> 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.
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.