Coppelion

In 2016, a meltdown of a nuclear power plant creates a big catastrophe in Tokyo. 20 years later, the city has become a ghost town due to the high levels of radiation. From that area a distress signal is received. The Self Defense forces dispatch three girls from the special unit Coppelion to search for survivors. But why aren't they wearing any protection against radiation?

(Source: MU, edited)