[BurningFrog]

I like to remind people that we already live on a radioactive planet. We can build nuclear reactors because radioactive stuff naturally is everywhere. There probably wouldn't be life here without it.

So to me the "let's get it off the planet" idea is an overreaction. Radioactive material just need to be handled with common sense.

[jazzyjackson]

Hmm... what's the over-under on dropping barrels into a volcano?

You get a little radioactive steam surely...but eventually turns into radioactive dust...

As an aside, ignorant physics question, does the half-life of something decrease with heat? Like does more beta-decay mean it gets to safe levels faster?

Maybe a few years in between tectonic plates would do a planet good eh?

[archgoon]

> As an aside, ignorant physics question, does the half-life of something decrease with heat?

Short answer: No. Definitely not in a Volcano.

Long Answer:

Decay rates are ultimately determined by the subatomic structure of the nucleus. This is why different chemicals, and different isotopes of said chemicals, will decay differently. A lone neutron will decay after about 15 minutes (which is a long time in subatomic scales), however, the two neutrons in (4/2)He will happily stick around forever.

So melting a material won't have any impact on the structure of the nucleus, you're just disassociating the intramolecular bonds; same goes for turning said material into a gas.

If you were to raise the temperature high enough, and we're talking sun-like (not the measly 5000k that you get on the surface, I mean like 27-million degrees you find in the core), then you'll actually start stripping and fusing nuclei, which will at that point change (but not necessarily decrease) the radioactive rates of whatever material you started with.

[AngryData]

In most cases a faster decay rate does mean the material becomes safer at a faster rate, but consequently produces more radiation in that same time. If it was reprocessed we could reuse the high-output waste over and over until all that was left was the low energy but long half life material, but old regulations based on poorly understood science in the past, public ill-will, and potential international political conflicts could appear as the reprocessing technology is basically the same technology needed to make nuclear or radiation bomb source material.

[BurningFrog]

The classic answer is to bury extremely long lived waste in a subduction zone at the bottom of the ocean, such as the Mariana Trench.

A "subduction zone" is where two tectonic plates collide and fold into the depth of the planet. So anything you bury there would naturally travel deeper into the planet over the eons.

I haven't heard any serious arguments against this, but I suspect it's impossible because people think it would "contaminate the oceans".

[fromthestart]

I dont think it is so easy. Subduction zones have what are called accretionary prisms, which are basically sediment that is sloughed off the top of the subducting plate. Thus, if you want the nuclear waste to be subducted, you have to bury it deep enough, though I can't say quite how far - given the scale of the crust, I'd say you're looking at something on the order of miles at least. Which is extra challenging considering subduction zones are already under thousands of feet of ocean.

[pfdietz]

And even if it were subducted, the descending seafloor sediments liberate water and other volatiles once they get deep/hot enough, and this produces volcanism.

[WalterBright]

Extremely long lived radioactive waste will, inevitably, have extremely low levels of radioactivity. I.e. not an issue.