Repairs at the Chalk River nuclear reactor that produces medical isotopes are taking longer than expected, which could delay its reopening until April.

Atomic Energy of Canada Ltd. said Wednesday it had hoped to have repairs done by March, but that may no longer be possible.

"The current schedule targets return to service by the end of March 2010," the agency said in a status report.

"However, if there are continuing challenges with the repair process, the NRU return-to-service schedule could extend into April."

After the repairs are done and the system restarts, it will take 10 days before the first isotopes will be ready, AECL said.

The reactor was most recently shut down in May 2009, leading to a worldwide shortage of isotopes used in diagnostic imaging for cancer and cardiac patients, and some cancer treatments.

A reactor in the Netherlands has been picking up the slack, but it is scheduled to go down for repairs in February, raising concerns about another isotope shortage.

Earlier this week, François Lamoureux, president of the Quebec Association of Nuclear Medicine Specialists, said hospitals were told to keep a tally of extra costs during the shutdown. A spokesperson for federal Health Minister Leona Aglukkaq's office refused to comment on whether it was still considering compensation for the provinces.

With files from The Canadian Press