Is it possible (and safer than burying) to package the waste up and dump it in outer space somewhere?
The safest option of space dumping would be to send it into the Sun, but that takes a godawful amount of fuel: you must climb out of Earth's gravitational well at 11,2 km/s and then nullify Earth's orbital velocity of 31,5 km/s before you can crash the stuff into the Sun. Per kg of waste you need about 565 MJ of energy to make the orbital corrections. Burning 4 kg hydrogen gives that energy, but once you consider that these 4 kg occupy about 60 litres
and that you require oxygen, containment devices, engines, and what-not too the numbers begin to look decidedly bleak. A more elegant way is probably to use hydrogen for the first stage, and then to use the material's own radioactivity to drive an ion engine. But this technology is still in its infancy. And it still discounts problems with exploding rockets and the like.
There's a third reason why you wouldn't want it in space: the supply of radioactive elements on Earth is limited, and while there is little practical use for the isotopes which are created during fission at the moment, you never know what we come up with in the future.
I think that people are not up to making the decision to power their needs for megawatts with nuclear fission. In the near future, coal and tar sands will be much more important: they're nasty and unclean, containing practically the entire periodic table, but there's enough to last us for centuries. If you couple that to clean fuel cell technology of the MCFC- or SOFC-kinds, and factor in a few decent pandemics killing off a few billion people, then we're all clear.
