Canada is getting out of medical isotope production, Prime Minister Stephen Harper said Wednesday as the world struggles with the shutdown of an aging Canadian reactor that makes a big chunk of the global supply.

"We anticipate Canada will be out of the business," Harper said at a joint news conference with Colombian President Alvaro Uribe.

The prime minister's comments confirmed speculation the federal government's decision to split up and sell off Crown-owned Atomic Energy of Canada Ltd. was a prelude to a pull out.

The government plans to spin off AECL's profitable nuclear reactor business as part of a major restructuring that will also mean private-sector management for the company's research facility in Chalk River, Ont.

AECL shut down the Chalk River reactor May 15 after discovering a heavy-water leak. Officials estimate it will be at least three months — and likely longer — before it's up and running again.

The shutdown has sparked a worldwide shortage of isotopes, which are used in scans to diagnose cancer and heart ailments.

The Chalk River reactor makes about a third of the world supply of medical isotopes. A Dutch reactor kicks in another third, with lesser amounts coming from reactors in France, Belgium and South Africa.

Harper said he plans to keep the Chalk River reactor running as often as possible, while working with other countries and provinces to develop alternative sources of treatment. But the prime minister made it clear that alternatives will need to be found by the time that facility closes — likely in 2016.

Government officials say the plan is to extend Chalk River's mandate until that year, by which point other countries, research facilities, new technologies, or private industry could help meet the global demand.

"It was a difficult decision. But we can't spend hundreds and hundreds of millions of dollars and never produce an isotope," Harper said.

The stage for that policy shift was set last year when the Conservative government announced it would scrap two next-generation Maple reactors, which were meant to replace the aging NRU reactor at Chalk River.

The Maples were millions of dollars over budget and years behind schedule when the Tories pulled the plug due to design flaws.

"For whatever reason, Atomic Energy was not able to make that project work. There was no prospect that it would work," Harper said.

"What we've decided to do instead was to invest money to repair the [Chalk River] reactor to keep it online for a longer period of time while other sources around the world come online.

"But obviously we will continue to have difficulties with a reactor that is very old, and whose operation is not always dependable and predictable ... That's just the tough reality of the situation."