50 megawatt small nuclear reactor

NuScale's mini-reactor design has been certified as safe and could be operational in the next few years.

NuScale's small nuclear reactor design. (Photo: NPR).

The US Nuclear Regulatory Commission (NRC) on September 4 granted a design certification to the first small nuclear reactor, meaning it meets safety standards and can be used in future projects. The design comes from NuScale, a company founded by the University of Oregon with investment from the US Department of Energy. NuScale's reactor is a steel cylinder, 23 meters high and 5 meters wide, and can produce 50 megawatts of electricity. The company plans to deploy 12 reactors in the large pools used in current nuclear power plants.

The reactor has a basic design, using uranium fuel rods to heat water in the pressurization tube. The steam is sent to a turbine, cooled, and then circulated back into the reactor. The design also uses passive cooling, so there are no pumps or moving parts needed to keep the reactor running safely. The pressurization tube is arranged to allow hot water to rise through the heat exchange coils and back to the fuel rods after they cool.

In the event of a problem, NuScale's reactors are designed to manage their heat automatically. The control arm can encase the fuel rods, blocking neutrons and stopping the nuclear chain reaction. A motor holds the arm above the fuel rods. In the event of a power outage or sudden shutdown, the arm slides over the fuel rods. The advantage of the small design is that each reactor contains only a small amount of radioactive fuel.

NuScale submitted its design to the NRC in 2016, which includes more than two million pages of documentation. The NRC concluded that the design features would ensure the plant would be shut down safely and without risk in an emergency. NuScale said the first reactors would be deployed in the mid-2020s.