Co-60 is made by irradiating rods of Co-59 inside a Candu reactor (Image: Bruce Power)

The medical isotopes were harvested from Bruce unit 8 during a scheduled maintenance outage and delivered to Ottawa-based Nordion for processing and distribution, the company said.

Co-60 is used to sterilise around 40% of the world's single-use medical devices, including syringes, catheters, IV sets, surgical gloves and gauze used in a wide range of health care applications: according to the head of the International Irradiation Association, a patient in surgery or receiving wound care or simply having a blood sample taken, is highly likely to be treated using products that have been sterilised using the radioisotope.

Medical-grade High Specific Activity - or HSA - Co-60 is an intense gamma emitter used in the treatment of certain brain tumours and breast cancers in a procedure known as gamma knife radiosurgery, delivering a single, high dose of radiation with a high degree of accuracy to the target. This limits damage to healthy tissues, lowering the risk of side effects for some patients when compared to other types of radiation therapy.

Canadian company Nordion (part of Sotera Health) is the world's leading supplier of Co-60 sources for gamma processing. "Cobalt-60 is critical for supporting global health care," Nordion President Riaz Bandali said. "Reliability of supply is key and Bruce Power continues to be a valued partner, supplying cobalt-60 for nearly 40 years."

Co-60 is made by irradiating rods of cobalt-59 inside a Candu pressurised heavy water reactor for up to three years (or in a RBMK light-water graphite-moderated reactor for up to five years). Around half of the current global supply originates in Canada, with reactors in Argentina, China, India, and Russia also producing the isotope.

With Ontario Power Generation's (OPG) Pickering plant, which also produces Co-60, pencilled in for closure in the mid-2020s, Bruce Power and OPG in 2016 signed a Memorandum of Understanding to work together to ensure the continued long-term supply of the isotope by expanding production to the Darlington and Bruce A plants.

On completion of October's Co-60 harvest, Bruce Power said it had installed "system innovations" to increase production for the next harvest to meet growing world market demands.