The final module - a 750,000 gallon (2.8 million litre) water tank - has been installed at Georgia Power's Vogtle Unit 3. The CB-20 module is a major part of the AP1000 reactor's advanced passive safety system.

The final module is lifted into place at Vogtle 3 (Image: PRNewsfoto/Georgia Power)

The component, which is 35 feet (10.6 metres) in height and weighs over 720,000 pounds (326 tonnes), was lifted into place on top of the containment vessel and shield building roof at the nuclear expansion project near Waynesboro, Georgia. It will hold water to help cool the reactor in an emergency. The water can also be directed into the reactor's used fuel pool, while the tank itself can be refilled from water stored elsewhere on site.

The tank is part of the plant's passive safety systems which require no operator actions to mitigate potential emergency situations, using natural forces such as gravity, natural circulation and compressed gas to achieve their safety function.

Two AP1000 units are being built at Vogtle, and the use of modules such as the CB-20 has helped streamline the construction process, Georgia Power said. Modules have been made in advance, then shipped by rail and truck to the project site where they have been assembled into larger components ready for installation. The last of the 1485 major modules required to complete construction arrived at the site in late 2019.

Placement of the CB-20 module follows the placement earlier this month of Vogtle 3's integrated head package.

Construction of Vogtle unit 3 began in March 2013 and unit 4 in November the same year. Vogtle 3 is scheduled to enter service by November 2021 and unit 4 by November 2022.

Georgia Power is a subsidiary of Southern Company.

Researched and written by World Nuclear News