Close to the sun still takes more energy than leaving the solar system, similar to how it's just as hard to charge a capacitor to -9V as to 9V. And in what sense would it "burn up"?
Bring it up does not change the fact that there is now radioactive material on an orbit which still potential overlaps the earth. Out of the solar system is a much better solution.
On the other hand it's not like the Sun isn't spewing out way more radioactive material continuously than we're talking about adding here.
EDIT: To give some orders of magnitude, the back of the envelope tells me that the sun inflicts about 700 TBq of carbon-14 on us every year. For comparison, countries like the USSR and UK have dumped 85,000 TBq of radioactive waste into the ocean (and Fukushima added another 15,000). I don't know how to judge how much of the vaporized waste would end up back on Earth so it's quite possible I'm wrong in the above.
That's only true up to a point. I suspect that if you exposed just about anything to 100,000 kelvin it ceased to look like any kind of matter we know anything about.
This experiment was performed thousands of times back in the 1950s and 1960s. A nuclear weapon's fireball is way hotter than 100,000K, and the exploding weapon contains lots of fissionable material and fission byproducts. The extreme temperatures don't destroy them, they just help spread it around.
Yes, but there is SOME temperature at which heating things up does start to cause things to act weirdly. You know, like in a fusion reactor. That definitely changes the radioactivity of certain elements.
http://i.imgur.com/SqdzxzF.png