When mining operations cease, the mine will be closed and the site will be rehabilitated. The milling facility, water treatment plant and other equipment will be dismantled. Much of this will be radiation contaminated and will require special handling. Special waste rock and contaminated material may be placed in the mine excavations before sealing the mine, or buried under non-mineralized rock. The mine site will then be graded and replanted.
A closure plan will be developed for each mine site that specifies the extent of rehabilitation and monitoring to be done over the medium term. The tailings pond must also be decommissioned and monitored. A decommissioning licence is required for this work to ensure that the decommissioning process meets government’s environmental standards.
Once a uranium mine site has been successfully decommissioned, the proponent may apply for a license to abandon the site. A license to abandon ends the proponent’s responsibility for the site, and the site can then be transferred to the government to provide long-term regulatory oversight. No uranium mines have been successfully and fully decommissioned in Canada; as a result, the CNSC has yet to grant a license to abandon.
The government’s policy is to minimize the reliance on active institutional controls after decommissioning. But what does this mean?
Given the long half-lives of uranium’s decay products, tailings will be radioactive for tens of thousands of years. This raises many questions that cannot be accurately answered. How will tailings ponds be decommissioned and monitored? Are dikes meant to last for that long? Are the impermeable membranes that are sometimes used in engineered tailings ponds going to last more than 20, 30, 40 years? Will the tailings be dewatered and placed in the excavated mine for long-term disposal? Is this feasible for such large quantities of solids? The exploration projects in Quebec have so far discovered uranium deposits where under 1% of the mineralized rock becomes uranium yellowcake, so the other 99% comes out of the milling facility as tailings. If placed in the mine, how will the leaching of the radioactive and toxic elements be prevented from contaminating groundwater? How will it be monitored and what can be done if contamination is detected? What sort of regulatory controls or agencies will be around in the future to ensure the stewardship of the site?
The decommissioning that has been done to date are not offered as examples to use in the future as decommissioning has mostly taken place at abandoned mines or mines developed and operated according to past practices that would not be acceptable today.
Under the current regulatory system, environmental impact assessments are done in phases, so a project that is at the exploration phase will have little information about the impacts at the operation or closure stages, as these only get defined and assessed later in the project’s life-cycle. This is frustrating when trying to understand the full impacts of a mining project. Residual risk after decommissioning is anticipated. Even if active institutional controls, such as water treatment, monitoring and maintenance, become unnecessary after some time, passive controls, such as land use restrictions and markers are likely to be required over the much longer term.