The House of Commons passed emergency legislation late Tuesday night to reopen an Ontario nuclear reactor that produces most of the world's supply of critical medical isotopes, even though the site has been shut down for safety maintenance.

'Will the minister [of natural resources] or the prime minister … tell Canadians what will happen if there's a nuclear accident?'— Liberal MP Omar Alghabra

To pass before Christmas break, the bill needed all party support. Both the Bloc Québécois and the NDP had said they could live with the government's plan to override the advice of the Canadian Nuclear Safety Commission and restart the 50-year-old reactor at Chalk River, Ont.

But Liberal deputy leader Michael Ignatieff said the Liberals would not sign off on the legislation until they were assured "that we've got some guarantees on safety."

Witnesses and experts were called in to the House to face questions about safety concerns and all parties eventually voiced support for the bill, which would effectively suspend CNSC's oversight role for 120 days.

The bill must still be passed by the Liberal-dominated Senate, which will likely deal with it swiftly on Wednesday.

Earlier, Harper declared in the House of Commons "there will be no nuclear accident" resulting from reopening the plant, citing an independent analysis of the site that already said there would be no safety risks.

The Chalk River reactor ceased operating on Nov. 18. Pressure on the government to restart operations began to build after delays in the shutdown of government-run site, which generates two-thirds of the world's radioisotopes, began to cause a critical shortage of radioisotopes.

Doctors around the world depend on the nuclear material for life-saving diagnostic scans, and imaging for fractures, cancers and heart conditions. 

The Conservatives, facing pressure to solve the shortfall, introduced Tuesday's bill to get Chalk River back online by circumventing the Liberal-appointed CNSC.

It was an unpalatable choice for the Liberals, who rejected the call earlier in the day and argued it was irresponsible.

"Attacking the regulator, taking [it] out of the process, is going to make the problem worse," deputy Liberal leader Michael Ignatieff said Tuesday, responding to Harper's assertion that the nuclear watchdog's legislative authority should take a back seat to the urgent need for radioisotopes.

'What will happen if there's a nuclear accident?'

Liberal MP Omar Alghabra noted that resolving the crisis should not come at the cost of lowering nuclear safety standards.

"Will the minister [of natural resources] or the prime minister, for that matter, tell Canadians what will happen if there's a nuclear accident?" Alghabra asked to raucous applause.

"There will be no nuclear accident," Harper answered in the Commons. "What there will be … is a growing crisis in the medical system here in Canada and around the world if the Liberal party continues to support the regulator obstructing this reactor from coming back on line."

The operator of the Chalk River reactor, Atomic Energy of Canada Ltd., had said it expected the plant to be up and running by the middle of this month, but the safety commission was refusing to allow it to restart production until it resolved a host of safety issues.

The Ontario Association of Nuclear Medicine estimates that in Ontario alone, 8,000 patients each month will have their tests delayed due to the complications at Chalk River.

Roughly 30,000 patients per week in Canada and 400,000 patients per week in the U.S. have nuclear medicine scans, according to the Canadian Society of Nuclear Medicine.

With files from the Canadian Press