates is the primary backer of TerraPower, Bellevue, Wash., which is pursuing two new ANR approaches. The larger of these, called a traveling wave reactor (TWR), is a baseload design, meaning it’s meant to match the output of traditional nuclear plants, at approximately 600 MW in a prototype and 1.1 GW in an eventual commercial plant.

The leading advantage of the TWR design is its use of fuel made from depleted uranium, which is a waste byproduct of the uranium enrichment process used to create fuel for traditional nuclear plants. Traditional enriched uranium is used to initiate the fission reaction, after which the process switches over to the depleted material to maintain operations. All U.S. uranium enrichment facilities undergo a rigorous licensing and inspection process with the NRC.

While enriched uranium rods in today’s nuclear plants need to be replaced every 18 to 24 months, the depleted uranium could maintain generation for decades. This could provide opportunities for recycling material now considered nuclear waste. The company said its proposed TWR plant would also be safer than that of traditional plants because it would operate at lower pressures.

The second technology TerraPower is developing is a molten chloride reactor, which could create both heat and power simultaneously. This is a smaller-style plant scaled to a 345 MW output. Also being pursued by the company Terrestrial Energy, Greenwich, Conn., the design adopts liquid salt as a coolant instead of water. This salt can absorb much more heat, which could allow the reactor to operate at higher temperatures. The absorbed heat could be used for industrial processes or stored to power, say, an adjacent turbine generator, which could enable total plant output to ramp up and down to follow electricity demand.

Bringing good things to life

As mentioned, NuScale Power’s SMR is the closest of any of these technologies to coming to market. The first module in its installation for Utah Associated Municipal Power Systems should be operational by mid-2029, with an additional 11 modules installed and running by 2030. TerraPower signed an agreement several years ago with the Chinese government to co-develop a TWR plant in that country, although that effort was shelved with a current moratorium on exporting nuclear technology to China. Just this August, the company formed a partnership with GE Hitachi Nuclear Energy, a cooperative venture between General Electric and Hitachi based in Wilmington, N.C., to commercialize its molten chloride technology under the brand name of Natrium. No specific installations have yet been announced.

Gilbert sees the next decade as especially important for the development of new ANR approaches, which he describes as “competitive collaborators.” Each faces funding and other hurdles by breaking into a utility marketplace with a known risk-aversion.

“The next 10 years are going to be critical, just in terms of what happens when you have an emerging industry,” Gilbert said. “There is going to be competition between these developers. Finding the utility customers is going to be a challenge.”

The DOE has recognized the uphill battle involved in bringing new nuclear technologies to market and has provided financial support of research and regulatory approval efforts companies pursuing ANRs. Such backing is vital, Gilbert said, to maintaining U.S. leadership in this emerging field.

“What happens in the U.S. in the advanced nuclear sector has global implications,” he said. “This is something the U.S. should see as a strategic interest, both domestically and for our foreign policy.”