Is Exposure To Radiation Actually As Bad As We Think?

Human beings are constantly evolving, or as I like to say: mutating. This evolution or mutation is an extremely slow process. But I feel that the evolution/ mutation process can be speeded up using radiation. If you look at incidents such as Hiroshima, Nagasaki and Chernobyl, terrible as they may have been, they cause some interesting growths and mutations in many of the children who were born after such incidents. I believe that these mutations are evidence of quickened evolution.
So why not expose pregnant mothers and young children to high doses of radiation to enhance evolution and send humanity forward to a better place at a faster rate? Yes, people may die from such treatment, but I believe that the more the human race is exposed to high doses of radiation the more we will become immune to such ‘poisons’ thus making us a stronger creature.