Report warns of medical isotopes shortage in USA

The current supply of molybdenum-99 (Mo-99) and technetium-99m (Tc-99m) is sufficient to meet domestic and global demand, but changes to the supply chain before year-end could lead to severe shortages and impact the delivery of medical care, according to a new report by the USA's National Academies of Sciences, Engineering, and Medicine.

The Washington DC-based Academies, which are private, non-profit institutions, said the "congressionally mandated" report examines the production and use of Mo-99, Tc-99m, and associated medical isotopes iodine-131 and xenon-133, and also assesses the progress made in eliminating highly enriched uranium (HEU) from Mo-99 production.

Canada's National Research Universal reactor, built at Chalk River in 1957, produces 40% of the world's supply of Mo-99.

Although current global supplies of Mo-99 are adequate to meet the USA's needs, the capacity to supply the isotope will be "reduced substantially" when the reactor in Canada stops production at the end of next month, the report noted. "Canada will then become a supplier of last resort - producing molybdenum-99 only in case of severe global shortages - until its reactor shuts down permanently at the end of March 2018," it added.

Tc-99m - derived from Mo-99 - is the most commonly used isotope for radionuclide medical imaging, which "noninvasively evaluates regional physiologic and metabolic processes, such as cardiac blood flow, with the ultimate goal of localizing diseased tissues and organs", the Academies said in a statement.

Nearly 95% of the world's supply of Mo-99 is produced by irradiating targets - typically a solid plate containing uranium clad in aluminium - in seven research reactors located in Australia, Canada, Europe and South Africa. This isotope has not been produced in the USA since the late 1980s.

Mo-99 and Tc-99m are distributed through an international supply chain on a weekly or more frequent basis, they noted. Such speedy delivery is essential, they added because these isotopes have short half-lives and therefore cannot be stockpiled.

There is a "substantial likelihood" of severe Mo-99 and Tc-99m shortages after next month, it said, "should any of the other current suppliers fail, and lasting at least until other global suppliers complete their planned capacity expansions, currently scheduled for 2017".

The committee that wrote the report therefore recommends that the US and Canadian governments continue to work to ensure there is an "executable and well-communicated plan in place" to restart the supply of Mo-99 from Canada between October 2016 and March 2018, if needed.

The USA uses about half of the Mo-99 produced worldwide, but demand has been declining there for at least a decade - by about 25% between 2009-2010 and 2014-2015. Domestic demand is unlikely to increase significantly over the next five years, the committee concluded, but international demand could increase in Asian markets.

About 75% of the world's supply of Mo-99 is produced using targets containing uranium enriched to greater than 90% uranium-235. Most of this HEU is of US origin. Converting Mo-99 production to targets using low-enriched uranium (LEU) would remove HEU from civil use and reduce the risks that it could be used for illicit purposes, the report noted. Four of the five global Mo-99 suppliers have committed to converting from HEU to LEU reactor targets, it said, and are "making uneven progress toward that goal". Conversion could be completed by the end of 2019 if current schedules are met, it added.

The report noted that Russia intends to become a global Mo-99 supplier and recommended that the US government engages with the Russian government to "clarify its schedule" for converting Mo-99 production from HEU to LEU targets.

Researched and written
by World Nuclear News