"Deep borehole disposal"
The inner earth is radioactive deep down, but it isn't done with some 4 kilometers of drill hole depth to get rid of radiating stuff.
You need liners and cementation and this whole idea may easily be more expensive than switching technologies all over.
At interesting reservoir dump depthts (interesting, financially speaking because any bit deeper it is not worth the drilling costs) you still have ground water, gas pressure releases, stress - strain cracks in the deeper ground. Guaranteed for the next some 10,000s of years to come ?
Scientists here already thought about that, and gave it up quickly.
But then as long as it's not visible any more lol
Greetings,
Catfish