User blog comment:SolZen321/Yeah, Ultraman is strong.../@comment-1733689-20160910235632/@comment-5527544-20160911010354

No, the Bomb is stronger, but remember Ultra Beams have that 'molecular disruptive' effect on what they hit. In terms of pure force and heat, the bomb is stronger, however the Specium Ray directly bypasses the resistance of the target.

As for the Specium, there is nothing in the series to imply that it is an anyway radioactive. However, in Mebius, humans were using it as a power source, so it could possibly be a source of clean energy.