Generating Electricity: Nuclear Energy

Nuclear energy provides about 15% of Canada's electricity. As of 2023, Canada has 19 nuclear reactors. 18 are in Ontario. One is in New Brunswick.

So how does nuclear energy generate electricity? Let’s find out.

People often use thermal energy to generate electricity. Thermal energy is another name for “heat energy.” Thermal energy heats water. The heated water forms steam. This steam powers an electricity generator. In many places, including Canada, people burn fossil fuels to get this heat. Some examples of fossil fuels are:

• coal
• oil (petroleum)
• natural gases

Nuclear reactors also use heat to generate electricity. But nuclear power plants don’t burn fossil fuels for heat. Instead, they use uranium for fuel. Uranium is a chemical element. It gives off energy naturally. A lot of uranium in Canada comes from the Athabasca Basin. That is a region in Northern Saskatchewan.

In nuclear reactors, uranium atoms are split apart through a process called fission. When many atoms split at the same time, there is a huge release of energy. This energy is released in the form of heat. The heat energy warms heavy water in a closed loop of pipes. Heavy water is water that uses an isotope of hydrogen called deuterium (D₂O) instead of regular hydrogen atoms (H₂O).

The heavy water heats normal water in a second closed loop of pipes. This boiled water forms steam. The steam flows to a turbine. The turbine is connected to a shaft that spins. This shaft runs through the turbine into a generator. The generator turns the shaft’s mechanical energy into electricity.

A third system of pipes contains cool water. This is pumped in from a nearby body of water like a lake. Heat energy from the steam is transferred to this water. This condenses the steam back into water. It also makes the cool water, from outside, warm. Then the warm water is released back into the nearby body of water and the water inside the closed pipes goes back to be boiled again.

Uranium fuel is radioactive. That’s why it can generate electricity. But as it gets used in a reactor, the fuel contains less and less energy. Over time, there is not enough energy to keep the fission reactions going. When that happens, the fuel is considered to be “spent”. However, this fuel is radioactive.

Nuclear reactors have the advantage that they do not give off carbon dioxide when they are running.

One of their disadvantages is that they produce radioactive spent fuel. This fuel can be dangerous to humans for thousands of years, so it must be stored carefully. Canada stores spent fuel in pools of water with concrete walls and floors about two metres thick. After seven to ten years, the fuel is safe enough to be moved to storage containers made of concrete and steel.

Another disadvantage is that the mining of uranium and the building of nuclear reactors and nuclear waste storage facilities, all produce carbon dioxide.

Overall, nuclear reactors are responsible for a small amount of greenhouse gases during their lifespans.