I'm pretty sure it was a fan, but due to graphical limitations they couldn't do anything with it.
Well... The way to find out is to ask Chris Avelone, but in the meantime... Compare and decide for yourself (that's all any of us can do).
http://i271.photobucket.com/albums/jj125/Gizmojunk/radiation-warning-symbol.jpg
http://i271.photobucket.com/albums/jj125/Gizmojunk/enclave-1.gif
http://i271.photobucket.com/albums/jj125/Gizmojunk/armor-4.jpg
Personally, I don't see the sense in designing a combat infantry suit with a moving bullseye on the back.
A fan means a weak spot in the armor.