Aerial view of the Underground Research Laboratory during its operation.
In November 2025, Canadian Nuclear Laboratories (CNL) achieved a major milestone by successfully closing the Enhanced Sealing Project (ESP) site at the former Underground Research Laboratory (URL) near Lac du Bonnet, Manitoba. This marks the last step in decommissioning an iconic legacy research facility, which will be remembered as the site where scientists gained knowledge on the safety of Deep Geological Repositories (DGRs), a design now established as best practice for disposal of used nuclear fuel.
The URL, built in 1978, was Canada’s first underground research facility dedicated to studying the safe storage of used nuclear fuel deep underground. In 2003, after the decision to close the URL, two large seals made of bentonite clay and concrete were installed in the shafts. These seals were designed to block water movement and maintain long-term safety. At no point did the URL house radiological waste, and no waste is stored at the URL site.
Recognizing an opportunity to learn more, CNL launched the ESP in 2008 to monitor how these seals perform over time under real-world conditions. The project involved international partners from Finland, France, and Sweden, reflecting a global commitment to protecting people and the environment for generations to come.
Despite challenges like the demolition of the original URL lab, the ESP continued for more than a decade beyond its initial timeline. The project produced invaluable data, demonstrated the feasibility of full-scale shaft seals, and was recognized by the Canadian Geotechnical Society as one of Canada’s Geotechnical Project Achievements in 2017.
The end of the ESP is the URL’s final gift to supporting safe nuclear waste disposal, a necessity to ensuring a sustainable nuclear industry and a carbon-free energy grid.
Composite bentonite-concrete seal monitored by the Enhanced Sealing Project (2008-2025)
Enhanced Sealing Project site closure (2025 November).
Inside the Underground Research Laboratory during its operation.
Collecting data using a stand-alone monitoring system.
