US Nuke Plants at higher risk of flooding: Engineers
When Fort Calhoun nuclear plant in the US flooded within months of the Fukushima meltdowns, it looked like a serious situation to me, especially when the barrier they set up around the reactors burst. But "authorities said there's nothing to be concerned about".
Now it appears that whistleblowers in the plant say the risks of flooding at this and other plants are higher than is being reported. In particular they are concerned with catastrophic dam failures:
Such failures are quite rare. But the point is if hundreds of nuclear plants operating over many decades, some of them are going to experience rare events like tsunamis. Hence they must be designed w/ such events in mind.