Sizewell A was a second-generation Magnox station, the carbon-dioxide-cooled, graphite-moderated reactor type that the UK essentially invented and that powered most of the British nuclear fleet from the late 1950s into the 2000s. The two reactors at Sizewell A came online in 1966 and ran for forty years before shutdown in December 2006. Magnox reactors used natural uranium fuel sealed in cladding made of a magnesium alloy called Magnox, which gave the design its name, and they produced both electricity and, in some cases, weapons-grade plutonium for the British nuclear deterrent. Sizewell A produced electricity. Defueling was completed in 2014. The decommissioning process is expected to continue until 2027, and the final site clearance is not anticipated until 2098. That timetable, more than seventy years from shutdown to clearance, is a faithful indicator of how long radioactive infrastructure outlives the working life of its reactors.

Sizewell B was the only pressurised water reactor ever built in the United Kingdom. Construction began in 1988, the plant came online in 1995, and it has been generating ever since. A PWR uses ordinary water under pressure to both moderate neutrons and cool the core, a design pioneered in American submarines and then spread around the world. Sizewell B was built to a Westinghouse SNUPPS layout licensed for the UK, and its distinctive white containment dome quickly became the visual landmark of the Suffolk coast. The reactor is rated at about 1,200 MWe. It is currently scheduled to close in 2035, although the operator EDF has announced plans to seek a twenty-year life extension that would carry it to 2055. The question of whether the plant will reach that extension is now bound up with the politics of the UK's energy transition, the price of gas, and what kind of carbon-free baseload the grid needs in the 2040s.

Sizewell C has been on the drawing board for more than a decade. The plant would consist of twin EPR reactors, the same Areva-Framatome design used at Hinkley Point C in Somerset and at Flamanville in France. By May 2013 there were significant public doubts about whether agreement with the UK government would be reached on financing. In October 2021 a new funding model was announced, the Regulated Asset Base, in which consumers help finance construction through electricity bills in exchange for lower long-term capacity costs. The model addresses the central difficulty of large nuclear projects in liberalised electricity markets: the up-front capital is enormous, the build takes a decade or more, and no private financier wants the risk. Local opposition in the surrounding Suffolk Coast and Heaths AONB, organised under Suffolk Energy Action Solutions, has focused on the impact of construction traffic, water use, and the cumulative scale of energy infrastructure now landing on this coast.

Sizewell is now one of the densest concentrations of energy infrastructure on the British coastline. The Sizewell A box is being slowly taken apart. The Sizewell B dome is generating. The Sizewell C site is being prepared. Offshore, the cables from East Anglian wind farms are landing here, and the SeaLink interconnector to the European grid is in development. The Sizewell Marshes Site of Special Scientific Interest survives between and around all of it, with rare invertebrates and the wetland flora that East Anglia's drainage of farmland has otherwise removed. The fishing hamlet of Sizewell itself sits between the power station perimeter and the open sea, a refreshment kiosk and a pub called the Vulcan Arms looking out at a horizon that has been steadily mechanised since 1966. The local view of nuclear power has been complicated for generations. Anti-nuclear campaigners once used the slogan, Welcome to Sizewell, twinned with Chernobyl. The campaigners are still here. So are the reactors.