""it will fix itself". By radiating the surrounding environment ?"
We humans have a bias. We live in the biosphere, and from our perspective, we are surrounded by it. Everywhere we go from day-to-day, life abounds.
But this is a very deceptive bias. Most of the universe is not the biosphere. Outside of the biosphere, the universe is rather nasty. High levels of radiation are the norm. Extreme temperatures (or what we consider extreme temperatures) are the norm. Very life-unfriendly chemical regimes are the norm, either by being full of nasty chemicals (Venusian sulpheric acid) or, more commonly, being so full of boring chemicals that life is very very difficult (Mars).
This comes up most often in space exploration, when I see someone being concerned about putting nuclear power on the moon, whatever will we do with the waste, and the answer is that the lunar surface is already a radiation hell-hole. If you dump something like that on the surface, yeah, we humans will want to stay away from it, but it's a lot less material change than our intuition thinks. Our intuition wants to say "but what about all the wonderful life that will be affected", because everywhere we go, there is life. But there isn't any on the moon. Nothing will die because we dumped a couple hundred pounds of waste on the surface.
Similarly, the subsurface of Earth below the biosphere... and I include the bacteria living in rocks and the water table and everything like that as part of the "biosphere", we know it goes deep but it doesn't go down forever... is already an incredibly harsh place. The chemistry is already nasty. It's already full of chemicals either too "interesting" or too "boring" to be useful for life.
I'd like to see a good analysis to make sure this isn't going to work its way back up into the biosphere, yes, but your intuition that anywhere we put something, some life is going to be affected, does not necessarily apply to a mile under the surface. "Radiating its surrounding environment" is definitely not an issue in the slightest. There is no "environment" there, in the sense you mean. I'm more worried about what might physically migrate around into something that does have an "environment", but a mile is a long way for anything to travel through solid rock, and it needs to move pretty quickly too to get up into the biosphere while it's still a danger.