What’s involved: islanding a nuclear reactor

Following the successful defuelling of Unit 2 nuclear reactor, the first of Darlington Nuclear Generating Station’s four units, the project has safely islanded it from the rest of the power plant.

But what does islanding mean?

Islanding creates a safe, precise work area, separated from the operating plant through a system of physical barriers and controls. The process significantly increases efficiency by allowing for the simultaneous opening of both of the unit’s airlock doors.

The airlock is a system consisting of two doors with a chamber separating them, to allow safe access to the reactor vault. During regular operations, only one door can open at a time.

“Now that the reactor’s been defuelled and islanded, conditions within the reactor vault have changed,” says Bert Boston, Islanding Project Manager at OPG. “As a result, the airlock doors can be opened to allow for the unobstructed movement of tools, equipment and personnel.”

Islanding was carried out through the installation of 16 bulkheads, each weighing about 5,443 kg (or 12,000 lbs).

Bulkheads are steel structures placed over openings between the reactor’s fuelling machine duct and its vault. They are brought into the vault in pieces or panels, which are then assembled and welded together side-by-side to seal the openings to systems connecting to the other operating units.

Watch how bulkheads are installed: