Operators discovered a technical failure in the cooling system during startup preparations for the high flux reactor operated by NRG at Petten in the Netherlands, but said there was no risk to staff or environment.

NRG said it did not know when the HFR will restart, but it had told Nuclear Medicine Europe, the Brussels-based industry association for medical isotope manufacturers and customers, so it can implement measures for the continuity of supply of medical isotopes.

NRG said it is investigating the root cause of the problem and expects to provide more information next week. It did not say why the HFR had been offline.