Doctors are warning that the shutdown of the nuclear reactor at Petten, which produces isotopes for medical use, is putting cancer treatment for tens of thousands of patients in danger, local broadcaster Noord Holland reports.

Petten, which is one of six isotope producers in the world and supplies 40% of the world’s isotopes, was put out of action five days ago because of a leak in the pumping installation. No start-up date has yet been set.

The closure could not have come at a worse time because reactors in Canada and South America have also stopped isotope production, the broadcaster writes.

According to Marcel Stokkel, a nuclear physician at the Antoni van Leeuwenhoek hospital in Amsterdam, the situation is worrying.

‘We are hoping that other reactors can take over temporarily but the care of cancer patients is at risk. It’s a worry that we have had for years because Petten has a long history of incidents,’ he told the broadcaster.

Safety issues have been a problem in Petten because of the great demand for isotopes, former employee Paul Schaap told television current affairs show Eenvandaag.

Schaap, who worked at the reactor 20 years ago, said he and his colleagues were forced to carry on working in the knowledge that something was wrong with the reactor cooling system. ‘Production just couldn’t be halted (..) and not much seems to have changed,’ he told the show.

The Antoni van Leeuwenhoek hospital will be supplied by other medical centres for the time being but should another reactor fail the problem will become world-wide, Stokkel said.

‘We need a new reactor as soon as possible. But it has to be in the Netherlands. We must keep the knowledge we are so renowned for in-house,’ the broadcaster quotes him as saying.

Update: The reactor was started up again late on Wedsnesday