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What is a small modular reactor?

Updated

General information, not a substitute for the advice of an attorney.

Short answer: A nuclear reactor far smaller than a conventional plant, designed to be built in repeatable units. The Department of Energy says advanced small modular reactors are "envisioned to vary in size from tens of megawatts up to hundreds of megawatts" (DOE Office of Nuclear Energy). For scale, the 94 reactors operating in the United States as of March 2026 are mostly large single units, and the average reactor is about 44 years old (EIA FAQ 207; EIA FAQ 228).

What makes it different

DOE lists the claimed advantages as smaller physical footprints, lower capital investment, siting in locations not practical for larger plants, incremental power additions, and safeguards, security, and nonproliferation benefits (DOE). These are the program's goals, not demonstrated results; DOE's page says light-water SMRs "will likely be deployed in the late 2020s to early 2030s" (DOE).

Licensing status

  • NuScale US460: a light-water SMR with six nuclear power modules of 77 MWe each, 462 MWe total. The NRC says "Standard Design Approval (SDA) was issued in May of 2025 - two months ahead of schedule," on an application NuScale completed by letter dated December 31, 2022 (NRC).
  • DOE's SMR page carries the headline "NRC Approves First U.S. Small Modular Reactor Design," referring to an earlier NuScale design, but gives no date on the page we opened (DOE).
  • Holtec's SMR-300: the NRC is in pre-application activities with SMR, LLC for a dual-unit SMR-300 facility at the Palisades site in Michigan; no construction permit application is listed (NRC Palisades page).
  • DOE partnered with NuScale and UAMPS to demonstrate a first-of-a-kind reactor at Idaho National Laboratory "this decade," under a program begun in FY2019 (DOE).

A standard design approval is not a license to build. Any specific plant still needs a site-specific construction permit or combined license from the NRC.

Why it matters for land and grid screening

An SMR's appeal to landowners and data-center developers is the siting flexibility DOE describes (DOE), but no SMR is generating power in the United States, and the newest operating U.S. reactor is the full-size Vogtle Unit 4, in commercial operation since April 2024 (EIA FAQ 207). Treat SMR announcements as development-stage until an NRC construction permit appears on the facility's docket.

See data centers and land, grid interconnection by market, and the permit finder.

General information from the sources linked above, not legal, tax, or financial advice.

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