The Nuclear Fuel Cycle

Uranium delivers a vast amount of energy – 20,000 times that of coal, by weight. But unlike coal, uranium ore is far from being ready for power plants when it is mined out of the ground.

This brochure describes how uranium ore becomes nuclear fuel, and how the fuel is handled after it is used in a reactor. These steps are called the nuclear fuel cycle.


Uranium oxide (U3O8) appears almost everywhere on land and in water. There are rich deposits in Canada, and some of the richest in the world are in northern Saskatchewan.

Mining ore near the surface is usually done through open pits, while deeper ores require underground mines. A third method, called in-situ recovery, works by dissolving uranium oxide from the ore directly at the mining site.

Drum filled with yellowcake. Source: Canadian Nuclear Safety Commission.

Turning ore into fuel

Through several steps, uranium ore turns into fuel pellets that can be loaded into a nuclear reactor.

Milling – To extract the uranium, a mill crushes the ore and grinds it into a pulp. Running sulfuric acid through the pulp removes waste, leaving uranium oxide (U3O8) as a powder, often called yellowcake.

Refining and conversion – Chemical processes purify the yellowcake and convert it into uranium trioxide (UO3). Further processing turns this chemical into uranium dioxide (UO2), which fuels reactors.

Blind River refinery, Canada’s only refining facility for uranium. Source: Cameco.

Enrichment – Uranium-235, the variety of uranium that produces energy, makes up only 0.7% of natural uranium. The rest is uranium-238, not used in energy production. Canadian reactors use this low concentration of uranium-235, but most of the world’s reactors need a stronger concentration. Enrichment boosts the uranium-235 to a level between 3% and 5% of the uranium oxide.

Fuel manufacturing – The uranium dioxide powder is pressed into small cylindrical pellets, which are then baked at high temperatures, and shaped precisely for loading into a reactor.

In the reactor, controlled nuclear reactions heat a fluid, usually water, to create steam. The steam drives turbines, generating electricity.


Storage and disposal

Pool for used fuel at the Bruce B facility. Source: Bruce Power.

Fuel removed from a reactor is hot and radioactive, and not yet safe for long-term disposal. Nuclear operators store the used fuel in cooling pools for several years. After the radioactivity and heat drop to manageable levels, nuclear operators place the used fuel in concrete and steel containers, which are stored onsite.

If the used fuel contains enough uranium-235 or plutonium, a by-product, it can be recycled to recover these valuable energy sources.

Plans are underway to build a permanent storage site for all of Canada’s used fuel. This site would be set deep in rock formations that will not be disturbed by earthquakes or activities on the surface for thousands of years.


Canadian Nuclear Association,