how much of the isotope waste half life is 80 years?

I am genuinely conflicted about this, honestly. The radioisotope fuel stock was someplace natural to begin with, and potentially vulnerable to disruption and exposure to the environment.

It's honestly a well managed and well understood problem.

Below chart shows the drop in radioactivity over time for different groups of isotopes. The blue line is the natural uranium. The fission products drop below the natural uranium level of radioactivity after 300 years (mind, it's a logarithmic chart). These fission products are the most dangerous part of what comes out of a nuclear reactor, as their short lifespans - ranging from seconds and minutes, to 30 years - is what makes them highly radioactive. The plutonium an actinides are fuel that could be recycled (it's really a waste to waste them).

So, to answer your question: after 80 years, we're well into the third half life on caesium-137, which is the longest lived of the fission products, clocking in at 30 years. By year 80 it's reaching around 15 to 20% of its original radioactivity. Still dangerous at that point, but sealed in a concrete casket, completely harmless.

Nuclear waste is the only waste that disappears on its own accord, and is a very small amount all in all. All other energy sources, including renewables, leave toxic waste streams that aren't (mostly) radioactive, meaning they'll be toxic until the end of time. That, I would say, is actually a far bigger problem that we still need to fix properly.