Radioisotope supplies stable but still vulnerable

26 September 2017

Positive actions have resulted in more stable supplies of key medical isotopes in 2017 than predicted three years ago, but vulnerabilities remain, a side event at the International Atomic Energy Agency's (IAEA) 61st General Conference in Vienna heard last week.

The medical isotopes side event in session at the IAEA General Conference (Image: F Nassif/IAEA)

The IAEA event examined the current supply scenario for molybdenum-99 (Mo-99) and its daughter isotope, technetium-99m (Tc-99m) and alternative production routes for the isotopes. Tc-99m is the most widely used radionuclide for medical imaging, used in more than 30 million nuclear medicine scans per year. It is extracted from Mo-99 using a Mo-99/Tc-99m generator device. Both radioisotopes have to be used quickly once they are produced, so hospitals worldwide need a constant supply of them.

Mo-99 has primarily been produced by a limited number of research reactors, many of which have been operating since the 1960s, and in the case of Canada's NRU, the 1950s. Over the past decade, these reactors have required more maintenance, and some have faced unexpected outages. This led to supply disruptions and significant radioisotope shortages, particularly in 2009 and 2010.

South African Nuclear Energy Corporation subsidiary company NTP Radioisotopes SOC Ltd (NTP) has become the first major producer of Mo-99 to convert all of its production process from the use of highly enriched uranium to low enriched uranium. NTP completed the conversion in August following a multi-year collaboration with the US Department of Energy's National Nuclear Security Administration (NNSA). David Huizenga, the NNSA's acting deputy administrator for Defense Nuclear Nonproliferation, said South Africa and NTP had demonstrated "outstanding global leadership" in completing the "lengthy and technically challenging" conversion project. "NNSA has been extremely pleased to support NTP's successful efforts to cease HEU-based Mo-99 production while continuing to play a key role in ensuring a reliable global supply of this crucial medical radioisotope," he said.

Medical practitioners responded by using isotopes more efficiently in medical scans, helping to lower demand to a level that could be successfully met by the remaining suppliers, who have also worked to increase production capacities.

"Following the unforeseen disruptions in supplies, we assessed the likely supply situation in 2014 and, at that time, the risk of shortages was expected to get worse as of 2017," Kevin Charlton, a medical isotope expert and analyst from the OECD Nuclear Energy Agency (NEA), said. "But now it's 2017, and we can report that positive actions taken by the players in the supply chain have increased the production capacity of existing facilities, and the supply situation is now more stable."

The current supply chain should be sufficient until "at least" 2022, Charlton said, but still requires "careful and well-considered planning for the foreseeable future". This includes monitoring supplies from alternative technologies as they enter the market, and monitoring the price changes needed to ensure a long-term, sustainable model.

New methods

At the same time as working to increase existing production capacities, work is also under way on new, alternative methods of producing radioisotopes such as the use of linear accelerators to produce Mo-99 from naturally occurring Mo-100 or to produce Tc-99m directly. Accelerators are relatively easy to establish for countries that require a facility solely for the production of radioisotopes. They can be operated only when needed and do not produce radioactive waste, Kennedy Mang'era, chief operating officer of Canadian Isotope Innovations, said.

The new method is economically competitive but the Mo-99 produced is of low specific activity, making it unsuitable for use in existing alumina-based Tc-99m generators, Mang'era said. Current generators must therefore be improved, or new ones developed. A research project launched earlier this year and coordinated by the IAEA is to further develop this method. It will also focus on optimising available generators and develop new ways to separate Tc-99m from Mo-99.

Researched and written
by World Nuclear News