Small modular reactors aim to shrink a nuclear plant to warehouse size

A conventional nuclear plant takes up hundreds of acres, costs tens of billions of dollars, and can take a decade or more to build, which has made new construction rare in the United States for most of the last 40 years. Small modular reactors are an attempt to break that pattern by shrinking the core technology down to a size that can be built in a factory, shipped on a truck or by rail, and assembled on site inside a footprint closer to a large warehouse than a sprawling industrial campus. The idea has moved from concept to regulatory reality in recent years, with the first American design clearing the federal safety review that conventional reactors have always had to pass.

What Makes a Reactor “Small” and “Modular”

The label covers reactor designs that generate roughly 300 megawatts of electricity or less, a fraction of the 1,000-plus megawatts a typical large commercial reactor produces, according to the overview of small modular reactor technology. The “modular” half of the name refers to how the reactor vessel and major components are meant to be manufactured as standardized units in a factory rather than custom-built and assembled piece by piece at each individual plant site. That shift is the whole point of the design philosophy: manufacturing identical units repeatedly is supposed to drive down costs and construction time the way factory production has done in other heavy industries, instead of every reactor being its own one-off construction project.

Building Reactors on a Factory Line Instead of a Construction Site

Conventional reactors are essentially custom structures poured and welded in place over years, with costs and schedules vulnerable to delays at any one of thousands of site-specific construction steps. A modular reactor, by contrast, is designed so its core components can roll off an assembly line and travel to the site nearly complete, needing far less specialized on-site labor and reducing the number of ways a project can fall behind schedule. The Department of Energy’s advanced small modular reactor program has backed this approach specifically because factory production offers a path to more predictable costs and shorter timelines than the megaprojects that have defined nuclear construction for decades.

NuScale’s Design and the First NRC Approval

The clearest sign that small modular reactors have moved beyond the drawing board came when NuScale Power’s design became the first SMR to clear the U.S. Nuclear Regulatory Commission’s full design certification process, a review the company’s original application entered in 2017. According to the Department of Energy’s account of the NRC’s approval of NuScale’s design, the review process examined more than 2 million pages of supporting technical documentation before regulators signed off, underscoring that a smaller reactor still has to clear the same rigorous safety bar as a full-scale plant. NuScale has since sought and received approval for an uprated version of its design as well, a step toward commercial deployment that other SMR developers are now working through their own versions of the same process.

Other Designs Racing Through the Same Regulatory Process

NuScale is not the only company pursuing NRC approval for a small modular design. Sodium-cooled, helium-cooled, and molten-salt-cooled concepts are all moving through their own versions of the same review, each betting on a different combination of coolant and fuel to solve the cost and schedule problems that have historically dogged nuclear construction, and each requiring its own multi-year evaluation before regulators will sign off. Some of the earliest customers lining up for these newer designs are technology companies rather than traditional electric utilities, a shift driven by the enormous and fast-growing electricity demand of data centers built to run artificial intelligence systems, which has made large technology firms among the most active backers of new reactor designs anywhere in the country. That customer base is itself a departure from the traditional SMR pitch of serving remote communities or replacing retiring coal plants, and it has pulled billions of dollars in private investment into a sector regulators are still learning how to evaluate at the pace the market now wants.

Where Small Reactors Could Fit That Big Plants Can’t

Because a small modular reactor needs far less land, water, and transmission infrastructure than a conventional plant, developers have pitched the technology for sites a traditional reactor could never use, including retired coal plant properties that already have grid connections and industrial sites, remote communities, and military bases seeking power independent of the commercial grid. The lower total power output per unit also means a utility can add capacity incrementally, installing one or two modules and adding more later as demand grows, rather than committing tens of billions of dollars upfront to a single enormous plant that either meets projected demand decades from now or doesn’t.

The Hurdles Still Facing Commercial Deployment

Regulatory approval is only one step toward small modular reactors becoming a meaningful part of the electricity supply; no SMR design has yet been built and connected to the U.S. grid at commercial scale, and earlier attempts to move NuScale’s design into construction ran into cost increases that led utilities to pull out of an initial project. Building the supply chains needed to manufacture reactor components at true factory volume, training a workforce for a technology still new to the industry, and proving out costs on a first full-scale project all remain ahead of the technology before it can deliver on the promise of a nuclear plant built more like a piece of industrial equipment than a decades-long megaproject.

This article was produced with the assistance of AI and reviewed by Morning Overview editors.

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