Learn How Units 3 and 4 Operate

Passive Safety Systems

Plant Vogtle Units 3 and 4 are designed with passive safety systems that utilize natural forces such as gravity, natural circulation and compressed gas – rather than electrical machinery (pumps, fans, diesels, chillers, etc.) – to keep the core and containment from overheating in the event of a design-basis accident, such as a main coolant-pipe break.  This significantly reduces dependency on machinery and need for AC/DC power.

These features provide:

• Water tanks inside and on top of the containment building provide enough water to keep the reactor in a safe condition – through gravity, natural circulation and evaporative cooling.
• Air cooling also is provided by a chimney effect with hot air flowing out of the top of the shield building.

Pressurized-Water Reactors

All of Plant Vogtle’s units are pressurized-water reactors (PWRs). Click here to see an overview of how they work.

In a nutshell, the fission in the nuclear reactor creates heat, which turns water into steam, which then turns turbines that produce energy.  The steam then goes through a condenser where it is cooled back into water and recirculated in the steam generator.

A note about cooling towers, the most iconic and visible structures in a nuclear plant: the clouds coming from the towers are clean water vapor.

Cool water flows through pipes that pass through the condensers, helping turn the steam back into liquid that is recirculated to the steam generator. After passing through the condenser, the now-heated water flows to the cooling towers where is is released as a spray. As the water falls, some of it evaporates and heats the surrounding air, which rises and turns into vapor as it exits the top of the tower.

Uranium Fuel

The Vogtle units utilize uranium pellets for fuel. Each pellet has as much energy as 149 gallons of oil or 1 ton of coal. A nuclear reactor can hold more than 13 million pellets!

Refueling the Core

Vogtle operators conduct refueling of the reactors every 18 months. They add new fuel and remove used fuel. Technicians also take advantage of the time to check, repair and replace systems as needed.

The spent fuel is stored in a holding pool before it eventually is transferred into dry cask storage units. These units are stored on site and ensure safe storage of the spent fuel for the life of the plant.