July 29, 2019 [Tank News International] – Georgia Power announced several key milestones at the Vogtle nuclear expansion near Waynesboro, Georgia, including the placement of the middle containment vessel ring for Unit 4. The containment ring is part of the structure that houses the reactor vessel.
Weighing more than a jumbo jet, the 2.4 million-pound, 51-foot tall containment vessel ring consists of dozens of individual steel plates and was fabricated on site. The middle ring is the second of three containment vessel rings to be set for Unit 4. Learning from previous ring placements, the construction team gained efficiencies by installing over 400 electrical and piping supports inside of the middle ring before it was placed.
Additionally, a placement of more than 930 cubic yards of concrete was completed inside the Unit 3 shield building. The Unit 3 shield building is now more than 80 percent complete as the construction team moves closer to completion of the protective barrier that surrounds the Unit 3 containment vessel.
The shield building is made of steel and concrete in what is known as a steel composite design. The panels are a unique feature of the AP1000 reactor design at the Vogtle nuclear expansion, providing an additional layer of safety around the containment vessel and protecting it from any potential impacts. Four of seven air inlet assemblies have been placed above the shield building panels. Each weighing up to 220,000 pounds, the air inlets are part of the AP1000’s passive safety system, allowing natural air circulation around containment through several openings to help with the cooling process.
Workers have also successfully set the fourth and final core make-up tank for the Vogtle 3 & 4 project. Placed inside the Unit 4 containment vessel, the 330,000-pound, stainless-steel tank is part of the safety core cooling system to keep the reactor vessel cool using gravity and natural water circulation.
In addition, the final section of the steel floor that sits atop the in-containment refuelling water storage tank (IRWST) has been set inside the Unit 4 containment vessel. The IRWST contains more than 500,000 gallons of borated water and provides heat removal from the reactor without operator action.