NRC approves NuScale's uprated 77-MWe small reactor design ahead of schedule

May 2025 — The U.S. Nuclear Regulatory Commission approved NuScale Power's US460 small modular reactor design on May 29, 2025, finishing a review it says came in ahead of schedule and under budget. Here's what happened, what it cost, and what went wrong.

Cost and outcome (as of June 4, 2025)

Outcome: standard design approval for the US460, issued May 29, 2025. (Federal Register)
Size: 77 MWe per module, up to six modules: 1,500 MWt or 462 MWe for a full plant. (NRC approval letter)
Review: application docketed July 31, 2023; approval May 29, 2025, "ahead of schedule and under budget." (NRC approval letter; NRC release 25-033)
Valid until: May 28, 2040. (NRC approval letter)
Cost: the NRC did not give a dollar figure.

What the approval does

A standard design approval "indicates that a proposed reactor design meets applicable agency safety requirements," the NRC said. Companies that want to use the US460 "would have to file applications seeking permission to build and operate a nuclear reactor using the approved design." (NRC release 25-033)

The Federal Register notice says the approval lets the design be referenced in an application for a construction permit or operating license, or for a combined licence or manufacturing licence. (Federal Register) The approval letter adds that it "does not constitute a commitment to issue a permit, design certification (DC) or license." (NRC approval letter)

The design

The US460 is a 77-megawatt-per-module SMR based partly on NuScale's US600 design, which the NRC certified in 2023. It relies on natural "passive" processes such as convection and gravity in its operating and safety systems. Its six modules, producing about 460 megawatts of electricity in total, are "all partially immersed in a safety-related pool built below ground level." (NRC release 25-033)

The approval enclosure gives the numbers precisely: a rated core power of 250 MWt, or 77 MWe, per module, with a capability for up to six modules, for 1,500 MWt or 462 MWe per plant. (NRC approval letter)

How long it took

NuScale told the NRC in November 2022 that it would submit the application in stages and filed the pieces between Nov. 23 and Dec. 31, 2022. After supplemental information, the NRC accepted it for docketing on July 31, 2023. NuScale filed Revision 2 on April 9, 2025. (NRC approval letter)

The NRC's Advisory Committee on Reactor Safeguards reported on the staff's safety evaluation "with no open items" in a May 21, 2025 letter. The approval is valid for 15 years and expires May 28, 2040, though it stays usable in any application docketed before then. (NRC approval letter)

What the NRC checked

The NRC staff reviewed NuScale's design control document against its rules for the content and review of design approval applications, and concluded, "on the basis of its evaluation and independent analyses," that the application met them. Issuing the approval "signifies completion of the NRC staff's technical review," the Federal Register notice says. (Federal Register)

Conditions come with it. Any applicant that references the design must adopt the operational requirements in NuScale's application, including its technical specifications, and parts of a plant outside the approved design must meet the interface requirements NuScale set out. (NRC approval letter)

What went wrong

Approval is not a plant. Builders still need their own permits and licences to use the design. (NRC release 25-033)
No commitment. The NRC says the approval doesn't commit it to issuing any permit or licence. (NRC approval letter)
Site limits apply. The design is approved only for sites whose characteristics fall within the parameters in NuScale's application. (NRC approval letter)
What we don't know yet: who will build the first US460, where, and at what cost. None of the NRC documents name a customer.

Our follow-up question for NuScale Power

Which customer will be first to file a construction application using the US460, and when?

Sources

U.S. Nuclear Regulatory Commission, “NRC Approves Standard Design for NuScale US460 Small Modular Reactor,” release No. 25-033, May 29, 2025. nrc.gov
U.S. Nuclear Regulatory Commission, “Standard Design Approval for the NuScale Power Company, LLC US460 Power Plant Design,” letter and enclosure, May 29, 2025 (ML25129A004). nrc.gov
Federal Register, “NuScale Power, LLC; NuScale US460 Small Modular Reactor; Standard Design Approval,” June 4, 2025. federalregister.gov

Disclosure: [not in copy] Editor placeholder