A containment building at a nuclear power plant has two main functions. First, it houses the nuclear reactor and other needed components. Second, it confines radioactive material, protects the plant from external natural and human-induced events, and provides shielding for radiation.
The containment buildings at our plants vary in size and shape: Plant Vogtle have domed containment vessels, while Plant Farley’s are somewhat domed, but more cylindrical. Plant Hatch has rectangular buildings, and the AP 1000 units that will be employed in Vogtle 3&4 are an even different shape – a cylinder with a wheel shape on top – but they all serve the same purpose.
During normal operation, containment is airtight, and personnel access the building through airlocks. Containment buildings in the U.S. are subject to mandatory leakage rate tests. When a unit is shut down for a refueling and maintenance outage, hundreds of employees will enter containment to safely perform scheduled work.