The science is very poorly understood. Waste disposal is one of the major question marks over the nuclear industry. In the UK there simply is no policy. They've been looking for a solution for decades, and they'll be looking for decades yet. And while that's true of the UK, it's also true worldwide.
Some countries believe they have found at least part of the answer.
Sweden puts LLW and ILW in a huge rock chamber carved out of the rock beneath the bed of the Baltic sea. Optimism And the nuclear industry itself remains hopeful. The disposal of HLW is surmountable.