Absorbs a Nuclear core

“You’re a sharp one son,” Admiral Willis said.  “Sea Base One found the nuclear core from that sunken submarine.  And it was drained of all nuclear energy.  Hell!  It wasn’t even radioactive anymore.”
“You mean that Godzilla is capable of absorbing nuclear energy?”  Nick asked.  “That he actually feeds on it?”
“Probably not exclusively,”  Dr. Nobeyama answered.  “Godzilla has a stomach and a heart, lungs, blood, probably a liver.  Godzilla is physically capable of eating more traditional fare.”
“But to survive long term, and to be able to use his most destructive weapon-- his so-called radioactive breath-- Godzilla must replenish his supply of radioactive material from time to time.”