Molybdenum-99

Molybdenum-99 decays with a 65.94-hour (about 2.75-day) half-life to technetium-99m, and its whole purpose in the supply chain is to act as a transportable parent: its longer half-life lets bulk 99Mo be irradiated, processed and shipped internationally to radiopharmacies, which then load it into 99Mo/99mTc generators and elute the six-hour daughter locally, on demand, for the roughly tens of millions of Tc-99m scans performed worldwide each year.

Historically some 90-95% of global 99Mo came from just five ageing research reactors, three in Europe (BR2 in Belgium, HFR in the Netherlands, and the now-closed OSIRIS in France), one in Canada (the now-closed NRU) and one in South Africa (SAFARI-1); by the OECD/NEA's 2025 accounting the surviving fleet, including BR2 and HFR, remains dominated by reactors that were not designed for continuous isotope production and were commissioned in the mid-20th century, so unplanned outages are a recurring risk: an October 2024 structural fault forced an unplanned shutdown of the HFR, which combined with scheduled maintenance elsewhere to worsen shortages of both 99Mo and 99mTc that winter.

The other defining event of the last fifteen years has been the conversion from highly enriched uranium (HEU, historically 45-98% 235U) fission targets to low-enriched uranium (LEU, under 20% 235U) for non-proliferation reasons: Curium's Netherlands processing facility completed conversion in January 2018, and IRE (Belgium) completed its conversion in March 2023, after which the OECD/NEA estimated that more than 90% of global bulk 99Mo production capacity came from non-HEU sources. LEU targets are less efficient and generate more waste per curie produced, and the industry's underlying economic problem, according to repeated OECD/NEA studies, is that irradiation and processing prices have historically been too low to fund the reactor and processing capacity replacement the ageing fleet needs; the 2010 NEA economic study estimated irradiation-service prices would need to rise by up to roughly a factor of nine to be sustainable. New non-fission routes are diversifying supply: NorthStar's RadioGenix System, which produces 99Mo by neutron activation of enriched or natural molybdenum targets rather than uranium fission, reached commercial scale in the 2020s (though NorthStar separately announced in 2023 a temporary halt to one production line), and Australia's ANSTO and South Africa's NTP Radioisotopes remain major LEU-fission suppliers outside the historic European/Canadian core.