The final module for unit 3 of Georgia Power's Vogtle nuclear power plant, a massive water tank, has been placed atop the containment vessel and shield building roof.

The installation represents the final module placement for Vogtle 3, a Westinghouse AP1000 reactor, marking another significant milestone for the project.

The large CB-20 module is a major part of the AP1000 advanced passive safety system. The component which is 35 feet tall and weighs more than 720,000 pounds, will hold approximately 750,000 gallons of water ready for use in the 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.

The modules used for Vogtle 3&4 help to streamline the construction process, since they were made in advance of arriving to the project site and ready to be assembled into larger components that make up the nuclear units, Georgia Power said.

Since 2011, major modules have been delivered to the site by rail and truck, and included a range of plant components such as floor and wall sections and supporting structures that surround the containment buildings and reactor vessels. The last of 1485 major modules arrived at the construction site in late 2019.

Photo: Vogtle 3 under construction (PRNewsfoto/Georgia Power)