1) Yes its extremely trivial, aside from shielding and non-homogenous and screwing up issues. 2) Yes because for example glass is stable in acid and unstable i

1) Yes its extremely trivial, aside from shielding and non-homogenous and screwing up issues. 2) Yes because for example glass is stable in acid and unstable in some alkali so neutralizing the "stuff" before mixing it into glass bricks for all eternity would be Highly advisable if you want the glass brick to be unchanged for 100K years or 1M years or whatever. Aside from acid/base reactions with the glass itself there are solubility situations where a simple reaction might convert some radioactive salt that is highly soluble in water to something that's essentially waterproof. Note that the glass for vitrification is not exactly mere window glass, its some weird stuff, and adjusting its mix might help depending on what you're trying to dissolve into it. (edited to extend answer #2, most of the waste you put into a vitreous block is not radioactive, you can't use the gear from answer #1 to tell what most of it is made out of) On a high level this overall discussion has gone off the rails because the 100K and 1M numerological numbers come from glass vitrification and stainless steel corrosion theoretical studies; it has little to nothing to do with radioactivity; you could vitrify coal ash or industrial waste or Atari 2600 game cartridges the same way for 1M years if you felt like it. Or at least people think that storage tech will last 100Kyrs Of course radioactive waste is harmless once it finished decaying whereas arsenic is forever so its kinda pointless to try and stockpile industrial waste for 1Myrs whereas nuclear waste is the only kind of waste that actually goes away with time. No human has ever made an industrial artifact that's lasted 1M years so things are kind of fuzzy at that kind of extrapolation.