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Benefits of Small Modular Reactors Underscored by Rising Reliability Threats


As the threats to the resilience and reliability of the electric power grid caused by extreme weather events rise, the advantages of small modular reactors are becoming more apparent.

Those threats were underscored recently when a prolonged heat wave and deadly storms knocked out power for hundreds of millions of people in an area of the South stretching from Texas to Mississippi.

Those outages, unfortunately, are part of a wider trend. The average annual number of weather-related power outages increased by roughly 78 percent during 2011-2021, compared with 2000-2010, according to a 2022 report from Climate Central. Between 2000 and 2021, the report found, about 83 percent of reported major outages in the United States were attributed to weather-related events.

Power outages are not just an inconvenience, they are also costly, particularly for commercial and industrial customers. In a 2017 report, Lawrence Berkeley National Laboratory estimated that power interruptions cost $59 billion per year, an increase of more than 68 percent since its initial 2004 study. The study also showed that 13 percent of customers in the commercial and industrial classes accounted for more than 97 percent of the costs incurred by the outages.

Recognizing the need to protect critical federal facilities from even momentary interruptions of electric power, the Department of Energy in 2018 recommended federal facilities explore the development of small modular reactors.

“NuScale Power’s VOYGR™ small modular reactor power plant features a wide variety of attributes well suited to provide reliable, carbon-free energy, even during extreme weather events,” John Hopkins, NuScale’s president and CEO, said via email.

Those attributes include fuel security, flexibility, operational security, and independent operation. Small modular reactors, for example, can store up to two years’ worth of fuel on-site, allowing them to generate power when extreme events disrupt supplies of gas or coal to thermal generators. And, unlike large, traditional nuclear plants that must run at nearly full capacity around the clock, some small modular reactors, such as NuScale Power’s, have the flexibility to vary their output over days, hours and even minutes, allowing them to respond quickly to grid conditions.

In addition, at a time when regulators and grid operators are looking for ways to bolster resiliency, NuScale’s SMR design offers several advantages for reliable grid operation. NuScale’s SMR design has black start capability, meaning it can generate power from a cold start without an external grid connection.

NuScale’s VOYGR SMR plant design includes two backup generators that have the ability to start one SMR. Once a single module is running, it can supply the electrical power to start up the rest of the plant.

NuScale’s SMR design is unique in that it is the only design certified by the U.S. Nuclear Regulatory Commission (NRC) that does not require class 1E power, a safety standard for electrical equipment and systems that are essential to emergency reactor shutdown, containment isolation, reactor core cooling, and containment and reactor heat removal.

NuScale’s design also includes a unique passive safety system that does not require operator or computer actions to implement safety procedures in the event there is a total loss of power to the plant.

A VOYGR plant may include up to 12 power modules. Each incorporates a reactor pressure vessel, which includes the nuclear core, steam generator, and pressurizer, and a containment vessel that surrounds the reactor vessel.

During normal operation, each containment vessel is fully immersed in a water-filled, underground stainless steel-lined concrete pool. The pool is housed in a Seismic Category I building, a Nuclear Regulatory Commission standard for structures that can withstand maximum potential earthquake stresses, making it capable of withstanding a Fukushima type earthquake, as well as hurricanes and tornados.

The pool is large enough to provide 30 days of core and containment cooling without adding water. After 30 days, the core decay heat generation is so small that the natural convection heat transfer to air at the outside surface of the containment, coupled with thermal radiation heat transfer, is sufficient to remove the core decay heat for an unlimited period.

Even in the face of more malicious threats, a VOYGR plant is armed with safety features that could make it a key asset in a time of emergency. A NuScale nuclear plant is also resistant to an electromagnetic pulse event that could cripple more conventional generation assets on the electrical grid.

With its passive shut-down capability, ability to operate in steam bypass mode, its electrical isolation of safety equipment, and its multi-layered shielding and redundant fiber optic cabling, NuScale’s VOYGR SMR power plant design is still able to perform and even shut down safely even when the electric grid is crippled.

The combination of those attributes also gives a NuScale Power Module™, the company’s trademark SMR design, the ability to operate in island mode during an outage or an emergency, that is, a single SMR could supply all the electricity needs of the plant while continuing to provide power to a mission critical facility without external grid connection via a micro-grid connection.

“NuScale SMR design can support microgrid or remote installations for customers anywhere grid stability is less than desirable or nonexistent,” Hopkins said.

The ability to operate in isolation from the grid, also gives NuScale’s VOYGR™ power plants first responder status. When the transmission system goes down and a conventional nuclear plant loses its external power, it is designed to automatically shut down. A VOYGR plant, however, would remain online, ready to provide electricity to the grid when the transmission system comes back online.

In a scenario in which a catastrophe resulted in the loss of the electric grid and of transportation infrastructure, NuScale said its 12-module plant design would be able to provide 154 megawatts of electricity for 12 years to a microgrid of a mission-critical facility without the need for new fuel.

And even when refueling becomes necessary, NuScale’s scalable plant design permits staggered refueling of a single module while the other 11 modules continue providing 92 percent of the facility’s electrical output.

“In short, NuScale’s SMR design has fewer and simpler systems, resulting in enhancements to safety and resilience compared to traditional large nuclear plants,” Hopkins said.

 “As energy demands rise, it makes sense that utilities, regulators and policymakers are looking closely at the unique features NuScale SMRs can provide to increase and safeguard the reliability of the electric grid,” Hopkins said.

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