Uranium Mine and Mill Tailings

Uranium mill tailings are a specific type of Low-Level Radioactive Waste (LLRW) that are generated during the milling (processing) of uranium ore to produce uranium concentrate. As noted previously, uranium concentrate, once refined and converted, is used to make fuel for Canadian and foreign power reactors. Today, tailings are placed in mined out open pits converted to tailings management facilities (TMFs). However, this was not always the case. Historically, tailings were placed in natural containment areas such as lakes or valleys, placed in engineered surface containment areas, or disposed as backfill in underground mines.

Owing to the large volumes and low activity levels, tailings sites are decommissioned in place. Decommissioning of surface tailings sites usually includes improvement or construction of dams to provide long-term containment, flooding or covering of tailings to reduce acid generation and the release of gamma radiation and radon gas, and management/monitoring of tailings and effluent.

At all of the newer operations in Saskatchewan, tailings are managed in mined out pits converted to TMFs. The TMFs feature hydraulic containment during operation (that is, the pit is maintained in a partially dewatered state relative to the surrounding natural water table so that all groundwater flow is towards the tailings facility), and passive long term containment following decommissioning. The latter results from a zone of high hydraulic conductivity material which surrounds the much lower hydraulic conductivity consolidated tailings that channels groundwater flow around rather than through the tailings. The high hydraulic conductivity zone may either be constructed as the tailings are emplaced, referred to as pervious surround (i.e., Rabbit Lake TMF), or exist naturally by virtue of the type of rock, referred to as natural surround (i.e., McClean Lake and Key Lake Dielmann TMF).

Uranium tailings exist at operating uranium mill sites in northern Saskatchewan and at inactive or decommissioned sites in Saskatchewan, Ontario and the Northwest Territories. The following table provides a list of uranium mine and mill facilities licensed by the CNSC.

Uranium Mine and Mill Facility Licences