Nuclear Energy Insight
March 2009—Many medical isotopes and radiation sources are produced when target material, usually uranium, is irradiated with neutrons, coming from the controlled fission taking place in a research reactor. Atoms in the target capture some of those neutrons, thus becoming heavier isotopes.
The most common radioisotope used in diagnosis is technetium-99m, with more than 30 million procedures per year. Four of five diagnostic imaging procedures in nuclear medicine use this isotope.
Just five research reactors produce about 95 percent of worldwide demand for molybdenum-99, from which technetium-99m is fabricated. These are the Petten High Flux Reactor in the Nether-lands; BR2 at Mol in Belgium; Osiris at Saclay, France; NRU at Chalk River, Canada; and the Safari-1 at Pelindaba, South Africa. These facilities are all more than 40 years old.
Several incidents in 2007 and 2008 have highlighted the unreliability of medical isotope supply, particularly technetium. Unexpected simultaneous maintenance outages of the aging research reactors caused critical shortages of the molybdenum-99 precursor element. Complicating the situation is the complex and constrained distribution of the isotopes, exacerbated by the short half-lives of the precursor and daughter isotopes. A need for increased production capacity and more reliable distribution is evident.
An international workshop held recently in Paris to discuss global solutions concerning the ongoing supply of medical isotopes brought together representatives of government, industry and the nuclear medicine community from 16 countries and several international organizations.
The workshop chairman, Nuclear Energy Agency Director General Luis Echávarri, said in a concluding report that the international community had become “increasingly concerned” about shortages of the isotope. “Outages of these reactors and of the downstream processing facilities have recently resulted in significant shortages of Tc-99m,” he said.
As a response to the most recent shortage, the Petten reactor was given permission by Dutch authorities to re-open before completing its scheduled maintenance. This echoes a similar situation last year in Canada.
Meanwhile, the new OPAL reactor in Australia has recently opened and is expected to commence molybdenum-99 production soon. And early in February, two companies in the United States (Babcock & Wilcox Technical Services Group and Covidien) signed an agreement for the manufacture of molybdenum-99 using an innovative liquid-phase technique involving low-enriched uranium.
The B&W-Covidien program could meet more than half of the demand in the United States, which currently imports all its molybdenum-99.
Even with these recent developments, the vulnerability of the isotope supply chain is expected to persist for several years because of the age and increasing maintenance requirements of the current reactors.
—Read more articles in Nuclear Energy Insight and Insight Web Extra.