Nuclear imaging practices are bracing for another long isotope shortage with the May 15 emergency shutdown of the National Research Universal (NRU) reactor at Chalk River in Ontario, Canada.
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The reactor was shut down after a small leak of heavy water was detected within the reactor facility, according to Atomic Energy of Canada Limited, the reactor's operator. It reported that some radioactive tritium was released outside the reactor's containment vessel through the NRU ventilation system.
Moly-99 production ceased with the shutdown. AECL reported that the reactor will remain out of operation for at least a month. As of May 23, the facility will no longer meet planned medical isotope production requirements, according to a release.
Moly-99 is the parent isotope for the production of technetium-99m, a radioisotope used in about 18 million diagnostic nuclear medicine studies annually. Moly-99 is produced in the core of nuclear reactors before refinement and distribution. The ability to store moly-99 is limited due to its 66-hour half-life.
MDS Nordion, a Canadian company that refines and distributes more than half of the moly-99 produced in the NRU reactor at Chalk River announced May 18 that it expects the shutdown will result in a significant worldwide isotope shortage. It expected to begin feeling the effects of the shutdown on Thursday, May 21.
In a letter, Nordion advised customers that it is working with the supply network to tap into additional isotope sources. A small portion of the company's supply originates from the High Flux Reactor at Petten in the Netherlands.
An investigation into the cause of and possible solution to the leakage began May 17. Reactor personnel found the leak originated at the base of the reactor vessel, where corrosion was discovered on the outside wall of the vessel.
The NRU reactor manufactures 30% to 40% of the world's supply of medical isotopes and about 50% of the North American supply, according to Nordion.
Lantheus Medical Imaging, another Tc-99m supplier, announced May 20 that it has signed a supply agreement with NTP Radioisotopes Ltd., a subsidiary of the South African Nuclear Energy Corporation, to manufacture and supply Lantheus with moly-99 from a reactor at Pelindaba near Pretoria, South Africa. Lantheus will receive a specified amount of moly-99 at regular intervals from NTP. The additional source will enhance the company's ability to meet or exceed customer demand, according to a release.
Lantheus noted the deal is part of a diversification strategy to reduce its reliance on aging reactors in the Netherlands and Canada for moly-99. The Petten reactor is reportedly Lantheus's primary source of the isotope. An emergency shutdown of the High Flux Reactor in September 2008 triggered a six-month shortage affecting hospitals throughout Europe. The crisis ended when the reactor came back on line in February.
Shutdowns have also affected operations at Chalk River's NRU reactor. A Tc-99m shortage arose throughout North America during an unscheduled 28-day shutdown of that facility in late 2007.
