You might be surprised to know that an accident, in a sense far more severe than what happened at Three Mile Island, happened at Pickering in August of 1983. One of the pressure tubes in Reactor 2 ruptured during full-power operation.
It's never talked about, because the operators were able to bring the reactor quickly to a "safe" condition. There were no radiation exposures to personnel, or radioactive releases to the environment, beyond normal (minimal) operating levels.