[ShadowFox01]

Zain asked the Naked Scientists:
   
Would it be possible to dispose of nuclear waste by casting the waste into an active Volcano?

What do you think?

[RD]

Nuclear waste is stored in a form which resembles volcanic glass ... http://en.wikipedia.org/wiki/Radioactive_waste#Vitrification

[Bored chemist]

Stuff comes out of volcanoes.

[CliffordK]

Despite the heat in the volcano, the elements are not changed.  So, if you put Plutonium down a volcano, the plutonium will come back out (except for what naturally decays).

One talks of a volcanic eruption of having the force of an atomic bomb, but it is not the same as spreading the radiation of an atomic bomb, and it is generally safe to return to the ash covered mountains a few days after an eruption.

There is a saying that "Dilution is the Solution to Pollution".

There are many natural radioactive elements in our environment including Uranium and Radium.  If you concentrate natural Uranium, then spread it back out, at some point it would be impossible to differentiate what was previously there (background radiation) and what you've added.  Some radioactive elements such as Americium and some Plutonium isotopes do not occur naturally, so any amount in the environment would be unnatural. 

Anyway, whether or not the volcanoes would spread the waste over a large area, perhaps around the globe, the result would still be a big mess.

[grumpy10]

That would be a good way of spreading radioactive pollution world wide!

[CliffordK]

You know...  I was thinking.

There are some volcanoes that only do cone building, and do not have explosive eruptions.  For example those in Hawaii.  One could potentially build a vessel that would be entombed in Lava.  One might even be able to direct the  molten lava to an entombment site.

However, I'm sure that the Hawaiians would be screaming NIMBY!!!!!

Some volcanoes also go through phases of explosive eruptions followed by an extended period of cone building (presumably leading to another explosive eruption).  But, it might be several thousand years between explosive eruptions.  With that in mind, one might be able to bury tritium and short halflife waste in the young cones, but it would not be suitable for long halflife materials.

The Lava flows in Oregon are far more porous than one might expect.  I assume those in Hawaii are also far from being monolithic.  So, entombing something in a lava flow would likely result in exposure to erosion and to the water tables.  And, one would likely be placing the waste fairly superficially.  So, it still seems unlikely to be beneficial.

[Mazurka]

In answer to the question - no - even if you picked your volcano to avoid dispersion through ash clouds or pyroclastic flows, most extrusive volcanic rock weathers relatively quickly compared to the half lives of the elements in the waste.

Interestingly (if you are a geologist at least) we know a lot about turbidity currents (and turbidite rocks) which form off the continetnal shelf/ submarine trenches as for a time it was thought to be a candidate for entombing radioactive waste in an irretriveable way.  I belive it was rejected on the grounds that we could not build containers strong enough to not be destroyed by the current.  They are also too unpredicatble as they tend to be triggered by events such as earthquakes...