US approves construction of its first commercial small modular reactor

What happened

The Tennessee Valley Authority, or TVA, is a utility owned by the United States federal government. Its Clinch River site is near Oak Ridge, Tennessee. The permit covers one reactor, called Clinch River-1. TVA sent its application to the NRC in late May 2025. According to the Breakthrough Institute, the NRC completed its safety review in 14 months, four months ahead of its own schedule.

The reactor design is the BWRX-300 from GE Vernova Hitachi. NucNet describes it as a 300-megawatt boiling water reactor, a smaller and simpler version of the company's larger ESBWR design, which is already licensed. The NRC said the permit creates a clear licensing path that later small reactor applicants can repeat. TVA is the first US utility to apply to build this design.

The permit has limits. It allows TVA to build the plant but not to run it. TVA must finish construction and then win a separate operating licence from the NRC before it can load fuel. The Breakthrough Institute notes that this is the NRC's second major new reactor construction approval in 2026, after a permit for TerraPower's Natrium reactor in Wyoming in March. Both reviews finished ahead of schedule.

The same design is already being built in Canada. NucNet reports that in May 2025, the province of Ontario and Ontario Power Generation approved a plan worth 20.9 billion Canadian dollars to build the first of four BWRX-300 reactors at the Darlington site. The first is expected to start commercial operation by the end of 2029. TVA, Ontario Power Generation and the Polish company Synthos Green Energy have all invested in the design together.

The engineering behind it

A boiling water reactor heats water directly in the reactor core. The water boils, and the steam goes straight to a turbine that drives a generator. The steam is then cooled, turned back into water and pumped back to the core. This is simpler than a pressurised water reactor, which uses a separate loop and steam generators. A smaller, simpler plant needs fewer pumps, pipes and valves, which can reduce cost and construction time.

Small modular reactors are designed so that more of the work can be done in factories and repeated from one project to the next. In general, a design that has been licensed once can be built again with less review work, which is the point the NRC made about a repeatable path. Large nuclear plants have often run late and over budget, partly because each one was a new design built for a single site. NucNet notes that only a few small modular reactors have been completed anywhere so far, all in Russia and China.

Site approval came first. The Breakthrough Institute reports that TVA already held an early site permit for Clinch River, with a combined limit of 800 megawatts, before choosing a reactor design. An early site permit lets an owner check the geology, flood risk, water supply and environmental effects of a site in advance. The institute says this earlier work helped make the construction review faster.

A nuclear plant also depends on instrumentation and control. Sensors measure temperature, pressure, water level and neutron flux in the core. Control systems keep these within limits, and separate safety systems shut the reactor down if they go outside them. The civil structures must hold the reactor safely during earthquakes, floods and other extreme events. All of this must be documented and checked against regulations before a licence is granted.

What it means in Nepal

None of the sources discuss Nepal, so this section is about the type of work. The main lesson is that the safety case and the licence can take as long as the design itself. TVA had to prove its site was suitable, prove its reactor met safety rules, and will still need a separate licence to operate. Every step depends on clear, complete technical documents that a regulator can check.

This applies to many large engineering projects, not only nuclear ones. Dams, tunnels, high-voltage lines and large buildings all need studies of geology, flood risk and earthquakes, plus approval from authorities before construction. Engineers who can write a clear design report, follow a code of practice and answer a reviewer's questions precisely are valuable on any project of this kind.

The story also shows how skills from several fields meet in one plant. Electrical and electronics engineers work on instrumentation, control, protection and the connection to the grid. Civil engineers design foundations and structures that must resist earthquakes and other loads. Both must work to strict standards and keep careful records. Students who learn to respect standards and documentation early will find these habits useful wherever they work.