Radioactive isotopes are widely used in basic and applied science and engineering, most notably as environmental and industrial tracers, and for medical imaging procedures. The majority of the radioisotopes in use today are artificially created by the bombardment of a stable chemical element or compound with subatomic particles in either a particle accelerator or a nuclear reactor such as MNR. Reactor-based radioisotope production relies on the (n,y) nuclear transformation that occurs when a suitable target material is exposed to the neutron flux in the reactor core. An example of this is the production of lutetium-177 from lutetium-176.

 Neutron Capture

Schematic representation of neutron capture event and direct production of radioisotopes.


A variation on this method is to generate a short-lived radioisotope that undergoes radioactive decay to yield the longer-lived radioisotope of interest. This strategy is used for the production of high specific activity iodine-125, which is a beta- decay product of xenon-125 formed when xenon-124 captures a neutron. A wide variety of radioisotopes can be produced at MNR by neutron irradiation of appropriate target materials.

 Capture Decay

Schematic representation of neutron capture event and indirect production of radioisotopes.


The McMaster Nuclear Reactor is well-suited to radioisotope production due to its reasonably high neutron flux and open-pool design, which facilitates the loading and removal of irradiation targets from the reactor core. In addition to the small quantities of radioisotopes produced and used by individual researchers, MNR is one of the world’s leading suppliers of I-125, which is used in nuclear medicine for the treatment of prostate cancer. Isotopes produced at MNR over the years include Na-24, P-33, K-42, Sc-46, Cu-64, Mo-99, Tc-99m, Sb-124, I-125, I-131, Tm-170, Lu-177, Re-186/188, Ir-192 and Au-198.