Medical isotopes could again be in short supply in Canada following an unscheduled shutdown of the NRU reactor facility which is expected to last at least a month.
A regional loss of electrical power on 14 May caused the reactor at the Chalk River facility to shut down. However, during routine monitoring prior to restarting the reactor, a small leak of heavy water was discovered. According to Atomic Energy of Canada Ltd (AECL), the water was discovered to be leaking at a rate of 5 kg per hour, and is being fully contained and stored. A small release of tritium has also resulted as a result of evaporation, below levels that would be a threat to the public or to workers but at a level requiring AECL to report it to the regulator, the Canadian Nuclear Safety Commission (CNSC).
The source of the leak is at the base of the reactor vessel, in a location where there is corrosion on its outside wall. Repair options are currently being considered and planned, said AECL, but the company anticipates the reactor being out of service for over a month.
AECL says it can meet production requirements for medical isotopes for the coming week, but based on current delivery schedules will not be able to meet demand from Saturday 23 May onwards.
Many radioisotopes used for medical purposes are extremely short-lived so an unexpected interruption to production can quickly affect supplies. An extended outage of the NRU at the end of 2007 prompted an isotope supply emergency when the reactor was shut down because required repairs had not been carried out. Within days isotope supplies began to run out and many thousands of medical procedures were cancelled.
World isotope supplies were rocked later in 2008 when key reactors in Belgium, Canada, France, South Africa and the Netherlands, which between them provide about 85% of the world's cobalt-60 supply and virtually all of the technetium-99m and molybdenum-99, were undergoing refuelling and maintenance within weeks of each other.
Researchers in several countries are working on ways to produce medical isotopes by novel routes that do not rely on nuclear reactors, but the techniques are not yet commercially available.