All modules for the Plant Vogtle units 3 & 4 nuclear expansion project have now been set, as a massive water tank has been lifted into place atop the Unit 4 containment vessel and shield building roof. The placement also represents the last major crane lift at the project site.
The Passive Containment Cooling Water Storage Tank, known as CB-20, is a major part of the AP1000 reactor's advanced passive safety system. Standing 35 feet tall and weighing more than 720,000 pounds, the large component will hold approximately 750,000 gallons of water ready to flow down in the unlikely event of an emergency to help cool the reactor. The water can also be directed into the used fuel pool, while the tank itself can be refilled from water stored elsewhere on site.
The AP1000 plant's passive safety systems require no operator actions to mitigate potential emergency situations. 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.
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