Safety issues have plagued the National Research Universal reactor at Chalk River Laboratories. Credit: P. RYAN

US and Canadian medical researchers last week intensified their calls to tackle a worldwide shortage of radioisotopes for medical imaging.

Sudden dips in isotope supply occurred regularly in 2007 and 2008 as elderly reactors were shut down for repairs. The issue flared up again this year after an unscheduled 14 May shutdown of a large 52-year-old nuclear-isotope-production facility in Chalk River, Ontario, revealed a heavy water leak that has kept the facility closed. The Ontario plant and a reactor in Petten, the Netherlands, itself set to close in July for a month's maintenance, produce the majority of the world's medical isotope supply.

On 19 June, Canada's natural resources minister Lisa Raitt appointed an expert panel to report by 30 November on how the country could ensure a stable long-term medical-isotope supply.

Three days earlier, US medical and nuclear non-proliferation groups wrote to Congress urging the United States to start its own domestic production of the isotopes, using low-enriched uranium.