Do you mean in terms of nuclear waste or some other toxic externality? Would you please clarify what you mean here?
Nuclear waste - The federal government charged a mandatory fee in exchange for a promise to dispose of the nuclear waste. Yucca Mountain never opened, ergo the federal government renegaded on it's deal, but it's still collecting the fees. Without them stepping in, the power companies would have figured something out themselves.
Not for pu-239, about 50 times more time is right. Remember it is still highly toxic even when you exclude its radioactive emmissions and that's what it will take to do that.
Lead is highly toxic by way of being a heavy metal and most versions of it are perfectly stable. My opinion is that if we bury it X deep, that any future humans that go digging it up should be able to determine that it's toxic and mildly radioactive and know how to handle it if they're going that deep into the ground.
Anything those reactors produced will be hot and as toxic to life as anything can be. No structure will last 10k years and siting them in a porus mountain is the same amount of effort to do it in a mountain which actually would last.
You're forgetting the 'more radioactive = shorter halflife' thing. The problem with nuclear waste and current standards isn't the short lived isotopes, it's the less radioactive long half life isotopes. Pull out the long-life ones, feed them through the reactors again until there's only short half-life isotopes left. Yes, they'd be radioactive as all hell. But only for a short period of time. "A Candle that burns twice as bright burns for half as long" type thing.
Oh, and I disagree with you on our ability to construct a facility that would last 10k years. It'd be expensive, but we can do it rather easily.