Canada's used nuclear fuel

Safety will always be our top priority as we implement Canada’s plan to manage used nuclear fuel for generations to come.

Canada has been using nuclear energy as a reliable, low-carbon power source for our homes and businesses for more than half a century. Now, as worldwide energy demand grows and the need to address climate change intensifies, nuclear power has become an increasingly important part of the conversation, with an active research sector dedicated to emerging technologies.


Used nuclear fuel is a byproduct of nuclear power and it must be safely managed long-term.

An icon showing a used fuel bundle
Learn more
A photo of an unused nuclear fuel bundle.

Canada's used nuclear fuel

What is used nuclear fuel?

Learn more
This photo shows a group of people in front of dry storage containers.

Canada's used nuclear fuel

How is it stored today?

Learn more

About Canada's used nuclear fuel

Together, nuclear power reactors in Ontario, Quebec and New Brunswick have been generating electricity from nuclear power for more than half a century. Used nuclear fuel is a byproduct of this process.

Canada’s used nuclear fuel is currently safely stored at existing reactor sites in Ontario, Quebec and New Brunswick, as well as at a laboratory in Manitoba. Today’s method is safe, but temporary, because it requires ongoing maintenance and management. 

This is why Canada has a plan for the safe, long-term management of used nuclear fuel.

#DidYouKnow: What is used nuclear fuel?

Despite how it is depicted in some comic books and movies, used nuclear fuel in Canada is not a liquid or a gas. It’s a stable solid — actually, a ceramic — sealed into a specially designed container and then bound in a “bundle.”

Each bundle weighs about 53 pounds (24 kilograms) and is roughly the size and shape of a fireplace log. When removed from a nuclear reactor, the bundle looks the same as when it went in, but it is highly radioactive and will remain that way for a long time.

That’s why Canada’s plan involves containing and isolating used nuclear fuel in a deep geological repository for generations to come.
A photo of a hydro tower

Adapting to emerging technology

Canada’s plan is designed to adapt to changes in technology, including emerging sources of used nuclear fuel like small modular reactors (SMRs). We are building flexibility into deep geological repository designs so we can be ready for future decisions.
Learn more

How is it stored today?

When used nuclear fuel bundles are removed from a reactor, they are placed in a water-filled pool where their heat and radioactivity decrease. After seven to 10 years, the bundles are placed in dry storage containers, silos or vaults. Dry storage is a proven technology that has been in use around the world since the 1980s.

Dry storage containers are made of reinforced high-density concrete about 510 millimetres (20 inches) thick — about the height of a border collie — and are lined inside and outside with 12.7-millimetre-thick (half-inch) steel plate. The thickness of the concrete provides an effective barrier against radiation.

The dry storage containers have a minimum design life of 50 years. They are actively monitored, and studies indicate that with ongoing maintenance and inspections these containers can be safely used for much longer periods of time. After 50 years, the life of the container could be extended, or the used fuel could be repackaged. These decisions will depend on a number of factors, including the timeline for implementing Canada’s plan for long-term management of the used fuel.

Although the used fuel's radioactivity decreases with time, chemical toxicity persists. To protect people and the environment, it requires safe, long-term management.

Learn more

How much used nuclear fuel is there?

3.3 million bundles

As of 2023, Canada’s existing inventory is about 3.3 million used nuclear fuel bundles. If stacked like cordwood, all this used nuclear fuel could fit into about nine NHL hockey rinks from the ice surface to the top of the boards. At the end of the planned operation of Canada’s existing nuclear reactors, the number of used fuel bundles could total about 5.6 million.

We are also monitoring multiple SMR projects closely to help us prepare for decisions that could change the volume and type of waste we are responsible for managing. The quantity of used fuel produced by potential new nuclear projects, including small modular reactors (SMRs), will depend on the size and type of reactor and number of units deployed. Proposed new nuclear project plans are at various stages of development. As those projects progress, the NWMO will update our inventory projections.

As of the end of 2023, we are aware of three SMR projects in the licensing process. We continue to monitor for other potential projects, and as these projects advance to later stages of development, this will be addressed in the NWMO’s planning and projections.

The NWMO publishes annual inventory reports which can be found here.

Learn more

Related FAQs

View all FAQs
How much energy does one fuel bundle produce?
One fuel bundle can provide enough electricity to power one home for 100 years or about 1,100 megawatt-hours (MWh).

A fuel bundle stays in a nuclear reactor for 12 to 20 months, depending on where it is located in the reactor core. Over time, the amount of Uranium-235 (U-235) in the fuel bundle decreases until it is no longer possible to sustain a nuclear reaction that creates enough heat to generate electricity. U-235 is the primary isotope of uranium that is used to generate electricity.
What is the difference between low-level, intermediate-level and high-level waste?

There are three types of radioactive waste produced by nuclear generating stations — low-, intermediate- and high-level waste.

Low-level waste consists of industrial items (such as mops, rags, cloths, paper towels, clothing and floor sweepings) that have become contaminated with low levels of radioactivity during routine cleanup and maintenance activities at nuclear generating stations. Low-level waste contains mostly short-lived radioactivity and can be handled safely with simple precautions.

Intermediate-level waste is more highly radioactive and consists primarily of used reactor core components and resins and filters used to purify reactor water systems.

High-level waste is the used nuclear fuel. When used fuel bundles are removed from the reactor, they are highly radioactive, contain long-lived radioactivity and generate significant heat. High-level waste requires careful management over the very long term.


Under the federal Radioactive Waste Policy Framework, waste owners such as OPG, NB Power, Hydro-Québec and Canadian Nuclear Laboratories are accountable for the low- and intermediate-level waste they create. They are also responsible for the interim storage and management of used nuclear fuel. Under the Nuclear Fuel Waste Act, the NWMO was created by the waste owners and is responsible for the long-term management of used fuel, with federal government oversight.

Can used fuel burn, explode or melt down?
No. Used CANDU nuclear fuel is not a liquid or a gas — it is a stable solid. Under Canadian and international regulations, it is not classified as flammable, explosive or fissile material.

Used CANDU fuel generates some heat from radioactive decay. However, when used fuel is moved to the repository, it will have cooled for several years in an interim storage facility. It can be air-cooled and will not generate enough heat to melt.

Used nuclear fuel pellets are made from uranium dioxide powder, baked in a furnace to produce a hard, high-density ceramic. Ceramics do not readily dissolve in water and are resistant to high temperatures.
Could you shoot the used nuclear fuel into space?

No. During a three-year dialogue with experts and the public on long-term management methods, disposal in space was one of the options of limited interest that we screened out.

Space disposal was dismissed as an option because it is an unproven concept that is not being implemented anywhere in the world, nor is it part of any national research and development plan. Concerns about the risk of an accident and the potential risk to human health and the environment have been reinforced by the U.S. Space Shuttle Challenger and Columbia accidents.


In addition to looking at several other approaches, we also discussed the three methods of long-term storage identified in the Nuclear Fuel Waste Act (NFWA):

  • Deep geological disposal in the Canadian Shield;
  • Centralized storage above or below ground; and
  • Storage at reactor sites.

Each had strengths and limitations, which led Canadians involved in the dialogue to identify another approach called Adaptive Phased Management (APM). APM incorporates the objectives people said were important, including safety, fairness, community well-being and the need to be adaptive and environmentally responsible.

What happens if used nuclear fuel is exposed to water?

The entire purpose of Canada's plan — the reason we are investing time, effort and money to implement it — is to protect people and the environment, including water.


Used nuclear fuel is a stable solid material. Fuel pellets are made from uranium dioxide powder, baked in a furnace to produce a hard, high-density ceramic. Like all ceramics, this material does not readily dissolve in water.


Even so, in the proposed repository, used nuclear fuel will be isolated far away from water using a series of engineered and natural barriers called the multiple-barrier system. The system is designed to keep the used nuclear fuel in and water out so the two do not come into contact with each other.

Continue reading

An icon of the nuclear symbol


Radiation risk and safety
An icon of the nuclear symbol


Regulatory standards and requirements