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.
Suddenly, a distress signal is received from that area and the Self-Defense Forces
dispatch 3 girls from the special Coppelion unit to search for survivors.
But why aren't they wearing any protection against radiation?