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86-489: Douglas Point was built and owned by Atomic Energy of Canada Limited (AECL) but operated by Ontario Hydro . It was in service from 26 September 1968 to 5 May 1984. The plant served as a teaching tool for the emerging Canadian nuclear industry, and the experience gained was applied to the later CANDU power plants. The first CANDU was a demonstration unit, the Nuclear Power Demonstrator (NPD). In 1958, before NPD

172-478: A Bailey bridge at tree-top level providing a view of the site. The site was cleared and excavated by 500 workers, including Hydro construction crews from Toronto and locally and provincially hired labour. Contractors included 600 Canadian, plus British and American, firms. Canadian manufacturers supplied 71% of the plant's components, with the remainder coming from British and American manufacturers. The relatively high share of domestic companies and resources used in

258-419: A critical state in which there is no increase or decrease in power, temperature, or neutron population. A numerical measure of a critical mass depends on the effective neutron multiplication factor k , the average number of neutrons released per fission event that go on to cause another fission event rather than being absorbed or leaving the material. A subcritical mass is a mass that does not have

344-425: A 5 centimetres (2.0 in) reflector, the critical mass of 19.75%-enriched uranium drops to 403 kilograms (888 lb), and with a 15 centimetres (5.9 in) reflector it drops to 144 kilograms (317 lb), for example. The critical mass is inversely proportional to the square of the density. If the density is 1% more and the mass 2% less, then the volume is 3% less and the diameter 1% less. The probability for

430-504: A 54% capacity factor . The plant made its first on-power fuelling (i.e. refuelling the reactor without having to shut down) on 1 March 1970. This CANDU feature was first demonstrated by NPD on 23 November 1963. While light water reactors are usually not capable of this feat, heavy water reactors like the CANDU and the related IPHWR as well as some graphite moderated reactors like the Magnox ,

516-430: A 6.1 metres (20 ft) diameter. The design was compact to reduce the required amount of heavy water moderator; the reactor required several tons of heavy water, which was very expensive at $ 26 per pound (roughly 5 cents per gram). The added cost of using heavy water was at least partially offset by the ability to use natural uranium and forego uranium enrichment - a technology which Canada did not have access to when

602-408: A fission event come immediately from that event, but a fraction of them come later, when the fission products decay, which may be on the average from microseconds to minutes later. This is fortunate for atomic power generation, for without this delay "going critical" would be an immediately catastrophic event, as it is in a nuclear bomb where upwards of 80 generations of chain reaction occur in less than

688-517: A fuel in CANDU reactors. Currently, AECL is developing the Advanced CANDU Reactor , or "ACR". This design is meant to improve the commercial CANDU 6 design in terms of capital cost and construction schedule, while maintaining the classic design and safety characteristics of the CANDU concept. Cernavoda Nuclear Power Plant Unit 2 began operation on May 6, 2007 . Preparatory work required for

774-434: A functional device from less material than more primitive weapons programs require. Aside from the math, there is a simple physical analog that helps explain this result. Consider diesel fumes belched from an exhaust pipe. Initially the fumes appear black, then gradually you are able to see through them without any trouble. This is not because the total scattering cross section of all the soot particles has changed, but because

860-511: A heavy water leak (May 14, 2009). The production from the NRU reactor represented a significant fraction of the worlds medical isotope supply and the disruptions caused a worldwide shortage. Due to maintenance requirements from the aging NRU reactor and the failure of the MAPLE 1 & 2 reactor projects, the long term production of medical isotopes at Chalk River became uncertain. The NRU reactor at Chalk River

946-431: A material is said to have a negative temperature coefficient of reactivity to indicate that its reactivity decreases when its temperature increases. Using such a material as fuel means fission decreases as the fuel temperature increases. Surrounding a spherical critical mass with a neutron reflector further reduces the mass needed for criticality. A common material for a neutron reflector is beryllium metal. This reduces

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1032-400: A microsecond, far too fast for a human, or even a machine, to react. Physicists recognize two points in the gradual increase of neutron flux which are significant: critical, where the chain reaction becomes self-sustaining thanks to the contributions of both kinds of neutron generation, and prompt critical , where the immediate "prompt" neutrons alone will sustain the reaction without need for

1118-514: A neutron per cm travelled to hit a nucleus is proportional to the density. It follows that 1% greater density means that the distance travelled before leaving the system is 1% less. This is something that must be taken into consideration when attempting more precise estimates of critical masses of plutonium isotopes than the approximate values given above, because plutonium metal has a large number of different crystal phases which can have widely varying densities. Note that not all neutrons contribute to

1204-567: A nuclear bomb made from plutonium manufactured by the CIRUS research reactor built by AECL in 1956, which was a commercial version of its NRX research reactor. In addition AECL built two power reactors in India based on the Douglas Point design, and many of India's other reactors are domestic variants of this design. The connection between India's nuclear weapons program and its CIRUS research reactor led to

1290-471: A precise value for critical masses, including (1) detailed knowledge of fission cross sections, (2) calculation of geometric effects. This latter problem provided significant motivation for the development of the Monte Carlo method in computational physics by Nicholas Metropolis and Stanislaw Ulam . In fact, even for a homogeneous solid sphere, the exact calculation is by no means trivial. Finally, note that

1376-415: A reactor), the neutrons reflected by a tamper are slowed by their collisions with the tamper nuclei, and because it takes time for the reflected neutrons to return to the fissile core, they take rather longer to be absorbed by a fissile nucleus. But they do contribute to the reaction, and can decrease the critical mass by a factor of four. Also, if the tamper is (e.g. depleted) uranium, it can fission due to

1462-514: A severance of nuclear technological cooperation between Canada and India. In 1977–1978 the Bruce A group went online and began commercial operation. Each Bruce unit produces about 800 MWe of power. In 1978, Whiteshell Labs began research into fuel waste disposal. Between 1983 and 1986, the Pickering B group went online and also in 1983 the single CANDU reactor at Point Lepreau began operation, as did

1548-584: A spherical critical mass of pure uranium-235 ( U) with a mass of about 52 kilograms (115 lb) would experience around 15 spontaneous fission events per second. The probability that one such event will cause a chain reaction depends on how much the mass exceeds the critical mass. If there is uranium-238 ( U) present, the rate of spontaneous fission will be much higher. Fission can also be initiated by neutrons produced by cosmic rays . The mass where criticality occurs may be changed by modifying certain attributes such as fuel, shape, temperature, density and

1634-417: A strong propensity toward spontaneous fission. Because of this, a reasonably sized gun-type weapon would suffer nuclear reaction ( predetonation ) before the masses of plutonium would be in a position for a full-fledged explosion to occur. Instead, the plutonium is present as a subcritical sphere (or other shape), which may or may not be hollow. Detonation is produced by exploding a shaped charge surrounding

1720-404: A sustained nuclear chain reaction . The critical mass of a fissionable material depends upon its nuclear properties (specifically, its nuclear fission cross-section ), density, shape, enrichment , purity, temperature, and surroundings. The concept is important in nuclear weapon design . When a nuclear chain reaction in a mass of fissile material is self-sustaining, the mass is said to be in

1806-407: A typical neutron "seeing" an amount of nuclei around it such that the areal density of nuclei exceeds a certain threshold. This is applied in implosion-type nuclear weapons where a spherical mass of fissile material that is substantially less than a critical mass is made supercritical by very rapidly increasing ρ (and thus Σ as well) (see below). Indeed, sophisticated nuclear weapons programs can make

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1892-582: Is a Canadian Crown corporation and the largest nuclear science and technology laboratory in Canada. AECL developed the CANDU reactor technology starting in the 1950s, and in October 2011 licensed this technology to Candu Energy . AECL describes its goal as ensuring that "Canadians and the world receive energy, environmental and economic benefits from nuclear science and technology – with confidence that nuclear safety and security are assured". Until October 2011, AECL

1978-428: Is a mass which, once fission has started, will proceed at an increasing rate. In this case, known as supercriticality , k > 1 . The constant of proportionality increases as k increases. The material may settle into equilibrium ( i.e. become critical again) at an elevated temperature/power level or destroy itself. Due to spontaneous fission a supercritical mass will undergo a chain reaction. For example,

2064-566: Is already part of Team CANDU, a group of five companies that manufacture and refurbish the CANDU reactors. The government will continue to own the Chalk River Laboratories (produces isotopes for medical imaging). The transaction puts 800 jobs at risk while improving job security for 1,200 employees. Due to safety concerns many countries are considering thorium nuclear reactors which AECL's CANDU reactors easily convert into (from uranium fuelled). Higher energy yields using thorium as

2150-459: Is always less reactive than cold fuel (over/under moderation in LWR is a different topic). Thermal expansion associated with temperature increase also contributes a negative coefficient of reactivity since fuel atoms are moving farther apart. A mass that is exactly critical at room temperature would be sub-critical in an environment anywhere above room temperature due to thermal expansion alone. The higher

2236-454: Is co-located with the newer Bruce Nuclear Generating Station . Bruce Power now leases the site and the newer plant from Ontario Hydro's successor company, Ontario Power Generation , although the Douglas Point structure and equipment remain owned by AECL. Bothwell R. Nucleus: The History of Atomic Energy of Canada Limited. University of Toronto Press, 1988 Atomic Energy of Canada Limited Atomic Energy of Canada Limited ( AECL )

2322-481: Is critical to nuclear weapons design, but some documents have been declassified. The critical mass for lower-grade uranium depends strongly on the grade: with 45% U, the bare-sphere critical mass is around 185 kilograms (408 lb); with 19.75% U it is over 780 kilograms (1,720 lb); and with 15% U, it is well over 1,350 kilograms (2,980 lb). In all of these cases, the use of a neutron reflector like beryllium can substantially drop this amount, however: with

2408-473: Is left over. As the lower burnup requires more frequent refueling, the CANDU was designed to be capable of online refueling , a feature successfully demonstrated at Douglas Point (see below) and still a distinguishing factor of the CANDU design. Sites along Lake Huron on the shoreline north of Manitoulin Island and along the shoreline from Tobermory to Goderich were considered. Low-lying Douglas Point, within

2494-448: Is only achieved once the thickness of this slab exceeds a critical value. Until detonation is desired, a nuclear weapon must be kept subcritical. In the case of a uranium gun-type bomb, this can be achieved by keeping the fuel in a number of separate pieces, each below the critical size either because they are too small or unfavorably shaped. To produce detonation, the pieces of uranium are brought together rapidly. In Little Boy , this

2580-399: Is proportional to the square root of the number of steps: Note again, however, that this is only a rough estimate. In terms of the total mass M , the nuclear mass m , the density ρ, and a fudge factor f which takes into account geometrical and other effects, criticality corresponds to which clearly recovers the aforementioned result that critical mass depends inversely on the square of

2666-514: Is the world's largest supplier of molybdenum -99 for diagnostic tests, and cobalt-60 for cancer therapy. AECL is funded through a combination of federal government appropriations and commercial revenue. In 2009, AECL received CA$ 651 (equivalent to $ 893.99 in 2023)   million in federal support. In October 2011 the federal government of Canada sold the commercial CANDU design and marketing business of AECL to Candu Energy for CA$ 15   million (including 15 years worth of royalties,

Douglas Point Nuclear Generating Station - Misplaced Pages Continue

2752-548: The AGR and the RBMK have this capability as part of their design specs to allow efficient operation at lower burnup with natural uranium or low enriched uranium fuel. Douglas Point suffered from early unreliability and heavy water leakage. The system was delicate and shut down frequently and easily; the plant was offline for more than half the time between 1968 and 1971. Repairs were expensive and time-consuming, and were made more difficult by

2838-628: The Gentilly 2 CANDU reactor. Between 1984 and 1987 the Bruce B group began commercial operation, and also in 1987 the CANDU design was ranked one of Canada's top-10 engineering achievements. Douglas Point was decommissioned in May, 1984. Between 1985 and 1987, a series of design flaws in AECL's Therac-25 medical accelerator caused massive overdoses of radiation on 6 different occasions, resulting in five deaths. In 1987

2924-756: The Hydro-Electric Power Commission of Ontario to build Canada's first nuclear power plant at Rolphton, Ontario, which is 30 kilometres (19 mi) upstream from Chalk River. On June 4, 1962, the NPD ( Nuclear Power Demonstration ) first reactor went critical to demonstrate the CANDU concept, generating about 20 MWe. In 1963, AECL established the Whiteshell Nuclear Research Establishment (now Whiteshell Laboratories ) in Pinawa , Manitoba , where an organically moderated and cooled reactor

3010-463: The NRX reactor at AECL's Chalk River Laboratories, when a combination of human and mechanical error led to a temporary loss of control over the reactor's power level. Undercooling of the fuel channels led to a partial meltdown . This caused a hydrogen-oxygen explosion inside the calandria . Several fuel bundles experienced melting and ruptured, rendering much of the core interior unusable. The reactor building

3096-538: The National Research Council of Canada to develop a design for a nuclear reactor. Canadian firms had American contracts from the Manhattan Project ; with Eldorado Gold Mines for mining and processing uranium ore and with by Consolidated Mining and Smelting (CMS) for a heavy water plant at Trail, British Columbia . In 1944, approval was given by the federal government to begin with construction of

3182-405: The CANDU design was developed. While the natural uranium fuel allows for lower burnup than enriched fuel as used in light water reactors, overall more thermal power is extracted from the same amount of uranium ore in a heavy water reactor than in a comparable light water reactor. However, a higher amount of spent nuclear fuel is produced. Foregoing enrichment also means that no depleted uranium

3268-514: The NRU ( National Research Universal Reactor ) first went critical. This was a natural-uranium fuelled, heavy-water moderated and cooled research reactor (converted to high-enriched-uranium fuel in the 1960s, and finally to low-enriched-uranium fuel in the 1990s). The NRU is a world-renowned research facility, producing about 60% of the world's supply of molybdenum-99, the principle isotope used for nuclear medical diagnosis. Canada also pioneered use of cobalt-60 for medical diagnosis in 1951 and currently

3354-472: The NRU reactor produces the medical-use cobalt-60, while selected CANDU reactors produce industrial-use cobalt-60, comprising 85% of the world's supply. NRU was primarily a Canadian design, and a significant improvement on NRX. Other than radioisotope production, the NRU provides irradiation services for nuclear materials and fuels testing, as well as producing neutron beams for the National Research Council's Canadian Neutron Beam Laboratory. On May 24, 1958,

3440-423: The NRU suffered a major accident. A damaged uranium fuel rod caught fire and was torn in two as it was being removed from the core, due to inadequate cooling. The fire was extinguished, but not before releasing a sizeable quantity of radioactive combustion products that contaminated the interior of the reactor building and, to a lesser degree, an area of the surrounding laboratory site. Over 600 people were employed in

3526-518: The United States". ZEEP put Canada at the forefront of nuclear research in the world and was the instigator behind eventual development of the CANDU reactors, ZEEP having operated as a research reactor until the early 1970s. In 1946 the Montreal research laboratory was closed and research was consolidated at Chalk River Laboratories. On July 22, 1947, the NRX (National Research Experimental) reactor,

Douglas Point Nuclear Generating Station - Misplaced Pages Continue

3612-687: The ZEEP (Zero Energy Experimental Pile) reactor at the Chalk River Nuclear Laboratories near Chalk River, Ontario , located on the Ottawa River approximately 190 km northwest of Ottawa . AECL was also involved in the development of associated technology such as the UTEC computer. On September 5, 1945, the ZEEP reactor first went critical, achieving the first "self-sustained nuclear reaction outside

3698-466: The ability to sustain a fission chain reaction. A population of neutrons introduced to a subcritical assembly will exponentially decrease. In this case, known as subcriticality , k < 1 . A critical mass is a mass of fissile material that self-sustains a fission chain reaction. In this case, known as criticality , k = 1 . A steady rate of spontaneous fission causes a proportionally steady level of neutron activity. A supercritical mass

3784-437: The assembly back to subcriticality once again. A mass may be exactly critical without being a perfect homogeneous sphere. More closely refining the shape toward a perfect sphere will make the mass supercritical. Conversely changing the shape to a less perfect sphere will decrease its reactivity and make it subcritical. A mass may be exactly critical at a particular temperature. Fission and absorption cross-sections increase as

3870-402: The assembly subcritical again). Similarly, if the perfect quantity of fuel were added to a slightly subcritical mass, to create a barely supercritical mass, the temperature of the assembly would increase to an initial maximum (for example: 1  K above the ambient temperature) and then decrease back to the ambient temperature after a period of time, because fuel consumed during fission brings

3956-594: The calculation can also be performed by assuming a continuum approximation for the neutron transport. This reduces it to a diffusion problem. However, as the typical linear dimensions are not significantly larger than the mean free path, such an approximation is only marginally applicable. Finally, note that for some idealized geometries, the critical mass might formally be infinite, and other parameters are used to describe criticality. For example, consider an infinite sheet of fissionable material. For any finite thickness, this corresponds to an infinite mass. However, criticality

4042-426: The chain reaction. Some escape and others undergo radiative capture . Let q denote the probability that a given neutron induces fission in a nucleus. Consider only prompt neutrons , and let ν denote the number of prompt neutrons generated in a nuclear fission. For example, ν ≈ 2.5 for uranium-235. Then, criticality occurs when ν·q = 1 . The dependence of this upon geometry, mass, and density appears through

4128-442: The clean-up. [2] [3] No immediate injuries resulted from AECL's two accidents, but there were over-exposures to radiation. In the case of the NRU cleanup, this resulted in at least one documented case of latent, life-changing injury, as well as allegations that radiation monitoring and protection were inadequate (meaning that additional latent injuries would have gone unrecognized or unacknowledged). In 1954 AECL partnered with

4214-414: The compact design that placed critical components in inaccessible locations. These engineering problems, including the vulnerability of the design to leaks in the primary coolant circuits, are seen and discussed in an official 1968 documentary on the reactor. Repairs were done by remote control or large teams; the latter was done to reduce the time an individual employee was exposed to radiation . Following

4300-411: The completion of Units 3 and 4 is scheduled to begin by the end of 2007. Company president Robert Van Adel announced that he would be stepping down from the position of president and retired from the company effective November 11, 2007. Energy Alberta Corporation announced August 27, 2007, that they had filed application for a license to build a new nuclear plant at Lac Cardinal (30 km west of

4386-493: The construction of this reactor continues to be a feature of CANDU reactors which can now claim a 90+% Canadian supply chain from uranium mine to replacement parts to intermediate storage of spent fuel. This high degree of autarky was a design consideration in the development of the CANDU and led to choices like the Calandria instead of "regular" reactor pressure vessels which were beyond the capabilities of Canadian heavy industry at

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4472-400: The density, the lower the critical mass. The density of a material at a constant temperature can be changed by varying the pressure or tension or by changing crystal structure (see allotropes of plutonium ). An ideal mass will become subcritical if allowed to expand or conversely the same mass will become supercritical if compressed. Changing the temperature may also change the density; however,

4558-446: The density. Alternatively, one may restate this more succinctly in terms of the areal density of mass, Σ: where the factor f has been rewritten as f' to account for the fact that the two values may differ depending upon geometrical effects and how one defines Σ. For example, for a bare solid sphere of Pu criticality is at 320 kg/m , regardless of density, and for U at 550 kg/m . In any case, criticality then depends upon

4644-585: The design was flawed. Unit 1 of the Cernavodă Nuclear Power Plant was commissioned on December 2, 1996. Rated at 706 MWe, it currently supplies approximately 10% of Romania's electrical needs. Unit Two achieved criticality on 6 May 2007 and was connected to the national grid on 7 August. It began operating at full capacity on 12 September 2007, also producing 706 MW. In the late 1990s, several reactors were built by AECL in South Korea . Wolsong 2

4730-427: The effect on critical mass is then complicated by temperature effects (see "Changing the temperature") and by whether the material expands or contracts with increased temperature. Assuming the material expands with temperature (enriched uranium-235 at room temperature for example), at an exactly critical state, it will become subcritical if warmed to lower density or become supercritical if cooled to higher density. Such

4816-416: The factor q . Given a total interaction cross section σ (typically measured in barns ), the mean free path of a prompt neutron is ℓ − 1 = n σ {\displaystyle \ell ^{-1}=n\sigma } where n is the nuclear number density. Most interactions are scattering events, so that a given neutron obeys a random walk until it either escapes from

4902-597: The fuel (1 tonne (0.98 long tons; 1.1 short tons) of thorium produces the same amount of energy as 200 tonnes (200 long tons; 220 short tons) tons of uranium) also makes it more attractive. OMERS has also shown interest in the company. AECL traces its heritage to the Second World War when a joint Canadian- British nuclear research laboratory, the Montreal Laboratory , was established in Montreal in 1942, under

4988-549: The government could get back as much as CA$ 285   million). The sale entered the exclusive negotiation stage in February, a month after the other bidder, Bruce Power pulled out). Poor sales and cost overruns ( CA$ 1.2   billion in the last five years) were reasons for the divestment though SNC-Lavalin expects to reverse that trend by focusing on new generation reactors . SNC-Lavalin Nuclear Inc, SNC's nuclear subsidiary

5074-471: The high energy neutrons generated by the primary explosion. This can greatly increase yield, especially if even more neutrons are generated by fusing hydrogen isotopes, in a so-called boosted configuration . The critical size is the minimum size of a nuclear reactor core or nuclear weapon that can be made for a specific geometrical arrangement and material composition. The critical size must at least include enough fissionable material to reach critical mass. If

5160-449: The installation of a neutron-reflective substance. These attributes have complex interactions and interdependencies. These examples only outline the simplest ideal cases: It is possible for a fuel assembly to be critical at near zero power. If the perfect quantity of fuel were added to a slightly subcritical mass to create an "exactly critical mass", fission would be self-sustaining for only one neutron generation (fuel consumption then makes

5246-551: The latter area, was chosen by the end of June 1959; its solid limestone base made it ideal. The Hydro Electric Power Commission acquired a 9.31 square kilometres (2,301 acres) area at the site for $ 50 to $ 70 an acre, the going price of farm land at the time (1.2 to 1.7 cents per square meter). Gordon Churchill , the Minister of Trade and Commerce, officially announced the decision to build the plant at Douglas Point on 18 June 1959. In 1961, Douglas Point set up an information office and

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5332-478: The machine was found defective by the Food and Drug Administration (FDA) and eventually recalled by AECL despite their multiple denials that the problems existed. Between 1990 and 1993, the 4 CANDU reactors at Darlington went online and represent the most recent reactor construction in Canada. In 1991, AECL decided to spin off its medical isotope production business under the name Nordion International Inc. The unit

5418-408: The medium or causes a fission reaction. So long as other loss mechanisms are not significant, then, the radius of a spherical critical mass is rather roughly given by the product of the mean free path ℓ {\displaystyle \ell } and the square root of one plus the number of scattering events per fission event (call this s ), since the net distance travelled in a random walk

5504-428: The most powerful reactor in the world at the time, went critical and was "used successfully for producing radioisotopes, undertaking fuels and materials development work for CANDU reactors, and providing neutrons for physics experiments". In 1952 AECL was formed by the government with a mandate to develop peaceful uses of nuclear energy. On December 12, 1952, one of the world's first major reactor accidents occurred in

5590-435: The number of neutrons which escape the fissile material, resulting in increased reactivity. In a bomb, a dense shell of material surrounding the fissile core will contain, via inertia, the expanding fissioning material, which increases the efficiency. This is known as a tamper . A tamper also tends to act as a neutron reflector. Because a bomb relies on fast neutrons (not ones moderated by reflection with light elements, as in

5676-575: The reactor debris. [1] The NRX was repaired, upgraded, and returned to service 14 months later and operated for another 40 years, finally being shut down in 1992. Throughout the 1950s the NRX was used by many researchers in the pioneering fields of neutron condensed matter physics, including Dr. Bertram Brockhouse , who shared the 1994 Nobel Prize in Physics for his work in developing the neutron scattering techniques. The NRU opened in 1957. On November 3, 1957

5762-455: The reactor design division, AECL will consist of the current Nuclear Laboratories division, including the Chalk River laboratory (produces isotopes for medical imaging), and will continue to be a Crown Corporation on paper but will privatise the operation of its facilities. Critical mass In nuclear engineering , a critical mass is the smallest amount of fissile material needed for

5848-421: The reactors. In June 2009 the province announced that only AECL's ACR-1000 submission met all the proposal requirements. The Ontario government has since suspended the acquisition process citing the cost and uncertainty surrounding the companies future ownership (discussed below). Medical isotope production using the 1957-built NRU reactor experienced two forced outages due to safety concerns (December 2007) and

5934-443: The relative neutron velocity decreases. As fuel temperature increases, neutrons of a given energy appear faster and thus fission/absorption is less likely. This is not unrelated to Doppler broadening of the U resonances but is common to all fuels/absorbers/configurations. Neglecting the very important resonances, the total neutron cross-section of every material exhibits an inverse relationship with relative neutron velocity. Hot fuel

6020-418: The size of the reactor core is less than a certain minimum, too many fission neutrons escape through its surface and the chain reaction is not sustained. The shape with minimal critical mass and the smallest physical dimensions is a sphere. Bare-sphere critical masses at normal density of some actinides are listed in the following table. Most information on bare sphere masses is considered classified, since it

6106-402: The soot has dispersed. If we consider a transparent cube of length L on a side, filled with soot, then the optical depth of this medium is inversely proportional to the square of L , and therefore proportional to the areal density of soot particles: we can make it easier to see through the imaginary cube just by making the cube larger. Several uncertainties contribute to the determination of

6192-406: The sphere, increasing the density (and collapsing the cavity, if present) to produce a prompt critical configuration. This is known as an implosion type weapon . The event of fission must release, on the average, more than one free neutron of the desired energy level in order to sustain a chain reaction, and each must find other nuclei and cause them to fission. Most of the neutrons released from

6278-628: The successful deployment of four larger 542 MWe reactors at the Pickering Nuclear Generating Station , the 220 MWe reactor was judged as inadequate. Plans to add another 220 MWe unit to Douglas Point were cancelled. Douglas Point was shut down on 5 May 1984, having achieved a capacity factor of 75% in 1982, and 82% just before retirement. Douglas Point was not wholly satisfactory as an operational power plant and, being too expensive to up-scale, Ontario Hydro refused to purchase it from AECL. AECL subsequently withdrew funding. The plant

6364-469: The time. The calandria was manufactured by the Dominion Bridge Company of Montreal . It was shipped by barge from Lachine, Quebec to Kincardine, Ontario ; from there it was moved 16 kilometres (10 mi) north by flatbed truck to the construction site. In May 1964, work began on transmission lines linking Douglas Point to the provincial power grid near Hanover . All the major equipment

6450-701: The town of Peace River . The application would see an initial twin AECL Advanced CANDU Reactor (ACR) plant go online in 2017, producing 2.2 gigawatt (electric). Point Lepreau, New Brunswick CANDU 6 plant refurbishment to begin as of April 1, 2008. In June 2008, the Province of Ontario has announced plans to build two additional commercial reactors for electricity generation at a site next to Ontario Power Generation 's Darlington Nuclear Generating Station Two companies, AREVA and Westinghouse Electric Company along with AECL submitted proposals to build

6536-411: The way for upscaling to commercial power CANDU reactors in subsequent years. In 1971 the first commercial CANDU reactor, Pickering A 1, began commercial operation. By 1973 the other three reactors of the A group at Pickering were online and constituted the most powerful nuclear facility in the world at that time. Each Pickering unit produces about 600 MWe of power. On May 18, 1974, India detonated

6622-462: The world's medical isotopes , meaning that the second reactor would be used as a back-up to ensure an uninterruptible supply. The first reactor was started but experienced malfunctions in its safety rods, and a positive nuclear power feedback coefficient was recorded. After running over the Schedule by more than 8 years and more than doubling the initial budget, AECL cancelled the project in 2008 because

6708-537: Was achieved by firing a piece of uranium (a 'doughnut') down a gun barrel onto another piece (a 'spike'). This design is referred to as a gun-type fission weapon . A theoretical 100% pure Pu weapon could also be constructed as a gun-type weapon, like the Manhattan Project's proposed Thin Man design. In reality, this is impractical because even "weapons grade" Pu is contaminated with a small amount of Pu, which has

6794-622: Was also the vendor of CANDU technology, which it had exported worldwide. Throughout the 1960s–2000s AECL marketed and built CANDU facilities in India , South Korea , Argentina , Romania , and the People's Republic of China . It is a member of the World Nuclear Association trade group. In addition, AECL manufactures nuclear medicine radioisotopes for supply to Nordion in Ottawa , Ontario, and

6880-500: Was built. Later work on developing a SLOWPOKE reactor , thorium fuel cycle , and a proposal for safe storage of radioactive waste were carried out at this site. AECL built a larger CANDU prototype (200 MWe) at Douglas Point on Lake Huron, first going critical on November 15, 1966. Douglas Point experienced significant problems with leakage of heavy water , which were eventually solved by much-improved valve design. Other important design refinements worked out at Douglas Point opened

6966-504: Was commissioned July 1, 1997. Wolsong 3 was commissioned on July 1, 1998. Wolsong 4 was commissioned October 1, 1999. All three reactors were rated at 715MWe Gross Output. They currently have some of the highest lifetime capacity factors of nuclear reactors. In 2001, AECL began tests at Chalk River Labs to determine the feasibility of using surplus mixed oxide fuel (MOX) from the Russian and U.S. defence programs (which contains plutonium) as

7052-575: Was complete, AECL formed the Nuclear Power Plant Division at Ontario Hydro’s A.W. Manby Service Centre in Toronto to manage the construction of a full-scale prototype for future CANDU commercial power plants. Ontario Hydro would operate the prototype. The plant would have a 200 MWe reactor and be built in Ontario . The reactor's stainless steel calandria would mass 54.4 tonne (60 ton) and have

7138-461: Was contaminated, as well as an area of the Chalk River site, and millions of gallons of radioactive water accumulated in the reactor basement. This water was pumped to a waste management area of the Laboratories and monitored. Hundreds of military personnel from Canada and the U.S. (including naval officer and later U.S. President, LT James "Jimmy" Carter ) were employed in the cleanup and disposal of

7224-453: Was installed by 1965. The total cost of the plant was $ 91 million. Douglas Point had an oil-filled window which allowed direct observation of the East reactor face, even during full-power operation. The Douglas Point reactor first attained criticality on 15 November 1966 at 16:26 hours. It began feeding power into the grid on 7 January 1967 and officially entered service on 26 September 1968 with

7310-605: Was shut down in 2018. In the summer of 2011 SNC-Lavalin won an international bidding process for the reactor design division of the company. Prior to the acquisition, 10% of SNC Lavalin's international power workforce (400 of 4000) were engaged in the production and refurbishment of nuclear reactors. Concerns raised about the deal include a lack of commitment by SNC-Lavalin to keeping the design division intact (its size makes it more capable of providing ongoing safety support). For 2010 and 2009 combined Atomic Energy of Canada Ltd lost CA$ 493   million. Following divestiture of

7396-466: Was sold to MDS Health Group and now operates under the name MDS Nordion With a contract signed in 1991, AECL, in partnership with MDS Nordion, began construction of the MAPLE dedicated isotope-production facility. Constructed on-site at AECL's Chalk River Laboratories this facility would house two reactors and an isotope processing facility. Each reactor was designed to be able to produce at least 100% of

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