The recently refurbished unit 1 reactor at Ontario Power Generation’s (OPG’s) Darlington Nuclear Generating Station is now producing cobalt-60 (Co-60) isotopes for world distribution. Co-60 is used to sterilise 30% of the world’s single-use medical devices, as well as certain food products.
OPG plans to modify Darlington’s three other units to allow them to also produce the isotope to help secure a stable, reliable global supply. During refurbishment, OPG made modifications to the unit to enable it to produce the critical medical product. The work will be undertaken in the course of the refurbishment of unit 4, the final unit to be overhauled in the Darlington Refurbishment project, as well as during planned maintenance outages on units 2&3.
Several isotopes, including Co-60, are produced in OPG’s nuclear stations. After three years of activation in the unit 1 reactor, Darlington’s new supply of Co-60 will be harvested during a maintenance outage and delivered to Nordion, an Ottawa-based health sciences company, to be packaged and distributed to gamma sterilisation facilities around the world.
For decades, Ontario’s Candu reactors have produced Co-60 isotopes for distribution around the world. “We are now proud to continue this legacy at our Darlington Nuclear station, which will be a critical source of this invaluable product for decades to come,” said OPG President and CEO Nicolle Butcher.
Currently, about 50% of the world’s Co-60 is supplied by Ontario’s nuclear reactors, with the isotope being first produced in the province in 1971 at OPG’s Pickering Nuclear Generating Station. Darlington’s new capability will ensure a stable and reliable when Pickering ends commercial operation in the coming years and prepares for its potential refurbishment.
“Cobalt-60 is essential to the safety of the healthcare industry and to our mission of Safeguarding Global Health,” said Riaz Bandali, President of Nordion. “OPG has been a trusted partner in this mission for more than 50 years, and we are proud of what we have accomplished together at Darlington.”
OPG subsidiary Laurentis Energy Partners currently produces molybdenum-99 (Mo-99) isotopes at Darlington’s unit 2 using a proprietary Target Delivery System, designed and commissioned in partnership with BWXT Medical, that allows harvesting of the isotope while the reactor is still in operation. Mo-99’s decay product, technetium-99m, is used in more than 40m medical procedures each year to detect illnesses such as cancer and heart disease. Laurentis soon hopes to use the same system to produce yttrium-90 isotopes, a potentially life-saving product instrumental in treating several diseases, primarily liver cancer.
The Co-60 life cycle begins with the mining of Cobalt-59, a naturally-occurring non-radioactive material. The element is removed from the ground and processed into pure Co-59 powder, which is then compressed into slugs. These are assembled into bundles to form Cobalt adjuster rods, which are then shipped to OPG’s Darlington Nuclear station.
There, the rods are inspected before being loaded into the reactor core of unit 1. During a planned maintenance outage of the unit, cobalt adjuster rods are placed into the reactor core. This unit has been converted to use cobalt adjuster rods, rather than stainless steel rods. Adjuster rods serve a vital function and are part of the Reactor Regulating System.
Over the course of about 36 months, the rods are irradiated and the Co-59 changes at the atomic level to become Co-60. During a unit outage, harvesting of the mature Co-60 adjuster rods begins. These are carefully extracted using special equipment and loaded individually into a protective flask container and transported from the reactor building to the irradiated fuel bay.
Each Co-60 adjuster rod is then removed from its flask and carefully lowered into the fuel bay to be inspected, measured, and organised into Co-60 bundles. Finally, the Co-60 bundles are loaded underwater into a purpose-built shipping flask, which is then craned out of the bay and into a decontamination room, where it is dried and purged with argon gas.
The prepared flasks are then loaded onto a trailer and delivered to the processing facility at Nordion in Ottawa-where it is processed for industrial or medical use and shipped to the customer.
