# How a Nuclear Plant Works

How a nuclear power plant turns splitting uranium atoms into heat, steam and electricity, from the reactor core to the cooling tower\.

By brave\-heron\-b1fa5422

Topic: Energy

[Open the interactive Jig](https://ask.jig.com/j/QyPikGXlnnmW)

## Transcript

### 1. A power plant for a whole city

This is a nuclear power plant\. Like most power plants, it boils water and uses the steam to spin a machine that makes electricity\. What makes it special is where the heat comes from\. Drag to look around\.

This kind is called a pressurized water reactor, the most common type in the world\.

### 2. Heat from splitting atoms

Inside the dome, the reactor holds fuel made of uranium\. When a uranium atom splits, it gives off heat and tiny particles called neutrons, which split more atoms\. This splitting is called fission\. Nothing burns, and there is no flame\.

The fuel is ceramic pellets about 1 cm across, stacked in metal tubes\. A big reactor holds over 18 million of them\.

### 3. Control rods: the brake

Control rods hang above the fuel\. They soak up neutrons, so when they slide down between the fuel, fewer atoms split and less heat is made\. Lower them and watch the core dim and the turbine slow down\.

Only 3\.5 to 5 percent of the uranium is the kind that splits easily\. Reactor fuel is very different from the material in weapons\.

### 4. Very hot, but not boiling

Water carries the heat away from the core\. It reaches about 300 °C, three times hotter than boiling water in a kitchen, yet stays liquid because it is kept under very high pressure\. Pumps push it round a closed loop\.

The tall blue tank, the pressurizer, keeps the pressure about 150 times higher than the air around us\.

### 5. The steam generator

The hot water flows through thousands of thin tubes inside the steam generator\. Around those tubes, a second supply of water boils into steam\. The two waters never mix, so the steam never touches the fuel\.

### 6. Steam spins the turbine

The steam rushes along a pipe to the turbine and pushes rows of blades, like wind on a pinwheel\. The turbine turns a generator, where spinning magnets make electricity\. Power lines carry it to homes, schools and hospitals\.

Look for the small brass maker's plate on the generator\.

### 7. Cooling the steam

After the turbine, the steam is cooled in the condenser and turns back into water, ready to be boiled again\. A third water loop carries the leftover heat to the cooling tower\. The white cloud on top is just water vapour, like the steam from a kettle\.

Only about a third of the heat becomes electricity\. The rest warms the cooling water\.

### 8. Layers of safety

The reactor sits inside a containment building with thick walls of concrete and steel\. If something goes wrong, the control rods drop in by themselves, and backup pumps and generators keep water cooling the fuel\. Close the dome to see the outer wall\.

The walls of many containment buildings are 1 to 1\.5 metres thick\.

### 9. From atom to light switch

Now follow it all at once: atoms split and make heat, hot water carries it to the steam generator, and steam spins the turbine and generator\. Then the steam is cooled back into water and the journey starts again\.

About a third of the fuel is replaced every 12 to 18 months\.