VANCOUVER, British Columbia (Reuters) - An aging Canadian nuclear reactor that produces a third of the world's medical isotope supply is expected to be out of operation for at least three months, officials said on Wednesday.
Crews have found the source of a heavy water leak at the Chalk River reactor in eastern Ontario, but more inspections will be needed before a repair plan can be worked out, Atomic Energy of Canada Ltd. said.
"Based on our preliminary findings to date, we now believe that the NRU reactor will be out of service for at least three months," AECL Chief Nuclear Officer Bill Pilkington said in a news release.
AECL said it cannot give an exact prediction on how long the facility will be down until the inspection is completed. The government-owned firm had previously estimated it would be out of operation for at least a month.
The 50-year-old facility was shut down May 17 so crews could find the cause of the small heavy water leak, which officials say does not pose a health threat to the public.
A medical isotope is a very small quantity of radioactive material used to perform nuclear medicine imaging tests. Isotopes are mixed with different solutions and injected into patients where they give off energy that is read by a special camera.
Isotopes have a short shelf life, so the unexpected shutdown has sent hospitals in the United States and Canada scrambling to find alternative suppliers. There are a limited number of reactors that can produce them.
"The real problem is that those other reactors don't have the excess capacity that (Chalk River) has," said Robert Atcher, president of the Society of Nuclear Medicine.
Atcher said there are also fears that AECL will now find other corrosion problems in the reactor that will lengthen the shutdown or force a permanent closure..
"To say we're concerned is an understatement," Atcher said.
MDS Inc, whose MDS Nordion Division has an exclusive agreement to distribute Chalk River's medical isotopes, is working to secure additional supply, but said last week it expected a significant global shortage.
A MDS spokeswoman was not immediately available for comment on Wednesday.
AECL said cameras located the heavy water leak at the base of the reactor vessel in a location where there is corrosion on the outside wall, and test equipment is being prepare to look at the interior area.
"Until all investigations are completed, it is premature at this point to set a definitive timeline for the return to service of the NRU reactor," said Hugh MacDiarmid, AECL's chief executive.
AECL said it slowed the rate of the leak by lowering the heavy water level in the reactor.
The water is being contained and stored, although a small portion does evaporate allowing tritium to be released into the air through the ventilation system. The amount of airborne release is below regulatory limits, officials said. (Editing by Doina Chiacu)