The AP1000® PWR uses extensively analyzed and tested passive safety systems to improve the safety of the plant. The Advisory Council on Reactor Safeguards (ACRS) and the U.S. NRC have scrutinized these systems and ruled that they meet the U.S. NRC single-failure criteria, and other safety criteria such as Three Mile Island lessons learned, and generic safety issues.
The AP1000 reactors’s passive safety systems require no operator actions to mitigate design-basis accidents. These systems use only natural forces such as gravity, natural circulation and compressed gas to achieve their safety function. No pumps, fans, diesels, chillers or other active machinery are used, except for a few simple valves that automatically align and actuate the passive safety systems.
With less safety-grade equipment, the seismic Category 1 building volumes needed to house safety-grade equipment are greatly reduced. In fact, most of the safety equipment can now be located within containment, resulting in fewer containment penetrations.
The AP1000 reactors’s passive safety systems include: