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Nuclear dawn

Sep 6th 2007
From The Economist print edition

Energy: Attitudes to nuclear power are shifting in response to climate change and fears over the security of the supply of fossil fuels. The technology of nuclear power has been changing, too

Alamy

OVER the next few decades global electricity consumption is expected to double. At the same time, many power plants in rich countries, built back in the 1960s and 1970s, are nearing the end of their projected lifespans. Meanwhile, concern is swelling both about global warming, and about the Western world's increasing dependence on a shrinking number of hostile or unstable countries for imports of oil and gas. The solution to this conundrum, in the eyes of many governments, is nuclear power.

Around the world, 31 reactors are under construction and many more are in the planning stages. Some of the most ambitious programmes are under way in developing countries. Both China and India are building several reactors and intend to increase their nuclear-generating capacity several times over in the next 15 years. Some countries, such as Turkey and Vietnam, are considering starting nuclear-power programmes, and others, including Argentina and South Africa, plan to expand their existing ones.

The rich world is also re-examining the case for nuclear. America is expecting a rush of applications to build new reactors in the coming months-the first in almost 30 years. Britain's prime minister, Gordon Brown, recently affirmed his support for a new generation of nuclear power plants. Construction of a new one in Finland, western Europe's first for 15 years, began in 2005; work is just starting on another of the same design in France. Other European countries that had frozen or decided to scrap their nuclear programmes are rethinking their plans.

There are good reasons for this enthusiasm. Nuclear reactors emit almost none of the greenhouse gases responsible for global warming. They are fuelled by uranium, which is relatively abundant and is available from many sources, including reassuringly stable places such as Canada and Australia.

At the moment 439 nuclear reactors in 31 countries supply 15% of the world's electricity. Even without a price on carbon emissions, says Fatih Birol, the chief economist of the International Energy Agency (IEA), the worldwide generating capacity of nuclear power plants will probably increase from about 370 gigawatts today to 520 gigawatts in 2030. But if there were a price on carbon dioxide, says Mr Birol, "it could grow even faster."

But there are also good reasons for scepticism. Nuclear plants are expensive: each can cost several billion dollars to build. Worse, in the past, ill-conceived designs, safety scares and the regulatory delays they gave rise to made nuclear plants even more costly than their hefty price-tags suggest. Vendors of new nuclear plants, such as Areva, General Electric (GE), Hitachi and Westinghouse, argue that things are different now. The latest designs incorporate suggestions from utilities and operators with decades of experience, and should, their creators say, make new plants safer and easier to operate. They believe the simpler new reactors, with their longer lifespans and reduced maintenance costs, will also improve the economics of the industry.

"The latest generation of reactors includes important improvements over prior designs."

All nuclear reactors rely on nuclear fission, a process that was discovered in the 1930s. When certain heavy atoms are struck by a neutron, they absorb it, become unstable and split apart. This results in two lighter atoms, and two or three neutrons are ejected. The process releases large amounts of energy, much of it in the form of the kinetic energy of the fast-moving fission products. This kinetic energy is converted to heat as the fission products slow down.

If the ejected neutrons go on to strike other unstable atoms nearby, those too can break apart, releasing further neutrons in a process known as a chain reaction. When enough of these neutrons produce further fissions-rather than escaping, bouncing off or being absorbed by atoms that do not split apart-the process becomes self-sustaining. An uncontrolled chain reaction within a large amount of fissionable material can lead to an explosive release of energy, as in nuclear weapons. But in nuclear reactors, which contain far less fissionable material, the chain reaction and the release of energy are carefully controlled.

War and peace
In 1942 the physicist Enrico Fermi led a group of scientists who built the first nuclear reactor as part of the Manhattan Project-America's effort to build the first atomic bomb. Although the reactor was simple in design, it included features that are part of almost every nuclear power plant today. The reactor core consisted of pellets of uranium fuel inside bricks made of graphite, which served as a "moderator", reducing the speed of the neutrons in order to maximise their ability to cause further fissions. (Most reactors today use water as the moderator.) In addition, the set-up included "control rods" made of a material that absorbed neutrons. These rods could be inserted into the core to slow or shut down the chain reaction if necessary.

Although all of this was done with a view to building an effective weapon, the scientists involved always knew that nuclear technologies also had promising peaceful uses. In 1953 America's president, Dwight Eisenhower, gave his famous "Atoms for Peace" speech before the United Nations General a__embly, in which he called for the controlled application of nuclear energy in a civilian context. In the mid-1950s the world's first civilian nuclear power stations appeared in America, Britain and Russia.

America's first civilian nuclear power plant, of a type called a pressurised water reactor (PWR), was designed by Westinghouse and adapted from the reactors used in nuclear submarines. Inside a PWR, water-which is kept under high pressure to prevent it from boiling-has a double function. In a closed "primary" loop, it serves as a coolant for the reactor core and as a moderator, to slow down the fast neutrons created during fission. As the water in the primary loop circulates, it becomes very hot. This heat energy is then transferred to a secondary loop of water. The resulting steam is used to spin turbines that generate electricity.

Nuclear's golden age
In the 1950s the pursuit of atomic energy was viewed as a largely positive endeavour. In a speech in 1954 before a group of science writers, the head of America's Atomic Energy Commission, Lewis Strauss, even declared that one day nuclear power would be "too cheap to meter". By the mid-1960s America's two leading reactor vendors, General Electric (GE) and Westinghouse, were involved in an intense competition. GE began to offer "turnkey" contracts to utilities, in which it delivered an entire nuclear plant for a fixed price. To keep up, Westinghouse followed suit, causing a surge in orders. But this sales ploy turned out to be a money-loser for both firms in the end.

The boom in reactor construction coincided with the beginnings of America's environmental movement and a sense of growing unease about nuclear power. By the early 1970s uncertainties over radioactive-waste disposal, the effects of radiation and the potential consequences of a nuclear accident prompted a backlash. One frightening scenario was the "China Syndrome": the idea that molten radioactive fuel undergoing a runaway reaction might burn its way through the bottom of the reactor's pressure vessel and containment structure, and then down into the Earth. Of course the fuel would never actually reach China, but were it to breach the containment structure, the result could be a huge release of radioactivity.

As electricity demand levelled off and interest rates shot up, applications to build nuclear reactors started to decline, at least in America. Then in 1979 a serious accident occurred at a plant at Three Mile Island, near Harrisburg, Pennsylvania. A combination of mechanical failures and operator errors caused a partial melting of the reactor core. Fortunately the pressure vessel housing the core held, and virtually no dangerous radioactive gases escaped from the plant, says J. Samuel Walker, the historian of the Nuclear Regulatory Commission, the agency that regulates America's nuclear power plants. Although the accident nearly killed off America's nuclear-power industry, it did not harm any people.

But a few years later a true disaster occurred. In 1986 a reactor at Chernobyl in Ukraine became unstable, and a power surge inside the core led to two explosions that destroyed the reactor and blew its roof off. As a result, significant amounts of radioactive material escaped into the environment. About 30 emergency workers died of radiation exposure shortly after the accident. Thousands more people who lived in contaminated areas developed serious health problems, some of them fatal. The cause of the accident was found to be a combination of operator errors and inherent flaws in the plant's design. Industry insiders pointed out that reactors based on this flawed design had not been deployed in Western countries. Even so, the accident further undermined public confidence in nuclear power.

Although the nuclear industry faced decline or stagnation in many Western countries in the 1980s, it thrived in one of them: France. After the oil crisis of 1973, France decided to pursue the goal of fossil-fuel independence. With few energy resources of its own, pursuing nuclear power seemed like the best strategy. All the commercial nuclear plants operating in France today were based on technology devised by Westinghouse, which licensed its PWR design to France in the 1960s. Today the country has 59 nuclear reactors supplying 78% of its electricity.

Nuclear has worked well in France in part because it is accepted by politicians and the public alike, so there are few delays due to protests or planning problems. Elsewhere, these have lengthened the construction period and enormously increased costs. Once up and running, however, nuclear plants have a distinct advantage over those run on coal or natural gas: they need comparatively little fuel to operate. Although the price of uranium jumped from about $70 per pound in January to about $130 in mid-July, operating costs of nuclear power plants have changed very little. (Construction accounts for as much as three-quarters of the cost of nuclear generation.) Moreover, the rise in the price has prompted an exploration boom that will ultimately lead to more mines and greater supply. Uranium is not thought to be particularly scarce-it has simply not been very profitable to look for it recently.

The latest generation of reactors, which evolved from models constructed in the 1970s and 1980s, include important improvements over prior designs. Westinghouse's new AP1000, for example, has "passive safety" systems that can prevent a meltdown during an emergency without operator intervention. If the reactor loses pressure because of a loss of coolant, for example, pressurised tanks deliver water to the core, since the pressure in the tanks is higher than that in the core, explains Howard Bruschi, who has worked for Westinghouse since the 1960s and is now a consultant to the company. The new reactor's simplified design also means that fewer motors, pumps and pipes are needed, reducing not only the potential for mechanical errors, but also costs of maintenance, inspections and repairs. Westinghouse recently agreed to provide four new plants to China.

Soul of a new reactor
Meanwhile, Areva, a French nuclear company, is engineering ever more powerful plants. Its first reactor, which began operating in 1977, was rated at 900 megawatts; its latest model, the evolutionary power reactor (EPR), is a 1,600-megawatt design. The company has already begun building two such plants in Europe: one in Finland, which is now expected to start operating in 2011, about two years late, and another in France. Both the EPR and the AP1000, along with GE's latest design, are among the plants under consideration by American utilities.

A demonstration plant of a completely different type, a "pebble bed" reactor, is scheduled to be built in South Africa starting in 2009. Based on technology that originated in Germany, its design is unique in several ways. For one thing, its small size (165 megawatts) should make it comparatively fast and cheap to build; depending on power needs, several units sharing a single control room could be constructed on one site. And the uranium fuel is encapsulated in rugged "pebbles", the size of tennis b____, which are designed to withstand a loss of coolant without disintegrating, making the reactor extremely safe. Andrew Kadak, a professor at the Massachusetts Institute of Technology (MIT), who has been developing a smaller, alternative pebble-bed design with his students, is convinced that "these reactors cannot melt down."

Even though new designs for nuclear plants may be safer, they still generate toxic waste. After about three years of use, the fuel is depleted of most fissile uranium but has accumulated long-lived radioactive materials that cannot be burned in conventional reactors. At the moment most such waste is stored near the plant until it can be moved to a permanent facility. But no country is yet operating a final disposal site for highly radioactive nuclear waste. America's Yucca Mountain repository, for example, is not expected to be ready for use for many years, if ever. In some countries nuclear waste is "reprocessed"-a procedure in which plutonium is separated from the rest of the spent fuel, which can then be made into new fuel. Plutonium, of course, can be used to make nuclear weapons. Because of concern over nuclear proliferation, America has not engaged in civilian reprocessing since 1977.

As part of a new multinational initiative called the Global Nuclear Energy Partnership (GNEP), however, America's Department of Energy is supporting a type of spent fuel reprocessing which does not separate the plutonium from other highly radioactive materials in the waste, thus making it more resistant to proliferation than traditional reprocessing. This mixture of plutonium and other radioactive elements could then be turned into fuel suitable for use in "fast" reactors. Most reactors in operation today are called "thermal" reactors, because they use a moderator to slow down the neutrons and promote fission. Fast reactors, in contrast, do not employ moderators and use much faster neutrons to produce fissions. So they can consume many of the long-lived radioactive materials that thermal reactors cannot.

They don't build them like they used to

This approach could extract far more energy from a given amount of nuclear fuel while at the same time reducing the volume and toxicity of nuclear waste. Proponents of fast reactors reckon that most of the remaining waste would need to be stored for only a few centuries, perhaps, rather than hundreds of thousands of years, once the most radioactive elements had been separated out. According to the Nuclear Energy Institute, a lobby group in Washington, DC, this could mean that America would need only one nuclear-waste repository. In the long term, a fleet of fast reactors could use nuclear fuel so efficiently that "for all practical purposes, the uranium would be inexhaustible," says William Hannum, a nuclear physicist who used to work at America's Argonne National Laboratory.

But opponents of this strategy call it a distraction that could hinder the renewal of the nuclear power industry. For one thing, many new fast reactors and fuel-reprocessing facilities would have to be built, adding billions of dollars to the enormous sums already required for new nuclear plants. In addition, some of the technologies in question have not been demonstrated on a commercial scale yet. And the GNEP reverses America's ban on civilian reprocessing, which critics say could encourage the proliferation of weapons-grade materials.

In the end, the deployment of new nuclear reactors will depend on many factors, including successful waste and proliferation management, improved economics, and perhaps most important, convincing the public that nuclear reactors can be operated safely. Despite these obstacles, there is an undeniable mood of optimism in the industry. Whether that will be enough to spark the deployment of the hundreds of reactors that will be needed to help mitigate the effects of global warming remains to be seen, cautions Richard Lester, a professor of nuclear science and engineering at MIT. Were there to be another disaster like Chernobyl, or a successful terrorist attack on a nuclear plant, all bets would be off. But for now most people in the industry agree that nuclear power's prospects look brighter than they have in a long time.