Patients in North America will face delays in medical treatment as a result of the month-long shutdown of an Ontario nuclear reactor that supplies medical isotopes, says a spokesman for the medical imaging industry. The shutdown is occurring at a time when three out of four other reactors in the world that produce the isotopes are also off-line.

"Lots of diagnostic examinations will not be able to be done during the next week," Jean-Pierre Cabocel, general manager of the Association of Imaging Producers and Equipment Suppliers, said on Tuesday.

Treatments that rely on diagnosis through imaging will not go ahead, he added.

"Patients will suffer."

Atomic Energy of Canada Ltd. (AECL) announced Monday that its Chalk River reactor, located about 185 kilometres northwest of Ottawa, will remain out of service for more than a month due to a leak at the base of the reactor vessel.

The agency noticed the heavy water leak on Friday, a day after the reactor was shut down due to a power outage in eastern Ontario and western Quebec. The leak, which also released a small amount of radioactive tritium, was traced to a corroded outer wall of the reactor vessel.

Natural Resources Minister Lisa Raitt said in a statement Tuesday that the Canadian Nuclear Safety Commission assured her the heavy water leak poses no health and safety risk "and that AECL's actions are in keeping with a strong safety culture."

Due to the shutdown, AECL said it will be unable to meet its production requirements for medical isotopes starting this coming Saturday.

Health Minister Leona Aglukkaq said in a statement that the federal government has been talking to the provinces and health-care providers and encouraging them to maximize the supply of medical isotopes available through measures such as modifying patient scheduling and triaging.

Medical isotopes are used for scans to diagnose cancer and heart disease. They have a very short shelf life because of their brief radioactive half-lives, and that means they become scarce two or three days after production ceases.

According to Dr. Jean-Luc Urbain, president of the Canadian Association of Nuclear Medicine, the reactor supplies about 60 per cent of the medical isotopes in the world, and the countries that will be most affected by the shortage are Canada and the U.S.

Dr. François Lamoureux, another spokesman for the association, expects an 80 per cent reduction in the availability of medical isotopes next week. Medical isotope users must reduce their activities by 60 to 70 per cent as a result of the shortage, he added in French, and that will lead to serious problems concerning accessibility to treatment. The few available will be used only for emergencies, he said, such as diagnosing whether someone may be having a heart attack.

Lamoureux estimated that about 30,000 nuclear medicine diagnostic exams are conducted each week in Canada.

Federal Industry Minister Tony Clement told The Canadian Press on Tuesday from the Bio 2009 conference in Atlanta that Canada has activated an emergency plan involving close contact with other producers of medical isotopes around the world.

Clement also acknowledged that Canada needs a long-term plan to prevent such problems from happening repeatedly.

Cabocel said part of the problem at the moment is that three out of the four other reactors in the world that supply nuclear isotopes — in Belgium, France and South Africa — are currently shut down as well for maintenance.

"So it means that really, we have only one reactor for the week coming," he said.

That one, the HFR reactor in the Netherlands, can supply about 30 to 35 per cent of world demand. Due to contracts between suppliers, however, most of that will not end up in North America.

Two of the non-Canadian reactors that are shut down will be up and running again at the end of May. The third is expected to be turned back on sometime in June.

Urbain said there have been at least five crises of medical isotope production in the past 18 months, and the situation is starting to become hard to bear for patients.

In addition, the price of medical isotopes in Ontario has jumped two to three times since October, and there is not a lot of information about why, Urbain told CBC's French-language service, Radio-Canada.

The Chalk River reactor previously sparked a global shortage of medical isotopes in November 2007 after it was closed for a month.

During routine maintenance, the Canadian Nuclear Safety Commission discovered emergency backup power wasn't connected to two pumps that prevent a meltdown. The shutdown ended when Parliament voted to bypass the regulator.