Sizewell nuclear power station. View at dusk of the reactor buildings of the Sizewell 'B' nuclear power station, Suffolk. Sizewell 'B' was the first pressurised water reactor (PWR) to be installed in the UK. Completed in 1994 at an estimated cost of #1200 million, it has an output of 1200 MW (million watts). The construction of Sizewell 'B' was the subject of the UK's longest public enquiry which lasted 340 days.