Q&A;: Why the Government is resorting to nuclear power

By DAVID DERBYSHIRE

Last updated at 12:40 10 January 2008

The Government has provoked controversy by giving the go-ahead for a new generation of nuclear power stations, claiming the move is essential to addressing Britain's energy needs for the future.

The stations are likely to be built on existing sites which ministers hope will ensure security of supply as well as help to create a balanced energy mix.

Why is the Government so keen to restart the nuclear programme?

Because the UK is facing a massive energy deficit. Today Britain's 10 working reactors produce 18 per cent of the UK's electricity. Yet under current plans, all but one will be closed by 2025. The remaining plant, Sizewell B in Suffolk, will shut down in 2035.

Why nuclear?

The Government is trying to reinvent nuclear power as the "green option". Unlike coal, gas and oil, it produces little carbon dioxide and will help Britain meet its climate change targets. The soaring cost of oil and gas also makes nuclear more attractive than at any time since the 1980s. Gordon Brown also believes it will Britain's reliance on gas and oil imports from unstable countries in Africa and the Gulf.

What sort of reactors will they be?

The new power stations have been dubbed third generation plus reactors. The first generation of 11 Magnox power stations were built in the 1950s, while a wave of seven second generation Advanced Gas Cooled plants were built in the 1970s and 1980s. Margaret Thatcher tried to restart the nuclear programme in the 1980s, but just one new plant - Sizewell B in Suffolk - was built.

Third generation reactors are based on the designs of the early power stations, but are safer, more efficient and built off site. Three designs for pressurised water reactors are among the contenders - the Areva EPR, the Westinghouse AP1000 and the Candu ACR1000. Each costs up to £1billion.

Where will they be?

No sites have been decided. British Energy - one of the two companies operating nuclear power in the UK - says it could build new stations alongside its reactors at eight sites at Dungeness in Kent, Bradwell in Essex, Sizewell in Suffolk, Hinckley Point in Somerset, Heysham in Lancashire, Torness in East Lothian, Hunterston in Ayrshire and Hartlepool.

The Government's Planning Bill will make it easier to force through new power stations and waste dumps without endless public inquiries.

How do nuclear power station work?

Coal, oil and nuclear power stations all work in a similar way - using heat to boil water which creates steam which drives an turbine which generates electricity.

In nuclear reactors, the heat comes from splitting uranium-235 atoms with a sub-atomic particle such as a neutron. Each split atom releases two or three other neutrons - some of which go on to strike more atoms, creating a chain reaction.

To made use of this chain reaction, rods of enriched uranium are placed in the core of the reactor. The reaction works best if the movement of neutrons is slowed down, so the rods are surrounded by a substance calls a "moderator".

In the most common type of nuclear power station - a pressurised water reactor - the moderator is water kept under high pressure. The water also carries heat away from the core to a chamber where it is converted into steam. Ordinary "light" water is most commonly used, although some reactors use "heavy water" - water with a higher proportion of deuterium, a type of hydrogen.In an advanced gas cooled reactor, carbon dioxide is used to carry heat away, while solid graphite acts as the moderator.

How safe are they?

Unlike the badly designed Chernobyl reaction, the UK's nuclear power stations are designed to shut themselves down automatically in an emergency.

The sticks of uranium are connected to control rods which are lowered and raised by electromagnets to alter the power levels. If the power fails, or if the reactor has to be shut down quickly, the rods drop automatically into the core, stopping the chain reaction in less than five seconds. The core of a pressurised water reaction is surrounded by a tank made from prestressed concrete lined with steel over 20cm thick.

What will happen to the waste?

Waste is the biggest practical problem of nuclear power and the biggest headache is the deadly high level waste which makes up 0.3 per cent of the volume of all nuclear waste. Engineers have yet to devise a man-made container that could hold it safely for the tens of thousands of years needed for it decay to a safe state. Britain is considering building a deep, underground waste dump.

High level waste is currently cooled for years in a water tank before being ground up and mixed with molten glass in a steel canister. The waste is stored in concrete bunkers above ground.

Intermediate waste is mixed with concrete and stored in vaults and tanks at nuclear sites. Lower level waste is kept in sealed concrete values at a store in Drigg, Cumbria. Some is considered safe enough to go into landfill sites.

Even if no more reactors are built, within 20 years there will be enough high level and intermediate level nuclear waste to fill 14 Olympic sized swimming pools.

Why not build more wind farms and tidal power stations?

The Government has committed the UK to generating 40 per cent of electricity from renewable sources by 2020. But it says renewable energy sources - such as wind, solar, wave and tidal - cannot meet the energy gap. Environmental groups disagree. They point to German which has 300 times as much solar power and 10 times as much wind power installed as the UK.

Environmental groups and some scientists also say money would be better spent reducing demand for electricity through energy efficiency and harnessing the UK's tidal and wind power.

Who will pay?

The Government says the private sector will pay for the cost of building the new power stations and decommissioning them at the end of their working life. However, in practice that means the cost will be passed to consumer in higher electricity bills.

It also wants the industry to pay its "fair share" of the costs of handling and storing nuclear waste. It is expected to charge industry "rent" for space in a central fuel dump paid for and maintained by the taxpayer.

No nuclear reactor has been built on time and within budget. According to the Nuclear Decommissioning Authority, it will cost £72 billion to clean up the existing reactors. The cost of building a waste dump could exceed £20 billion.

What are other countries doing?

There are 173 working nuclear reactors across Europe, excluding Russia, of which 59 are in France. France gets more than three quarters of its electricity from nuclear power. Some European countries, including Germany and Spain, are phasing out their nuclear programmes. However, Finland recently approved the building of a new nuclear plant.