A temporary European shortage of radionuclides, caused by the closure of several nuclear reactors, has highlighted potential long-term problems with the supply of radioactive isotopes for medical imaging.

Since early September, planned and unplanned shutdowns in the five main reactors that produce isotopes for medicine and industry have drastically cut the supply of technetium-99m (Tc-99m), a radioactive tracer generated from molybdenum-99 (Mo-99) which is a by-product of nuclear fission. 

Hospitals affected by the shortage have been receiving on average around 60 per cent of their normal supply of Tc-99m, causing them to ration diagnostic procedures which use the isotope, says Wendy Waddington, a medical physicist at the UCL Institute of Nuclear Medicine. Without Tc-99m to rely on, hospitals are turning to alternative isotopes, such as thallium-201, that produce inferior images and expose patients to higher radiation doses - or are avoiding radioactive diagnostic imaging altogether.

The key loss, says Alan Perkins, honorary secretary at the British Nuclear Medicine Society, was the closure of the High Flux Reactor at Petten in the Netherlands. Air bubbles were found in the reactor’s cooling system in late August, forcing an unscheduled shutdown. This closure coincided with planned maintenance at other European nuclear medicine reactors - the BR2 reactor in Belgium and the Osiris reactor in France - as well as the Safari-1 reactor in South Africa. The large Chalk River nuclear plant in Ontario, Canada (which mainly supplies the US with medical isotopes) was also temporarily closed due to an electrical storm. Long-term storage of radiopharmaceuticals is impossible because both Mo-99 and Tc-99m have short half lives. 

The problems follow an unrelated incident last November, in which the Chalk River nuclear plant was closed for five weeks, causing radiopharmaceutical shortages in the US.

As a result of such problems, the European Commission has asked the European Medicines Agency (EMEA) to analyse the radiopharmaceutical shortage, in a bid to avert future problems.  EMEA have already approved the transport of nuclear material from the Osiris reactor in France to processing facilities at Petten to compensate for the closure of Fleurus, a Belgian production facility shut down because of a release of iodine-131. Collaborations with reactors in Canada and South Africa should also help to boost Europe’s supplies. 

The current shortage is only a temporary blip - mainly dependent on the reopening of Petten, estimated to be sometime in December. ’The question now is, how do we solve the long term issues?’ says Guy Turquet de Beauregard, vice president of the Brussels-based Association of Imaging Producers and Equipment Suppliers. There are few reactors able to generate Mo-99 due to safety and security issues surrounding the use of uranium-235, which is irradiated to give Mo-99. ’But these reactors are around 40 years old and there will be more problems with them as they get older,’ says Turquet de Beauregard. Plans for a new reactor in Canada, which would have boosted the supply of Mo-99, were scrapped in May this year due to design faults and legal disputes. 

While getting approval to build a new reactor is a lengthy and difficult process, demand for radiopharmaceuticals is fast increasing. Wolfram Knapp, president-elect of the European Association of Nuclear Medicine, suggests     that better international cooperation is needed to ensure reactor maintenance schedules don’t clash in the future. He also thinks existing reactors should be upgraded to allow them to produce Mo-99. Without further investment in nuclear programmes, agrees Perkins, the shortages seen this year could easily reoccur.

Manisha Lalloo

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