Unstable?

Hello there.

    I've been toying around with a notion that I believe some of you might find interesting. The premise hinges upon a single question: are Godzilla's nuclear reserves in any way unstable? This notion stands to reason in multiple lights, not the least of which is the fact that all nuclear material is quite, um, energetic unless somehow dampened. Bearing this in mind (and assuming that the nuclear energy inherrant to Godzilla's physiology behaves according to scientific observation), do you believe Godzilla actually utilizes his long periods of submersion within the deepest, coldest depths of the ocean as a natural baffle to keep his biological atomic reactor stable - much like cooling vats for nuclear power plants? Could it be that Godzilla's species evolved into amphibians as a necessity to keep themselves from going into a terminal meltdown?

    As always, your thoughts and conjecture on this topic are most appreciated, even if you choose to keep them to yourself. :)