Many years ago the French developed a method of Vitrification for nuclear wastes. The theory being that by turning it into a glass-like substance you reduce the chance of any container leaks causing contamination as far as you possibly can. For all that it’s still just as radioactive and dangerous, that is the best solution I’ve heard of. The US refuses to use that process though. I’ve never heard why, though the person who first told me about it thought it was because the French invented it.