Radiation Decay: The reduction in radiation over time follows an exponential decay model. The half-life of a radioactive substance determines how quickly it decays. For example:
After 7 hours (one half-life), radiation is reduced by half.
After 49 hours (about two days, with approximately 5 half-lives), radiation is reduced by a factor of 100 (10 half-lives would be a factor of 1,000).
After 2 weeks (about 14 days, with approximately 20 half-lives), radiation is reduced by a factor of 1,000 (10 half-lives would be a factor of 1,024).
Modern Nuclear Weapons: You’re correct that modern nuclear weapons are designed to minimize residual radiation. They use cleaner fission reactions and have lower fallout compared to early designs. However, the initial blast and thermal effects remain significant.