How long after a nuclear explosion will the radiation linger?

Answer 1

the tests in the marshal islands gave reason to believe that the damage is irreversable but after 50 years the coral reefs are beguining to revive again.

Overall though it depends on the half-life of the fission-materials being used to produce the detonation of the bomb, the primary isotope which is usually used in the production of Nuclear-Weapons (From what I read) is Plutonium-239 which has a half-life of 24,000 years. So they can probably linger as long as any radiation from a Nuclear-Power-Plant meltdown!!!

It takes very little Plutonium or Uranium to make a nuclear weapon and a significant fraction of this is consumed in the detonation. Both Plutonium and Uranium, though they have long half-lives present minor radiation hazards (except in the form of inhalable dust) as they are alpha emitters and can be completely shielded by one sheet of paper or the outer layer of dead cells making up your skin.

The worst radiation hazard is the fission products that emit gamma radiation. But their half-lives vary from 8 days to 40 years. They will all be effectively gone in about 200 years.

Answer 2

The duration of lingering radiation after a nuclear explosion depends on factors such as the type of radioactive materials involved and the size of the explosion. Some radioactive materials decay quickly, leading to less lingering radiation, while others have longer half-lives. In general, it can range from days to years.