Quebec's only nuclear power plant will shut down on Dec. 28, Hydro-Québec announced Wednesday, but the process of dismantling it will take 50 years and cost $1.8 billion.

The official statement confirms what the new Parti Québécois government has been saying for weeks: that the province won't pay to refurbish the Gentilly-2 reactor and instead will have it decommissioned.

Hydro-Québec's most recent economic analysis, made public on Wednesday, recommends against spending the billions of dollars that would be required to rebuild the reactor to allow it to continue operating.

The Crown corporation says it now estimates the refurbishment would cost $4.3 billion, up from the $2 billion that the previous Liberal government had budgeted.

"This report shows that refurbishing the Gentilly-2 reactor isn't an economically viable option for Quebecers. We have to learn from the example of the cost overruns during the refurbishment of the reactor at Point Lepreau, New Brunswick," Natural Resources Minister Martine Ouellet said in a release.

NB Power's Point Lepreau generating station was the first Candu-6 reactor to be refurbished. The process was supposed to take 18 months but suffered three years of delays and more than $1 billion in cost overruns, and the power plant still isn't back online.

Hydro-Québec said that example gave it a more precise sense of the economics of refurbishing Gentilly-2, located in Bécancour, across the St. Lawrence River from Trois-Rivières. The latest estimates are that the electricity it would produce would cost 12.3 cents per kilowatt hour, the company said — substantially higher than the average price Quebec consumers currently pay, which is about seven cents per kilowatt hour.

Decision criticized

The reactor has been in commercial operation since 1983, and its operating licence runs out at the end of the year. Refurbishing it would extend that by up to 30 years.

The former Liberal provincial government decided in 2008 to rebuild it at a then-projected cost of about $2 billion, but stopped work after the Fukushima disaster in Japan in 2011 and in the wake of the Point Lepreau delays.

The new PQ government announced its decision to close the nuclear plant on Sept.11.

The decision drew swift criticism from the union representing the more than 700 employees at the facility, as well as Liberals, now Quebec's Official Opposition.

On Wednesday, Hydro-Québec said Gentilly-2 will stop producing electricity on Dec. 28, following which workers will take 18 months to render it dormant. That involves removing the reactor's uranium fuel, processing its heavy water and deactivating various systems.

The plant will then stay dormant for 40 years to allow the worst of its radioactivity to disperse. Over the ensuing decade, the facility will finally be dismantled and the site cleaned up.

The total cost of decommissioning the nuclear plant is expected to hit $1.8 billion, Hydro-Québec said.