TIVERTON, Ont. - Ontario Premier Dalton McGuinty says he's not ready to commit to new nuclear reactors at the Bruce Power plant just yet, but believes the province will be better equipped to keep a lid on costs in the future if it were to go ahead with a proposed expansion.

A review is currently underway for the environmental impact of the proposed Bruce C power plant on the shore of Lake Huron, which involves building four new reactors alongside the eight at Bruce A and B. The province also has to decide whether to refurbish Bruce B or build a new unit there.

"What we need to do (to decide on Bruce C) is wait until we get all the information that we need when it comes to costs associated with the refurbishment of (Bruce) B, weigh that against costs and time associated with new build," McGuinty said Monday during a tour of the power plant.

"The commitment we've made is to maintain existing capacity, provincially, and also here at Bruce."

Ontario is expanding its nuclear network, already the most extensive in Canada, with new reactors to be built at the Darlington nuclear generating station east of Toronto by 2018.

Bruce's proposal would potentially add 4,000 megawatts at the power plant, up from the 3,200 megawatts currently being produced by Bruce B.

Critics have charged Ontario electricity consumers will be the ones stuck with a $237.5-million bill for escalating costs to restart a Bruce Power nuclear station, which the company estimated in April will cost 24 per cent more than initially expected.

The nuclear electricity generator said the cost of returning two idle reactor units to service at between $3.1 billion and $3.4 billion, up from an original 2005 cost projection of $2.75 billion.

But McGuinty said the province can now benefit from experience gained in Ontario and throughout the world after decades of dealing with nuclear plants.

"There has been some real challenges associated along the way, but I think we've learned better how to ensure that we're sharing the risks, putting in some more parameters with respect to building on time," he said.

Bruce Power CEO Duncan Hawthorne said the results of the restart project on Bruce A will allow the company to calculate the cost of refurbishment while it moves along with approvals for building the proposed plant.

"We don't have to make an imminent decision on new build or refurbishment because Bruce B is good until 2017, 2018," he said.

"I don't think I needed to lobby the premier today; the premier knows that we have an interest and an appetite to expand the site."

Hawthorne declined to comment on which technology he'd rather see in the reactors, but conceded losing out on the proposed project would be a blow for bidder Atomic Energy of Canada Ltd., a 4,800-employee federal Crown corporation.

"A lot of people have said it's a dynasty issue for AECL, and of course it would be a major setback for them since they are the domestic vendor," he said.

"But at the same time AECL has got a good future in terms of all these refurbishments. One of the important things is whichever technology is chosen, it better leave behind a strong Canadian nuclear industry -- because whatever we have we're going to operate for 60 years, so I'm very much of the view that it cannot be allowed to be a dynasty issue for the Canadian nuclear industry."

Shawn Patrick Stensil, an energy expert at Greenpeace, said he'd rather see a focus on renewable energy such as wind power when Bruce B shuts down.

"The government says it prioritizes renewable energy but the money goes into nuclear," he said.

"It has never stated this explicitly but they give right of way (on the transmission lines) to nuclear."

The Bruce region, he added, has some of the best potential for wind development in the province.

"The closure of Bruce B is an opportunity for accelerating wind power in the region."

Nuclear provides about 52 per cent of Ontario's electricity, and the province plans to build the two new reactors as part of a $26-billion nuclear replacement and refurbishment program to maintain that level in the power supply mix.

Overall, nuclear power comprises roughly 15 per cent of Canada's electricity, the bulk of it coming from Ontario.