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TORONTO Tue Mar 22, 2011 9:14pm GMT

TORONTO (Reuters) - Canadian regulators see no big environmental impact from a plan to expand a nuclear power station 70 km (45 miles) from Canada's biggest city, Toronto, but Greenpeace activists halted a second day of hearings with pleas for a delay while Japan unravels its nuclear mess.

The government-appointed joint review panel hearings into adding up to 4,800 megawatts of electrical capacity to the four-reactor Darlington nuclear power plant are scheduled to last until April 8. However, officials said extra days might be possible to allow more time to examine the accident at Japan's Fukushima reactor.

But Greenpeace protesters locked themselves to a table at the hearing on Tuesday after failing to win a delay of the hearings into expanding the plant on Lake Ontario, east of Toronto.

"We need to learn from (Japan) what went wrong," said Shawn-Patrick Stensil, a Greenpeace nuclear analyst.

"Large scale accidents like Fukushima aren't considered within the environmental assessment because those types of events are called by the industry 'incredible' therefore they don't merit consideration."

Workers are struggling to cool down overheating reactors at Fukushima, which is still leaking radiation after Japan's earthquake and tsunami earlier this month.

Officials from the Canadian Nuclear Safety Commission (CNSC) told the Ontario hearing that earthquakes were not going to be a problem for Darlington. The region around Lake Ontario is one of low to moderate seismic activity, and earthquakes that can be felt in Eastern Canada are small, rare, and produce only minor damage.

ENVIRONMENTALLY SAFE

The hearings address the environmental impact of the project as well qualifications of provincially owned Ontario Power Generation to win a license to prepare the site, something the CNSC said it backed.

In pre-released documents ahead of the hearings, the regulator said, "the proposed project is unlikely to cause significant environmental effects" and that "the applicant is qualified to carry out the activity authorized by the license."

The site preparation license is the first of several steps in a multi-year approval process for the new reactors.

Around the world, there are 477 proposed or planned nuclear plants, with 441 already in operation. Japan's crisis has raised concerns over safety and reignited opposition to nuclear expansion plans. [ID:nN13291193]

The Darlington generating station currently has four reactors that provide roughly 20 percent of Ontario's electricity. Fifty percent of the power in Canada's most populous province comes from nuclear stations.

(Reporting by Solarina Ho; editing by Janet Guttsman and Rob Wilson)