What difference does it make if Yucca Mountain leaks waste in 1000 years, or even 100 years?
Seriously. Not that it’s at all likely to, but so what if it does?
There are two possible scenarios. Either we’ll continue advancing, and this planet’s entire population (much less the Yucca Mountain area) will be a minority of the human race in 3005, or we’ll stagnate, and then revert to savagery when our fuel runs out, in which case there won’t be very many people living in the desert and the human population as a whole will have much, much bigger problems than a bit of radioactive waste in an environment that most of them won’t be able to go anywhere near without dying of thirst.
Anything that maximizes the odds of the first scenario coming to pass, and minimizes the odds of the second, is worth doing at just about any cost. Including radioactive waste in Yucca Mountain, and even including leaking radioactive waste in Yucca Mountain.
After Peak Oil, nuclear power is our only hope of not reverting to the worst aspects of the 19th Century (you know, the horse-and-buggy level of energy and industry and technology that caused all the misery that the spectacularly successful laissez-faire economic policy keeps getting the blame for). With a sensible (i.e., much lower and stable, particularly with respect to plants already under construction!) level of regulation on the nuclear power industry, the risk associated with possible meltdown is still impressively low; our plants would have to be many, many orders of magnitude more shoddily built to duplicate the Chernobyl plant, and even with that sort of disaster happening occasionally, which it wouldn’t with any nuclear plants we’re ever going to build, we’re still bearing far less overall risk than we would be running out of oil with no large-scale replacement available.
Of course, any high-density terrestrial energy source is only a stopgap to get us to space so we can use the abundant energy found there. If we screw around until every form of stored energy here is used up, then we’ll be stuck forevermore using energy at a lower rate than it arrives from the sun, which as far as I can tell would leave us stranded on this damned rock until the Sun swallows it whole, or until someone manages to produce antimatter or a fusion generator using only the infrastructure that can be built and operated in such a low energy environment, which may amount to the same thing.
There is no such thing as perfectly safe. Every course we take has risks, and the one with the lowest overall risk involves nuclear power, and lots of it.
What about automotive fuel and fertilizer? How are we going to replace that with nuclear power?
Chemical synthesis, powered by nuclear reactors. There are several schemes for getting fuel from corn, organic waste, and so forth, that show little energy profit. Hook up a nuke plant, and even fuel processes that show a loss would, in effect, ship nuclear power to cars and cargo vehicles. Nuclear plants dedicated to this process can run at constant load as cheaply as physically possible, without dealing with continuously variable load. Given cheap enough energy and high enough demand, nuclear powered synthesis of everything we’re getting from oil should do the trick.