"...places so hot in Japan from the atomic bombs dropped there that nothing will ever grow or be built on the bomb sites."
This is not true.
There is a park built at the epicenter of the Hiroshima explosion. There are trees, grass, and other park stuff all around. Thousands of people visit there every day.
Except for the memorials and things kept in remembrance there is no way to tell that an atomic bomb was ever dropped on Hiroshima.
There is also stuff growing around the Trinity Test Site at White Sands in NM. People also regularly visit there too.