Dude, that's not how radiation works, nor is it how Godzilla works.
Godzilla consumes radiation as a food source, but his body has shown no signs of expelling radioactive waste outside of the Toho franchise. Godzilla 2014 had people all around him when he was down for the count when the fight was over, and if he was known to expel radioactive waste they would have blocked the area around Godzilla's body off and told people to keep a minimum safe distance. That did not happen. So far, this Godzilla does not leak radiatoin like the old one did.
Even if he expelled radiation, dying would not leak radiation on the same level as a nuclear meltdown. They were worried that killing the MUTO when it was in the process of absorbing radiation from the nuclear reactors would release the radiation of the reactors, not the energy in the MUTO. That is a misconception on your part and it is not part of how the MUTO's worked either. They didn't want to leak the reactor radiation becuase if the MUTO stopped absorbing it, it had nowhere else to go but out to the surrounding area.
Also, if this theory of yours was true, the death of the male and female MUTO's would have turned San Fran into a death zone and Ford and everyone else would have died and we'd have nothing except Godzilla there to walk away without any humans around to see it or cheer it.
So no, Godzilla's death will do absolutely nothing if it does happen (which I doubt it will anyway).