IN Brief:
- Bruce Power began its Unit 5 Major Component Replacement outage on 1 November 2026.
- The refurbishment programme covers 480 fuel channels and calandria tubes, 960 feeder tubes, and steam generator replacement.
- Units 6 and 3 have returned to service following refurbishment, while overlapping outages are scheduled to continue at the Bruce site until 2033.
Bruce Power has taken Unit 5 offline at its nuclear generating station in Ontario, Canada, beginning a major component replacement outage intended to extend the reactor’s operating life by approximately 30 to 35 years.
The scheduled disconnection took place on 1 November, with Bruce Power confirming the start of the programme the following day. Unit 5 becomes the fourth reactor to enter the company’s Major Component Replacement (MCR) programme, which covers six generating units at the Bruce site.
Units 6 and 3 have already returned to electricity production following refurbishment, while Unit 4 remains under reconstruction. The addition of Unit 5 creates overlapping work programmes involving major reactor components, specialist installation activities, and the coordination of engineering contractors across several generating units.
The MCR programme includes the removal and replacement of 480 fuel channels and calandria tubes, 960 feeder tubes, and major steam generator equipment within the relevant reactor refurbishment scope. These components form part of the systems responsible for containing nuclear fuel, circulating coolant, and transferring reactor heat to the equipment used for electricity generation.
Bruce Power’s reactors use Canadian Deuterium Uranium (CANDU) technology. Unlike reactor designs that contain their fuel within a single large pressure vessel, CANDU reactors use individual pressure tubes arranged through a vessel known as the calandria, allowing coolant to circulate through separate fuel channels.
The pressure tubes contain the fuel bundles and carry the pressurised coolant that removes heat generated within the reactor core. Calandria tubes surround the pressure tubes and form part of the physical separation between the fuel channels and the moderator, which slows neutrons within the reactor.
During refurbishment, ageing fuel channel components must be removed and replaced while preserving the required alignment and integrity of the reactor’s internal structures. The work involves specialised tooling, controlled installation procedures, and extensive inspections to establish that the renewed assemblies satisfy their design requirements.
Each fuel channel connects to the reactor’s heat transport system through feeder pipes. These pipes carry coolant between the reactor channels and the wider circulation equipment, making their condition and installation important to the performance of the primary heat transport system.
Replacing feeder components requires carefully controlled work around the reactor structure and its connected systems. Pipe connections, materials, dimensions, and inspection requirements must meet the applicable nuclear engineering specifications before the renewed equipment can be returned to service.
Steam generators provide the next stage of the heat transfer process. Thermal energy carried by the reactor coolant is transferred to a separate water and steam circuit, allowing steam to drive turbine generators without mixing the reactor’s primary coolant with the secondary working fluid.
The replacement and integration of steam generators involves substantial mechanical handling and pressure system engineering. The associated piping, supports, inspection procedures, and system interfaces must be coordinated with the wider refurbishment programme before commissioning activities can proceed.
Bruce Power has developed its replacement methods through successive outages. Unit 6 returned to service in 2023 after refurbishment was completed ahead of schedule and below its approved cost, with the company reporting C$52 million returned to Ontario ratepayers.
Unit 3 returned to service in June 2026, more than seven months ahead of schedule. Bruce Power reports that the early completion and associated financial performance resulted in approximately C$150 million being returned to ratepayers through arrangements with Ontario’s Independent Electricity System Operator.
The Unit 3 programme also introduced robotic tools for work on a CANDU reactor face. These systems allowed selected operations to be mechanised, providing additional precision and repeatability for activities undertaken around the reactor’s internal components.
Experience gained from Unit 3 has subsequently informed the work at Unit 4, which began its MCR outage in 2025. Bruce Power reports that Unit 4 is progressing ahead of the comparable stage of the preceding refurbishment, although its overall outage remains incomplete.
Several simultaneous refurbishment projects require careful coordination of specialist labour, manufacturing capacity, equipment access, and inspection resources. Work programmes must account for the availability of replacement components and the sequence in which existing systems can be dismantled, renewed, tested, and restored.
The company states that approximately 95% of its expenditure remains in Canada. Its ongoing site activities and refurbishment programme are estimated to sustain 22,000 direct and indirect jobs annually, with approximately C$4 billion of economic activity across Ontario.
Those figures describe the company’s wider operations and life-extension programme rather than employment or expenditure attributable solely to the Unit 5 outage. The duration and eventual cost of the individual refurbishment will depend on the engineering work completed and the performance of its delivery programme.
The final stages of reactor refurbishment extend beyond the installation of new components. Renewed systems must undergo inspections and commissioning checks, with the operator demonstrating that the plant satisfies the applicable technical and licensing requirements before the reactor can return to power operation.
Return-to-service work also involves controlled reactor restart, progressive power testing, and verification of the generating equipment. Those activities establish the conditions under which a refurbished unit can be synchronised with the electricity network and subsequently returned to commercial operation.
Bruce Power intends to begin the Unit 7 refurbishment in 2028 and Unit 8 in 2030, with overlapping MCR outages continuing until 2033. Ontario is also evaluating a further refurbishment of Units 1 and 2, which returned to service in 2012 following an earlier period out of operation.
The Unit 5 outage marks another substantial phase of engineering activity within that programme. Completion of the component replacement, commissioning, and regulatory requirements will determine when the reactor returns to service with its renewed operating capability.
