Final step in Darlington Unit 2's removal phase now complete

With extraction of the final calandria tube from the Unit 2 reactor on May 3, 2018, the removal phase on the Darlington Refurbishment Project is now complete, and the team is ready to rebuild.

A calandria tube (CT) is a long cylinder made of zirconium that sit inside the reactor’s core, housing the fuel bundle-containing pressure tubes. There are 480 CTs per reactor.

They were removed using specialized tooling, operated remotely. CTs were then transferred to protective flasks and transported to the Retube Waste Processing Building, where they are being processed for storage.

Completion of this work sets the stage for reactor reassembly.

This phase began with four days of calandria vessel inspection. During this time, a camera is inserted and remotely controlled to allow viewing of key areas, such as high-stress welds, reactivity mechanisms and moderator nozzles.

“The only time we can look at these key features of the calandria vessel is after the fuel channels and other components have been removed, so this can only happen now,” said Mike Allen, Senior Vice President, Nuclear Refurbishment.

This is followed by inspection and reconditioning of a number of components. Then, the rebuilding of the reactor begins with installation of calandria tubes, fuel channel assemblies, and lower feeders.

“After years of planning, we’re excited to move forward with rebuilding this reactor, so it can provide Ontarians with an additional 30 years of clean, reliable, affordable power,” Allen said.