Safe until it kills millions when a plant blows up.
Unlike, say, coal, which kills millions under normal operations, right?
Or didn't you know that routine coal-mining fatalities are a couple of orders of magnitude more numerous than all fatalities associated with nuclear power? Hell, coal mining fatalities in the 20th century in the USA ALONE were comparable to the death-toll from the Hiroshima and Nagasaki bombings.
And then there's the rest of the world's coal mining casualties, plus secondary effects from the pollution.
And never mind that nuclear plants don't "blow up". Unless you fill them up with TNT and set it off, of course.