Sellafield and radiation symbol. Sellafield (formerly Windscale) is a nuclear fuel reprocessing plant in Cumbria, UK. The buildings seen here include the inoperative prototype Advanced Gas-cooled Reactor (AGR, dome), and the Windscale Piles (chimneys). The Windscale Piles were the first two reactors to be used at Sellafield, and were part of a secret nuclear weapons programme. The piles were closed in 1957 following a fire in reactor no. 1 at Sellafield. The superimposed yellow and red radiation symbol is used as a warning symbol in areas containing radioactive material.