The nuclear reactor is needed to generate neutrons that bombard uranium-235 targets, with the resulting fission reaction producing Mo-99 around 6% of the time. This Mo-99 then decays into Tc-99m. Unfortunately, over 90% of the world's Mo-99 is produced by just five ageing reactors, resulting in an extremely fragile supply chain - the vulnerability of which was highlighted recently when unexpected shutdowns and routine maintenance closures combined to create serious shortages. But there are other ways to create Tc-99m, and ways that don't require nuclear reactors or a uranium target – itself a cause for concern as most facilities currently process highly-enriched (weapons-grade) uranium. Instead, researchers are investigating production methods based on cyclotrons and linear accelerators. Such processes exploit nuclear reactions within targets of Mo-100, bypassing the need for uranium completely.
In a bid to advance such technologies, the government of Canada has invested $35 million in four development programmes. The projects are headed up by: TRIUMF (Vancouver, BC); Canadian Light Source (Saskatoon, SK); Advanced Cyclotron Systems (Richmond, BC); and Prairie Isotope Production Enterprise (Winnipeg, MB) – a partnership between the University of Winnipeg, Acsion Industries and Health Sciences Centre Winnipeg.
"If Canada was going to build a new nuclear reactor, it'd cost a billion dollars," said Jeff Martin, professor of physics at the University of Winnipeg. "But with these proposed electron accelerators and cyclotrons, you have a smaller capital investment and can be up and running fast."
Read about Proton bombardment in the next article.
About the author
Tami Freeman is editor of medicalphysicsweb.