I have the same problem, my radioation meter stays at +13 but I don't gain any radiation, only the meter is broken, if I get close to the megaton bomb for example the radiation there is +1 or +2 if I get to it very near, my radiation meter shows +14 or +15 when very near the bomb, also that noise comminig from radiation wont go away until I restart the game, same as with you, Does anyone have a solution for this?