Safety and security are built
into every NuScale system


The NuScale plant includes a comprehensive set of engineered safety features designed to provide stable long-term nuclear core cooling under all conditions, as well as severe accident mitigation. They include a high-pressure containment vessel, two passive decay heat removal and containment heat removal systems, a shutdown accumulator, and in-vessel retention for severe accident mitigation.

Safety

The design implements passive safety systems that use natural circulation for emergency feedwater cooling, decay heat removal, and containment cooling.  This eliminates the need for primary pipes and pumps and any failures associated with pipe breaks and pump failures. No external power is required to operate these systems and there is no need for emergency power on site or off site. The submerged containment vessel is capable of withstanding the pressure transient produced by a complete and simultaneous rupture of any or all of the reactor piping internal to containment.

With the NSSS entirely inside the containment vessel (which is fully immersed in water_, there is greater resilience to seismic forces.  The likelihood of releasing a large amount of radioactive materials into the environment is already extremely low for the existing large-scale commercial nuclear plants that generate approximately 1,000 MWe. Each 45 MWe NuScale power module houses just about 4% of the fuel inventory of a conventional nuclear reactor.
In the extremely unlikely event that a NuScale power module is damaged or fails for any reason, consequences would likely be well below the threshold to warrant off-site evacuations. With the NSSS entirely inside the containment vessel (fully immersed in water) there is greater resilience to seismic forces. The safety of the plant is further enhanced because the simpler design, lower operating pressures and temperatures, the reduced amount of piping, valves, and components significantly reduce the overall failure probability.

Security

The NuScale design incorporates new remote security features and secure refueling facilities. Furthermore, the low profile reactor building, submerged containment, and containment-pool radiation and impact shields provide a hardened target against external threats.  The NuScale system addresses post 9/11 security threats in the following ways:

  • The reactor building has a lower profile than a conventional nuclear plant.
  • The reactor and containment vessel are completely submerged in a water-filled pool below ground creating a low profile target.
  • The reactor is housed in a high pressure containment vessel capable of seven times the internal pressure of conventional containments.
  • A high-impact biological shield covers each module "bay."
  • Each module is submerged in water, which further reduces post-impact jet fuel fire concerns.
  • Nuclear core cooling can be done without any external power, which limits plant vulnerability and loss of off-site power is not an issue.