The Chalk River reactor, a chief source of medical isotopes, will be off-line for more than a month in the spring as part of regular maintenance on the aging facility.
The shut-down announcement came as the first sample of a Russian nuclear isotope was shipped to Canada for testing. It is hoped that the Russian source will make up for any possible shortages.
The leading Canadian supplier of Molybdenum-99, an isotope used in approximately 80 per cent of nuclear medical procedures, struck a deal with the Russian state-owned company Isotope last year.
Under the terms of the agreement, the Russian company will supply Ottawa-based Nordion Inc. until 2020.
But before shipments can start arriving for distribution, the sample must be tested to obtain product registration and regulatory approval.
According to Nordion's vice-president of quality and regulatory affairs, the preliminary sample now on its way to Canada represents a "key milestone."
"In collaboration with Isotope, we look forward to completing the evaluation and moving forward on providing our customers with greater stability in their supply chain," Jill Chitra said in a statement Thursday.
The company hopes to have approval for a steady supply of the isotope early next year, ahead of the planned shut-down of the Canadian Government-owned National Research Universal reactor in Chalk River, Ont. in May.
The Canadian reactor is usually closed for five-day maintenance sessions every month, but other work needs to be done in May. It's expected the improvements will result in a 33-day closure.
"We want to do an extended outage to perform these planned maintenance activities that require a bit longer time," said Atomic Energy of Canada Ltd. spokeswoman Robin Forbes Thursday.
The Chalk River reactor, which had been one of the world's leading suppliers of medical isotopes, has been shut for repairs several times. Each closure has caused concern over possible shortages.
Last August, Chalk River again began producing isotopes after being shut for more than a year. The shut-down was the result of a tiny radioactive water leak at the facility.
With files from The Canadian Press
