Sizewell B nuclear power plant is the UK's only commercial pressurised water reactor (PWR) power station: it was built and commissioned between 1987 and 1995, first synchronised with the national grid on 14 Feb 1995. The single reactor was supplied by PWR Power Projects Ltd and the turbines by GEC. The main civil engineering contractor was John Laing plc. The Sizewell B nuclear power plant is operated by EDF Energy.

The 'nuclear island' at Sizewell B is based on a Westinghouse '4-loop' plant known as SNUPPS (Standard Nuclear Unit Power Plant System) initially designed in the 1970s and used at Wolf Creek and Callaway but with additional redundancy and diversity in the safety systems, and other modifications such as the addition of a passive Emergency Boration System. The containment design was not based on SNUPPS however, but was designed by NNC in conjunction with Bechtel.

The Wolf Creek and Callaway plants each have single half speed, 1,800 RPM (60 Hz), steam turbine-alternator sets which use the steam produced from the heat generated in the reactor to produce about 1,200 MW of electricity at the US grid frequency of 60 Hz. Such large turbo-alternator sets were not available in the UK at the time Sizewell B was designed. So that orders could be given to UK manufacturers, and to avoid project risk in dealing with what were at the time newly designed very large turbo-alternator sets, Sizewell B uses two full speed, 3,000 RPM (50 Hz), nominal 660 MW turbo-alternator sets similar to those used at Drax coal fired power station, and at the last of the AGRs Heysham 2, but adapted to cope with the wetter steam conditions produced by the PWR steam supply system. PWR steam supply systems produce saturated steam at lower temperature and pressure than the dry superheated steam produced by AGR reactors or coal fired power stations, and the high and intermediate pressure stages of the steam turbines have to be designed cope with this.

A distinctive white hemisphere envelopes the outer shell of the twin-walled Containment building that protects the pressurised water reactor and its steam generators.