The half life of Plutonium is ~24k years. That's way beyond a time frame we have any grip on. Then its still very, very dangerous. Uranium (nuclear fuel) has a half life of 200k - 4.4 million years. Then its half as dangerous.
CO2 has a half life of ~ 10 years in our atmosphere btw.
Elements with very long half-lives aren't very radioactive. Something with a half life of millions of years is essentially not radioactive at all.
Nuclear fuel itself isn't radioactively dangerous, it's dangerous because it's a heavy metal (like lead).
After nuclear fuel is reacted, it produces a bunch of nuclear decay products. Some of these decay products have a half-life of 10s of years, which are the problems: they're short enough to be dangerously radioactive, but long enough that they need to be handled carefully for a long time. But not for 10s of thousands of years.
And those things aren't very radioactive. Just as I said.
Most of what you've read about plutonium is patent nonsense. For one, it isn't even close to being the "most toxic substance known". You can pick up a lump of it and hold in in your hand. You'll be fine. Really. It is an alpha emitter, and alpha radiation can be stopped by your skin or even a piece of paper. You'd have to eat it before you saw any ill effects.
Not to mention that plutonium is a useful nuclear fuel. It's not going to be left lying around.
You do know that the ocean has megatons of uranium in it? Why aren't you concerned about that?
For that matter, we could grind up all the nuclear waste ever produced and disperse it in the ocean. It wouldn't change the radioactivity of sea water by any significant degree.
The Soviets used to dump their scrap sub reactors in the Arctic Ocean whole. There are a bunch of them up there.
> CO2 has a half life of ~ 10 years in our atmosphere btw.
Oh? So we can just wait until things start to get uncomfortably warm, then stop cranking out CO2 for a decade or two and everything will be better?
No, we absolutely are not.
"Long half-life" = "less radioactive". By definition.
Do you know what the half life of CO2 is? Infinity.