A Belgian nuclear reactor, BR2, is at the centre of an isotope shortage in Canada.

The reactor that produces the isotope Technetium-99m (Tc-99m), which is used in medical scanners to search for tumours and blood flow, started having problems Oct. 28. Workers discovered mechanical issues and it had to be taken offline.

Tc-99m is created from Molybdenum-99 (Mo-99) as it decays. Mo-99 has a 66-hour half-life, when it decays into Tc-99m, the isotope must be used in six hours.

The problem occurred just as three of the five reactors were scheduled for routine maintenance. BR2 is one of only six global Tc-99m plants worldwide and supplies Canadian hospitals.

Without the isotope, imaging specialists have "rearranged" appointments in order of urgency.

"So the shortage became very important because … in Canada, for example, we do about 1.1 million of those tests for cancer, for heart disease, for infection," Francois Lamoureux, president of the Canadian Association of Nuclear Medicine, told CTV's Your Morning on Thursday.

Although the brief period of disruption has caused scheduling issues in hospitals, Lamoureux says the shortage should be resolved by Nov. 21, as other reactors are set to delay schedule maintenance to aid the situation.

Radioactive isotopes are critical for imaging, but also for treating common forms of cancer, including skin and prostate cancer.

"This week was the worst, some departments had to cancel 90 per cent of their tests," Lamoureux said, expressing hope for a swing back to normal starting the end of next week.

This comes as the Canadian Cancer Society released a report detailing how 1.5 million Canadians have or are living with cancer. During the pandemic, cancer screenings took a backseat as hospitals were overwhelmed with COVID-19 patients. Pandemic-related disruptions have since caused delays and interrupted care for cancer patients, which may result in later diagnoses, the report reads.

Canada used to be one of the largest global suppliers of Tc-99m, which was produced at the Chalk River NRU reactor, northwest of Ottawa. In 2013, the federal government cut funding for the reactor. It fell into disrepair and stopped production in 2016.

During its heyday, the Chalk River reactor supplied the world with isotopes and in 2007, when it went offline unexpectedly, it is remembered as the most severe shortage of Tc-99m ever.

A reactor in B.C is producing the isotope, but because of the short six-hour lifespan, Lamoureux says it can only be used locally.

"So this is a major problem," he said of the technology around scanning. "They (researchers) will try to develop new technology, but it will take years."