Energy companies building the next generation of nuclear power stations will choose between four models, the manufacturers of which have already applied to have their designs approved for use in Britain.

The four reactor types were all accepted into a “prelicensing process” in July. This will assess their safety and efficiency before any orders are placed or sites chosen.

This year the Nuclear Installations Inspectorate, the Health and Safety Executive and the Environment Agency are expected to select three models to be examined in detail over the next three years. The successful candidates would then be awarded a generic design assessment certificate, allowing their construction provided that suitable sites are proposed.

The licensing and planning could be complete by about 2012, and the quickest practical contruction time is generally considered to be about four years. John Hutton, the Business Secretary, said yesterday that he hoped the first new reactors would be generating electricity by 2018.

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Each of the competing designs is safer and more environmentally friendly than Britain’s present reactors. Whereas atomic plants now use safety systems that must be activated mechanically or electronically, their replacements will have passive safety features based on natural forces such as gravity or convection. This means that even in the event of a catastrophic failure the core where the nuclear reaction takes place cannot melt down or explode. If something goes seriously wrong, the nuclear reaction will cool itself and eventually stop of its own accord, rather than requiring intervention.

The new reactors also produce much less radioactive waste than their predecessors - about 10 per cent by most estimates.

The most advanced, and by consensus the safest, modern reactor is the AP1000 made by Westinghouse, a company sold to Toshiba in 2006 by the government-owned BNFL. It is a 1,150 megawatt pressurised water reactor that features an advanced passive cooling system based on convection, and uses control rods operated by gravity to stop fuel from melting. Its chief drawback is that, although the design is already licensed in the United States, it has yet to be built.

The second option under consideration is the European pressurised water reactor, developed by the French company Areva. This design is being built at Olkiluoto, in Finland, and at Flamanville, in France.

Its safety systems are considered slightly less sophisticated than those of the AP1000, but are still much more advanced than those of existing models – one feature is a “core catcher” based on gravity, to prevent a melt-down. At 1,600MW, it has the greatest generating capacity of the candidates, so fewer plants would be needed.

The third main option is the 1,000MW Candu reactor, from Atomic Energy Canada, which has already been built in South Korea and China. Unlike the other two designs, it is not a pressurised water reactor. Instead, it uses heavy water as a coolant.

The requirement for heavy water, which is based on an isotope of hydrogen called deuterium, makes it more expensive to build than the other models under consideration, but its running costs would be cheaper. There is no need to use enriched uranium dioxide fuel, and it can be refuelled without shutting the reactor down. Its safety systems are the most conventional, but it is also the most tried and tested.

A final possible choice would be General Electric’s 1,000MW boiling water reactor, which has been built in China. General Electric bid for the Finnish nuclear contract, but lost to the European pressurised water reactor.

The Government would like to see a single model chosen, which would then be built at multiple sites, in similar fashion to South Korea. This would streamline the planning and licensing process and keep maintenance costs to a minimum, though the choice will be left to individual power companies.

A possible hitch in the plans, however, could be a shortage of nuclear engineers in the UK, and growing global demand for nuclear power plants. In the White Paper issued yesterday, the Government notes that there could be a worldwide demand to build up to 2,000 gigawatts of new nuclear capacity over the next 25 years, and that this is at times likely to outstrip manufacturers’ ability to meet all orders.

New plants are almost certain to be built on the sites of nuclear stations. Candidates in the South such as Size-well, Bradwell and Hinkley Point are expected to be among the first selected, because of their proximity to energy-hungry population centres. Sites in Scotland are unlikely to be chosen because of the opposition of the Scottish Executive.

The Government will also make a policy statement on the need for nuclear power, which will expedite planning applications under new legislation. Local objections will be heard, but inquiries will not be able to question the broader case for new reactors.

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