High-level radioactive waste

High-level radioactive waste (HLW) is used (irradiated) nuclear fuel whose owners have declared it as radioactive waste and/or which generates significant heat through radioactive decay. HLW typically has levels of activity concentration 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, 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 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 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 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 7 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 Atomic Energy of Canada Limited (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 New Brunswick Power's Point Lepreau Generating Station, as well as prototype reactors that are operated or decommissioned by Canadian Nuclear Laboratories (including those at Chalk River Laboratories (CRL), 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 Ontario Power Generation (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 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 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.

Other high-level radioactive waste

A small amount of non-nuclear-fuel high-level radioactive waste exists in Canada, and all of it is stored at Chalk River Laboratories.  

This waste comes from 2 main sources: the production of medical isotopes and waste generated from early reprocessing experiments conducted from the 1940s to the 1960s.

Early reprocessing experiments

CRL stores liquid from fuel reprocessing (done 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, and no liquids have been added since then.

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.

Transportation of high-level radioactive waste

The CNSC certifies the design of the packages required for the transport of used nuclear fuel and other high-level radioactive waste.

The design of certified transport packages must demonstrate the ability of the packages to retain their contents under accident conditions. 

Canadian regulatory requirements state that all certified transport packages shall undergo stringent testing, including the ability to withstand the cumulative effects of a 9-metre drop onto an unyielding surface, a 30-minute thermal test at 800 °C, and immersion in 15 metres of water for 1 hour without a breach of containment.

High-level radioactive waste has been transported safely nationally and internationally for over 45 years by road, rail, water and air, without a single radiological incident.

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. At this time, the CNSC has not yet received any applications for site preparation and construction of a deep geological repository that will provide long-term management of radioactive waste.

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