I've read that the Tsar Bomb used a lead casing for the second and third stages of the bomb instead of a uranium casing. A uranium casing would have resulted in fast fusion but would have created too much fallout. Typical Hydrogen bombs use uranium casings. A uranium casing would have indeed resulted in fast fusion but would have created too much fallout therefore the soviets chose to use lead instead. My question is, what happens to lead after it has absorbed so much radiation? Does it change and become another element?