The Conservative government is under fire over the shutdown of the Chalk River Atomic Energy Plant.

The publicly-owned plant will be closed for repairs longer than expected, perhaps into the new year. That's left medical facilities in Canada and around the world without radioisotopes that are necessary for diagnosing diseases such as cancer, heart disease, and bone ailments.

Critics say the government didn't do enough to make sure health facilities and patients weren't affected by the shutdown.

"The Canadian Society of Nuclear Medicine says this crisis could affect almost 50,000 patients a month," Liberal MP Hedy Fry said in the House of Commons.

"When will the minister admit that his incompetence has put patients' lives at risk?"

The Canadian Nuclear Safety Commission also blasted Atomic Energy of Canada Limited, the Crown corporation that runs the plant. At a hearing this week, the Canadian Nuclear Safety Commission, a federal regulator, criticized the AECL for violating safety standards.

The commission's Linda Keen said, "I have a great deal of problem with the use of verb tenses that 'we were going to do it' or 'it could have been done' or 'it was optional' or 'it was in some list.' I find that absolutely unacceptable to the commission."

On Friday, the government had few answers about the controversy.

"We are very concerned about this situation. The government has spoken to the agencies involved to have it resolved," said Peter Van Loan, the Government House Leader.

He noted that the government is trying to set up contingency plans.

Van Loan said Health Canada has been working on alternative means to obtain a necessary supply of isotopes for emergency procedures. He added that the Harper government did have a contingency plan in place -- but that the reactor's closure extended "beyond the period contemplated."

Van Loan blamed the previous Liberal government for a lack of preparation, inciting raucous cries from the Opposition.

"I will point out that this is a situation that dates back to 2005. The previous Liberal government never had any kind of alternative process in place," he said.

The government-run Chalk River NRU reactor, which supplies two-thirds of the world's radioisotopes, shut down in November for scheduled maintenance.

Inspectors found more problems to repair than expected and extended the shutdown beyond the scheduled five days.

The longer-than-expected interruption has led to shortages across the country and around the world including the United States, which gets 80 per cent of its radioisotopes from Canada, Asia and South America.

The government says that there's a 75 per cent chance that the reactor could be operating again this month and a 95 per cent chance that it could be running in the first week of January. The plant is currently waiting for spare parts from Europe.

About 150 seriously ill Nova Scotians had their medical tests cancelled this week in Halifax and Sydney. And hospitals in Toronto are reporting to CTV News that they are triaging their patients, allowing only patients of the highest priority to undergo diagnostic scans and asking others to wait.

Shortage is 'ludicrous'

Christopher O'Brien, president of the Ontario Association of Nuclear Medicine, told CTV Newsnet that doctors were "blindsided" by the shortage and are now unable to treat their patients.

"This is ludicrous, what has occurred here," he said.

"Our understanding is there was not an emergency situation in Chalk River. There were things that had to be done to bring it up to specifications but there wasn't an urgent situation that the reactor was going to blow up or that there was a risk of leakage radiation into the environment."

O'Brien said patients requiring emergency procedures are now unable to receive care.

"Yesterday I did not have enough isotopes to perform an emergency lung scan for blood clots in the lung. And today, one of our hospitals was only able to do two patients when they would have done about 12 to 14 patients," he said.

Radioisotopes are used in nuclear medicine in a number of ways at the cellular level. They can be injected into patients to allow nuclear imaging equipment to produce scans of the body to help diagnose diseases.

More than 20 million patients in North America, most of them with cancer or heart disease, are treated using nuclear medicine every year.

"We've estimated that in Ontario alone for each month nearly 8,000 patients will have their tests delayed. And if you look at the entire North American market, taking the United States and South America, it's approximately about 160,00 patients a month are impacted by this," O'Brien said.

The Canadian Nuclear Safety Commission said it would try to accelerate processing import requests for isotopes. The group said it is willing to convene on short notice as required to approve the startup of the Atomic Energy of Canada Ltd. reactor.

AECL said a plant designed to replace the aging Chalk River facility is six years behind schedule and will not produce radioisotopes until late 2008.

With files from The Associated Press and a report by CTV's David Akin.