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 "Windscale fire"): The fire took place in Unit 1 of the two-pile Windscale facility on the northwest coast of England in Cumberland (now Sellafield, Cumbria).
Relevant evidence: No