Nagasaki and Hiroshima were small first generation weapons from over seventy years ago.
Chernobyl's radiation was leaked over an extended period.
https://theecologist.org/2019/nov/20/where-wind-blowsTo see past this number, we need to trace again the path of the wind from Chernobyl. Before turning south towards Kyiv at the beginning of May, it had been blowing north-east from the plant towards Moscow. To prevent a radioactive thunderstorm deluging the capital of the Soviet Union, Soviet air force pilots were ordered to intercept and seed the clouds over rural Belarus.
On the twentieth anniversary of the Chernobyl accident, major Aleksei Grushin, who led the operation, received an award for bravery from the hands of Vladimir Putin. As a result of that human-made rain, the south of the Belarusian Republic was covertly blanketed with a radioactive soup.
The contamination from Fukushima has also been detected as far away as South America.