Britain’s most recent nuclear power station, Sizewell-B, began construction in 1987 and was commissioned into operation in 1995.

The history and design of Sizewell-B power station

The £2.8 billion Sizewell-B reactor was ordered by the Central Electricity Generating Board (CEGB), a national state-owned public sector electricity utility that was later privatised. Sizewell-B is a Westinghouse 1,195 MWe pressurised water reactor, the first PWR to be built in Britain.

Sizewell-B is based on a Generation III Standard Nuclear Unit Power Plant System (SNUPPS) developed in the 1970s by Westinghouse in the United States. The single 1,195 MWe reactor unit is almost twice as large as Britain’s previous Generation II fleet of twin 625 MWe Advanced Gas-Cooled Reactors (AGRs). The switch from British AGR to American PWR technology in the 1980s effectively signalled the end of Britain’s independent nuclear power design capability. But more importantly it also signalled that nuclear energy technology had successfully matured to become fully commercialised within a global marketplace.

This was important because nuclear power stations had all previously been ordered by governments rather than private companies. In hindsight this was an important step to establish nuclear power for the first time as a serious investment option for private energy utility companies that would later emerge during various national electricity privatisations in the 1990s and 2000s.

Why has Britain not built another nuclear power station since 1995?

Britain has not built another nuclear power station since Sizewell-B mainly because it has been cheaper to construct and operate Combined Cycle Gas Turbine (CCGT) gas-fired power stations. Gas-fired power stations supply 46% of electricity consumption today, dominating electricity generation in Britain.

Privatisation of electricity companies in the 1990s resulted in a dash-for-gas, switching away from nuclear and coal-fired generation towards gas generation. For the same GWe power output, gas-fired power stations are 20% of the capital cost of nuclear stations to build and they are relatively more adaptable, able to quickly increase their electrical power output in response to peaks and dips in electricity demand, reducing output when no longer needed.

This highly flexible and fuel-efficient load-following capability, coupled with the ready availability of cheap North Sea gas supplies made gas-fired power stations much more economically attractive to private energy utility companies during the 1990s.

Nuclear power stations are better suited to near-constant, always-on baseload electricity generation rather than the peaks and troughs of load-following generation. Wholesale electricity prices in the energy market over the past decade have tended to favour flexible load-following gas generation over nuclear baseload, although all forms of generation are profitable when electricity prices are high.

On the other hand, when electricity prices are very low and unprofitable, gas-fired power stations are able to shut down until prices improve, whereas nuclear reactors must continue operating even if the nuclear station makes a loss. For example after a sustained period of low electricity prices, Britain's FTSE-100 nuclear energy utility British Energy effectively went bust in summer 2002, requiring an emergency government financial take-over between 2002-2005 with the government as the major shareholder.

British Energy returned to profitability as wholesale electricity prices improved, and was later sold to the French state-owned energy utility EDF in 2009 for £12.5 billion, a major turn-around.

Dr Jenifer Baxter

Dr Jenifer Baxter

Energy policy spokesperson

Dr Jenifer Baxter joined the Institution as Head of Energy and the Environment in May 2015. Jenifer works closely with members to raise the profile of engineers and engineering potential, to generate discussion and provide thought leadership in the energy and environment sectors.

Read Jenifer's full biography