Ontario Power Generation starts rebuilding Darlington 2

Work has begun to reassemble Darlington unit 2, Ontario Power Generation announced yesterday. The 878 MWe Candu unit is the first of Darlington's four reactors to undergo refurbishment to enable it to operate for a further 30 years.

The reactor face of Darlington 2 (Image: Ontario Power Generation)

Refurbishment of Darlington 2 began in 2016 when the reactor was shut down and isolated from the operating station, after which it was defuelled. The reactor was then completely disassembled, with the last of the unit's 480 calandria tubes removed on 3 May.

Reassembly began with inspections of the calandria vessel - the tank which holds the reactor's core of nuclear fuel as well as the heavy water moderator - using a remotely controlled camera to allow viewing of key areas such as high stress welds, reactivity mechanisms and moderator nozzles to assess their integrity. These features of the calandria vessel can only be inspected when the fuel channels and other components have been removed.

Bruce contract for NuviaNuvia Canada is to provide radiation protection services to Bruce Power's Major Component Replacement (MCR) programme.The MCR is part of a CAD13 billion, multi-year Life-Extension Programme that will see six of the eight Candu units at Bruce A and B undergo refurbishment between 2020 and 2053.

Rebuilding of the reactor will begin with the installation of calandria tubes, fuel channel assemblies and lower feeders. In total, 58 connected systems will need to rebuilt in sequence, in a precision operation which will take about a year to complete.

The refurbishment project also includes the rehabilitation of steam generators, turbine generators and fuel handing equipment, as well as system improvements and plant upgrades to meet current regulatory requirements.

The CAD12.8 billion (USD9 billion) project to refurbish Darlington's reactors is scheduled for completion in 2026. Refurbishment of unit 3 is scheduled to begin after completion of work on unit 2 to allow the implementation of lessons learned.

Researched and writtenby World Nuclear News