18K is pretty warm given the circumstances.. (Score 3, Interesting)

All of the very high K superconductors (>100 K) are (IIRC) brittle ceramic compunds that could not be easily constructed into something of commercial use.

While Plutonium is "extremely radioactive and chemically toxic", it is just a base metal, not a compound. I am not to familiar with the metallic properties of Plutonium (malleability, brittleness, etc) but I would imagine that if one metal (even if it is trans-uranic) has high K properties like Plutonium, others may as well...