In fairness chocolate can burn really easily if you don't know the right method.
One way is to use a double boiler, you don't need any special equipment for this just a bowl (glass/ceramic/metal they all work) and a pot.
simply fill the pot with water, make sure the water doesn't touch the bottem of the bowl. Bring it to a boil place the chocolate filled bowl on top and stir until smooth. The key thing is you never want the chocolate to come into direct contact with a heat source (burner/boiling water).
You can also just microwave it on a lower setting. Personally, I don't like to do this. The double boiler is just so much more satisfying.
Also that's clearly not radioactive waste, it's charcoal that could be used to melt the next batch.