Canada's deep geological repository

Canada’s plan to construct a deep geological repository for the safe, long-term management of used nuclear fuel is consistent with international best practices. This approach is the culmination of more than 30 years of research, development and demonstration of technologies and techniques.


Canada's deep geological repository will use a multiple-barrier system designed to safely contain and isolate used nuclear fuel over the very long term. Constructed more than 500 metres below ground, the repository will consist of a network of placement rooms that will store the used nuclear fuel.

Rigorous safety standards govern the project. We have committed to meet or exceed all applicable federal and provincial regulatory requirements to protect the health, safety and security of people and the environment for generations to come.

#DidYouKnow: What is a deep geological repository?

A conceptual layout for a deep geological repository 

The deep geological repository is designed to safely contain and isolate Canada's used nuclear fuel over the long term, including that generated by new or emerging technologies. It will include a network of underground tunnels and placement rooms for used nuclear fuel containers.

An animation of the deep geological repository.

A conceptual layout for a repository would require an underground footprint of about 2 km by 3 km (about 600 hectares or 1,500 acres). The depth of the repository would be such that future inadvertent human intrusion into the closed repository would be very unlikely.

At the surface, there will be facilities where the used fuel is received, inspected and repackaged into purpose-built containers encased in a bentonite clay buffer box, before being transferred to the main shaft for underground placement. There will also be facilities for administration, security, processing of sealing materials, quality control and ongoing operation and monitoring of the site.

This diagram shows the layout of Adaptive Phased Management surface facilities for a deep geological repository, all of which are described on this page.

The repository will include a centralized services area that will allow for underground ventilation through three shafts located within a single, secure area. The layout also includes multiple access tunnel arms that will let our technical specialists situate the placement rooms in areas with the most suitable rock. The buffer boxes will be arranged in the horizontal placement rooms, and any spaces left over will be backfilled with bentonite clay pellets or chips.

The actual underground footprint at any particular site would depend on a number of factors, including the characteristics of the rock, the location of underground features in the rock, the final design of the repository and the total inventory of used fuel to be managed.

To construct the deep geological repository, rock excavation would primarily be done using a method that involves controlled drilling and blasting. Rock boring technology may also be used depending on the final design and site conditions.

To prepare for the regulatory decision-making process and construction, the NWMO has begun work on site-specific conceptual designs of the repository layout based on information from geoscience assessments and initial borehole drilling in the potential siting areas. This is an iterative process; as the NWMO develops additional site-specific information, we will continue to evolve the design of the repository. The proposed site in the Wabigoon Lake Ojibway Nation-Ignace area would be located in crystalline rock, and in the Saugeen Ojibway Nation-South Bruce area, it would be in sedimentary rock. After site selection, additional site characterization work will begin to further inform the design.

A photo of the engineered barrier system

Multiple-barrier system

In the deep geological repository, a series of engineered and natural barriers will work together to contain and isolate used nuclear fuel to protect people and the environment. Each barrier provides a unique and stand-alone level of protection. If any of the barriers deteriorates, the next one comes into play.
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Confidence in safety

Confidence in safety

In 2022 we published Confidence in Safety reports for each of the two potential sites being considered to host a deep geological repository to safely manage Canada’s used nuclear fuel.

The reports are based on years of research and fieldwork. They summarize the NWMO’s understanding of each siting area, including geological characteristics that indicate the sites can meet the project’s requirements to contain and isolate used nuclear fuel to protect people and the environment.

After a site is selected, additional studies will be undertaken to further inform the repository design and long-term safety case.
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There will be an extensive environmental and operational monitoring program for ground and surface water, radiation, air quality, fire and more. This monitoring will start prior to construction and will continue through operations. There will also be an extended monitoring period following placement of the used nuclear fuel to ensure the repository is performing as expected.


Deep geological repository

View all FAQs
How will people and the environment be protected?
Canada's plan for the safe, long-term management of used nuclear fuel involves containing and isolating it in a deep geological repository.

The safety of people and the environment is the top priority in the process for selecting a repository site. We will need to demonstrate that any site selected can safely contain and isolate used nuclear fuel for a very long period of time. There cannot be any credible risk from the repository to the public or the environment.

The repository will be located deep underground in a suitable rock formation, which must meet site selection technical criteria for the development of a robust safety case. This approach is consistent with international best practices, and is the culmination of more than 30 years of research, development and demonstration of technologies and techniques.

The repository uses multiple barriers that include the waste form, container, sealing materials and host rock. The system is designed such that the failure of one component would not jeopardize the safety of the containment system as a whole.

The project will also be subject to a thorough regulatory review process, including an environmental assessment and a licensing review to ensure that it is implemented in a manner that protects people and the environment.

Once placed in the repository, the used nuclear fuel will be monitored for an extended period of time.
What facilities will be constructed?
Canada's plan for the long-term management of used nuclear fuel involves its containment and isolation at a repository site. Facilities associated with the project will include:
  • A Centre of Expertise that will support the multi-year testing of the site. It will include public viewing galleries to showcase both the technology and science, and the engagement efforts that have gone into the implementation of Canada's plan;
  • A deep geological repository to contain and isolate Canada's used fuel over the long term; and
  • Surface facilities, including security, quality control laboratories, sealing materials production plants and all the other functions required to support the safe receipt and storage of used fuel bundles. These facilities will also support the repackaging and transfer of used fuel bundles to the underground repository.
Where will the repository be located?

No site has been identified yet.

Canada's long-term plan for used nuclear fuel requires that the deep geological repository be located in an area with an informed and willing host at a site that meets rigorous technical and safety criteria.


In 2010, the NWMO began a multi-year site selection process to identify a suitable location for the deep geological repository and Centre of Expertise. The process is designed to ensure the site selected is safe and secure, meeting or exceeding all regulatory requirements. Only areas where communities expressed an interest in learning about the project were considered.

Over time and through increasingly detailed technical and social studies and engagement, we have narrowed our focus to the areas with the strongest potential to safely host the project. The NWMO plans to select a site in 2024, and two areas remain in our site selection process: the Wabigoon Lake Ojibway Nation-Ignace area in northwestern Ontario and the Saugeen Ojibway Nation-South Bruce area in southern Ontario.

What is the best type of rock for hosting a deep geological repository?
The international consensus is that both crystalline and sedimentary rock formations have properties that make them potentially suitable for the safe containment and isolation of used nuclear fuel. Both of these rock formations are found in Ontario, and each of the remaining potential sites has either crystalline or sedimentary rock formations.

The site selection process, with its progressively more detailed studies, will ensure the selected site is located in a suitable rock formation. The geology must meet all scientific and technical site evaluation factors for the protection of present and future generations and the environment over the long term.
What type of container will hold the used fuel in the repository?
The used fuel container is one of the principal engineered barriers in a multiple-barrier deep geological repository. The important features of the design are corrosion resistance, mechanical strength, geometry, capacity and compatibility with surrounding sealing materials.

Our current conceptual design is for a used fuel container with lateral placement in the repository. This particular container has a length of 2.5 metres. The container holds 48 used CANDU fuel bundles (four layers of 12 bundles) in a steel basket within a standard carbon steel pipe which is protected by a copper-coated, corrosion-resistant outer layer.
How long will you monitor the used nuclear fuel?
The transport, handling and placement of the used nuclear fuel in the deep geological repository is expected to take place over a period of about 40 years. The repository will be monitored throughout all these activities.

There will also be an extended period of monitoring, which could last several decades (70 years has been assumed for financial planning purposes). Many decades from now, in collaboration with regulatory authorities, the community will decide the form and duration of this monitoring.

Following the period of extended monitoring, the decommission and closure of the facility is expected to take about 30 years. Details for the monitoring following closure will be decided in collaboration with a future society.

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Canada's plan

Selecting a site
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Canada's used nuclear fuel