The Energy Crisis (parts 1 & 2)
The world demand for energy is rapidly increasing. We need energy to warm our homes, to cook our meals, to travel and communicate, and to power our factories. The amount of energy available to us determines not only our standard of living, but also how long we live. Detailed statistics from many counties show that in countries where the available energy is 0.15 tons of coal equivalent per person per year the average life expectancy is about forty years, whereas countries in Europe and America where the available energy is a hundred times greater have an average life expectancy of about seventy-five years. It is well to remember that a shortage of energy is a minor inconvenience to us, but for people in poorer countries it is a matter of life and death.
The world energy demand is increasing due to population growth and to rising living standards. World population in doubling about every thirty-five years, though the rate of growth is very different in different countries. The world energy use is doubling every fourteen years and the need is increasing faster still. One of the main energy sources is oil and the rate of production is expected to peak in the next few years. There are still plentiful supplies of coal, the other principal energy source, but it is even more seriously polluting than oil, leading to acid rain and climate change. This combination of increasing need and diminishing supply constitutes the energy crisis. The world urgently needs a clean energy source that is able to meet world energy needs.
This is without doubt the most serious problem facing mankind. If we simply let things take their course, the world is heading for a catastrophe during the present century. To see what can be done about it, all possible energy sources have to be critically examined and their potential evaluated (1).
Before considering the various energy sources in detail it is useful to list some of the difficulties in doing so. These arise partly from the complicated nature of the subject, which involves a range of scientific and technological specialties, and partly from the fierce political debates that surround it. The only way to assess the various criteria is to express them numerically as far as possible. Without the numbers it is all just a matter of words spiced with emotion, and it is never possible to reach an objective decision. These numbers seldom have the precision of scientific measurements, and some of them are inherently imprecise but it is better to have approximate numbers rather than no numbers at all. It is important to distinguish between precise measurements, reasonable estimates, guesses, commercial or political propaganda, and speculations. The speculations can be plausible and in accord with known scientific laws, or in contradiction to such laws. A further complication is that new scientific data often alter the picture; this is notably the case for climate change. The people providing the information can be completely objective, or they can be strongly influenced by commercial and political concerns.
The criteria used to assess the various energy sources are their capacity, reliability, cost, safety, and effects on the environment. No single source satisfies all these criteria so an energy mix is essential for each country. The optimum energy mix depends on the natural resources of that country, and so there is no general solution; each country must be considered separately.
No energy source is completely safe, so it is relatively easy to make a case against any particular source by emphasising its hazards. What is needed is an objective comparison between the hazards of all the energy sources, based on numbers. This may be done by estimating the numbers of workers killed and injured in the course of producing a stated amount of electricity. This excludes the contribution of long-term effects. It is worth mentioning that the casualties due to energy production are small compared with those due to natural disasters. Thus, for example, the Chinese Seismological Bureau estimated that in the years from 1949 to 1976 about 27 million people died and 76 million were injured following about a hundred earth quakes. Huge numbers were also killed by tsunamis and hurricanes.
Every energy source has to be constructed and maintained, and this requires energy. It is thus some time before the energy produced by a device is sufficient to pay back the energy used initially. This payback time is an important parameter when comparing energy sources, but data are rather sparse.
There is one general classification of energy sources that provides a useful guide. This is the degree of concentration. To do anything useful the energy must be concentrated. Energy sources can be divided into three categories: the concentrated sources wood, oil, coal, gas, and nuclear; the intermediate category of hydro which is partly concentrated by the mountain valleys; and the least concentrated such as wind, solar, geothermal, wave, and tidal. These sources contain vast amounts of energy but it is thinly spread and only becomes useful when it is concentrated.
We tend to think that environmental degradation is a recent problem, beginning only with the Industrial Revolution; but in ancient times, when wood was the main fuel, the forests of the Mediterranean were cut down, often leaving deserts. Later on, many of the forests of northern Europe were also cut down for fuel. Wood together with crop residues and dried animal dung is still the principal fuel for most people in poorer countries. This practice impoverishes the soil and makes more deserts. Other ancient energy sources like windmills and water wheels, although less polluting, produce limited quantities of power. The windmill is especially unreliable, although the waterwheel has developed into hydro-electric power in moderntimes.
Before considering the possible energy sources individually it is useful to make a few general remarks. While it is essential to express as much as possible numerically, the limitations on the numbers must be borne in mind. These numbers are vital to a proper assessment but are inevitably approximate. They differ from one county to another, and vary with time as new safety measures are introduced. They include all the direct hazards; in the case of coal for example, they include mining and transport hazards as well as those involved in the day to day running of the power stations. The manufacture of safety devices in factories brings with it more hazards, so it is just not possible to make any energy generating device absolutely safe.
The costs of energy generation vary from one country to another and with the distance from mine to power station, where appropriate. Power stations remain in operation for many decades, and during that time inflation affects the costs. The rate of interest on the dividends paid to the shareholders has a critical effect on the final cost.
The power output from energy generating devices estimated by the designer often differs substantially from what is actually achieved. It is therefore necessary to base figures for the power output and the costs on actual operating experience over a number of years. It is thus practically impossible to evaluate a new device without running it for several years.
It is often said that our energy problems could be solved if we used energy more carefully and avoided waste. There is certainly much that can and should be done. We can insulate our homes to conserve heat and avoid heating rooms that are not used. We can turn the heating down and wear more clothing. We can install energy-saving light bulbs. We can walk or use smaller automobiles and avoid unnecessary journeys. If everyone were to carry out these and many similar measures the energy use would be much reduced. It has even been suggested that in this way we can reduce energy use by a factor of four (2). Some of these measures are easy and some are not. It is much easier, for example, to build an energy-saving house than to modify an existing house. Many of these measures, such as insulating our homes, require new materials that have to be made in factories. This inevitably requires energy, and we have to consider how long it will take to recover the energy expended. The main difficulty is to convince people to change their way of life. Certainly we have a serious obligation to do what we can to reduce energy use, but even if we do we will still need to generate large amounts of energy.
Energy-saving measures are most important. They can ameliorate the situation but are not able to avoid the energy crisis. We must therefore consider how the available sources of energy can be enhanced and used wisely.
Coal
Coal, together with oil and natural gas, is one of the fossil fuels, which come from the decay of vegetation many millions of years ago. They are all very reliable sources of energy and are not unreasonably expensive. Their main disadvantage is the pollution they cause, of the land, the sea, and the atmosphere.
The world consumption of coal has risen from 100 millions tons of oil equivalent energy in 1860, to 330 in 1900, to 1300 in 1950 and to 2220 in 2000. In 1950 it was by-far the world's largest energy source, but by 2000 it was easily exceeded by oil. The lifetime of world coal supplies is often calculated by dividing the coal reserves by the annual consumption, and this gives about 250 years. However Lomborg (3) has found that this ratio seems to stay the same from year to year, the increased consumption being balanced by the discovery of new reserves. This cannot go on indefinitely, but we can conclude that the above figure is an underestimate. There is plenty of coal for the foreseeable future.
The main concern about coal is the pollution it causes. A typical coal power station produces as solid waste over a million tons of ash, 21,000 tons of sludge, and half a million tons of gypsum and discharges into the atmosphere eleven million tons of carbon dioxide, 16,000 tons of sulphur dioxide, 29,000 tons of nitrogen oxides, and a thousand tons of dust, plus smaller amounts of aluminum, calcium, iron, potassium, nickel, titanium, and arsenic.
This anthropogenic pollution can be compared with that due to natural causes, such as bush fires due to lightning strikes and volcanic eruptions. Although the short term effects may be severe, the earth has great natural recuperative powers; and once the source of pollution is removed the land, lakes, and seas return to their previous state.
Unlike these natural events the pollution from energy generation builds up continuously, and so the earth cannot recover. The solid waste has to be deposited somewhere, often in the sea, hazarding aquatic life. The atmospheric waste produces acid rain and climate change. The acid rain causes plants and trees to weaken and die, and renders lakes sterile and kills the fish. By the 1980s, nearly 4,000 lakes in Scandinavia were dead and 5,000 had lost most of their fish.
It has been suggested that the carbon dioxide, which is the principal ingredient in atmospheric pollution, could be sequestered, that is put into liquid form and pumped into empty oil wells. This process is expensive and could increase the price of coal by a factor of two or three. Even if this were done, there would still remain the hazards of the other atmospheric discharges.
The vicinity of a coal power station is hardly an object of beauty. The waste from burning the coal is usually stored nearby and forms large, unsightly, and dangerous slag heaps. They are dangerous because after heavy rain they can collapse, overwhelming nearby buildings. This happened some time ago in the Welsh village of Aberfan. The slag flowed over the village school, killing over a hundred children.
Coal is by far the most hazardous of the energy sources. Mining is dirty and dangerous; over 80,000 miners were killed in accidents from 1873 to 1938. A detailed study (4) found that about forty miners are killed to produce a thousand megawatt years of energy, and many hundreds of thousands have had their health permanently impaired by silicosis and other diseases. For all these reasons it is imperative to phase out coal power stations as soon as possible.
Oil
The world consumption of oil increased very rapidly throughout the twentieth century, partly because it is easier to extract from the earth than coal and partly because it is easier to transport by pipeline or tanker from well to power station. It also has a higher calorific content than coal. In 1900 the world oil production was twenty million tons, 470 in 1950, and 3400 in 2000.
The safety of oil occupies an intermediate position with about ten deaths per thousand megawatt-years. This is mainly due to oil well fires. There were 63 accidents in the period 1969-1986, with an average of fifty deaths per accident.
Oil is serious threat to the environment because tankers are sometimes wrecked and the oil discharged into the sea, killing fish and seabirds, and destroying marine plant life. The polluted area soon recovers and it is worth mentioning that more oil pollution is caused by tankers cleaning out their tanks.
The main disadvantage of oil is that world oil production is expected to peak in about ten years and thereafter fall. This may be offset by new discoveries, although no large oilfields have been discovered since 1980. The demand for oil continually increases. Burning oil also produces large quantities of carbon dioxide, just like coal. Furthermore, oil is a valuable chemical with many applications principally as airplane fuels and in the pharmaceutical industry, and so burning it is very wasteful. A further complication is that the bulk of the remaining oil reserves are in the Middle East.
Oil can also be extracted from tar sands. There are enormous deposits in Northern Canada, estimated to be able to yield at least 170 billion barrels compared with about 260 billion barrels in Saudi Arabia. Venezuela also has substantial reserves. The oil is extracted by boiling water, and is an expensive and very polluting process. It costs about $25 to extract a barrel of oil, so the process is economic as long as it remains less than that from oil wells, as is the case at present.
Oil in the form of ethanol can be extracted from sugar cane and from maize. Already there are large plantations growing crops for this purpose; Brazil plans to plant 120 million hectares and an African consortium 380 million hectares. This takes up valuable agricultural land, however, leading to food shortages, and is also highly polluting. It is, therefore, unwise to rely on oil, even from vegetable sources, for our future energy supplies.
Natural Gas
Sometimes associated with oil and sometimes on its own, gas is an attractive energy source. It comes out of the ground easily and can be transported over large distances either by pipeline or less conveniently in liquid form by road, rail, and ship. It is widely used for domestic heating and cooking. It is one of the cheapest and safest energy sources, so many gas power stations are now being built. These power stations can be brought into action rapidly and so are useful when dealing with fluctuating demand. Natural gas is also the safest energy source, with an average of half a death per thousand megawatt years.
The contribution of natural gas to world energy consumption has risen from 170 million tons of oil equivalent in 1950 to 2020 million tons in 2000. A large gas field in Siberia now supplies around 20 percent of western European gas. Gas consumption in Britain is rising rapidly and with it the price. The calculated lifetime is about sixty years, but as in the case of coal and oil this is likely to be an underestimate. Ultimately gas production will fall, like that of oil.
The Renewable Energy Sources
Recognition of the pollution caused by fossil fuel power stations has led to strong advocacy of what are sometimes termed the "benign renewables." This label is somewhat misleading, as statistics show that they are by no means benign. The word "renewable" implies that they do not rely on sources that are limited in amount; they rely on the practically inexhaustible sun. In all cases the energy available is enormous, but it is thinly spread and therefore costly to concentrate. It is regrettable that this renders most of them uneconomical for large-scale energy generation, except for hydro where nature does the concentrating for us. They have many attractive and valuable features, but the laws of physics are inexorable.
Hydropower
Hydropower (hydro for short) is a well-established and reliable source that supplies most of the electrical power in mountainous countries like Norway and Switzerland. It is however limited worldwide by the number of suitable mountains and cannot ever supply more than about three per cent of the world's energy needs. There are untapped sources in remote areas, but the electricity produced there has to be transported over long distances and the power lines are exposed to attacks by guerillas.
Hydropower is relatively safe, with a death rate of about four per thousand megawatt years. The dams that hold back the water seem so solid that even this hazard is surprising. However, it sometimes happens, especially with earthen dams, that water starts to trickle through small channels, grade-ally weakening the dam until it collapses. A wall of water then surges down the valley, obliterating everything in its path. If people are living there, a large number could be drowned. In the period 1969-1986 there have been more than eight dam collapses, with an average death toll of more than 200 people. In one case, about 2500 people were killed.
The lakes behind the dams provide a habitat for wild life, and they can be popular for boating. However in times of drought the water level falls and exposes ugly bands of mud. In addition, these lakes often inundate picturesque valleys and their villages, and destroy valuable agricultural land.
Wind
Of the remaining renewable energy sources, wind is the most promising. Windmills have been used since ancient times, and now wind turbines are a familiar sight in the countryside. They have several disadvantages, however, the main one being that the wind does not always blow and so the power output fluctuates instead of remaining steady. The fluctuations are magnified because the power output is proportional to the cube of the wind velocity. This means that energy is available only over a limited range of wind velocities; when the velocity is small very little energy is produced, while if it exceeds the safety limit the blades have to be feathered to avoid catastrophic damage.
The total energy in the wind is more than enough to satisfy all our energy needs but this cannot be realized because of the high cost (two or three times that of coal power), the unreliability, and the large amount of land required. It may however make a useful contribution if the costs can be substantially reduced.
Wind power is surprisingly dangerous at five deaths per thousand megawatt-years. This is due to the large number of turbines required, about a thousand, to equal the output of one coal power station. These have to be made in factories by processes which are inevitably hazardous. In addition, there are the hazards of construction and maintenance.
The environmental impact of wind turbines is increasingly recognised. They must be built in exposed positions where they can be seen for miles around. They emit a persistent humming sound which people living nearby find intolerable. Often people who moved to the country for peace and quiet are forced to leave and then find that no one wants to buy their house. Wind farms can also be built offshore but this increases the cost and may pose a danger to shipping.
In spite of intensive work over many years wind power is still uneconomical, and in most cases it relies on massive Government subsidies. It is fair to propose that research continues until this difficulty is overcome, but that until this is achieved it is unwise to deploy wind turbines on a large scale.
It is sometimes argued against wind power that turbine blades kill large numbers of birds, estimated to be about 70,000 a year in the United States. This figure should be put into perspective by comparing it with the numbers killed on motorways, amounting to 57 million per year in the United States, by colliding with glass windows (98 million per year), and by domestic cats (55 million a year in Britain) (3).
At present wind contributes only about 0.2 percent of Britain's energy. The Government has announced that the energy-from all the renewables must be raised to 10 percent by 2010. This requires about 8,400 turbines spread over an area of about 1300 square kilometres. There is no hope of doing this, and even if it were achieved there would still be the problem of generating the remaining 90 percent. The situation is very similar in the United States.
Tidal
Some river estuaries are so formed that they experience high tides. When there is a high tide, the sea water flows in, sometimes to a surprising distance from the sea. Around low tide this water flows again back to the sea. If a barrier is put across the river the water flows through pipes to the sea. It is then easy to make this flow rotate a turbine and generate electricity. Such a device has operated in the La Rance estuary in France for many years, producing 65M W. It is reliable, although the peak periods vary according to the moon and not the sun, so the electricity is not always available when it is needed.
A similar though much larger scheme has been proposed for the Severn estuary between England and Wales. It would cost about fifteen billions pounds spread over about ten years to build and would produce about 7GW. The environmental effects are expected to be severe as the whole ecology of the area would be altered. The cost of the energy produced would be about twice that from a conventional power station. It is a practicable but hardly attractive prospect.
Wave
Once again the energy in the waves is enormous, but it is difficult to concentrate. A number of devices to do this have been built, but the output is not cost-effective. One such device, costing over a million pounds, had a power output of 75 kW, enough for 25 domestic electric heaters. Wave machines are, moreover, always at the mercy of storms, which can destroy them in a few minutes.
Solar
The sun pours energy on to the earth at the average rate of about 200 watts per square metre so that the amount of energy that we obtain is proportional to the area of the collectors. It has been estimated that to supply the energy needs of four houses requires a collector the size of a large radio telescope. The sunlight can be used directly to heat domestic water circulating in pipes on the roof. This process is reasonably economic and is widely used. Nevertheless, there has to be an additional source of energy for times when the sun is not shining. On a larger scale it is possible to focus the sun's rays on a boiler at the center of an array of hundreds of mirrors. The steam produced can be used to drive a small turbine to produce electricity. The disadvantage is that the mirrors have to be constantly turned by servomechanisms to keep the sun's rays focused on the boiler so the whole process is uneconomic.
Electricity can also be obtained using photoelectric cells. These are expensive to make and produce electricity with a low voltage. They are not economic for large-scale generation, but are very useful to generate electricity in situations where the other sources are impossible or impracticable, such as in satellites and traffic signals in remote areas.
Thus solar power has useful but small-scale applications that will certainly be developed further when the cost of photoelectric cells is reduced. It is not a practical economic source of energy for the major needs.
Geothermal
The interior of the earth is hot, and in some places hot water gushes out. This can be used as an energy source, but on a small scale in rather few places. Elsewhere it is possible to drill two nearby shafts, pulverize the rock between their ends, and then pump water down one and extract it by the other. Passing through the rock, the water is heated and is an energy source. However if the shafts are close the heat in the vicinity is soon used up, whereas if they are far apart the water has difficulty in passing from one shaft to the other. Trials show that this process is absolutely uneconomical.
Costs
In our society, costs are crucial. Even a small difference is enough to ensure the dominance of one product over another. With energy sources the situation is more complex because the choice depends on weighing the advantages and disadvantages of each source. This is difficult because they are often incommensurable: how much, for example, are we prepared to pay for increased safety or to reduce the effects on the environment? Finally, it is impossible to estimate the cost of delayed damage, such as that due to global warming and climate change. These costs could well be the greatest of all.
Several studies have been made of the costs of generating electricity in various ways, and these are given in the Table. Oil is not included because the impending shortage will drive its cost upwards, and it is not a long-term option.
Examination of this Table shows both a fair measure of agreement as well as substantial differences among various authorities. This is to be expected because of differing criteria and the uncertainties of the estimates. It is clear that anyone wanting to make a case for a particular source can choose his figures accordingly. The costs quoted for wind are uncertain because they are not based on actual experience for a sufficient number of years.
| TABLE Costs of Electricity Generation in p/kWh | |||||
| Energy Source | Belgian Costs * | PIU + | RAE " | BNFL ** | Fr ^ |
| Coal | 2.34 (3.5) | 3.5 | 2.5-3.2 | 7.2 | 4.88 |
| Gas | 1.74 (2.6) | 2.0 | 2.2 | 3.8 | 4.24 |
| Wind (off-shore) | 2.39 (3.6) | 3.0 | 5.5 (7.2') | 6 | -- |
| Wind (on-shore) | 3.26 (4.9) | 2.5 | 3.0 (5.4') | -- | -- |
| Nuclear | 1.25 (1.8) | 4.0 | 2.3 | 3.5 | 3.3 |
| * Figures in brackets normalized to PIU coal. | |||||
| + Performance and Innovation Unit. | |||||
| " Royal Academy of Engineering (backup costs in brackets). | |||||
| ** British Nuclear Fuels, including external costs. | |||||
| ^ French estimates in ecents/kWh, including external costs. | |||||
It is sometimes said that more research will improve existing sources and thus remove some current disadvantages. Generally this is true. But in some cases the disadvantage is a consequence of the laws of physics, and then it can never be overcome. An example is the fluctuating nature of wind energy; it is just not possible to make the wind blow steadily all the time.
The worldwide need for energy is so urgent that it is essential to use existing energy sources. It is of course necessary to continue research into new sources, but we cannot wait. Already over the years millions of people have been killed or had their lives impoverished, by energy shortages.
This survey shows that at a time of increasing energy demands the sources listed all have serious disadvantages: oil and natural gas are fast running out, and in any case, all fossil fuels, especially coal, are polluting. Hydropower is limited, and wind and solar energy are unreliable. If that were the end of the story the future would be bleak indeed. However there is another energy source, the nucleus of the atom. The potentialities of this energy source, its advantages and disadvantages, will be considered in the next article.
References: (1.) There are many books where more detailed accounts may be found: Wolf Hafele, ed., Energy in a Finite World: A Global Systems Analysis (Ballinger Publishing Company, 1981). P.E. Hodgson, Nuclear Power, Energy and the Environment (Imperial College Press, 1999). (2.) E. von Weiszacker, A.B. Lovins, and L.H. Lovins, Factor of Four: Doubling Wealth--Halving Resources (Earthscan Publications Ltd, 1996). (3.) Bjorn Lomborg, The Skeptical Environmentalist (Cambridge: Cambridge University Press, 1998). (4.) H. Inhaber, Risk of Energy Production (Ottawa: Atomic Energy Control Board, 1981).
Part 2: Nuclear Power and the Energy Crisis
The previous article in this series drew attention to the energy crisis that faces the world today. Energy is essential to maintain and increase our standards of living. The demand for it is also increasing due to the world's rising population. At the same time the available sources of energy are proving inadequate to satisfy the demand: oil production will soon peak and then start to fall; coal and the other fossil fuels are serious polluters; hydroelectric power is limited by geography, and wind, solar, and the other renewable sources are unable to deliver energy in the huge quantities required. This combination of rising demand and falling supply is the basis of the energy crisis. If that were all that could be said, there would be no possibility of resolving the crisis. There is, however, another source — the nucleus of the atom.
In 1939 it was found that when the nuclei of certain heavy elements such as uranium are irradiated by neutrons they became unstable and split into two pieces, a process known as fission. The fission fragments fly apart with great energy and also emit more neutrons. These neutrons can enter nearby uranium nuclei and cause them to fission, resulting in a chain reaction and a large release of energy. This energy release can be controlled and used to drive a turbine to generate electricity.1
Many nuclear reactors have now been built, and are making a growing contribution to world energy supplies. They have, however, encountered bitter opposition for a variety of reasons that will be discussed below. The question we have to face is whether nuclear power can provide the solution to the energy crisis, or whether nuclear reactors pose such a threat that they should be phased out as soon as possible. This question can be tackled by applying the same criteria as those already used to evaluate the other energy sources, namely capacity, reliability, cost, safety and effects on the environment.
The Capacity of Nuclear Power
Nuclear power reactors each have an output similar to coal power stations, namely around 1000 MW. There are now about 440 nuclear reactors worldwide delivering about 2,500 TWh per year, around a fifth of world electricity consumption. The numbers of nuclear power stations built in each country depends on its natural resources, principally coal and oil. France, which lacks these resources and is unwilling to become dependent on imports, generates about eighty percent of its electricity from nuclear reactors. It is unlikely to rise higher than this because nuclear reactors take time to get started and therefore cannot react quickly when there is a sudden demand. They are best suited to supply the base load, supplemented by other methods of generation (such as gas power stations) to handle the fluctuations in demand.
Many other countries generate around fifty percent of their electricity from nuclear power, and now nuclear has outstripped coal in Western Europe. There is thus no doubt that nuclear power stations are able to provide a large contribution to the world's energy needs.
It has been objected that this program, while possible in principle, is unable to solve the energy crisis because of the limited supplies of uranium. At present the rate of uranium use is seventy thousand tonnes per year, whereas the known economically recoverable sources of uranium amount to over three million tonnes, sufficient for about forty-five years. In addition, there are about twelve million tonnes of highly probable deposits. If eventually there is a uranium shortage the price will rise, increasing the number of economically-recoverable deposits. Since the cost of fuel is a small part of the overall costs of reactors, this will have very little effect on the price of the electricity generated.
The present reactors are thermal reactors that burn uranium-235, which constitutes only 0-7 percent of natural uranium. The remaining 99.3 percent consists of uranium-238 that can be burnt in fast reactors. Prototypes have shown that these reactors can be built, although at present they are uneconomic. If the uranium price rises to the level that they become economical, they can take over, increasing the amount of energy obtainable from uranium by a factor of about sixty. Since it is also possible to use the fissile element thorium, which is even more abundant than uranium, there is thus no danger that nuclear reactors will ever suffer from shortage of fuel.
Reliability
Nuclear reactors are unaffected by the weather and rarely suffer breakdowns- The best reactors operate for over 90 percent of the time and nearly all the remainder is for planned maintenance, which is arranged for periods of low demand. Nuclear reactors are thus highly reliable.
Cost
Nuclear power stations are more costly to build but cheaper to run than other power stations, and therefore the cost of the electricity produced depends strongly on the rate of interest required on the initial capital expenditure. The cost is also affected by the lifetime of the reactor, which may be around fifty years, and in that period the effects of inflation may be very large. This makes it difficult to give a precise figure for the cost of nuclear power.
Some estimates of the cost of nuclear power compared with those of other energy sources were given in the previous article. Such comparisons are affected by many factors, but on the whole, they show that nuclear costs are similar, or perhaps rather less, than those of coal. This comparison takes no account of the huge and unquantifiable costs of global warming and climate change due to the carbon dioxide emitted from coal power stations. The carbon dioxide emissions from nuclear power stations are less than one percent of those from coal power stations.
The decommissioning of nuclear reactors after they have reached the end of their useful life has to be carried out with great care due to the large amounts of radioactivity they contain. The fuel rods are easy to remove, and much of the building and parts of the reactor are not radioactive and can also be removed easily. This leaves the highly radioactive reactor core which can either be allowed to decay for many decades before dismantling or could be sealed and buried under a mound of earth. Dismantling the core greatly increases the cost, since it must be carried out by remote control. This cost can easily be covered by setting aside a small fraction of the profits during each year of the reactor's life. As a reactor can operate for fifty years or more this accumulates sufficiently to cover the cost of decommissioning. It has been estimated that the cost of decommissioning is about 0.05 p/k Wh for pressurized water reactors.
Safety
The safety of nuclear reactors can be quantified in the same way as the other sources as one death per thousand megawatt-years. The deaths are attributable to normal causes, such as those incurred in building, and are unrelated to specifically nuclear causes. This is less than all other sources except for natural gas. Negative public perception of safety is more influenced by rare and spectacular accidents rather than by such statistics. Thus in the years from 1969 to 1986 there have been one hundred eighty-seven mining disasters, three hundred thirty-four oil well fires, nine dam bursts, and one severe nuclear accident at Chernobyl, which is discussed below.
Environmental Effects
Nuclear reactors have four principal effects on the environment, first by emitting carbon dioxide, second by taking up valuable land, third by producing waste, and fourth by emitting radioactivity.
The amounts of carbon dioxide emitted by various power sources in grams per kWh are nuclear: 4, wind: 8, hydro: 8, geothermal: 79, gas: 430, oil: 828, and coal: 955. Other estimates give similar figures. These show that the fossil fuels — gas, oil, and coal — are the greatest emitters, and the other sources — nuclear, wind, and hydroelectric — emit less than about one percent of their amounts.
The land areas occupied by the various types of power stations in square meters per megawatt are nuclear: 630, oil: 870, gas: 1500, coal: 2400, solar: 100,000, hydro: 265,000 and wind: 1,700,000.
The radioactivity emitted by various power sources in man-sieverts per gigawatt-year are coal: 4.0, nuclear: 2.5, geothermal: 2, peat: 2, oil: 0.5 and gas: 0.03. These are all extremely small amounts, and it is noteworthy that coal power stations emit more radioactivity than nuclear power stations. This is because coal contains small but significant amounts of uranium, and a small fraction of this is emitted into the atmosphere. The amounts of uranium vary with the type of coal, and the above figure is a world average obtained by the International Atomic Energy Agency.
Every year, a nuclear power reactor produces about four cubic meters ([m.sup.3]) of high level radioactive waste, 100 [m.sup.3] of intermediate-level waste, and 530 [m.sup.3] of low-level waste. The total amount of high-level waste produced in Britain from 1956 to 1986 was about 2000 [m.sup.3], about the same volume as an average house. This is very small compared with the vast amounts of poisonous chemical waste produced by the manufacturing industries, much of which is buried in the sea or emitted into the atmosphere.
The low-and intermediate-level nuclear waste can safely be buried in deep trenches, but the high-level waste requires special attention. As the uranium or plutonium is burnt in the nuclear reactor, the products of fission accumulate in the fuel rods until they absorb so many neutrons that they prevent the reactor from working. To avoid this, spent fuel rods are continually removed from the reactor and replaced by new ones. The spent fuel rods are taken to the reprocessing plant where the uranium and plutonium are separated and used to make new fuel rods. The remaining portion contains the highly radioactive fission fragments, The first step in the disposal of this high-level waste is to store it in tanks above ground for a few decades so that most of the radioactivity from the short-lived nuclei decays. Then the remainder is concentrated and fused to form a glassy or ceramic substance. For extra safety this is placed in stainless steel containers and then buried far below the surface in a stable geological formation. There is then no chance that the fission products will escape and cause harm. This has been checked by a detailed study sponsored by the European Union. Eventually, over the years, the radioactivity of the fission fragments will decay until it is similar to that of the surrounding rocks.
It has been suggested that the radiation emitted from nuclear power stations increases the number of cases of leukaemia in the area. It has also been suggested that this radiation is responsible for long-tem genetic effects. These possibilities are discussed below.
Nuclear Radiations
One of the main differences between nuclear and other power stations is the presence of nuclear radiation. The fission fragments produced when the uranium nuclei split are highly radioactive and emit alphaparticles and beta and gamma rays until finally a stable nucleus is formed. There are many different nuclei among the fission fragments, and the rates of emission vary from a small faction of a second to many thousands of years. These decay rates are characterized by a half-life, which is the time taken by the radioactivity of a sample of a particular type of nucleus to decay to half its initial value.
When it passes through the human body, nuclear radiation can break up the complicated molecules inside the cells, releasing reactive radicals that can cause more damage. If the level of radiation is small, few cells are affected; they are soon replaced and no harm is done. If, however, the radiation level is high, serious damage will be caused, and cancers may develop during the following years. In the case of massive whole-body irradiation, death can also take place. It is vital, of course, to specify just what we mean by low and high levels of irradiation, and this will be done later.
The three types of nuclear radiation have different effects on the human body. Alphaparticles are helium nuclei and, since they are doubly charged, they lose energy rapidly and ionize strongly and are very destructive. Their short range means that they are harmful only if the radioactive material is inside the body. The beta rays are energetic electrons, and the gamma rays are short-wavelength electromagnetic radiation. They can both penetrate for inside the human body.
Nuclear radiation can easily be detected by very sensitive instruments that can record the passage of a single particle, so it is possible to detect the presence of extremely small amounts of radioactive substances. This enables us to learn how they move through the atmosphere, the oceans, and our own bodies. This property has proved to be extremely useful in medical research.
When considering the effects of nuclear radiation on people, it is necessary to take account of the different sensitivities of the different organs of the body. This is done by defining the rem, which is the dose given by gamma radiation that transfers a hundred ergs of energy to each gram of biological tissue, and for other types of radiation it is the amount that does the same biological damage. A new unit, the Sievert, has now been defined as 100 rem.
Nuclear radiation is often feared because it is unfamiliar and can cause great damage to living organisms without our being aware that anything untoward is happening. The damage only appears afterwards, sometimes very long afterwards, when it is too late to do anything about it. Our senses warn us of many dangers, such as excessive heat and some poisonous gases, and we can take avoiding action. Nuclear radiation is not alone in being invisible; many poisonous gases such as carbon monoxide have no smell, and we don't know that a wire is live until we touch it and receive an electric shock.
When nuclear radiation was first discovered, it was welcomed with enthusiasm, and to some extent this was justified. In the form of X-rays it improved medical diagnosis and treatment, and bottles of health-giving mineral waters were advertised as radioactive. It was only much later, when pictures were released of the radiation damage to the victims of Hiroshima and Nagasaki, that the public image of nuclear radiation switched to one of fear.
Undoubtedly this reaction has gone too far. Nuclear radiation is indeed dangerous in large amounts, but so are fire and electricity. Properly used, nuclear radiation has numerous beneficial applications in medicine, agriculture, and industry. Like so many of God's gifts, it can be used for good or evil.
Nuclear radiation is not new; it did not first enter the world with the experiments of Henri Becquerel or Madame Curie. It has been on the earth since the very beginning. Many rocks and minerals, such as the pitchblende refined by Madame Curie to produce the first samples of radium, are naturally radioactive and emit radiation all the time. The nuclei formed by such radioactivity include radon, a gas that seeps up through the soil and enters our homes. The natural radioactivity of the earth varies greatly from one place to another, depending on the concentration of rocks containing uranium. In addition, the earth is bathed in the cosmic radiations from outer space, and they are passing through our bodies all the time. Cosmic rays are attenuated as they pass through the atmosphere and so they are more intense at the top of a mountain than at sea level. There are radioactive materials in our own bodies, such as a rare isotope of potassium. Thus the human species has evolved through millions of years immersed in nuclear radiation. This natural radioactivity is important for estimating the hazards of nuclear radiation in general, since if the additional source emits radiation at a level far below that of the natural radiation it is unlikely to be injurious to health.
In addition to this natural radiation, we are exposed to radiation from medical diagnosis using X-rays, medical treatment, atomic bomb tests, and the nuclear industry. Estimates of the radiation exposure in the United Kingdom due to all these sources (in millirem per year) are 186 mrem for natural radiations, including 50 mrem for radon, and 53 mrem for man-made irradiation, nearly all due to medical treatment and diagnosis. That for medical purposes is quite high, but in the long term what is important is the average exposure over a long time weighted by the age distribution of those exposed. This is because the effects of radiation at levels typical of medical uses do not appear for many years so that the irradiation of young people before the end of their reproductive age is more serious than that given to older people. Since the larger part of the medical irradiation is received during the treatment of cancers, which more often afflict older than younger people, the dangers to health due to medical irradiation are not so great as might appear.
Nearly half the radiation exposure due to the natural background is attributable to radon. This is a radioactive gas formed by the radioactive decay of uranium. In regions where the soil contains uranium the radon seeps upwards into the atmosphere or into our homes where it collects unless the house is well-ventilated. Radon decays with the emission of alpha-particles and when breathed in can irradiate the inside of the lung, causing lung cancer. According to the National Radiation Protection Board a radon gas concentration level of 200 Becquerels/m3, equivalent to an effective dose of 10 mSv per year, is the level at which action should be taken to reduce the level. This involves creating a cavity under the floors and pumping out the radon at a cost of up to [pounds sterling]1000. Many local authorities are now recommending that such action be taken.
Before doing this, however, it is necessary to establish the relation between the level of exposure and the probability of lung cancer. Many studies worldwide, in Canada, China, Finland, France, Germany, Japan, Sweden, and the USA have failed to establish any positive correlation and, indeed, in three of these studies, there was an inverse relationship. Other studies2 find that the increased risk of lung cancer due to a lifetime dose of 100 Becquerels/m3 is about 0.1 percent and twenty-five times greater for smokers. The data used in this study were consistent with a linear dose relationship but do not exclude different behavior at very low exposures. The validity of this assumption is discussed in more detail below. It thus seems that, particularly for non-smokers, the level of irradiation due to radon is so low that when compared with other much greater hazards it is difficult to justify such expensive precautions.
Radioactive isotopes have many medical applications. If, for example, we want to know how salt is taken up by the body, we can feed a patient with some salt that contains a very small amount of a radioactive isotope of sodium. This emits radiation that can be detected by a counter outside the body, and so we can follow the progress of the sodium as it is absorbed. The amount of radiosodium needed is so small that it does no harm to the patient. In this way radioisotopes provide a valuable diagnostic tool. Radioisotopes can also be used for treatment. For example, it is known that iodine tends to concentrate in the thyroid gland. If therefore we want to treat cancer of the thyroid we can feed the patient with radioiodine, and it will go to the thyroid gland and irradiate the tumor, without appreciably affecting the rest of the body.
The powerful nuclear accelerators that are used to explore the structure of the nucleus and to produce new unstable particles can also be used to irradiate tumors. The radiation emitted by radium and other natural sources has the disadvantage that it is relatively low in energy and so can penetrate only a small distance into the body. In addition, the radiation comes out in all directions equally. If we want to treat a tumor deep inside the body we need a way of irradiating the tumor that minimizes the irradiation of the surrounding healthy tissue. The only way to do this is to have a collimated beam of radiation of sufficient energy to penetrate the body, and such beams are produced by accelerators. During the treatment, the patient is rotated so that the beam always passes through the tumor but irradiates a particular part of the surrounding healthy tissue for only a small part of the time. This is a difficult technique, but with great care it can be used successfully. Many nuclear accelerators such as that at Faure in South Africa are used partly for medical treatment and partly for nuclear research.
Sometimes it is difficult to know whether the benefits of radiation outweigh the hazards. Thus X-rays can detect cancers early enough for effective treatment, and yet they can also themselves cause cancers. A detailed study of stomach tumors showed that for young people the dangers outweigh the benefits, whereas for older people the opposite is the case.
There is widespread public anxiety about the effects of nuclear radiation, particularly concerning the genetic effects and the cases of leukemia in children near nuclear installations. The children of the survivors of the atomic bombing of Hiroshima and Nagasaki, who all received massive doses of radiation, have been studied in detail by Professor S. Kondo, who personally visited Nagasaki soon after the bombing and saw the devastation. He has studied the effects of the bombing for forty years and has recorded the indicators of genetic damage for 20,000 children of atomic bomb survivors exposed to an average dose of 400 mS. The numbers of the genetic indicators such as chromosome abnormalities, mutations of blood proteins, childhood leukemia, congenital defects, stillbirths, and childhood deaths showed no differences between the children of the atomic bomb survivors and a control group. There is thus no evidence of genetic damage due to the atomic bombs.
To estimate the biological damage due to a particular dose of radiation we must know the relation between the two quantities. The difficulty is that the doses that cause measurable damage are hundreds of thousands of times larger than the extra doses received by people living around nuclear installations. It is often assumed that there is a linear relation between the two, so that the probability of contracting cancer is proportional to the dose. As it seems the safest assumption to make, it is widely adopted in setting safety standards. There is, however, no direct evidence for this, and indeed there is much contrary evidence.3 This is not unreasonable, since the body has an innate capacity to repair damage, and it is only when the defenses of the body are overwhelmed by a massive dose that harm occurs. Thus a dose received dose that harm occurs. Thus a dose received over a long period is less harmful than if it were received all at once.
A direct result of the linear dose assumption is the setting of unreasonably strict limits on permitted radiation exposure in many industries, thus greatly increasing costs. This leads to reluctance to accept vital radiodiagnostic and radiotherapeutic irradiations, and restricts the use of radiation in industry and research. Adherence to these exposure limits led to large-scale evacuation from the region around Chernobyl, causing much unnecessary distress and suffering.
It is also possible that small doses stimulate the body's repair mechanisms, so that small doses are beneficial. This is supported by an extensive study made by Frigerio et. al. at the Argonne National Laboratory in 1973.4 They compared the cancer statistics for the USA from 1950 to 1967 with the average natural background for each State, and found that the seven States with the highest natural background had the lowest cancer rates. Unless there is some other explanation for this result, it implies that the chance of contracting cancer is reduced by 0.2 percent per rem. Further evidence is provided by "the higher life expectancy among survivors of the Hiroshima and Nagasaki bombs; many times lower incidence of thyroid cancer among children under fifteen exposed to fallout from Chernobyl than the normal incidence among Finnish children; and a 68 percent below-average death rate from leukemia among Canadian nuclear energy workers."5 Many studies on animals have given similar results.
Furthermore, it is found that people living in areas of high background radiation show no evidence of detrimental effects; thus in Kerala the life expectancy is seventy-four years compared with fifty-four years for India as a whole. Aircrews are exposed to higher doses of cosmic radiation, and their union asked for compensation. Studies of the mortality rates of 19,184 pilots in the period from 1960 to 1996 showed, however, that they actually decreased with increasing dose. The skin cancer rate was, on the other hand, higher because of the time they spent lying in the sun on tropical beaches. Such evidence has been widely discounted because it seems counter-intuitive.
In favour of the idea of a threshold dose, it can be argued that the passage of a single nuclear particle through a cell, the lowest possible dose, can cause DNA double strand lesions. Such lesions occur naturally at the rate of about ten thousand per cell per day, whereas exposure to radiation at the current population exposure limit would cause only two lesions per cell per day. Thus radiation-induced lesions are insignificant compared with those occurring naturally.
A new technique for evaluating the effects of small doses of radiation has been developed by Professor Feinendegen.6 His results show conclusively that the linear dose assumption is incorrect; at low doses there is an additional quadratic term. Furthermore, a Joint Report of the Academie des Sciences (Paris) and of the Academie National de Medicine concludes that estimates of the carcinogenic effects of low doses of ionizing radiations obtained using the linear assumption could greatly overestimate those risks.7
The concern about nuclear radiation has diverted attention from other threats to our health. Radiation is responsible for only about 1 percent of diseases worldwide, and most of this comes from the natural background and from medical uses. The nuclear industry is responsible for less than 0.01 percent. The vast sums spent to reduce this still further could be spent far more effectively on simple disease prevention. It is greatly in the public interest that these matters should be treated as objectively as possible, taking full account of the scientific evidence. This would avoid much unnecessary anxiety and enable the best decisions to be taken concerning our future energy supplies.
Reactor Accidents
The two reactor accidents that have received wide publicity are that at Three Mile Island in 1979 and the much more serious one at Chernobyl in 1986. The accident at Three Mile Island was initially due to the breakdown of the pumps circulating water in the secondary cooling system. The standby cooling systems failed to come into action, and the reactor temperature rose. The automatic safety system then shut down the reactor, but the radioactive core still emitted heat. The operators at first misinterpreted a dial reading but eventually they brought the reactor under control. A small amount of radioactivity was emitted giving people nearby a dose of about one millirem, which is what they receive every day from natural sources. During the incident several alarming announcements were made to the public, which naturally caused much distress. It was a major financial disaster, and it took more than ten years to remove the damaged reactor at a cost of nearly a billion dollars.
The disaster at Chernobyl was immeasurably worse. It happened by a combination of bad design and operator irresponsibility. The reactor was designed to produce weapons-grade plutonium as well as electrical power. It was thermally unstable at low power, so that overheating would cause further overheating, with catastrophic consequences. The operators were therefore instructed to raise the power rapidly through this dangerous region to ensure stable operation. Such a design would never be accepted in the West. On the fatal night the operators wanted to find out what happened at low power. Fearing that the safety circuits could shut the reactor down before they finished their experiment they switched then off. The power rose rapidly, the graphite caught fire, the cover was blown off, and radioactive materials were discharged into the atmosphere and deposited over much of Europe. Firemen fought the blaze heroically; many received lethal doses of radiation, and fifty-six of them died.
There was, nonetheless, no evidence of excess cases of leukemia or other types of cancer among the hundreds of thousands of workers employed in the clean-up after the accident. Using the discredited linear dose assumption a large increase in cancer victims all over Europe due to the radioactivity released into the atmosphere was predicted, causing much public anxiety. For the same reason large numbers of people were needlessly evacuated from the region around the reactor, causing much distress. Many countries immediately lost faith in nuclear power and opposed the construction of new nuclear power stations. Since that time, more realistic appraisals, especially by industrialists, have convinced them of the necessity of nuclear power, and many new power reactors are being built or are planned.8 The reactors now in operation are so designed that such accidents can never happen again.
References: (1.) P. E Hodgson, Nuclear Power, Energy and the Environment. (London: Imperial College Press, 1999). This book contains many references to the topics discussed in this article. (2.) Sir Richard Doll, H. J. Evans, and S. C. Darby, Nature 367.678.1994.(3.) B. L. Cohen, "Validity of the Linear No-Threshold Theory of Radiation Carcinogenesis at Low Doses," Nuclear Energy 38.157.1999. (4.) see also J. A.Simmons and D. E. Watt, Radiation Protection Dosimetry — A Radical Reappraisal. (Wisconsin: Medical Physics Publishing, 1999). (5.) Lord Taverne, Speech in the House of Lords. SONE Newsletter No. 71.(6.) Ludwig E. Feinendegen, lecture at the Conference on Nuclear Radiations and their Effects. Nagasaki, August 2004. (7.) M. Tubiana and A.Aurengo, Nuclear Issues (October 2005), 3. (8.) See Ref. 1, pp 81-94 for discussion of Chernobyl. Further details in Nuclear Issues (October 2005).
P. E. HODGSON is Senior Research Fellow Emeritus in Physics at Corpus Christi College, Oxford.
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