After the announcement of Coppelion in Anime serialization in 2011, the plans were put on hold because of the Fukushima Daiichi nuclear disaster which was also somewhere related to the theme of the anime. The Anime adaptation was announced in September 2010 issue of Young Magazine. After a long hiatus the anime is set to reboot its works and they have already posted a preview of the anime check it above.
The story as you heard is based on the radioactive contamination from a nuclear accident has put Tokyo under a blockade. The series is set 20 years after a 2016 nuclear meltdown devastated Japan. So to stop and prevent further contamination three girls are sent to the affected city and also the fact that they are genetically engineered they are not affected by the radioactive elements. They form a special forces unit, codenamed ‘Coppelion,’ in the 3rd Division of Japan’s Ground Self-Defense Force.
The Anime is coming somewhere around in the Fall this year which seems to have already packed some great anime’s.