The Canadian Nuclear Safety Commission is denying it heard about a radioactive leak at the Chalk River nuclear facility days after it happened. Instead the organization is saying it heard about the incident "within hours" of it happening.

Atomic Energy of Canada Limited has confirmed a radioactive leak occurred at the Chalk River, Ont. plant in early December.

The details were included in a detailed report from AECL that was provided to CTV.ca.

According to the AECL report it wasn't until Dec. 9 that the leak was reported to the CNSC -- four days after it occurred. The CNSC contradicted that remark in a statement to the media.

The AECL report states that radioactive tritium gas was released during the incident, along with 47 kilograms of "heavy water loss."

The leak was never mentioned in a news release about the shutdown that resulted from the spill. The release only cited "unanticipated technical challenges" in describing why the stoppage was necessary.

The AECL report suggested the incident wasn't serious.

"Heavy water leaks and discharge of elevated tritium wastewater to waste management have occurred in the past. Actions taken are specific to the event with goals to locate the leak, stop it, and prevent recurrence," it stated.

While workers at the facility were able to stop the leak, they were unable to determine its cause.

The report states that the heavy water, which had higher than normal tritium levels, was transferred to storage drums and will eventually have to be disposed of.

The leak occurred soon after medical isotope production levels were ramped up at the plant.

Several months earlier, the plant had increased its production of isotopes, which are used in radiation therapy as well as for medical diagnostics.

About 70 per cent of the global supply currently comes from the Chalk River facility.

By mid-December the plant was producing almost double its normal amount of isotopes to meet world demand.

But it has only recently been revealed that the spill occurred in early December at the aging facility, which was built in 1958.

'Canadians deserve truth'

The CNSC insisted the public and the environment are not at risk as a result of the leak, saying that they have on-site staff consistently monitoring the NRU in order to ensure that it is operating safely and in compliance with its licence conditions.

"Releases to the environment are closely monitored and in this case were well below regulatory limits," the organization said in a statement. "The site has mitigation measures to protect against releases to the public and the environment."

The CNSC also praised AECL, saying it "acted appropriately by keeping the reactor shutdown to investigate even a very small leak."

AECL continuously monitors for leaks from NRU's cooling system, the CNSC added.

"(They are) required take prompt action if a leak, as well as any other event, is detected, as part of standard reporting requirements."

The group also said the AECL submitted both a preliminary and final report within their regulatory timeframe.

Meanwhile, Halifax West Liberal MP Geoff Regan demanded answers from the Conservatives at Tuesday's question period session.

"Canadians deserve truth and transparency when it comes to nuclear safety oversight but they have a government that interferes with independent regulators and keeps them in the dark," he said. "What is being done to solve this and why hasn't the public been informed?"

Lisa Raitt, the minister of natural resources, said she has asked for a written report on the incident.

"At no time did any of the events that took place at Chalk River deem to have an adverse affect on human health or on the environment," she said.

"The reactor at Chalk River continues to operate consistently and meets all safety regulations and security regulations."

Raitt also said that the CNSC and AECL were in constant communication throughout the incident and worked together to find a resolution.

"The health and safety of Canadians is always at the foremost of our concern," she said.

Chalk River controversy

Last year, controversy erupted over the Chalk River plant when Prime Minister Stephen Harper's government overrode a decision by Linda Keen, then head of the CNSC, to close the plant for safety upgrades to the water pump system.

Parliament issued an emergency order to restart the reactor, despite Keen's objections.

Keen was eventually fired over the controversy, but has always maintained she was simply doing her job. She says her firing was politically motivated, with the government responding to fears over a potential isotope shortage.

Keen was removed from her role as president and CEO of the CNSC, and was moved to a position as a full time Commission member

She eventually resigned, claiming she had been "demoted."