Glossary

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Deep geological repository is a facility for the placement of used nuclear fuel deep underground where both natural and engineered barriers contain and isolate it from people and the environment for generations to come. There is the potential for retrieving the used nuclear fuel.

Fuel for CANDU nuclear reactors is manufactured by sintering uranium oxide powder into pellets. The pellets are loaded into Zircaloy (a corrosion-resistant alloy of the metal zirconium) tubes, which are then welded into a bundle of tubes — a fuel bundle. Each bundle contains about 1,000 uranium oxide pellets.

High-level waste includes mostly used nuclear fuel, and there is a very small amount of non-fuel high-level waste that comes from other activities such as medical isotope production. This waste generates a significant amount of heat and radioactivity and requires containment and isolation for hundreds of thousands of years in a deep geological repository.

Intermediate-level waste includes used components such as filters, resins and pumps from power plants, research reactors and medical isotope manufacturers. This waste produces minimal heat, but requires a higher level of containment and isolation for longer time periods than is needed for low-level waste.

Long-term management of used nuclear fuel involves containment and isolation of the radioactive material. The radioactivity decreases substantially with time, due primarily to the decay of short-lived radionuclides. The radioactivity of used nuclear fuel decreases to about one per cent of its initial value after one year, decreases to about 0.1 per cent after 10 years, and decreases to about 0.01 per cent after 100 years. After approximately one million years, the radioactivity in used nuclear fuel approaches that of natural uranium.

Low-level waste mostly comes from power plants, and medical, academic, industrial and other commercial uses of radioactive materials (e.g., mop heads, rags, paper towels). These items do not produce heat and contain radioactive levels that require containment and isolation for up to a few hundred years.

Safety in this document refers to the protection of people and the environment from the harmful or dangerous effects of used nuclear fuel, now and in the future.

Small modular reactors (SMRs) provide an alternative to large-scale nuclear reactors. SMRs can be purchased and constructed in a modular way. The NWMO would be responsible for the long-term management of used nuclear fuel created through new or emerging technology such as SMRs, if it is implemented in Canada.

Used nuclear fuel is the irradiated fuel removed from a commercial or research nuclear fission reactor. Used nuclear fuel is classified as a high-level radioactive waste.

Willingness is fundamental to the siting process. From the very beginning, the NWMO outlined a number of principles regarding willingness. These include a commitment to only site the project in an area with informed and willing hosts, time and resources for communities to learn about the project before making a decision, and a compelling demonstration of community willingness.

Beyond the demonstration from the communities, the NWMO also needs to ensure the other requirements and commitments outlined in the siting process can be met in order to implement the project in an area.