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Radioactive waste classes

In Canada, the radioactive waste classification system is divided into 4 general classes:

  • low-level radioactive waste
  • intermediate-level radioactive waste
  • high-level radioactive waste
  • uranium mine and mill waste

Waste should be classified according to the degree of containment and isolation that is necessary to ensure safety, with additional consideration given to the hazardous potential of different classes of waste and the time frame associated with the hazard. For a description of each of the classes of radioactive waste, consult CNSC regulatory document REGDOC-2.11.1, Waste Management, Volume I: Management of Radioactive Waste.

Transcript

What is radioactive waste? Radioactive waste is any liquid gas or solid that contains a radioactive nuclear substance and for which there is no foreseeable use. There are four general classes of radioactive waste in Canada. Uranium mine and mill waste, low level radioactive waste, intermediate level radioactive waste and high-level radioactive waste. The first of the four general classes is uranium mine and mill waste. This includes tailings and waste rock generated by the mining and milling of uranium ore. Tailings have the consistency of fine sand, while waste rock is simply gravel and broken up rock. Next, we have low level radioactive waste, which is more radioactive than clearance levels and exemption quantities allow. It requires isolation and containment for up to several hundred years. Nuclear power plants, research reactors, test facilities, radio isotope manufacturers or users, uranium refining and conversion and nuclear fuel fabrication facilities produce low level waste. It can come in various forms, such as used equipment, paper, cable, clothing, decommissioned parts and even mops. Thirdly, we have intermediate level radioactive waste, which contains concentrations of long-lived radionuclides elements that emit radiation. It requires isolation and containment for longer than several hundred years. Nuclear power plants, prototype and research reactors, test facilities and radio isotope manufacturers and users produce intermediate level waste. It could come in the form of refurbishment waste such as old components, ion exchange resins and some radioactive sources used in radiation therapy. Lastly, we have high level radioactive waste, which is primarily used nuclear fuel along with small amounts of waste that generate significant heat and radioactivity. It requires long term isolation. Nuclear power plants prototype in research reactors and test facilities produce high level waste. It comes in the form of used nuclear fuel that is still significantly radioactive.

The Canadian Nuclear Safety Commission regulates all classes and forms of radioactive waste in Canada to protect the health and safety of people and the environment. You can find more info at Nuclearsafety.gc.ca

Low-level radioactive waste

In Canada, low- and intermediate-level radioactive waste refers to all forms of radioactive waste, except used nuclear fuel, limited waste from the production of medical isotopes, and the waste from uranium mining and milling.

Low-level radioactive waste (LLW) contains material with radionuclide content above the established unconditional clearance levels and exemption quantities (set out in the Nuclear Substances and Radiation Devices Regulations), but generally has limited amounts of long-lived radionuclides. LLW requires isolation and containment for periods of up to a few hundred years and is suitable for disposal in near-surface facilities.

LLW includes the following subclasses:

  • Very low-level radioactive waste (VLLW) has a low hazard potential and exceeds the criteria for unconditional clearance levels and exemption quantities. Long-term waste management facilities for VLLW do not need a high degree of containment or isolation. Concentrations of longer-lived radionuclides in VLLW are generally very limited.
  • Very short-lived low-level radioactive waste (VSLLW) is waste that can be stored for a decay period of not more than a few years and that can subsequently be cleared for release. VSLLW includes radioactive waste containing only short half-life radionuclides typically used for research and biomedical purposes. The main criterion for VSLLW is the half-life of the predominant nuclides. In general, the storage for decay option for managing VSLLW should only be chosen when the radionuclides have a half-life on 100 days or less.

LLW includes contaminated equipment from the operation of nuclear power plants (for example, protective shoe covers, clothing, rags, mops, equipment and tools).

The owners of LLW are responsible for managing the waste they produce. This usually takes place onsite, within a facility specifically for the LLW.

LLW that requires long-term management may be returned to the manufacturer or transferred to an authorized waste management operator – such as the waste management facility operated by Canadian Nuclear Laboratories (CNL) at its Chalk River Laboratories site – on a fee-for-service basis.

Intermediate-level radioactive waste

Intermediate-level radioactive waste (ILW) generally contains long-lived radionuclides in concentrations that require isolation and containment for periods greater than several hundred years. ILW needs no provision, or only limited provision, for heat dissipation during its storage and disposal. Owing to its long-lived radionuclides, ILW generally requires a higher level of containment and isolation than can be provided in near-surface repositories.

ILW includes refurbishment waste, ion-exchange resins, and some radioactive sources used in radiation therapy.

The owners of ILW are responsible for managing the waste they produce. This usually takes place onsite, within a facility specifically for the ILW.

ILW that requires long-term management may also be returned to the manufacturer or transferred to an authorized waste management operator – such as the waste management facility operated by CNL at its Chalk River Laboratories site – on a fee-for-service basis.

Main sources of low- and intermediate-level radioactive waste

Since 2019, Atomic Energy of Canada Limited (AECL) and Ontario Power Generation (OPG), which, combined, own 20 of Canada’s 22 nuclear power reactors, are responsible for approximately 90% and 99%, respectively, of the annual accumulated volume of low- and intermediate-level radioactive waste (L&ILW). AECL’s accumulation rate represents the waste generated from research and development activities at CNL’s Chalk River Laboratories (including from decommissioning and environmental remediation), and the long-term management of L&ILW from a number of smaller producers and users of radioactive material (e.g., hospitals and universities). OPG’s accumulation rate stems from nuclear power production in Ontario. The other 2 nuclear power reactors, owned by New Brunswick Power (NB Power) and Hydro-Québec (HQ), and Cameco’s uranium processing and conversion facilities in Ontario generate the majority of the remaining waste. The owners of L&ILW are licensed by the CNSC to manage and operate interim storage facilities for their radioactive waste.

Long-term management of low- and intermediate-level radioactive waste

The CNSC requires facility operators to ensure that they have sufficient funds to cover the costs associated with the long-term management of low- and intermediate-level waste.

Canada’s largest radioactive waste owners – AECL, OPG, HQ and NB Power – and other selected stakeholders continue to meet under the sponsorship of the CANDU Owners Group Radioactive Waste Leadership Forum to discuss opportunities for coordination and collaboration on long-term management matters, including relevant technologies and communication strategies.

High-level radioactive waste

High-level radioactive waste (HLW) refers to used (irradiated) nuclear fuel whose owners have declared it as radioactive waste and/or which generates significant heat through radioactive decay. HLW typically has activity concentration levels in the range of 104 to 106 TBq/m3. HLW is associated with penetrating radiation, which means that shielding is required. HLW also contains significant quantities of long-lived radionuclides, which necessitates long-term isolation.

Used nuclear fuel from nuclear power plants and prototype and research reactors

Canada's inventory of used nuclear fuel comes mostly from the operation of nuclear power plants. The remainder of the used nuclear fuel – which accounts for approximately 2% of the total inventory – comes from prototype reactors (used to test full-power reactor designs) and research reactors.

Since the 1960s, Canada's nuclear power reactors have used over 2.5 million fuel bundles. If these bundles were packed end to end, they would fit into a space the size of 7 hockey rinks, stacked to the top of the boards.

Used nuclear fuel from the operation of nuclear power plants is kept in onsite interim storage facilities. The storage consists of 2 phases: wet storage and dry storage.

Wet storage

After being removed from the reactors, used nuclear fuel bundles are stored for 6 to 10 years in storage bays (pools of water), which provide cooling and shielding against radiation.

The pools for the used nuclear fuel are constructed both above- and in-ground and are seismically qualified (which means they are built to meet seismic standards for withstanding earthquakes). The pools are located in buildings that are separated from the reactor buildings.

The walls and floors of the pools are about 2 metres thick and are made of concrete reinforced with carbon steel.

Robust, heat-resistant and water-tight liners are installed in the pools to prevent water from leaking through possible defects in the concrete.

CNSC-certified inspectors regularly inspect the pools.

Since the March 2011 accident in Fukushima, Japan, all nuclear power plant operators in Canada have acquired additional transportable equipment (such as portable generators and pumps) to ensure that pools can be filled with water regardless of an accident's severity.

Did you know?

Each year, 4,500 to 5,400 fuel bundles per power reactor are added to the pools (based on 80% to 95% of full-power reactor operation).

Dry storage

After 6 to 10 years in wet storage, the used nuclear fuel can be safely transferred to dry storage.

There are 3 main types of dry storage units used in Canada:

  • concrete canisters
  • Modular Air-Cooled STORage (MACSTOR) units
  • dry storage containers

Concrete canisters, or silos, were developed in the 1970s by AECL at Whiteshell Laboratories in Manitoba to demonstrate that dry storage for used reactor fuel was a feasible alternative to underwater storage.

Silos are now used to store the used fuel from NB Power's Point Lepreau Generating Station and from prototype reactors that are operated or decommissioned by CNL (including those at Chalk River Laboratories, Whiteshell Laboratories, Gentilly-1 and Douglas Point). Each silo can hold between 325 and 600 bundles and is built on reinforced concrete foundations.

The MACSTOR units, also developed by AECL, are similar to silos but much larger. Each MACSTOR unit can store 12,000 bundles of used fuel.

MACSTOR units are currently installed at the Gentilly-2 Facilities. These facilities are currently in a safe shutdown state and have been granted a decommissioning licence.

Dry storage containers were developed by OPG and are made of reinforced concrete encased in interior and exterior shells made of carbon steel.

The containers are transportable and are filled with helium (an inert gas), which protects the fuel bundles from potential oxidation.

Each dry storage container unit is designed to hold 384 fuel bundles and weighs approximately 60 tonnes when empty and 70 tonnes when loaded.

The dry storage containers are currently used to store the used nuclear fuel from the Pickering, Darlington, and Bruce A and B nuclear power plants.

Operating experience and rigorous inspections carried out over the last 35 years have demonstrated that the different types of dry storage units used in Canada can all effectively contain radiation.

All transfers of used nuclear fuel from wet storage to dry storage are conducted under the surveillance of the International Atomic Energy Agency.

Used nuclear fuel from research reactors is either repatriated to the fuel’s country of origin or safely managed through interim storage in Canada.

Early reprocessing experiments

Chalk River Laboratories stores liquid from fuel reprocessing carried out between 1949 and 1956. The waste is stored in 3 tanks. The last transfer of radioactive liquid solutions to any of these storage tanks occurred in 1968.

Between 1958 and 1960, AECL conducted some experiments to convert high-level radioactive liquid solutions into a solid (glass). The program generated 50 glass blocks, each weighing about 2 kilograms, which are now safely stored onsite.

Long-term management of used nuclear fuel

The Nuclear Waste Management Organization (NWMO) is responsible for the long-term management of Canada's used nuclear fuel.

In May 2010, the NWMO launched its site selection process for a willing and informed community to host a deep geological repository for the long-term management of Canada's used nuclear fuel.

As Canada's nuclear regulator, the CNSC is responsible for licensing geological repositories intended to provide long-term management of radioactive waste. The CNSC has not yet received any applications for the site preparation and construction of a deep geological repository that will provide long-term management of radioactive waste.

Uranium mine and mill waste

Learn more about radioactive waste from uranium mines and mills and how it is stored and disposed.

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