No Need To Worry
And then I thought "Who bloody cares?".
It makes no sense to worry about something that will happen in 1000 or more years from now. Ten thousand years ago humans were little more than brutes living in caves and huts and using stone instruments; one thousand years ago running water was an utmost luxury and people couldn't even imagine bacteria and the like. Radioactivity has been studied scientifically only in, what, the last century and half.
There's no way to predict with any practical reliability the state of humanity in 1000 or 10 000 years from now. We may be either extinct or travelling across interstellar space, or some other unforeseen alternative.
In any case, an aliquote of radioisotopes escaping a nuclear waste repository appears to be of very little consequence. And other species? Evolving is something they have to do by themselves.
It sounds pretty stupid to reject what's probably our best energy source on the basis that some bad things might eventually happen at some remote point of the future (and by the way, building repositories which will remain safe for >10 000 years is well within our technological possibilities - but very expensive).