Pripyat took a far larger hit of radioactive particulates and has persistently unhealthy radiation. They knocked all the doors and windows out of the buildings to keep the radioactive drift from building up inside them.
IIRC, scientists were startled at how fast the radiation levels at Hiroshima and Nagasaki dropped to negligible levels.
Fukushima might be a better one to make your point - the 10km zone is going to be unlivable for a generation or more, and dangerous to visit for many years.