Question: Cumbrians Opposed to a Radioactive Environment has campaigned against all aspects of the operation of Sellafield, formally known as which worst nuclear accident in Great Britain's history, ranked in severity at level 5 out of a possible 7 on the International Nuclear Event Scale? 
Sentence (from "Three Mile Island accident health effects"): The American Nuclear Society concluded that average local radiation exposure was equivalent to a chest X-ray, and maximum local exposure equivalent to less than a year's background radiation.
Relevant evidence: No