Along-promised, never-quite-delivered revival of nuclear energy may finally be underway in Canada and one of the key reasons is, at first glance, counterintuitive -- the environment.

Unlike coal, nuclear power plants produce negligible greenhouse gases, meaning the once-unpopular energy option is gaining currency in a post-Kyoto world.

Another factor that was once considered a negative for nuclear energy has also become a benefit: cost. Unlike plants fired by natural gas, nuclear ones are relatively unaffected by the rising price of fuel.

And in comparison to 30 years ago, when local protestors fought plans to build nuclear facilities, communities now woo the projects. Ontario will soon announce the sites for two new nuclear plants, possibly as soon as today. New Brunswick, Alberta and Saskatchewan are flirting with their own projects. Everything finally seems to be in nuclear power's favour but, as one environmentalist put it, "never underestimate the sector's ability to fall on its own sword."

Canada's nuclear industry does have success stories, but they mostly occur overseas.

Atomic Energy of Canada Limited's construction of two of its Candu reactors in China took less time or money than expected when completed five years ago, while three Candu reactors operating in South Korea regularly rate among the world's most productive.

These triumphs are partly responsible for Canada's renewed interest in nuclear power, but more important are upswings in concern about global warming and fossil fuel prices.

"It boils down to a very simple calculus," said Steve Alpin, an Ottawa-based energy consultant. "Our major fuel sources are coal, nuclear and natural gas. Coal is politically incorrect, because of the greenhouse gas issue and air pollution. Up until three years ago, natural gas was a realistic alternative, but prices went up and people realized it is in very short supply [in North America]. That leaves nuclear. It's really that simple."

Recent moves toward putting a price on carbon emissions has only heightened the interest, Mr. Alpin said. Nuclear power emits one-twentieth of the greenhouse gases of gas-fired plants, a statistic that looks good for both the environment and the economy.

"When you look at options for baseload electricity generation that's environmentally friendly -- while being reliable and economic -- nuclear seems to come out on the top," Hugh MacDiarmid, AECL's president, said in an interview.

The notion of a nuclear reactor as a green energy source has caused deep divisions among activists. Several prominent environmentalists, including Greenpeace founder Patrick Moore, are vocal proponents. Others dismiss nuclear's environmental benefits as propaganda put forward by the industry. "You'd have to have a pretty high price on carbon for that benefit to start to show because of the large up-front costs involved in building a new nuclear plant," said Shawn-Patrick Stensil, a Greenpeace campaigner. Indeed, a 2003 Massachusetts Institute of Technology study found a tax of between $100 and $200 per tonne of carbon would be needed to justify construction of new nuclear plants. By way of comparison, the carbon pricing plan recently announced by the NDP called for a price of $35 per tonne.

High construction costs remains one of nuclear's major drawbacks. The country's nuclear history is glutted with projects that cost too much, took too long to complete or never worked as promised. The Darlington Nuclear Generating Station, the last plant built in Canada, was five years behind scheduled when it was finished in 1993. Its price tag ballooned to $14-billion from $5-billion. The federally owned AECL last month cancelled plans to build new reactors to produce medical isotopes near Chalk River, Ont., while the refurbishment of the Bruce Power plant in Kincardine, Ont. is currently more than $300-million over budget. Dalton Mc-Guinty, Ontario's Premier, admitted last week that his province's $26.5-billion plan to refurbish old reactors and build two new ones is "an expensive proposition." Nonetheless, proponents argue the low operation costs -- and freedom from fluctuating resources prices --more than justify the sticker price. "When you talk about nuclear, the cost of the uranium is such a small portion of running a reactor," said Martyn Wash, president of the Organization of Candu Industries, an industry group. "With gas or oil, 80% to 90% of the cost of producing power is the fuel, compared with 10% for nuclear. The price of uranium can jump and it doesn't have a big impact of electricity prices."

With natural gas prices rising by more than a third in the past year, even provinces rich in natural resource, s such as Alberta, are starting to consider nuclear power as an option. The provincial government this spring appointed an expert panel to study Bruce Power's $10-billion proposal to build the province's first nuclear plant.

New Brunswick is also considering construction of new reactor in Point Lepreau, where the province's existing nuclear reactor is located. AECL and several partners are working on the $6-billion project, which could be the first nuclear plant in the world that is built and then operated by a private consortium.

"We are going to be breaking some new ground in taking that project forward," Mr. MacDiarmid said. "There's no question it raises the bar in terms of the economics and imposes the highest possible standard in terms of your power purchase agreements and ability to forecast demand."

Details of the ground-breaking plan will likely take months to work out, according to Mr. MacDiarmid.