Yes, the wiki isn't super-specific, yet...
I haven't crunched the numbers but basically it prevents the 'red orbs of death' from doing {your lv x 5 dmg - armor} to {your level - armor}. So, wearing an Anti-Rad item reduces the damage so it's doing 10% of what it could do. Something like this anyways.
My experience with this new area: lv 16 ranged rouge.
*Much evasion, hp potions, and speed potions were used...My companion, dead 90% of the time I was running around outside...haha
*Decided to kill Valerian, cleared all of Bapp cave (all 'dem dragons, rawr), completed the Matrisian Codex quest, before clearing the Sunken Citadel. Hadn't figured out what to do with the anti-rad equipment so never used it till I came back for the Ark, -facepalms-.