Nuclear safety: When positive is negative

WHEN news spread in December 2007 that an ageing nuclear reactor in Canada might shut down for much longer than its scheduled two weeks, the world caught its breath. The reactor, at Chalk River in Ontario, is the world's biggest supplier of radioactive isotopes for medical use, and diagnostic tests for cancer and heart disease were put on hold while radiologists scrambled to find alternative supplies. It was called a crisis. All the while, lay people couldn't help but wonder: did no one foresee this? Did no one think that this half-century-old reactor might someday need to be replaced?

As it happens, not only did someone think about it, they designed and built its successors right next door. Maple 1 and Maple 2 are two brand-new reactors, constructed at a combined cost of over C$350 million ($330 million) specifically to produce medical radioisotopes. A single Maple reactor can supply the world's total current needs; the second one is a back-up to keep the supply flowing during routine repairs.

But the sad truth is that the Maples have never been officially switched on, and the chances are they never will be. This has led to a furious row over who is to blame for this costly and embarrassing debacle. Many in the nuclear industry point the finger at Canada's nuclear regulator. The regulator's view is that the reactors' manufacturer failed to deliver a crucial safety feature that it had promised would underpin the design.

Others blame the Canadian government for killing off the project before crucial technical questions had been resolved; in May 2008 it announced, to everyone's surprise, that the Maples were being shuttered for good. "It makes absolutely no sense to me," says Jatin Nathwani, an engineer at the University of Waterloo, Ontario, who gave evidence to a parliamentary committee now looking into the affair. It's time the Canadian government reversed its decision, says Nathwani: "If the will was there, the Maples could be brought back in six to 18 months, with just one phone call from the prime minister."

Radioisotopes have a vital role to play in modern medicine. They are used in almost 40 million medical procedures each year, mostly for treating and diagnosing diseases such as cancer and heart disease. Over 80 per cent of the diagnostic procedures rely on technetium-99m, a short-lived isotope that is produced by bombarding uranium-235 with neutrons inside a reactor (see diagram).