The items that govern the life of each unit are the pressure tubes or the reactor core components. The life starts as soon as those components are replaced. On a unit-by-unit basis, the lifespan is dictated from when those components are replaced. Each unit will be replaced initially with a three-year interval and then 19-month after that. It's 30 years following that component replacement. It can be up to 40 years, depending on how those pressure tubes perform.
That's part of the evaluation of the life of the plant. We look at the health of the pressure tubes and how they are aging. We complete the necessary inspections and studies. From that we're able to forecast the life of the pressure tubes. The minimum would be 30 years. I would expect 35, 40, or beyond, in fact. That's how we govern the life of the plant. At that time you can make a decision on whether to refurbish it again or retire it.
In the case of Darlington and Bruce Power, the economics are pretty clear. They're large units. It's very economic to refurbish the power plants. With Pickering they're smaller units, so it's less economic to do so, and that's why the decision was to retire Pickering. The decision for Pickering would be to build a new facility, one that is more economic than Pickering.