Gentilly Nuclear Generating Station

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Gentilly Nuclear Generating Station
Centrale nucléaire Gentilly.jpg
The Gentilly-2 (left) and Gentilly-1 (right)
nuclear generating stations
Official nameCentrale nucléaire de Gentilly
LocationBécancour, Quebec
Coordinates46°23′45″N 72°21′25″W / 46.39583°N 72.35694°W / 46.39583; -72.35694Coordinates: 46°23′45″N 72°21′25″W / 46.39583°N 72.35694°W / 46.39583; -72.35694
Statussafe storage (pools)
pending dismantling
Construction began1973
Commission dateOctober 1, 1983 (October 1, 1983)
Decommission dateDecember 28, 2012 (December 28, 2012)
Construction costCAD 1.3 billion
Nuclear power station
Reactor typeCANDU-BWR
Reactor supplierAtomic Energy of Canada Limited
Power generation
Units operationalNone
Units cancelled1 × 640 MW
Units decommissioned1 × 250 MW
1 × 675 MW
Nameplate capacity925 MW
Capacity factor76.4%
Annual net output3,491 GW·h
External links
WebsiteHydro-Québec: Gentilly-2
CommonsRelated media on Commons

Gentilly Nuclear Generating Station (Centrale nucléaire de Gentilly in French) is a former nuclear power station located on the south shore of the St. Lawrence River in Bécancour, Quebec, 100 km north east of Montreal. The site contained two nuclear reactors; Gentilly-1, a 250 MW CANDU-BWR prototype, was marred by technical problems and shut down in 1977, and Gentilly-2, a 675-MW CANDU-6 reactor operated commercially by the government-owned public utility Hydro-Québec between 1983 and 2012. These were the only power generating nuclear reactors in Quebec.[note 1]

The Gentilly reactors were constructed in stages between 1966 and 1983 and were originally part of a plan for 30-35 nuclear reactors in Quebec.[1][2] A third reactor, Gentilly-3, was scheduled to be built on the same site but was cancelled because of a drop in demand growth in the late 1970s.[3]

In October 2012, it was decided for economical reasons not to proceed with the refurbishment of Gentilly-2 and decommission the power plant instead, a process that will take approximately 50 years to complete.[4] In December of that same year, the remaining reactor was shut down and the decommissioning process started.[5]


Gentilly-1 was a prototype CANDU-BWR reactor, based on the SGHWR design. It was designed for a net output of 250MW(e). The reactor had several features unique amongst CANDU reactors, including vertically oriented pressure tubes (allowing for the use of a single fuelling machine below the core), and light-water coolant. These features were intended to reduce the cost and complexity of the unit, again to make it an attractive export unit. However, the design was not successful, and over 7 years recorded only 180 on-power days. Gentilly-1 is no longer in operation.


Hydro-Québec embarked on discussions during the summer of 1964 and Atomic Energy of Canada Limited (AECL) studied the possibility of constructing a 250 MW reactor, an enlarged version of the experimental reactor at Douglas Point, in Ontario. As a condition of financial aid from Ottawa, the crown corporation required the reactor to be an experimental type. The president of AECL, Lorne Gray, therefore suggested to the Québec public utility a boiling light water reactor, which offered several advantages, notably the fact that the steam produced in the reactor could be used in the turbine.

Before committing itself further, the Lesage government imposed certain conditions. In a letter addressed to prime minister Pearson on April 6, 1965, Lesage proposed a site at Saint-Édouard-de-Gentilly, today a district of Bécancour. Québec also requested that Ottawa pay a portion of the costs of the construction of the plant, which had been the case during the construction of Douglas Point. The Québec cabinet approved the project in February 1966, a few months before being defeated in a provincial election.

The new government of Daniel Johnson pursued the same policy with respect to the development of nuclear power and construction began on the site in the autumn of 1966 under the direction of Hydro-Québec, acting as general contractor for AECL. Despite a strike, which paralyzed the site for five months in 1967, work advanced rapidly due to several innovations, such as the use of a continuous pour of concrete with sliding formwork for the construction of the reactor building—a structure 49 m high with an internal diameter of 36.6 m and walls 1.22 m thick—in 17 days, which would have required five to six months using conventional methods.

After a little more than four years of work, the CANDU Boiling Light Water Reactor at Gentilly-1 produced its first chain reaction in November 1970. Its construction cost $128 million. It achieved its nominal output of 250 MW for the first time in May 1972 and produced 650 GWh of electricity during its first six months of operation.

However, the plant had its share of problems. To begin with, a shortage of heavy water forced the station to be shut down between November 1972 and August 1974, the available supply being diverted as a priority for the reactors at Pickering, in Ontario.

Moreover, the plant was plagued by various technical defects. Contrary to other reactors in the CANDU family, the Gentilly-1 reactor used light water as its heat transport fluid, which was boiled in the reactor and supplied directly to the turbine. Steam being less dense than water, it absorbs fewer neutrons, which required constant adjustments in the nuclear reaction and the turbine inlet valves in order to avoid reactor power running away and activating the shutdown systems. To alleviate this problem, engineers developed a new control system that was installed at the beginning of 1976, but the plant could then be operated at no more than two-thirds of its nominal capacity.

On May 21 and 22, 1977, ten tonnes of heavy water containing 31,000 curies of tritium were released from the plant into the St. Lawrence River due to a failure in a moderator heat exchanger caused by corrosion. The plant ceased electricity production on the 1st of June, 1977, and remained the property of AECL, given that Hydro-Québec refused to take formal possession of it. Gentilly-1 produced electricity only for two brief periods, for a total production of 837.7 GWh, the equivalent of 183 days of production at full power.

In 1980, AECL decided to place the plant in layup, with a view to its possible dismantlement. After looking at the possibility of transforming the plant into a laboratory or converting it into a thermal station, AECL proceeded with the partial dismantling of the buildings in 1985 and 1986. The irradiated fuel was transferred to dry storage silos set up in the turbine hall. In 1985, Hydro-Québec purchased sections of the service building in order to create a technical training centre intended for the staff of Gentilly-2. The centre includes classrooms, offices, laboratories, and a Gentilly-2 simulator for the training of its operators.


Gentilly-2 is a standard CANDU 6 reactor, similar to the Point Lepreau Nuclear Generating Station. The plant has a net output of 675MW(e). Unlike the adjacent Gentilly-1 reactor, Gentilly-2 has had a good service record since start-up in 1982, with a cumulative operating factor of 76.4%.[6]

In an August 19, 2008 announcement, Québec planned to spend $1.9B to overhaul Gentilly-2 in order to extend its lifespan to 2040.[7] Refurbishment of the reactor was eventually cancelled when on 3 October 2012, Hydro-Quebec's CEO, Thierry Vandal, announced the decommissioning of the Gentilly-2 generating station for economic reasons, scheduled to occur on 28 December 2012 at 10:30 p.m.[5][8] At that time, a decommissioning process will proceed over a period of 50 years and is expected to cost $1.8 billion.[9] The permanent shut down and decommissioning of the power plant followed an election pledge from Quebec premier, Pauline Marois.[4]

The Gentilly site also houses a 411MW gas turbine generation plant. The Bécancour generating station was commissioned in 1992-1993.[10]


Gentilly-3 was a proposed nuclear reactor at the Gentilly site. It was cancelled by Quebec Premier René Lévesque.[11] A white book study published by the Parti Québécois (PQ) before ascending to power found that Gentilly-3 was not needed for Quebec's future energy needs and that it could be fulfilled with hydroelectricity.[12] After the election of the PQ government, a moratorium on construction of nuclear plants was put into place. The reactor had been scheduled to be completed before 1990, and was the last reactor firmly committed to by Hydro-Québec and the Province of Quebec, though Quebec had committed to buy enough heavy water for four Candu style reactors, processed by the La Prade heavy water plant (near Trois-Rivières), scheduled for 1982 opening.[13]

The La Prade Heavy Water Plant[edit]

After the heavy water shortages of 1972 and 1973 which disrupted the commercial operation of the Gentilly-1 station, the federal government initiated a program of construction of facilities for the production of heavy water, an essential component for the proper functioning of CANDU reactors. AECL acquired 101 hectares of land immediately to the east of the Gentilly site to allow the construction of a plant intended to produce 800 megagrams (Mg) of heavy water per year.

Construction of the complex began in 1974 without the prior authorization of the environmental protection services. In the meantime, the project was openly contested by the government of Ontario, whose two heavy water plants built by Ontario Hydro had transformed the shortage into a surplus, as well as raising safety concerns due to the use of hydrogen sulfide (H
) in the Girdler-Sulfide process of heavy water extraction.

In 1977, the federal government raised the possibility of stopping work on the La Prade plant. Concerned about the loss of a project providing employment for over 1,500 people, Québec premier René Lévesque reached an agreement with his federal counterpart, Pierre Elliott Trudeau. According to the contract signed in January 1978, Ottawa committed to restarting construction on La Prade, in exchange for which Hydro-Québec would buy enough heavy water to supply three reactors, modify the concept of the Gentilly-2 station to provide process steam to the heavy water plant, and construct a third CANDU, Gentilly-3, by the end of the 1980s. In August of the same year, Ottawa made an about-face and gave in to the arguments of the Ontario minister of energy, Reuben Baetz. A moratorium on the construction of the heavy water plant, 35% complete, was announced in the context of a program of budget austerity, raising the ire of the Québec minister of energy, Guy Joron.

After threatening to sue the federal government for breach of contract, the Parti Québécois government accepted, as compensation, the creation of a $200 million economic diversification fund offered by Joe Clark during the 1980 federal election campaign, and cancelled preliminary planning for Gentilly-3 in 1981.

The partially constructed facility was long left abandoned in the hope of a possible resumption of demand for heavy water. It was sold in 1995. The new owner, a metal recycling firm, demolished the ten towers of the complex in the autumn of 1998.

See also[edit]


  1. ^ There is also a SLOWPOKE research reactor at Montreal's École Polytechnique.
  1. ^ "Minister wants referendum on nuclear power plants". Calgary Herald. Canadian Press. 10 February 1977. Retrieved 2012-09-11.
  2. ^ Marie-Claude Fafard (15 September 2010). "Québec : le dangereux retour de l'énergie nucléaire ?". Afrique Expansion Magazine (in French). Archived from the original on 2014-10-30. Retrieved 2012-09-11.
  3. ^ Baril, Hélène (October 3, 2012). "Libéraux et péquistes, promoteurs du nucléaire au Québec". La Presse (in French). Montreal. Retrieved December 28, 2012.
  4. ^ a b "Pauline Marois ferme Gentilly-2" (in French). Retrieved 2012-09-20.
  5. ^ a b Canadian Broadcasting Corporation (December 28, 2012). "Gentilly-2 nuclear plant shuts down after 29 years". Retrieved December 28, 2012.
  6. ^ International Atomic Energy Agency (March 23, 2012). "Gentilly-2". Power Reactor Information System. Retrieved 2012-12-14.
  7. ^ "Quebec to spend $1.9B on lone nuclear power plant". 2008-08-19. Retrieved 2008-08-19.
  8. ^ "Hydro-Québec confirms Gentilly-2 closure at the end of 2012" (Press release). Hydro-Québec. October 3, 2012. Retrieved October 12, 2012.
  9. ^ CBC News (3 October 2012). "Quebec nuclear reactor shutdown will cost $1.8 billion". Canadian Broadcasting Corporation. Retrieved 4 October 2012.
  10. ^ Hydro-Québec. "Thermal generating stations". Retrieved 2012-03-24.
  11. ^ Vincent Broussea-Pouliot (1 September 2012). "Les enjeux oubliés de la campagne". La Presse (in French). Montreal. Retrieved 2012-09-11.
  12. ^ François Cattapan (5 April 2011). "Partisanerie sur le dos de Gentilly" (in French). Retrieved 2012-09-11.[permanent dead link]
  13. ^ Ian Anderson (8 December 1977). "Quebec Reprieves Heavy Water Plant". The Gazette. Montreal. Retrieved 2012-09-11.

External links[edit]