Iisdude1 said:
If it takes a couple hours for vegeta to die then he really starts feeling the effects he'll probably go for a galic gun or something
I think it would help to explain some lore here
The movie Godzilla vs Destoroyah can be understood to explain this.
To sustain the fission of the atoms in his reactor, external energy supply is needed or he will be overburdened by too much of fission, an imbalance evidenced when Godzilla headed to a nuclear reactor for power despite already being in his burning state.
Fissioning uranium seems to act as Godzilla's primary attack power, an extremely radioactive process to keep putting out.
Specialized weapons are required to even fight Godzilla at all in order to not to disturb his struggling internal organs, during his last-appearance film
For the sheer damage of the finallity of his scenario, it was said to be beyond the global nuclear arsenal going off.
This applies to Godzilla's abnormal progress rather than an on-screen powerup. Burning is moreso a progressed appearance compared to temporary powerups such as Keizer or Fire Godzilla. The often mentioned power surge discussed by Godzilla fans occurs only after a point of stabilization and interference, and only after being freed from his downward-spiralling energy source does Godzilla get a powerup to have an endlessly more efficient arsenal from the energies left over.
When affected by human counter-measures, his attacks amp up towards raw power and heat, and the new result is overloading with power until his death, rather than an overly malfunctioning system alone as the threat.
For the exact specifications on your radiation question, it was still beyond measure even after entering the last Meltdown sequence, by a branch of military that kept secret a nuclear warhead.
One translation says its a hundred times that of an A-bomb in the surrounding context of radioactive subject matters, but I doubt its legitimacy.