What would happen if a large amount of nuclear material was placed inside a volcano?
If it erupted it would disperse radioactive material. As to where it goes, it depends on where it was injected and what kind of volcano. If injected into lava near the surface, it would largely vitrify, that is become part of the stone lava formation after it cools. That would not be too dangerous. Vitrification is one method proposed to store waste safely, in fact. It would mingle with gases, though, if injected via a deep well that penetrated a magma chamber before eruption. Much of it would them mix with the ash and disperse into the air. That would be bad – the ultimate dirty bomb.
