Preliminary assessment: Safety

To determine: Is there potential for a safe site at this location?

Any site selected to host the project must be able to protect present and future generations, as well as the environment, including water. The preferred site will have a host rock with desirable characteristics (geological, hydrogeological, chemical and mechanical) that support containment and repository performance.

Safety will be assessed by evaluating the following safety-related questions and performance objectives, as well as potential factors identified by Indigenous Knowledge: 

1. Safe containment and isolation of the radioactive waste. Are the characteristics of the rock at the site appropriate to ensure the long-term containment and isolation of intermediate- and high-level waste from people, the environment, including water, and surface disturbances caused by human activities and natural events?
2. Long-term resilience to future geological processes and climate change. Is the host rock geologically stable and likely to remain stable over a long term in a manner that will ensure the repository will not be substantially affected by geological and climate change occurrences such as earthquakes and glacial cycles? 
3. Safe construction, operations and closure of the repository. Are conditions at the site suitable for the safe construction, operations and long-term monitoring and decommissioning of the repository? 
4. Isolation of the radioactive waste from future human activities. Is human intrusion at the site unlikely, for instance through future exploration or mining? 
5. Amenability to site characterization and data interpretation activities. Can the geological conditions at the site be practically studied and described on dimensions that are important for demonstrating long-term safety? 

The above questions and objectives must be addressed in an iterative manner throughout the preliminary and detailed assessments to gradually develop confidence in safety, based on a series of safety criteria, as described in more detail in Table C1. 

These safety criteria were selected in order to ensure that the expectations of Canadian regulators, as outlined in legislation and guidance documents, will be addressed through the site assessment process. Regulatory authorities will independently review the project and site to ensure safety and the protection of people and the environment, including water, before the project can proceed. The safety criteria are also comparable to those of other countries, as well as those recommended by the International Atomic Energy Agency.

Safety criteria in detail

Table C1: Safety criteria

Factors affecting safety	Performance objectives	Suggested evaluation factors to be considered
Containment and isolation by the host rock at the repository site	The geological, hydrogeological, chemical and mechanical characteristics of the host rock should:  Promote long-term isolation of intermediate- and high-level waste from humans, the environment and surface disturbances; Promote long-term containment of intermediate- and high-level waste within the repository; Restrict groundwater movement; and  Prevent the movement of any released radioactive material.	The depth of the host rock formation should be sufficient for isolating the repository from surface disturbances and changes caused by human activities and natural events. The volume of available competent rock at repository depth should be sufficient to host the repository. The volume of available competent rock at repository depth should provide sufficient distance from active geological features such as zones of deformation or faults and unfavourable heterogeneities.  The mineralogy of the rock, and the geochemical composition of the groundwater and rock porewater at repository depth, should not adversely impact the expected performance of the repository multiple-barrier system.  The hydrogeological regime within the host rock should exhibit low groundwater velocities.  The mineralogy of the host rock, and the geochemical composition of the groundwater and rock porewater, should be favourable to slowing radionuclide movement.  The host rock should be capable of withstanding natural stresses and thermal stresses induced by the repository system without significant structural deformations or fracturing that could compromise the containment and isolation functions of the repository.
2. Long-term stability of the repository site	The containment and isolation functions of the repository should not be unacceptably affected by future geological processes and climate changes, including earthquakes and glacial cycles.	Current and future seismic activity at the repository site should not adversely impact the integrity and safety of the repository system during operation and in the very long term.  The expected rates of land uplift, subsidence and erosion at the repository site should not adversely impact the containment and isolation functions of the repository.  The evolution of the geomechanical, hydrogeological and geochemical conditions at repository depth during future climate change scenarios such as glacial cycles should not have a detrimental impact on the long- term safety of the repository.  The repository should be located at a sufficient distance from geological features such as zones of deformation or faults that could be potentially reactivated in the future.
3. Repository construction, operations and closure	The surface and underground characteristics of the site should be favourable to the safe construction, operations, closure and long-term performance of the repository.	The strength of the host rock and in situ stress at repository depth should be such that the repository could be safely excavated, operated and closed without unacceptable rock instabilities. Natural hazards in the repository area are unlikely or can be mitigated against through facility design so as not to affect operations. The available surface area should be sufficient to accommodate surface facilities and associated infrastructure.
4. Human intrusion of the repository	The site should not be located in areas where the containment and isolation functions of the repository are likely to be disrupted by future human activities.	The repository should not be located within rock formations containing economically exploitable natural resources at repository depth such as gas/oil, coal, minerals and other valuable commodities as known today.  The repository should not be located within geological formations containing groundwater resources at repository depth that could be used for drinking, agriculture or industrial uses.
5. Site characterization	The characteristics of the site should be amenable to site characterization and site data interpretation activities.	The host rock geometry and structure should be predictable and amenable to site characterization and site data interpretation.