This is probably a question that the CNSC should answer, but essentially, the way we understand it is that, during its environmental assessment and before a plant can have its licence, the CNSC has to consider design-basis accidents. The plants have to be designed in such a way that they can't have accidents beyond that. They have to address those types of accidents.
Again, in reference to the Magellan report, some of these catastrophic accidents that they say should perhaps be studied further are things in the order of one in a hundred million years. That's why the CNSC does not consider those accidents, because one in a hundred million years is not very frequent.