Radioisotope Shortages in Nuclear Medicine: How We Got There and Developing Solutions

  • Powe J
  • Worsley D
  • Ruth T
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Abstract

In recent years, almost all ^sup 99^Mo for medical uses has been produced by irradiating uranium targets in just 5 reactors [3]. The largest and most productive reactors have been the Canadian NRU reactor and the Dutch HFR-Petten reactor. These 2 reactors accounted for 60%-80% of worldwide production, although the NRU reactor alone was capable of supplying up to 80% of the world's supply of ^sup 99^Mo. Much smaller amounts are produced at reactors in Belgium, France, and South Africa (the Safari reactor). All of these reactors are aging and are at or even beyond their projected life span, with the Safari reactor being the newest, at 43 years of age. For some time, Canada has been preeminent in the world's supply of ^sup 99^Mo by using the NRU reactor. In 1991, MDS purchased Nordion from the Canadian government, and a secure long-term medical isotope supply was considered a key component of that purchase. Nordion acts as the processing facility for purification of ^sup 99^Mo from the NRU reactor and sells the ^sup 99^Mo to the generator manufacturers based in the United States (currently Covithen in St Louis, MO, and Lantheus in Boston, MA) who supply the entire North American market. The radiopharmaceutical market is relatively small, and, because the production of ^sup 99^Mo has often benefited from direct government support for research reactor operations, there has been little impetus or profit for other suppliers to get into the business of ^sup 99^Mo production. Currently, ^sup 99^Mo production uses nuclear bomb grade highly enriched uranium (HEU) targets that contain about 93% uranium 235. HEU is produced in the United States and has been made available as a target material through a loop hole in nuclear nonproliferation agreements. With the continued proliferation of nuclear weapons and terrorism in recent years, the United States has made it clear that it will not supply HEU outside the United States for much longer and has encouraged ^sup 99^Mo suppliers to switch their production to the use of low enriched uranium (LEU) targets that contain less than 20% uranium 235. The switch to LEU targets may be expensive and will likely require more suppliers because of the lower ^sup 99^Mo yields when bombarding LEU. Under the Energy Policy Act of 2005, the US Secretary of Energy contracted with the National Academy of Sciences to conduct a study on the elimination of HEU targets. This review was also to evaluate the demand and availability of medical isotopes in regular domestic use and recommend various solutions to the problem of repeated shortages. The Committee on Medical Isotope Production Without Highly Enriched Uranium included 3 Canadian experts in the field. Their report, issued in January 2009, concluded that conversion to LEU targets was possible, although may be more costly than anticipated and may require government subsidies [5]. This report also discusses a number of alternative sources of the ^sup 99^Mo supply. It was obvious to the committee that the supply of ^sup 99^Mo was tenuous at best and that reliability of supply was more of an immediate issue to patient and public welfare than conversion to LEU, a prediction that was sadly proven to be true only a few months later when the NRU reactor was shutdown.

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Powe, J., Worsley, D., & Ruth, T. (2010). Radioisotope Shortages in Nuclear Medicine: How We Got There and Developing Solutions. Canadian Association of Radiologists Journal, 61(1), 19–22. https://doi.org/10.1016/j.carj.2009.11.004

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