Sizewell B


Duration:8 years

Cost:£2bn (£5.3bn today)

Country: Suffolk, UK

What did this project achieve?

Build the UK's first commercial pressurised water reactor power station

Sizewell B is one of two nuclear power stations near the village of Sizewell on the coast of Suffolk. Its predecessor Sizewell A is currently being decommissioned.

Sizewell B was first announced as a gas-cooled reactor in 1969 and then as a steam-generating heavy water reactor in 1974. It was finally announced as a pressurised water reactor (PWR) in 1980 – the first of its kind in the UK.

Originally based on the design of a plant in Portland, Oregon in the US, Sizewell B faced strong opposition from local groups and anti-nuclear campaigners. A lengthy public enquiry between 1982 and 1985 took over 16 million words of evidence – a record at the time.

Construction of the station, with its distinctive white 'golf ball' dome, started in 1988 and was completed on schedule. It cost £2bn at 1987 prices. About a quarter of this went on civil engineering works.

The plant was designed for a commercial life of 40 years. Similar plants have had their lifespan extended to 60 years.

Sizewell B currently supplies 1,198MW to the UK national grid.

Difference the reactor has made

Sizewell B has made a significant contribution to the generating capacity of the UK since it started producing electricity in 1995.

The plant produces 3.1% of the UK's energy needs. This represents low carbon electricity for around 2.5m homes and businesses.

Additionally, the power station and its construction had a direct effect on the economy. Over 20,000 jobs were created to build the station – many for people working for local firms.

The plant continues to contribute to the local economy as it currently employs around 770 full-time or contract workers.

How Sizewell B was built

Safety was a key challenge for engineers working on the construction of Sizewell B.

The nuclear reactor, along with its cooling circuit and steam generators, is contained inside a 65m high, 45m diameter pre-stressed concrete building. The walls are 1.4m thick and designed to withstand 'catastrophic' events such as plant failure or an earthquake without leaking.

Engineers lined the station interior – floor, walls and dome – with gas-tight steel 6mm plate. This weighs 2,000 tons and is fastened to the concrete.

Producing concrete to build the plant was a major part of work on the project. Enough was poured during construction to fill the Royal Albert Hall 5 times over.

Engineers used 70,000 tonnes of steel bars for Sizewell B's pipework. The cabling used for instrumentation alone would run from London to Brighton.

Additional safety measures designed into the plant include an exact replica of the power station's control room. Employees are trained here before they're allowed access to the real thing.

Sizewell B won the Supreme Award at the British Construction Industry Awards in 1994.


Sizewell B… delivers world class safety and operational results, providing much needed reliable, low carbon electricity for the UK.

Mark Gorry

chief nuclear officer for EDF Energy

Fascinating facts

Construction of the plant saw one of the UK's longest non-stop concrete pours: 5,200m3 of concrete was poured over 55 hours for the station's 4m thick base.

All residents in the nearby village of Sizewell are given potassium iodide tablets to take in case of an accident. The tablets are designed to flood the thyroid with iodine and prevent the absorption of radioactive iodine.

Since the sale of British Energy to state-backed Électricité de France (EDF) in 2009, the plant has effectively been owned by the French government.

People who made it happen

  • Architects: Yorke Rosenberg Mardall (now part of RMJM)
  • Civil engineering contractor: John Laing plc
  • Reactor system: Westinghouse
  • Turbines: GEC Alsthom

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