The former head of the Canadian Nuclear Safety Commission (CNSC) said Tuesday that the safety risk at the Chalk River nuclear reactor was 1,000 times higher than acceptable international standards prior to its temporary shutdown late last year.

"Safety at a nuclear facility needs to meet the same high standards that we expect from a space shuttle or a jumbo jet," said Linda Keen.

"The regulations the commission enforces and the standards it upholds are about far more than pushing paper. They're really about protecting lives. That's why when it comes to nuclear facilities, ignoring safety requirements is simply not an option."

The reactor, operated by the Atomic Energy of Canada Ltd. (AECL), a Crown corporation, stopped production for scheduled repairs on Nov. 18 and was expected to restart within five days.

But the CNSC -- responsible for setting licensing, health and safety rules for the country's nuclear facilities -- refused to allow the reactor to restart after finding it had been operating without a backup emergency power system for cooling pumps for 17 months.

The closure led to a worldwide medical isotope shortage and prompted the House of Commons to unanimously vote to reopen the reactor and resume isotope production.

Keen, recently fired by the government, said Tuesday that Canadians shouldn't have to choose between nuclear safety and medical isotopes.

Keen made the comments during testimony before a House of Commons natural resources committee probing the circumstances surrounding the shut down.

"Nuclear reactors are in communities where Canadians live," said the former CNSC president.

"They need to know that the commission will make its decision based on what's right."

Natural Resources Minister Gary Lunn axed Keen two weeks ago, the evening before she was originally scheduled to testify before the committee. As a result, Keen rescheduled her appearance for Tuesday.

Health Minister Tony Clement also testified before the committee on Tuesday, saying he was in full support of Keen's firing.

"We had to act," he said. "Repeated requests to the regulator to see about an expeditious hearing were not met."

Clement said if the crisis had continued it would have "led to deaths."

He later told CTV's Mike Duffy Live that Canada was just days away from a medical isotope crisis.

"When you look at the facts, and we had facts coming in from hospitals all over the country, the very night that Parliament passed legislation to reopen the reactor we were 65 per cent down in our nuclear isotopes in this country," he said.

"We were within days of that impacting on the health and safety of Canadians who needed cancer treatment and cardiac treatment."

Lunn, during his testimony two weeks ago, told the committee that Keen showed a "lack of leadership" and did not get the facility up and running quickly enough.

Auditor-General testifies

Auditor-General Sheila Fraser was first to appear before the committee Tuesday and she said the firing raised concerns about the independence of regulatory bodies.

"Clearly, I think there are questions that arise around the independence of regulatory bodies, how they are to be dealt with, what is the protocol with government,'' Fraser said.

"There would certainly seem to be, as a minimum, a lack of clarity around some of this.''

Last September, Fraser sent Lunn a report highlighting "three strategic challenges" that AECL faced, including "the replacement of aging facilities at Chalk River Laboratories (CRL)."

The report said the Chalk River facility needed at least $600 million to deal with "urgent health, safety, security and environmental issues.''

Lunn told CTV's Question Period last Sunday that he was briefed on the audit during the first week of October, about two months before the reactor was shut down.

He insisted that he had no way of anticipating the crisis because the report said "absolutely nothing about the situation."

Lunn said the auditor general's concerns were focused on MAPLE reactors at Chalk River that had yet to come online.

"There's absolutely nothing, nothing in this auditor general's report that would have allowed me to foresee that we were going to have this problem that we did in early December. It's simply not in the report."

Lunn also said that AECL, a Crown corporation, never alerted him to the fact the Chalk River reactor was operating without a back-up pump in violation of its licence.

On Tuesday, Fraser criticized the government for not having a strategy for nuclear energy.

With files from The Canadian Press