Why are Hiroshima and Nagasaki safe to live while Marie Curie’s notebook won’t be safe to handle for at least another millennium?
In: Physics
Hiroshima and Nagasaki were bombed with nuclear weapons using uranium-235 and plutonium-239 as the fissile materials (Little Boy and Fat Man, Hiroshima and Nagasaki respectively).
Radiation is a release of energy, and the goal of these weapons was to release as much of their potential energies as quickly as possible. This means that the vast, vast majority of radiation was released in the initial detonations.
Both bombs were also “air burst” weapons, meaning that they’re designed to explode long before they impact the ground. Something like 90% of the radiation was blown into the atmosphere.
“Half-life” is a measure of how long a radioactive material takes for half of its total quantity to “cool off” as radiation. Uranium-235 has a half-life of 704 million years. Plutonium-239 has a half-life of 24 thousand years. They’re both radioactive, but leeching radiation pretty slowly.
The super dangerous stuff made as a result of the nuclear reaction would have cooked off the majority of itself within days, or even hours. Combined with intentional and organized cleanup/containment, this means that both cities were relatively safe again in a surprisingly short amount of time.
Marie Curie, on the other hand, was a pioneer in radioactive science. She discovered Polonium and Radium, two *extremely* radioactive elements. Polonium-210 has a half life of only 138 days, whereas Radium-226 is sitting at about 1600 years.
Nothing was known about radioactivity at the time – Curie and her husband quite literally coined the term. They didn’t know to take precautions against radiation exposure, or that radiation could leech into other materials. She walked around with radioactive materials in her pocket. She stored them in her desk. She then worked as a radiology technician in WWI, giving unshielded x-rays and further exposing herself.
They (and other scientists of the era) eventually started to figure it out, but by that point it was far, far too late. Marie Curie died of aplastic anaemia, likely the result of the radiation exposure throughout her life damaging her bone marrow. The reason that her stuff is so radioactive is because she was experimenting with *extremely* radioactive elements through her entire career.
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