The problem is Congressional mandate: Any storage cask must survive 10,000 years without leakage (yeah, citation needed, looking for it). Staying intact through train wrecks and 30 foot drops is trivial - can you build a device that will withstand 10,000 years of erosion/corrosion/whatever? And be recoverable/countable for the duration... There are lots of technically possible disposal methods - I personally like the "drop it into the deep ocean trench off SoCal." As the plates move (Farallon plate going into subduction), the waste just goes down into the bowels of the earth where it came from. Problem? Congress wants it countable - and once it goes down, you can't get it back.