Canada still unsure on isotope reactor repair plan

VANCOUVER, British Columbia Wed Jun 24, 2009 7:46pm EDT

VANCOUVER, British Columbia (Reuters) - Repair crews are still trying to determine how to fix an aging Canadian nuclear reactor that produces a third of the world's medical isotope supply, officials said on Wednesday.

The Chalk River reactor in eastern Ontario has been out of operation since May 17 because of a heavy water leak, and officials say they cannot predict exactly when it can be restarted until a repair plan is completed.

They tentatively estimated in mid-May that the facility would be down for at least three months.

Atomic Energy of Canada Ltd said operators had removed the reactor's fuel, control and isotope rods, and reduced the rate of the leak -- which officials say does not pose a threat to the general public.

One test of the area of the reactor where the leak was discovered found significant weakening of the aluminum vessel's wall, but another test found no evidence of wall thinning, AECL said in a statement.

Additional testing was expected to take several weeks to complete, the government-owned company said. AECL said it was constructing a full-size mock-up of the vessel to help it develop a repair plan.

The unexpected shutdown of the 52-year-old reactor has sent hospitals in Canada and the United States scrambling to find replacement sources of medical isotopes, which have a short shelf life.

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 read by a special camera.

Chalk River is one of the few nuclear reactors able to produce the isotopes, and health experts have warned that the other facilities do not have the production capacity needed to make up for the lost Canadian production.

"Further guidance on a return to service date will be provided as soon as sufficient data has been collected and analyzed from the non-destructive examination and a decision has been made with respect to the repair technique chosen," AECL said in a statement.

(Reporting Allan Dowd; Editing by Peter Cooney)

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