|Gentilly Nuclear Generating Station|
The Gentilly-2 (left) and Gentilly-1 (right)
nuclear generating stations
|Official name||Centrale nucléaire de Gentilly|
|Status||safe storage (pools)|
|Commission date||October 1, 1983|
|Decommission date||December 28, 2012|
|Construction cost||CAD 1.3 billion|
|Nuclear power station|
|Reactor supplier||Atomic Energy of Canada Limited|
|Units cancelled||1 × 640 MW|
|Units decommissioned||1 × 250 MW|
1 × 675 MW
|Nameplate capacity||925 MW|
|Annual net output||3,491 GW·h|
|Commons||Related 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 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. 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.
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. In December of that same year, the remaining reactor was shut down and the decommissioning process started.
Summary: 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.
Brief History: 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%.
In an August 19, 2008 announcement, Québec planned to spend $1.9B to overhaul Gentilly-2 in order to extend its lifespan to 2040. 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. At that time, a decommissioning process will proceed over a period of 50 years and is expected to cost $1.8 billion. The permanent shut down and decommissioning of the power plant followed an election pledge from Quebec premier, Pauline Marois.
Gentilly-3 was a proposed nuclear reactor at the Gentilly site. It was cancelled by Quebec Premier René Lévesque. 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. 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.