Action stations

Richard Mayson says that concerns about vvaste should not prevent us building nuclear reactors

Over the past few months, the wind of public opinion has seemed to be blowing in favour of nuclear energy. Tony Blair told a committee of senior MPs in July that there was no way nuclear power could be removed from the agenda if you are serious about the issue of climate change'. He also revealed that the door to establishing a fresh round of nuclear stations had been kept open in last year's Energy White Paper at his personal insistence. 'I have fought long and hard, both within my party and outside, to make sure that the nuclear option is not closed off.'

Dr James I,ovelock, the originator of the Gaia theory, has said that Britain and the world cannot reduce carbon dioxide emissions by the required 60 per cent by 2050 without the help of nuclear power.

But what type of nuclear power stations could the United Kingdom govern ment look at building? Most of the UK's nuclear reactors were built in the 1960s and 1970s and the technology for new reactors has progressed rapidly since then.

Two of the front-runners for new build in the UK in the future arc the AP1000, which is available now, and, looking a few years ahead, the Pebble Bed Modular Reactor. The AP1000 is a water-cooled reactor with an electricity output of over 1,000 megawatts. Worldwide, there are hundreds of water-cooled reactors in operation today with thousands of reactoryears of operating experience.

In September 2004 the Westinghouse API000 was the first Generation III+ reactor to receive Final Design Approval (FDA) from the United States Nuclear Regulatory Commission (NRC). A P1000 is now the safest, most economical nuclear power plant available with an FDA from the US NRC in the worldwide commercial nuclear-power marketplace.

While clearly advanced in its application of passive safety features, AP1000 is still based on the same Westinghouse Pressurised Water Reactor (PWR) technology that has accumulated thousands of reactor-years of successful operation internationally since the first PWR went on line in Shippingport, USA, in 1957.

Jack Allen, Sr Vice President of Nuclear Power Plants for Westinghouse, says simplicity is the key to AP1000's excellent safety and economic characteristics. AP1000 contains significantly fewer pumps, piping, valves and cables, so there are fewer items to install, inspect and maintain than in a traditional plant,' he says.

From a safety perspective, Mr Allen emphasised that the plant relies on naturally occurring phenomena such as gravity, and natural circulation and condensation, which guarantee a safe shutdown of the plant even in the highly unlikely event of an accident. According to Westinghouse, the AP1000 will be cost-competitive with both coaland gas-fired plants, at today's fuel costs.

IMF], has taken a significant share in a project to develop the South African Pebble Bed Modular Reactor (PIIMR). Each reactor will be designed to produce about 165 megawatts of electricity and will have a 40-year life span. Four modules would fit inside a football stadium. The pioneering concept is based on previ

ous experience in Germany where prototype reactors were operated for a number of years between the late 1960s and late 1980s. As the design is modular, additional units can be added to suit demand.

One of the concerns over new build remains the issue of nuclear waste. There is no doubt about the formidable challenge presented to the UK, and lo other countries, by the legacy of nuclear waste that accumulated during the formative years of the nuclear industry.

The UK's legacy of wastes comes from a wide variety of early military and civil nuclear programmes, so a broad mixture of waste types is involved: many of these require unique treatment processes to prepare for prolonged storage. For example, our early Magnox reactors have large reactor cores compared with modern reactors, producing -when 'decommissioned — significant volumes of irradiated graphite.

There are many different reactor technologies, but after decades of experience, simplified quick-build designs which produce much less . waste are likely to be chosen in the future.

For example, during its life, an AP1000 would produce the following by-products: spent nuclear fuel; solid wastes; liquid and gaseous emissions. After the reactor has been shut down after 60 years of operation, it would be dismantled to produce additional so-called 'decommissioning wastes'.

Adding up all these by-products of AP1000 allows a comparison to be made with the UK's projected total legacy of nuclear waste. If ten A P1000s were to be built in the UK to replace all our existing nuclear capacity, it would make only a small addition (less than 10 per cent) to the UK's existing Waste inventory as shown in the following chari. Over its lifetime, an AP1000 would need about 1,500 tonnes of uranium to make its oxide fuel. This is substantially less than previous quantities from UK reactors as shown here: Spent nuclear fuel can he stored on the reactor site for many years. Modern dry stores are capable of holding spent fuel for at least 100 years, giving plenty of time to deploy a long-term waste solution. Such solutions are already defined in the US, Finland and Sweden.

There are well-established processes that have worked well for many years to treat and safely store reactor solid wastes. Over 60 years an AP1000 would produce the equivalent in volume to one lorry freight container every two rears of low-level waste, and one lorry freight container every six years of intermediate-level waste. These are smaller volumes than those produced by previous generations of reactors. Low -level waste would be disposed of at the Drigg repository in Cumbria. Intermediatelevel waste would be stored until a long-term solution is as ailable.

In operation, reactor-cooling water is cleaned and the gases given off are decontaminated. After cleaning, these liquid and gaseous streams are released into the environment. They contain trace quantities of radioactivity with a tiny but quantifiable environmental impact. If all UK nuclear capacity, which provides about a quarter of our electricity., were to be replaced by new reactors it would require 10 AP1000s. Even so, the impact would be much less than that from our existing nuclear stations.

A recent EC study shows that nuclear power electricity generation makes only a small contribution (2 per cent) to radioactive discharges into North European seas. Radioactive discharges are highest from the phosphate industry and oil production.

After the reactor has ceased operation, it is decommissioned. This is done in several stages. There is growing experience of decommissioning reactors globally. In the UK all bar one test reactor have been closed and most of these were taken apart to return the land to alternative use. Good progress is being made on decommissioning in the UK, Europe and the US.

.earning from the past has allowed reactor technology to mature and advance to produce predictable, treatable wastes in much reduced volumes: new nuclear build does not mean new waste problems.