Technology Overview

How the NuScale Module Works

NuScale Power is creating a new kind of nuclear power plant, one that is smarter, cleaner, safer and cost competitive. The innovative concept incorporates all of the components for steam generation and heat exchange into a single integrated unit called the NuScale Power Module (NPM). Each NPM operates independently within a multi-module configuration. Up to 12 modules are monitored and operated from a single control room. The compact design of the NPM allows it to be built and assembled in a U.S. factory, then shipped to a prepared site for easy deployment.


The reactor measures 65 feet tall x 9 feet in diameter. It sits within a containment vessel measuring 72 feet tall x 15 feet in diameter. The reactor and containment vessel operate inside a water-filled pool that is built below grade. The reactor operates using the principles of buoyancy driven natural circulation; hence, no pumps are needed to circulate water through the reactor. Water is heated as it passes over the core. As it heats up, the water rises through the central riser within the interior of the vessel.

Once the heated water reaches the top of the riser, it is drawn downward by water that is cooled passing through the steam generators. The cooler water has a higher density. It is pulled by gravity back down to the bottom of the reactor where it again flows over the core. Water in the reactor system is kept separate from the water in the steam generator system to prevent contamination.

As the hot water in the reactor system passes over the hundreds of tubes in the steam generator, heat is transferred through the tube walls and the water inside the tubes turns to superheated steam. The steam is directed to a small skid mounted turbine that is attached by a single shaft to the electrical generator. After passing through the turbines, the steam loses its energy. It is cooled back into liquid form in the condenser then pumped by the feed water pump back to the steam generator where it begins the cycle again.

NuScale Reactor Diagram   
Thermal capacity 200 MWt
Electrical capacity 60 MWe (gross)
Capacity factor >95 percent
Dimensions 76' x 15' cylindrical containment vessel module containing reactor and steam generator
Weight ~700 tons in total are shipped from the factory in three segments
Transportation Truck, rail or barge
Cost Numerous advantages due to simplicity, modular design, volume manufacturing and shorter construction times
Fuel Standard LWR fuel in 17 x 17 configuration, each assembly 2 meters (~ 6 ft.) in length; up to 24-month refueling cycle with fuel enriched at less than 5 percent