Canada's supply of medical isotopes has been interrupted after an unexpected halt in production at an aging Ontario reactor.

Earlier this week, Atomic Energy of Canada issue a bulletin announcing repairs to a fuel rod flask at its facility in Chalk River, Ont., would prevent it from meeting isotope deliveries. The agency said deliveries were expected to resume this weekend.

Dr. Norman Laurin, president of the Canadian Society of Nuclear Medicine, said doctors have noticed the difference in isotope supply.

"Today, for example, we were down to probably less than 50 per cent of the normal delivery we get," Laurin said from Trois-Riviรจres, Que.

"Preliminary indications we were given are that the problem should be resolved some time tonight."

Laurin said the nuclear medicine community is crossing their fingers that there will be sufficient isotope production early next week.

Health Shared Services BC, which helps co-ordinate the operations of B.C.'s six health authorities, also reports the unplanned interruption of medical isotope molybdenum 99 from Chalk River Laboratories.

B.C. health officials say there is no immediate impact to patients but they're working on contingency plans.

Molybdenum-99 isotopes produce technetium-99 isotopes, which are used for bone scans and to check if a patient may need heart bypass surgery.

The reactor at Chalk River had a prolonged shut down in 2009 because of a leak.

The Canadian reactor provides about 30 per cent of the world's supply of the isotope. A reactor in the Netherlands that also supplies about 30 per cent and a reactor in South Africa that gives 15 per cent are also currently down, Laurin said.

Corrections

  • A previous version of this story misidentified the isotope used in nuclear medicine.
    Nov 23, 2013 1:11 PM ET
With files from Canadian Press