Skip to Content
Workers in hard hats train for their work on a full-scale nuclear reactor mock-up.

Nuclear power: how it works

Nuclear energy is one of Canada’s safest and most-efficient energy sources. It produces clean, baseload power 24/7/365, and its extensive use in Ontario is why our electricity system is 96% free of smog and carbon emissions.

Learn how nuclear works and how it benefits Ontarians.

Nuclear: The core of Ontario’s power

Learn how nuclear power works – it may surprise you.

Understanding nuclear

Like traditional power-generating equipment, nuclear reactors produce heat to convert water into steam, which then spins a turbine and turns a generator that creates electricity.​​​​​​​​​​​​​

The main difference is that nuclear reactors produce heat by splitting uranium atoms.

Instead of coal, oil or natural gas, Canadian nuclear reactors use natural uranium for fuel.

But contrary to popular belief, the uranium is not burned. Uranium atoms make heat by splitting. This process is known as fission.

Nuclear power boiled down

Learn how fission works, and generates the power needed to create electricity.

Nuclear Fission is often misunderstood. In brief, it involves capturing the energy released when a uranium atom is split and harnessing that energy into efficient use.

When a neutron (a tiny sub-atomic particle that is one of the components of almost all atoms) strikes an atom of uranium, the uranium atom splits into two lighter atoms (which are called fission products) and releases heat at the same time.

The fissioning process also releases from one to three more neutrons that can split other uranium atoms. This is the beginning of a "chain reaction" in which more and more uranium atoms are split, releasing more and more neutrons (and heat).

In a nuclear reactor, the chain reaction is tightly controlled to produce only the amount of heat needed to generate a specific amount of electricity.

The fission process generates a huge amount of heat. In order to be useful, the heat has to be moved to boilers to make steam. In a CANDU® reactor, heavy water does this job. It is pumped constantly through the fuel channels in the reactor and takes the heat from the fuel bundles up to boilers above the reactor.

In the boilers, the heated heavy water heats up ordinary water to make steam. This steam is piped out of the boilers and over to the turbine hall where it drives the huge turbines/generators that make the electricity we use.