Nuclear Energy FAQs
Bruce Power has four reactors in each Bruce A and Bruce B.
Since 2003, all four Bruce A units have been refurbished and returned to service, adding an additional 3,000 megawatts (MW) of low-cost, clean and reliable power to the provincial electricity grid.
Each has a net rated output of 750-840 MW, and when all units are operating, we generate 6,300 MW, or nearly a third of the province’s energy.
A pellet of uranium fuel weighing about seven grams – the weight of two nickels – contains as much energy as three barrels of oil. A single 25 kg CANDU fuel bundle, about the size of a fire log, can supply 100 homes with electricity for a year. The same electricity from a fossil station would require 400 tonnes of coal, or 270,000 litres of oil, or 300 million litres of natural gas.
Electricity generation from nuclear power creates virtually no CO2 or other greenhouse gases, and does not contribute to smog. . By contrast, 400 tonnes of coal would produce about 100 tonnes of ash, 1,000 tonnes of CO2 gas, and five tonnes of acid gas. The 300 million litres of natural gas would produce 600 tonnes of CO2 and two tonnes of acid gas.
Uranium fuel is formed into ceramic pellets then sealed in metal tubes. A fuel bundle is an assembly of 37 fuel elements – which are thin, pencil-like tubes about two feet long – containing 29 uranium dioxide pellets in a metal sheath that is welded together at both ends.
The pencils are assembled into roughly 22-kg fuel bundles. Each reactor has 480 fuel channels that each hold 12 or 13 fuel bundles, placed end to end.
The calandria is the cylindrical reactor vessel that contains the heavy water moderator. It is penetrated from end-to-end by hundreds of calandria tubes, which accommodate the pressure tubes containing the fuel and coolant.
CANDU stands for Canada Deuterium Uranium. Deuterium is another name for heavy water, which occurs naturally in all bodies of water. In Lake Huron, it occurs one part in every 7,000. Once extracted, heavy water is 10 per cent heavier than ordinary water due to an extra neutron in its nucleus giving it added weight.
Developed in Canada, the first CANDU reactor came on line in 1962. There are now 22 CANDU reactors in Canada and 17 abroad.
The CANDU system employs a unique, on-power refueling system for optimum performance. Two identical fueling machines rise from a fueling duct under the reactor and latch onto opposite ends of a designated fuel channel. Each machine is operated remotely from the control room.
With both machines latched on and brought up to system pressure, the ends of the fuel channel are opened and new fuel is exchanged for used fuel – one machine discharging and the other accepting. The on-power refueling system allows Bruce Power the ability to refuel everyday to avoid refueling outages as is with other types of nuclear reactors.
Each bundle stays in the reactor from 12 to 20 months, depending on where it’s located in the core.
Once fuel is removed from a reactor, it is transferred by remote control to a water-filled storage bay. The bay is 27.5 metres deep and is double-walled reinforced concrete.
Used fuel is safely stored and each bundle is accounted for and monitored. Fuel bundles are stored in the cooling bays at each station for at least 10 years.
After that, they are taken out of the bays and transported to a dry fuel storage facility owned and operated by Ontario Power Generation (OPG) on the Bruce Power site.
The used fuel from Bruce Power’s operations is owned by OPG and as part of the lease agreement with OPG, Bruce Power pays a fee to OPG for storage of our used fuel.
Radioactivity of used fuel diminishes rapidly, falling to one per cent of its initial value after one year, 0.1 per cent after 10 years and 0.01 after 100 years.