Glassification (mixing waste with sand, heating, and turning the stuff into glass) works really well. Stable, leak-proof, easy to handle. Hanford was going to start glassifying waste there a couple of decades ago, and some idiots gave the contract to Bechtel. Bechtel put up a building, got the equipment delivered, found it wouldn't fit into the building, and left it out in the rain all winter while they cashed their check. Not sure why the project didn't get re-started, I've never heard any actual objections to the process.
The best place for waste disposal is the bottom of the oceanic trenches, where it will be subducted into the Earth's mantle. The military objects of course, claiming that unidentified "enemies" might steal it. Of course if they have the ability to reach the bottom of the oceanic trenches and dig shit up then they probably already have the technology and money necessary to do considerably worse things than spread around some radioactive glass.