A visible, glowing core
Submerged in a pool of light water 10 meters deep, the McMaster Nuclear Reactor (MNR) core is fully visible during operation. It first went critical in April 1959, becoming the first university research reactor in the British Commonwealth. The reactor is an open-pool type, meaning its fuel is not enclosed in a vessel but is suspended in water, which acts as both a coolant and a moderator. This design allows for easy access for experiments and a clear view of the core.
The blue glow emanating from the reactor is Cherenkov radiation. This phenomenon occurs when charged particles, in this case beta particles from decaying fission products, travel through the water faster than the speed of light in that medium. The speed of light in water is about 75% of its speed in a vacuum. As these energetic particles outpace light, they create an electromagnetic shockwave, analogous to a sonic boom, which is visible as blue light. This glow is a direct visual confirmation of the nuclear reactions taking place within the core. The reactor is fueled with low-enrichment uranium and has a thermal power output of 5 megawatts.
A hub for research and medicine
The McMaster Nuclear Reactor does not generate electricity; its its primary purpose is to be a source of neutrons for a wide range of applications. One of its most significant activities is the production of medical radioisotopes. The MNR is the world's leading producer of iodine-125, accounting for more than 60% of the global supply. This isotope is an important component in brachytherapy, a type of internal radiation therapy used to treat cancers, including prostate, brain, and eye tumors. The reactor produces enough iodine-125 to treat over 70,000 cancer patients annually.
Beyond isotope production, the facility is a center for materials science research. Scientists use neutron beams from the reactor for Neutron Activation Analysis (NAA), a highly sensitive technique for determining the elemental composition of materials. This non-destructive method has been used on everything from geological samples for the mining industry to irreplaceable archaeological artifacts. Researchers have also used neutrons from the MNR to analyze engine turbine blades for commercial aircraft and even to discover a hidden composition beneath a Van Gogh painting.