Q. What does “CANDU” mean?
A. CANDU (a registered trademark) stands for "Canada Deuterium Uranium". It is a pressurized-heavy-water, natural-uranium power reactor designed first in the late 1950s by a consortium of Canadian government and private industry. All power reactors in Canada are of the CANDU type (of varying vintage). It is also the power-reactor product marketed by Canada abroad.
Q. What are the distinguishing characteristics of CANDU reactors?
A. The CANDU reactor uses natural uranium fuel and heavy water (D2O) as both moderator and coolant (the moderator and coolant are separate systems). It is refueled at full-power, a capability provided by the subdivision of the core into hundreds of separate pressure tubes.
Q. What is “heavy water”?
A. Heavy water is the common name for D2O, deuterium oxide. It is similar to light water (H2O) in many ways, except that the hydrogen atom in each water molecule is replaced by "heavy" hydrogen, or deuterium. The deuterium makes D2O about 10% heavier than ordinary water.
Q. How does a CANDU reactor refuel on-power?
A. On-power refueling is one of the unique features of the CANDU system. Due to the low excess reactivity of a natural-uranium fuel cycle, the core is designed to be continuously "stoked" with new fuel, rather than completely changed in a batch process (as in LWRs and BWRs).
Q. How do CANDU reactors rank in performance against other designs?
A. CANDU performance ratings (percentage of production against rated capacity) have traditionally led all other designs, primarily due to the on-line refueling capability. Today the average lifetime performance rating of the world-wide CANDU fleet is comparable to its nearest competitors (PWRs and BWRs), and over 10 points higher if one considers only the commercial CANDU 6 units that actually compete against PWRs in the market for new capacity.
Q. Are CANDU reactors sold to other countries?
A Yes. In 2003 AECL completed construction of one of two 728-megawatt CANDU reactors at Qinshan in eastern China. We have also sold CANDU power plants in Romania, Korea and Argentina.
Q. How safe are CANDU reactors?
A. Very safe. All Canadian nuclear reactors are equipped with special safety systems whose sole function are to automatically shut down the reactor in the event of any major equipment malfunction. The design assures safety for three reasons:
- It’s impossible for a CANDU plant to “explode”.
- The safety systems take into account, human error, equipment failure and external risks such as an earthquakes.
- If an accident occurred, CANDU reactors are designed to contain radioactive emissions within reactor buildings.
Q. Why did Canada develop its own reactor design?
A. During World War II Canada participated in an Anglo-Canadian-American project to build an atomic bomb. As the Manhattan Project intensified the American cooperation in this technological alliance decreased greatly, leaving the Canadians and British to follow an almost independent path towards the creation of controlled nuclear power. Due to war-time security risks in Britain, the Anglo-Canadian project was located in Canada, and unlike in the Manhattan Project, was centred around the technology of a heavy-water chain reaction for weapons-plutonium production.
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Q. How much electricity is produced in Canada from CANDU nuclear power?
A. In Ontario nuclear power contributes about 50% of the total electricity supply. The other two provinces with nuclear power, New Brunswick and Québec, receive about 21% and 3%, respectively, of their supply from CANDU nuclear.
Q. Where is nuclear power generated in Canada?
A. There are 17 power reactors, all CANDU designs, currently operating in Canada (plus 5 undergoing refurbishment). Taken together, these 17 reactors supply approximately 16% of Canada's electricity needs. Most reactors are owned by Ontario Power Generation (formerly Ontario Hydro), in the province of Ontario.
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Q. How is nuclear fuel managed?
A. The fuel for CANDU nuclear power reactors is in the form of bundles of tubes containing pellets of uranium oxide. The bundles are inserted and removed from the reactors by remotely operated fuelling machines.
Q. How long does one of these bundles last?
A. Typically a bundle will stay in the reactor for about two years.
Q. Is it still radioactive when the fuel is used up?
A. When the fuel is discharged from the reactor it is highly radioactive and cannot be handled directly.
Q. Is this used fuel (waste) a danger to the public?
A. Like many non-radioactive but toxic materials that require permanent isolation, the potential hazard can be eliminated by careful isolation and management.
Q. How do we manage hazardous radioactive waste materials?
A. Used fuel from nuclear generating stations in Canada is stored on-site and at Atomic Energy of Canada Limited Chalk River Laboratories. The fuel is placed in water filled bays, which cools the fuel and shields from radiation. After several years, the radioactive materials have largely decayed and the heat has diminished. The fuel can then be transferred to dry storage on-site in large concrete cylinders.
Q. Will we run out of space to store all of this radioactive material?
A. There is enough space at each nuclear generating station to store all it’s used fuel for the operating life of the station.
Q. How much space does it take to store this hazardous waste?
A. A 600 MW CANDU nuclear reactor produces only 20 cubic feet of used fuel bundles per year.
Q. What are the alternatives to on-site storage of used fuel?
A. There are a number of alternatives to on-site storage. One, gather all fuel in a central place and store it in concrete canisters. Permanent isolation is another method considered by nations with nuclear power programs. These options include isolation in granite, in salt domes and other solid rock formations underground.
Q. Who is responsible for protecting the public from these storage areas?
A. Concrete storage facilities above ground would have to rely on long-term human supervision. Storage underground would require passive safety precautions.
Q. Who pays for fuel management?
A. The cost of storage of used fuel is included in the total operating costs of a nuclear station and is reflected in the electricity rates we pay.
Q. What is an isolation Vault?
A. AECL has done extensive research on a concept for disposal of used fuel in a vault deep in stable granite rock in the Canadian Shield. A single vault could hold all the used fuel arising from 100 years of operation of all existing Canadian nuclear generating stations.
Q. Where would an isolation vault be located?
A. Many sites in the Canadian Shield would meet the geological requirements by Canadian and international scientist for the safe isolation of high-level nuclear waste. Many of the rock formations have been in place for two billion years.
Q. Is permanent isolation of nuclear waste material safe?
A. A number of uranium ore deposits around the world provide valuable evidence about geological containment. A federal Environmental Assessment Panel reported in 1998 that the safety concept had been adequately demonstrated from a technical perspective but there were questions about public acceptability.
Q. What is the difference between, low-level, intermediate-level and high-level nuclear waste?
A. Low-level waste includes slightly contaminated clothing and items that come from hospital departments of nuclear medicine and research laboratories. Most nuclear waste falls into this category.
Intermediate-level waste is typically items such as ion exchange columns from the system of a nuclear power plant containing a higher level of radioactivity
High-level waste would be spent fuel bundles.
Q. Can these high-level radioactive waste fuel bundles be recycled?
A. The spent fuel has considerable potential energy, which many believe can eventually be reused
Q. Is CANDU nuclear energy a good choice for the environment?
A. To provide Canada with a reliable and continuous supply of electricity only three sources can do the job. These are fossil fuels, hydraulic power and nuclear energy. When all factors are considered, nuclear is the best choice from an environmental point of view.
Q. Does nuclear energy contribute to climate change and global warming?
A. Nuclear power plants emit no noxious gas emissions that contribute to climate change and global warming.
Q. How harmful is radiation?
A. We are all exposed to natural sources of radiation every day in the form of waves. Sunlight, microwaves, radio waves, TV signals. The various uses of nuclear energy contribute only a small addition to that natural radiation.
Q. Is nuclear waste dangerous?
A. The radiation form high-level radioactive waste can be dangerous. That is why it is handled remotely and stored in suitable, monitored facilities.
Q. Are Canadians insured against damage from nuclear plant accidents?
A. Yes. Canada’s nuclear liability act makes provision for compensation for injury or property damage caused as a result of an accident at a nuclear power plant.
Q. How is the Canadian nuclear industry regulated?
A. All nuclear activities in Canada are regulated by the Canadian Nuclear Safety Commission (CNSC)
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Q. What kind of training do our nuclear power plant operators have?
A. Nuclear station control room operators spend approximately eight years in training. They must be authorized by the CNSC. Training and testing is done on simulators that replicate normal and emergency operating procedures.
Q. Does Canada contribute to nuclear weapons proliferation?
A. No. Canada’s nuclear program is dedicated to peaceful purposes only.
Q. Do we sell uranium to other countries?
A. Canada exports uranium and radioisotopes for medical and industrial purposes. These exports are subject to stringent nuclear non-proliferation policies.
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Q. How does the cost of nuclear power compare to other sources in Canada?
A. According to a 1994 report from Ontario Hydro, nuclear power in Ontario has a 35% cost advantage over fossil power.
This cost advantage is still evident: a statement by Ontario Power Generation in January 2002 claimed that electricity from the refurbished Pickering A plant would cost $0.03/kWh, compared with $0.045/kWh for a new gas-fired cogeneration plant .
Q. Why was the cost of Ontario’s Darlington plant so high?
A. About 70% of Darlington's final cost increase was due to schedule delays and financial policy changes. The remainder of the increase is attributable to changes in scope, including that imposed by an evolving regulatory environment over the course of the project.
Q. Who said that nuclear electricity would be “too cheap to meter”?
A. The oft-quoted prediction, "too cheap to meter", was made in 1954 by an American bureaucrat, Lewis Strauss, in a speech that very much reflects the public's post-war euphoria over nuclear technology (and technology in general), galvanized by President Eisenhower's vaunted "Atoms for Peace" program launched in December 1953. Strauss' comments predated the first nuclear power plants by three years, and included other optimistic references to wiping out world hunger and extending human life expectancy.
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Q. Why is food irradiated?
A. Food irradiation is a cold, non-chemical process that can virtually eliminate harmful bacteria such as E coli and Salmonella from meat and poultry.
Q. What does food irradiation do?
A. It extends shelf life by destroying microorganisms that cause spoilage, make food safe to eat by destroying parasites and provide quarantine treatments for fruits and vegetables to ensure insect pests are not transported across borders.
Q. How is food irradiated?
A. The food is passed through a thick walled chamber containing a source of ionizing radiation that passes through the food, destroying insects, bacteria and microorganisms.
Q. How nutritious is irradiated food?
A. The treatment process can be designed and controlled so that benefits can be realized safely without any significant reduction in the nutritional value of food.
Q. Is irradiated food radioactive?
A. No. Just as dental x-rays do not make you radioactive, neither is irradiated food radioactive.
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