All major global molybdenum-99 (Mo-99) production facilities are now using low-enriched uranium (LEU) targets instead of proliferation-sensitive highly-enriched uranium (HEU) following the completion of work to convert Belgium's National Institute of Radioelements (IRE) medical isotope production facility.
The production of Mo-99 using LEU at IRE's Fleurus facility (Image: IRE)
Historically, Mo-99 - the most widely used radioisotope in nuclear medicine for diagnosis - was usually produced by irradiating HEU, which is seen as a potential nuclear proliferation risk, in nuclear reactors and then processing the irradiated material to extract the Mo-99.
Fulfilling a commitment made at the 2012 Nuclear Security Summit, the US Department of Energy's National Nuclear Security Administration (NNSA) provided financial and technical assistance to global Mo-99 producers for the conversion from HEU to LEU targets. These conversions were technically complex, requiring qualification of new LEU targets for irradiation in nuclear reactors, modification of specialised equipment for processing irradiated targets, and extensive reviews from both nuclear safety and medical regulators.
With help from NNSA, South Africa's NTP Radioisotopes converted to LEU targets in 2017 and the Netherlands' Curium converted in 2018. The fourth major Mo-99 producer, the Australian Nuclear Science and Technology Organisation, has always used LEU targets.
Preliminary consultations between the IRE - the world's leading producer of Mo-99 - and the Belgian nuclear regulator, the Federal Agency for Nuclear Control (FANC), on the conversion from HEU to LEU targets began in 2015. IRE requested in July 2016 to amend its licensing conditions to enable the switch. On 24 October 2017, the permit for the development of LEU production was granted by Royal Decree. FANC and its technical subsidiary Bel V approved the start of Mo-99 production using LEU on 14 April 2020. IRE produced its first batch of Mo-99 using an LEU target in May that year.
In February 2021, IRE announced that its first commercial deliveries of iodine-131 (I-131) - used for therapeutic purposes - based on the irradiation of LEU targets had started.
IRE has now announced the complete conversion of its production process to LEU, ending the global civil use of HEU for the production of medical isotopes.
"This complete conversion to a LEU process represents the culmination of years of work and collaboration between the R&D, production, safety, quality assurance and regulatory teams of IRE around an entirely new industrial process for supplying Mo-99 and I-131 to healthcare professionals, without impacting the site's production capacity," IRE said. "This outcome would not have been possible either, without the upstream collaboration of the research reactors which irradiate the uranium targets, but also downstream thanks to IRE customers who had to modify the application files of their Mo-99 and I-131-based drugs and have them approved."
"IRE will continue to innovate in order to contribute even better to saving lives thanks to nuclear medicine applications, while increasing the safety of our processes and our facilities," said IRE CEO Erich Kollegger.
"For decades, access to life-saving medical isotopes depended on the shipment of proliferation-sensitive nuclear material across continents," noted NNSA Administrator Jill Hruby. "With IRE's production facility converted to LEU, all major producers across the Mo-99 industry can perform their vital work without HEU targets."
NNSA is also helping research reactor operators convert from HEU to LEU fuel - some of these reactors provide irradiation services for Mo-99 production. Of the six research reactors with a major role in Mo-99 production, five now use LEU fuel, and the sixth - Belgium's BR2 research reactor - is expected to convert in 2026. LEU test assemblies are current being irradiated in this reactor as the final major technical step towards conversion.
