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Nuclear reactor shutdown shows problems with isotope supply

Monday’s announcement by Atomic Energy of Canada Limited that its nuclear reactor at Chalk River, Ontario, will be shut down for at least a month, has prompted global concerns of a shortage of key medical isotope over the next few weeks.

But it has also highlighted that, despite over a year of planning and research on alternatives, the supply of the isotope remains precarious, dependent on a small number of aging nuclear reactors.

The NRU reactor at Chalk River sparked a political firestorm when a dispute with the regulator resulted in an extended shutdown in late 2007. Since then, both researchers and policy-makers have been working to develop alternate sources of the short-lived isotopes, but these remain years away from production.

Experience gained from the previous shortage has resulted in some improvements. Dr. Douglas Abrams, a radiopharmacist at the University of Alberta’s Cross Cancer Institute, said that communication with medical professionals “has been much better.”

Abrams was part of a group of experts that advised Health Canada following the 2007 reactor shutdown -- the same group is monitoring the current shortage.

But with Chalk River supplying approximately 80 per cent of the isotope used in Canada, “it’s going to be a problem, no matter what your contingency plans are,” said Abrams.

The 52-year-old NRU reactor is one of only five reactors worldwide that commercially produce the isotope Molybdenum-99, which is used in hospitals to generate the medical isotope Technetium-99. Technetium-99 is used in medical scans to diagnose some types of cancer as well as heart problems. Since both isotopes decay quickly, they cannot be stockpiled.

When the NRU was shut down in 2007, the international shortage only ended when Parliament passed emergency legislation to override the licensing problems.

This time, there is no debate over whether the reactor needs to be shut down. During a routine inspection after a power outage last week, AECL workers discovered a small but steady leak of (radioactive) heavy water from a corroded tank.

Officials have assured the public that the leak is being contained and there is no risk from the resulting trace releases of radiation.

But there is currently no firm schedule for restarting the reactor. Even after the supply resumes, there is a concern that “nuclear medicine will get the perception of being unreliable,” said Abrams. It’s unfortunate, he said, because the isotope scans are better than other tools for diagnosing some conditions.

In the long term, a number of projects could increase the supply of these medical isotopes – and hopefully lessen the impact whenever a reactor is shutdown.

Abrams pointed to new reactors being built in Australia and Argentina as potentially more reliable sources of isotopes, as well as plans to adapt some existing research reactors for isotope production.

In Canada, a decades-long project to replace the NRU in Chalk River with two reactors dedicated to isotope production was cancelled by AECL and the federal government last spring, after a long history of technical problems and delays. A replacement project is still in design stages.

A technology to create Molybdenum-99 without a nuclear reactor is being pursued by TRIUMF, a nuclear and particle physics laboratory located at the University of British Columbia’s Vancouver campus. Their plan would use a high-intensity particle accelerator to generate the isotope.

The laboratory recently signed an “an agreement to study the feasibility” of the technology with MDS Nordion, the company that currently makes medical isotope generators from the material produced at Chalk River.

If all necessary funding for the accelerator is approved, demonstration projects will be carried out in 2012, and the technology could be licensed to commercial producers for isotope production as early as 2015, according to Tim Meyer, TRIUMF’s head of strategic planning and communications.

But that sort of timeline is little consolation for medical professionals dealing with the current unreliability in the isotope supply.

“The outlook … for the next four to five years is difficult right now,” said Abrams.

Amelia Bellamy-Royds reports for The Tyee.

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