Lesnoy CIF 2008 Benchmark 1

Vasil’ev school №76

The Project:

Nuclear Renaissance: Risks versus Benefits

Pupil: Ekaterina Pushneva,

10 «А» grade,

Vasil’ev school № 76,

Lesnoy.

Teacher: Galina Romanova,

Vasil’ev school № 76,

Lesnoy.

2007/2008

Benchmark I

In Benchmark I our task is to examine the objectives from the point of view of the scientific and environmental; social and cultural; economic; political and geopolitical domains to demonstrate a comprehensive understanding and comparison of conventional energy and nuclear energy.

Contents:

Introduction 4

Benchmark 1.1 5

The glossary 5

Energy sources in the modern world 7

Non- renewable energy 7

Gas 7

Coal 10

Oil 13

Nuclear energy 14

Renewable sources of energy 17

Biomass energy 17

Geothermal energy 20

Solar energy 22

Water energy 24

Wind energy 26

Bibliography 28

Benchmark 1.2 29

The role of nuclear energy in power production 29

The nuclear energy industry 32

The nuclear fuel cycle 34

Professions 41

Civil and military uses of nuclear energy 42

Conclusion 43

Bibliography 48

Presentation

Introduction

All the forecasts of world energy demand for the next 50 years point towards very significant increases in consumption. A big share of this new demand will come from areas of the world where existing energy consumption is now relatively low in comparison with the European countries, and which are becoming increasingly integrated in the global economy. As energy demand grows, all societies world wide will face a real challenge in providing the energy needed to feed economic growth and improve social development while enhancing protection of the environment.

It is not difficult to conclude that it is the great responsibility of politicians to establish energy policies that meet that challenge while being robust enough to cope with the risks associated with the globalization of the world economy. Diversification, security of supply, protection of the environment and technology development are key elements of any energy policy that tries to provide enough energy at a reasonable price.

It is rather difficult to find one source of energy that will be able to provide energy for all the world. In our project we would like to describe all the existing sources of energy in the modern world, because our civilization has reached the level it can’t survive without energy. We need energy in every sphere of our life: in houses, official and institutional buildings, at nuclear plants, in laboratories…You can’t find the place without using energy. It is necessary for lighting, heating, cooking, using electrical devices, driving, launching rockets, etc. If we are short of energy we can’t use all the inventions of the civilization.

Benchmark 1.1

In this part of Benchmark I, part 1 our task is to demonstrate an understanding of energy sources in use in the world today and their availability, distinguishing between renewable and non – renewable sources of energy, to describe the processes involved in the production of energy around the world, showing the energy resources of different major countries of the world.

Energy sources in the modern world

We’ll demonstrate different sources of energy, revealing their strengths and weaknesses (the glossary), we’ll also present the table “Using different energy sources in past 106 years in the USA and on the territory of the Russian Federation”, we’ll make the table to show reserves of oil, coal and gas in different countries, we’ll create the diagrams to show world reserves and extraction of the main energy resources, we’ll demonstrate the world usage of all energy resources, we’ll also reveal the period of complete depletion of some energy resources, we’ll give predictions of scientists about using energy sources in the future.

1.1 Energy sources in the modern world:

- the glossary of energy terms;

- non-renewable and renewable sources of energy;

- positive and negative traits of different sources;

- the development of these sources in past 106 years;

- the perspectives of energy development.

The glossary

The definition of energy

Energy is the name given to the ability to do work. Work and energy are measured in the same units. People often confuse energy, power, and force. Force is a push or a pull on an object or body. The amount of work is determined by the strength of the force used and the distance through which it moves. Power measures the rate at which work is done.

Energy is one of the two fundamental ideas in physics. The other is matter. These two ideas are not completely separate. Many physicists believe that energy and matter are merely two aspects of the same thing, much as ice, water, and water vapor are three different aspects of water. The tiny electric particles (electrons) inside the atom give off the energy we know as light. A body loses part of its mass when it releases energy. It gains mass when it absorbs energy.

Biomass is substances of a vegetative or animal origin, and also the waste received as a result of their processing.

Coal is a black or brown rock that can be ignited and burned. As coal burns, it produces useful energy in the form of heat.

Gas is a substance is not liquid or a solid; any substance that has no shape or size of its own and can expand without limit.

Geothermal Energy is energy produced by underground steam or hot water.

Nuclear Energy –the energy that exists in atom. Nuclear energy, also called atomic energy, is the powerful energy released by changes in the nucleus (core) of atoms.

Oil is any one of several kinds of fatty or greasy liquids that are lighter than water, that burn easily, and that will not mix or dissolve in water but will dissolve in alcohol.

Solar energy is energy given off by the sun. Solar energy is produced by nuclear reactions that take place inside the sun.

Water energy is energy given off by water sources: rivers, waterfalls, tides, etc.

Wind energy is energy got from the power of the wind.

Energy sources in the modern world

There are two kinds of energy sources in the world. They are renewable and non- renewable ones.

Gas

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Gas is a substance is not liquid or a solid; any substance that has no shape or size of its own and can expand without limit. Gas fuels include natural and manufactured gases. Such fuels flow easily through pipes and are used to provide energy for homes, businesses, and industries. In many countries, vast networks of pipelines bring gas fuels to millions of consumers.

Natural gas is used to heat buildings, cook food, and provide energy for industries. It consists chiefly of methane, a colorless and odorless gas. Natural gas is usually mixed with compounds of the foul-smelling element sulfur so gas leaks can be detected.

Butane and propane, which make up a small proportion of natural gas, become liquids when placed under large amounts of pressure. When pressure is released, they change back into gas. Such fuels, often called liquefied petroleum gas (LPG) or liquefied natural gas (LNG), are easily stored and shipped as liquids. They provide energy for motor homes and can serve as fuel for people who live far from natural gas pipelines.

Manufactured gas, like synthetic liquid fuels, is used chiefly where certain fuels are abundant and others are scarce. Coal, petroleum, and biomass can all be converted to gas through heating and by various chemical procedures. Gas can also be produced by treating such biomass as animal manure with bacteria called anaerobes, which expel methane as they digest the waste.

Gas (fuel) is of the most important resources. We burn it to provide heat and to produce energy to run machinery. The chemical industry uses the chemicals in gas to make detergents, drugs, plastics, and many other products.

People sometimes confuse gas with gasoline, which is often called simply gas. But gasoline is a liquid. On the other hand, gas fuel--like air and steam--is a gaseous form of matter. That is, it does not occupy a fixed amount of space as liquids and solids do.

Gas has many uses as a fuel. Millions of people use it to heat their homes, cook meals, burn garbage, heat water, dry laundry, and cool the air. Hotels, restaurants, hospitals, schools, and many other businesses and institutions burn gas for cooking, heating buildings and water, air conditioning, and generating steam. Gas produces little air pollution when it is burned.

Industry has many uses for gas in addition to using it as a raw material in making products. These uses range from burning off the quills of chickens to hardening the nose cones of spacecraft.

Almost all the gas used in the United States and Canada is natural gas. Most scientists believe that natural gas has been forming beneath the earth's surface for hundreds of millions of years. The natural forces that created gas also created petroleum. As a result, natural gas is often found with or near oil deposits. The same methods are used to explore and drill into the earth for both fuels. Manufactured gas is produced chiefly from coal or petroleum, using heat and chemical processes. Manufactured gas costs more than natural gas and is used in regions where large quantities of the natural fuel are not available.

Before its breakup, the Soviet Union was the leading producer of natural gas. The United States was the second largest producer. Until the 1960's, large quantities of natural gas were not available in most European countries, and manufactured gas was used widely. In the 1960's, the development of newly discovered gas fields led to the rapid expansion of Europe's natural gas industry. Expansion was especially rapid in the Soviet Union and the Netherlands. The world's largest known gas field was found in the Soviet Union in 1966. Great Britain began to produce much natural gas from deposits found under the North Sea in the mid-1960's.

The gas industry consists of three main activities: producing gas, either by drilling natural gas wells or by manufacturing gas; transmitting gas, usually by pipeline, to large market areas; and distributing gas to the user. Each part of the gas industry requires its own special skills and equipment. Some gas companies conduct all three activities, but most companies handle only one.

The natural gas industry began in the United States. The industry started to expand rapidly in the late 1920's with the development of improved pipe for transmitting gas great distances economically. By the 1930's, gas produced in Texas was being carried by pipeline to the Midwest. Today, long-distance gas pipelines serve many parts of the world.

In the 1970's and 1980's, the gas industry launched a number of programs to meet an increasing demand for gas. For example, the industry began seeking ways of producing gas from coal.

Coal

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Coal is a black or brown rock that can be ignited and burned. As coal burns, it produces useful energy in the form of heat. People use this heat to warm buildings and to make or process various products. But the main use of the heat from coal is the production of electricity. Coal-burning power plants supply more than half the electricity used in the United States and nearly half that is used throughout the world. Another major use of coal is the production of coke, a raw material in the manufacture of iron and steel. In addition, the coke-making process provides raw materials used to make such products as drugs, dyes, and fertilizers.

Coal was once the main source of energy in all industrial countries. Coal-burning steam engines provided most of the power in these countries from the early 1800's to the early 1900's. Since the early 1900's, petroleum and natural gas have become the leading sources of energy in much of the world. Unlike coal, petroleum can be easily made into gasoline and the other fuels needed to run transportation equipment. Natural gas has replaced coal as a source of heat for some applications. However, people are rapidly using up the world's supplies of petroleum and natural gas that can be removed from the ground economically. If the present rates of use continue, little may remain of these supplies by about 2050. By contrast, the world's supply of coal can last more than 250 years at the present rate of use. Increased use of coal, especially for producing electricity, could relieve a shortage of gas and oil.

Coal as a fuel

Coal is a useful fuel because it is abundant and has a relatively high heating value. However, coal has certain impurities that limit its usefulness as a fuel. These impurities include sulfur and various minerals. As coal is burned, most of the sulfur combines with oxygen and forms a poisonous gas called sulfur dioxide. Most of the minerals turn into ash. The coal industry refers to ash-producing substances in coal as ash even before the coal is burned.

Coal known as low-sulfur coal can be burned in fairly large quantities without adding harmful amounts of sulfur dioxide to the air. Medium- and high-sulfur coals can cause serious air pollution if burned in large quantities without proper safeguards.

The United States Department of Energy (DOE) classifies sulfur content according to the weight of the sulfur in a sample of coal that can produce 1 million British thermal units (Btu's) of heat. Such a sample is low-sulfur coal if it contains 0.60 pounds (0.272 kilograms) or less of sulfur, medium-sulfur coal if its sulfur content is 0.61 to 1.67 pounds (0.277 to 0.758 kilograms), and high-sulfur coal if it contains 1.68 pounds (0.763 kilograms) or more of sulfur.

Some of the ash produced by burning powdered coal may also escape into the air. Like sulfur dioxide, such fly ash can contribute to air pollution. However, devices have been developed to trap fly ash in smokestacks and so prevent it from polluting the air.

Coal is used as a fuel chiefly in the production of electricity. Electric power plants use more than three-fourths of the coal mined in the United States.

Bituminous coals have long been the preferred coals for electric power production because they are the most plentiful coals and have the highest heating value. Subbituminous coals and lignites have the lowest heating value. However, nearly all the subbituminous coal and about 90 percent of the lignite in the United States have a low sulfur content. On the other hand, about 50 percent of the nation's bituminous coal has a medium- or high-sulfur content. To meet federal and state pollution standards, power plants are burning more subbituminous coal and lignite. However, these coals cause problems for industry because they quickly lose their moisture, break up, and become dusty. This dustiness makes them difficult to handle and transport.

Other uses of coal as a fuel. In parts of Asia and Europe, coal is widely used for heating homes and other buildings. In the United States, natural gas and fuel oil have almost entirely replaced coal as a domestic heating fuel. However, the rising cost of oil and natural gas has led some factories and other commercial buildings to switch back to coal. Anthracites are the cleanest-burning coals, and so they are the preferred coals for heating homes. However, anthracites are also the most expensive coals. For this reason, bituminous coals are often preferred to anthracites for heating factories and other commercial buildings. Subbituminous coals and lignites have such a low heating value that they must be burned in large amounts in order to heat effectively. As a result, they are seldom used for domestic heating.

In the past, coal also provided heat for the manufacture of a wide variety of products, from glass to canned foods. Since the early 1900's, manufacturers have come to use natural gas in making most of these products. Coal is used mainly by the cement and paper industries. However, some industries have switched back to coal to avoid paying higher prices for natural gas.

Coal is used chiefly to produce electricity. It is burned to create heat to turn water into steam. The steam is then used to rotate turbines, machines that generate electricity . Some coal is made into coke, a charcoallike solid that is an essential raw material in the production of iron and steel. Coal is also used to heat buildings and to provide energy for industrial machinery. There are four forms of coal: lignite, or brown coal, subbituminous coal, bituminous coal, and anthracite. Bituminous coal is the most plentiful and important coal used by industry. It contains more carbon and produces more heat than either lignite or subbituminous coal. It is also the coal best suited for making coke. Anthracite is the least plentiful and hardest coal. It contains more carbon and produces more heat than other coals. However, anthracite is difficult to ignite and burns slowly.

Peat is partially decayed plant matter found in swamps called bogs. It is used as a fuel chiefly in areas where coal and oil are scarce. In Ireland and Scotland, for example, peat is cut, formed into blocks, and dried. The dried blocks are then burned to heat homes.

Oil

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Oil is any one of several kinds of fatty or greasy liquids that are lighter than water, that burn easily, and that will not mix or dissolve in water but will dissolve in alcohol. Mineral oils such as kerosene, are used for fuel.

Ecological point of view

Oil is a major source of ocean pollution. Most oil pollution enters the ocean from oil spills on land or in rivers used to transport petroleum. Oil also seeps into the ocean naturally from cracks in the sea floor. Oil tanker and oil well accidents at sea account for only a small portion of ocean oil pollution, but their effects may be disastrous. The world's largest accidental oil spill occurred in June 1979, when an oil well blew out off the east coast of Mexico and spilled about 130 million gallons (490 million liters) of oil. The world's worst tanker oil spill occurred in March 1978, when a tanker ran aground off the coast of France, spilling 68 million gallons (257 million liters). The worst oil spill in the United States occurred in March 1989, when a tanker ran aground off Alaska and leaked nearly 11 million gallons (42 million liters). The world's largest oil spill occurred when Iraq deliberately released about 465 million gallons (13/4 billion liters) of oil into the Persian Gulf during the Persian Gulf War (1991). In water, much of the oil forms tarlike lumps, which litter beaches and other coastal areas. Oil also coats fish, birds, and marine mammals, killing many of them.

Scientists and engineers have devised several methods to clean up oil spills. One method involves placing a ring of floating devices around the spill to prevent it from spreading. Pumps or skimming devices then collect the oil, which floats on the surface of the water. Oil may also be recovered by placing sheets or particles of floating, oil-absorbing material on the ocean surface. Burning the oil cleans a spill, but it produces air pollution. Detergents help break up spills, but they may cause additional harm to marine life.

Nuclear Energy

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Nuclear Energy –the energy that exists in atom. Some atoms can be made to release some of their energy, either under control or uncontrolled.

Nuclear energy, also called atomic energy, is the powerful energy released by changes in the nucleus (core) of atoms. Tremendous amounts of energy can be produced by this source. The heat and light of the sun result from nuclear energy. Scientists and engineers have found many uses for this energy, including the production of electric energy and the explosion of nuclear weapons.

Scientists knew nothing about nuclear energy until the early 1900's, though they knew that all matter consists of atoms. Scientists then further learned that a nucleus makes up most of the mass of every atom and that this nucleus is held together by an extremely strong force. A huge amount of energy is concentrated in the nucleus because of this force. The next step was to make nuclei let go of much of that energy.

Scientists first released nuclear energy on a large scale at the University of Chicago in 1942, three years after World War II began. This achievement led to the development of the atomic bomb. The first atomic bomb was exploded in the desert near Alamogordo, N.Mex., on July 16, 1945. In August, U.S. planes dropped bombs on Hiroshima and Nagasaki, Japan. The bombs largely destroyed both cities and helped end World War II.

Since 1945, peaceful uses of nuclear energy have been developed. The energy released by nuclei creates large amounts of heat. This heat can be used to make steam, and the steam can be used to generate electric energy. Engineers have built devices called nuclear reactors to produce and control nuclear energy.

A nuclear reactor operates somewhat like a furnace. But instead of using such fuels as coal or oil, almost all reactors use uranium. And instead of burning in the reactor, the uranium fissions--that is, its nuclei split in two. As a nucleus splits, it releases energy that is converted largely into heat. The fission of 1 pound (0.45 kilogram) of uranium releases as much energy as the burning of 1,140 short tons (1,030 metric tons) of coal.

Electric power production is by far the most important peaceful use of nuclear energy. Nuclear energy also powers some submarines and other ships. These vessels have a reactor to create heat for making the steam that turns the ship propellers. In addition, the fission that produces nuclear energy is valuable because it releases particles and rays called nuclear radiation that have uses in medicine, industry, and science.

However, nuclear radiation can be extremely dangerous. Exposure to too much radiation can result in a condition called radiation sickness.

Electric power production. Most electric power plants are steam-turbine plants. All nuclear power plants and almost all plants fueled by coal, gas, or oil are steam-turbine plants. They use high-pressure steam to generate electricity. The steam spins the wheels of turbines, which drive the generators that produce electricity. Steam-turbine plants differ mainly in how they create heat to make steam. Nuclear plants create the heat by splitting uranium atoms. Other plants burn coal, gas, or fuel oil. Steam-turbine plants produce about 70 percent of the electricity used in the United States. Coal-burning plants account for most of this output.

Renewable sources of energy

The biomass energy

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Biomass is substances of a vegetative or animal origin, and also the waste received as a result of their processing. In the power purposes energy of a biomass is used doubly: by direct burning or by processing in fuel (spirit or biogas).

Biomass is any organic material that can be converted into energy or into a source of energy. It includes such waste products as cornstalks, spoiled grain, tree limbs, scrap paper, garbage, and manure. Farmers grow sugar cane, certain trees, seaweed, and other crops as biomass. The term biomass also refers to the amount of living material in a specific area.

One can convert biomass by burning, by fermentation, or by treatment with chemicals or bacteria. Fermentation produces the fuel ethanol. Chemical treatment produces such fuels as synthetic gas, methane, and fuel oil. Treatment with bacteria yields alcohols, chemicals, or methane.

Biomass may someday become an important source of energy. Today, most of our energy comes from fossil fuels, including coal, oil, and natural gas. Supplies of these fuels are running out, however. Furthermore, the burning of fossil fuels adds to the amount of carbon dioxide in the atmosphere, which may well contribute to a warming of the atmosphere known as the greenhouse effect.

Biomass, on the other hand, is plentiful and can be continually replenished. In addition, use of biomass can return to the atmosphere no more carbon dioxide than the amount that the biomass removed from the atmosphere as it grew.

Wood has been used as a fuel since prehistoric times--longer than any other material. Today, it is an important fuel chiefly in developing countries, where it is used for cooking and heating. In industrialized nations, it is not a major source of energy. But some paper and pulp factories, which make wood products, obtain the energy for their manufacturing processes by burning bark, sawdust, and other wood waste. Wood is also used to make charcoal. Biomass materials other than wood are also used as fuel. For example, heat produced by burning nutshells, rice and oat hulls, and other by-products of food processing is often used to operate plant equipment.

Positive	Negative
1.There are two basic directions of getting of fuel from a biomass: by means of thermo chemical processes or by biotechnological processing. Experience shows that biotechnological processing of organic substance is most perspective. One of the most perspective directions of power use of a biomass - manufacture from it the biogas consisting on 50-80 % from metane and on 20-50 % from carbonic acid. Its ability - 5-6 thousand in kcal/¼3. Manufacture of biogas from manure is the most effective one. It is possible to receive 10-12 cube M of metane from one ton. For example, processing 100 million tons of such withdrawal of field husbandry as straw of cereal cultures, can give nearby 20 billion cube. M of metane. In areas annually there is 8-9 million tons of stalks of cotton from which it is possible to receive cube up to 2 billion. M of metane. Recycling vegetable tops of cultural plants, grasses is possible for the same purposes.	1.Not found (may be expensive technologies for mass production)
2. Biogas can be converted in thermal and electric energy, be used in internal combustion engines for getting the synthesized gas and artificial gasoline.
3. Manufacturing biogas from organic waste can solve simultaneously three problems: power, agrichemical and ecological.
4. Installations of manufactures of biogas place can be located in large cities and in the centers of processing agricultural raw material.

Geothermal energy

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Geothermal Energy is energy produced by underground steam or hot water. Several countries, including New Zealand and the United States, use geothermal energy to generate electricity.

Positive	Negative
1. The geothermal power is based on use of natural heat of the Earth. Bowels of the Earth conceal in itself enormous, practically inexhaustible energy source. The annual radiation of internal heat on our planet makes 2,8 * 1014 billion in kw * hour.	1. Radiation of internal heat is constantly compensated by radioactive disintegration of isotopes in the earth's crust.
2. Sources of geothermal energy can be two types. The first type is underground pools of natural heat-carriers - hot water or pair, or a steam-and-water mix. The second type is warm and hot rocks.	2. The main lack of two types is perhaps very weak concentration of geothermal energy.
3.However, in places of formation of original geothermal anomalies where hot sources or breeds approach rather close to the surface and where at immersing deep into on everyone of 100 m the temperature raises on 30-40°С, concentration of geothermal energy can create conditions for its economic use.
4.Its stocks are practically inexhaustible.
5.Geothermal energy is widespread enough. Its concentration is connected basically with belts of active seismic and volcanic activity which borrow 1/10 areas of the Earth.
6. The use of geothermal energy does not demand great costs because it is « ready to the use », the energy source is created by the nature.
7.Geothermal energy in the ecological attitude is absolutely harmless and does not pollute the environment.

Hot springs

Hot springs are a source of geothermal energy. Hot springs are springs that discharge water heated by natural processes within the earth. Most hot springs are steadily flowing streams or calm pools of water. But many are fumaroles, geysers, or bubbling pools of mud called mudpots or mud volcanoes. Hot springs are also called thermal springs.

Hot springs originate when surface water, which results from rain and snow, seeps into the ground. Many springs occur in volcanic regions where hot molten rock called magma lies near the surface of the earth. Surface water trickles down through layers of rock until it is heated by the magma. Then the water rises to the surface through channels in the rock.

Hot springs also occur in regions that have faults (breaks) or folds (bends) in the layers of rock beneath the earth's surface. The temperature of the earth increases toward the interior. Faults and folds enable surface water to penetrate to depths where it is heated.

Volcano

Volcanoes are among the most destructive natural forces on the earth. In many volcanic regions, people use underground steam as a source of energy. This geothermal energy is used to produce electricity in such countries as Italy, Mexico, New Zealand, and the United States. In Reykjavik, Iceland, most people heat their homes with water piped from volcanic hot springs.

Solar energy

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Solar energy - the most grandiose, cheapest and the least usable source of energy. Solar energy is energy given off by the sun. It consists of light, heat, and other forms of electromagnetic radiation. Solar energy is produced by nuclear reactions that take place inside the sun.

Every 40 minutes, the sun delivers as much energy to the earth's surface as all the people on the earth use in a year. People directly use only a fraction of the solar energy that reaches the earth. Scientists are developing new ways to capture solar energy and to put it to use where and when it is needed.

Positive	Negative
1.In total for three days the Sun sends to the Earth so much energy, how much it contains in all reconnoitered stocks of minerals fuel, and for 1 second. - 170 billion DJ. All energy which is let out by the Sun, more than that its part which is received by the Earth, in 5 billion times. But even such "insignificant" size is more in 1600 times energy which other sources together can give.	1.The most part of this energy disseminates or the atmosphere, especially clouds absorbs, and only its third reaches a terrestrial surface.
2.Solar energy - the most grandiose and cheap energy source.	2.But this energy source is least used by the mankind.
3. The potential opportunities of power based on the use of the direct sunlight, are extremely great. The use only 0,0125 % of energy of the Sun could provide all today's needs of world power, and the use of 0,5 % completely could cover needs on prospect.	3. Weak density of a solar energy.
	4. Necessity to use collectors of the huge sizes besides entails significant material inputs.
5. Solar radiation by means of solar power plants will transform to the thermal or electric energy that is convenient for practical application. In southern areas of our country tens of solar installations and systems are created.

Water Energy

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Water energy is energy given off by water sources: rivers, waterfalls, tides, etc.

The total amount of water resources makes 1390 mln. cubic km, near by 1340 мln. cubic km of them - waters of the World ocean. Less than 3 % make fresh waters, only 0.3 % from them are technically accessible to use .

Water power is a valuable source of energy. When such fuels as coal, oil, and even nuclear fuels are burned up as a source of energy, they cannot be reused. But water used as a source of energy is not used up. The earth's constant flow of water can be harnessed to produce useful mechanical and electric power.

Wheels mounted on a frame over a river were the first devices used to harness water power. Blades around the outside of the wheels dipped into the river, and the flowing water striking the blades turned the wheels. The ancient Romans connected water wheels to grinding stones and used the power to mill grain.

During the Industrial Revolution, large water wheels were used to run machinery in factories. The power was not completely reliable, however. Floodwaters created more power than was needed, and droughts left the factories without power. By the end of the 1800's, the steam engine had replaced water power in most factories.

The first water-powered plant for generating electricity was built in Appleton, Wis., in 1882. This hydroelectric plant established water power as an important source of electricity. Hydroelectric power is now used all over the world. Today, almost all water power is used to generate electricity. Many hydroelectric plants are combined with thermal power plants (those using fuel). With this combination, the thermal plant can supply power if the hydroelectric plant is affected by drought. Hydroelectric plants are especially useful for producing electricity during periods when it is in great demand, because they can be turned on and off rapidly.

The mechanics of water power. Water cannot create power unless it is flowing from a higher place to a lower place as in a river, a waterfall, or a dam. People use the effects of gravity (the attraction the earth exerts on an object) pulling the water downward when they harness water for power. For example, in the customary system of measurement, a cubic foot of water weighs 62.4 pounds. The pull of gravity then creates a pressure of 6,240 pounds per square foot at the base of a body of water 100 feet tall. If this water were released from a nozzle at the bottom of its source, the stream of water would travel at a speed of about 80 feet per second. The force of this stream striking the blades of a water wheel would cause the wheel to turn, producing useful mechanical energy.

World water power production. The potential water power of the world is about 21/4 billion kilowatts of electric power. This is a very general estimate, because the flow of many large rivers has not been measured. Of this potential, about 600 million kilowatts is developed.

The United States has about a sixth of the world's developed power. Canada and Europe have most of the rest of the developed power. The potential of Asia, Africa, and Latin America is just beginning to be developed.

The world's largest hydroelectric power plants in operation include the Grand Coulee on the Columbia River in the United States and the Sayano-Shushensk on the Yenisey River in Russia. Each plant has a capacity to produce about 61/2 million kilowatts. The Guri power plant located on the Caroni River in Venezuela has the capacity to produce 10 million kilowatts. The Itaipu power plant of Brazil and Paraguay on the Parana River has a capacity of approximately 121/2 million kilowatts.

Positive	Negative
1.The total amount of water resources makes 1390 million m3.	1. Infringement ecological systems.
2. It is harmless for eсology.

Wind energy

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Wind energy is energy got from the power of the wind.

This plentiful accessible and ecologically pure energy source is poorly used. Wind energy turns windmills and propels sailboats. Private uses of the clean energy that is provided by wind occur all over the world. But wind power is commercially practical only in areas that have strong, steady winds.

Positive	Negative
1.The development of 40 billion in kw is technically possible, but even it exceeds more than in 10 times a hydroenergy potential of a planet.	1.Today the engines using a wind, cover only one thousand world needs of energy.
2.The wind energy potential of the Earth is very great.	2.Obstacles for development of the energy of the given kind is dispersedness and inconstancy of wind energy. Inconstancy of the wind demands a construction of accumulators of energy, that is more expensive than the cost price of the electric power. Because of dispersedness it is required five times more areas.
3.But on the Earth there are also such areas where winds blow with a sufficient constancy and force. (a wind blowing with speed of 5-8 km/s., refers to the moderate, 14-20 km/s. - strong, 20-25 km/s. - storm, and over 30 km/s. - hurricane). The examples of similar areas are coasts Northern, Baltic, the Arctic seas.	3. It is not enough areas where wind blows constantly.
4. Today windelectrical units reliably supply with a current of oilmen; they successfully work in the remote areas, on the distant islands, in Arctic regions, on thousand agricultural farms where there are no nearby large settlements and power stations of the general using. The basic direction of use of the wind power - reception of the electric power for independent consumers, and also mechanical energy for rising of water in droughty areas, on pastures, drainages of bogs, etc. By estimations of experts, the wind power can be used effectively in the places where without essential economic damage short-term breaks in submission of energy are admissible. Such installations are already used in Russia, the USA, Canada, France and other countries.	4. The high cost price.

Bibliography

1). http://ru.wikipedia.org

2). http://www.know-house.ru

3). http://images.yandex.ru/yandsearch

4). Аугусто Голдин. Океаны энергии. – Пер. с англ.

Оксфорд-пресс.1983 г.

5). Гончар В.И. Нетрадиционные возобновляемые

источники энергии в Энергетической программе

СССР – География в школе. 4/90 – М.:

Педагогика, 1990 г.

6). Кондаков А.М. Альтернативные источники энергии –

География в школе. 4/88 – М.: Педагогика. 1988 г.

Benchmark 1.2

In this part of Benchmark I, part 2 our task is to demonstrate an understanding of the processes involved in the production of nuclear energy in countries around the world, to describe the nuclear fuel cycle and to show places in the cycle where diversion of materials could take place.

The processes involved in the production of nuclear energy

We’ll demonstrate strengths and weaknesses of nuclear energy,

we’ll explain the steps of the nuclear fuel cycle, we’ll demonstrate

locations of realizing the nuclear fuel, cycle in the world, we’ll

show some professions of a nuclear power plant, we’ll reveal the

difference between the military and civilian, uses of nuclear power.

The processes involved in the production of nuclear energy

- the positive and negative points of nuclear energy;

- the nuclear fuel cycle;

- The various steps that together make up the entire Nuclear Fuel Cycle;

- professions;

- civilian and military uses of nuclear energy.

The role of nuclear energy in power production

Almost all the world's electric energy is produced by hydroelectric and thermal power plants. Hydroelectric plants use the force of rushing water from a dam or waterfall to generate electricity. Thermal plants use the force of steam from boiling water. The great majority of thermal plants burn fossil fuels--coal, oil, and natural gas--to produce heat to boil water. The remaining thermal plants fission uranium.

Few countries have enough water power to generate large amounts of hydroelectricity. Most countries depend mainly on fossil fuels. But fossil fuels are a non-renewable resource. Therefore, many experts predict that nuclear power will become increasingly important.

Worldwide distribution of nuclear energy. In the mid-1990's, about 425 nuclear power reactors operated in about 30 countries. Nuclear power plants produced less than 20 percent of the world's electric energy. The United States had about 110 nuclear reactors and was the world's largest producer of nuclear energy. Reactors produced about 20 percent of the country's electricity. Canada had 22 reactors, which produced about 15 percent of Canada's electricity. Other countries, notably France and Japan, have a large nuclear power generating capacity.

Advantages and disadvantages of nuclear energy. Nuclear power plants have two main advantages over fossil-fuel plants. Once built, a nuclear plant can be less expensive to operate than a fossil-fuel plant, mainly because a nuclear plant uses a much smaller volume of fuel. Uranium, unlike fossil fuels, releases no chemical or solid pollutants into the air during use.

However, nuclear power plants have three major disadvantages. These drawbacks have slowed the development of nuclear energy in the United States. Nuclear plants cost more to build than fossil-fuel plants. Because of the need to assure that hazardous amounts of radioactive materials are not released, nuclear plants must meet certain government regulations that fossil-fuel plants do not have to meet. For example, a nuclear plant must satisfy the government that it can quickly and automatically deal with any kind of emergency. Used nuclear fuel produces dangerous radiation long after it has been removed from the reactor.

Positive points	Negative points
1.Very large amount of energy is got from a small mass of the material.	1. Building nuclear plants costs more than building fossil-fuel plants.
2. Huge resource potential is possible if the fuel is recycled.	2. Used nuclear fuel produces dangerous radiation long after it has been removed from the reactor.
3.It doesn’t produce carbon dioxide.	3. Nuclear plants must meet certain government regulations that fossil-fuel plants do not have to meet.
	4.Nuclear proliferation

The full development of nuclear energy. Many experts believe that the benefits of nuclear energy outweigh any problems involved in its production. According to these experts, oil may be so scarce by the mid-2000's that it will be too expensive to drill. Canada, Germany, Russia, the United States, and some other countries have enough coal to meet their energy requirements for hundreds of years at present rates of use. However, coal releases large amounts of sulfur and other pollutants into the air when it is burned. If nuclear energy were fully developed, it could completely replace oil and coal as a source of electric power.

But a number of problems must be solved before nuclear energy can be fully developed. For example, almost all today's power reactors use a scarce type of uranium known as U-235. If U-235 continues to be used at its present rate, the world's supply of it will become so small that it will be too expensive to mine and process by about 2050. Therefore, for nuclear energy to replace other energy sources, it must be based on fuel that is much more plentiful than U-235.

The nuclear energy industry

In every country that has a nuclear energy industry, the government plays a role in the industry. But the government's role varies greatly among countries. We will talk about the U.S. and Canadian nuclear energy industries.

Organization of the industry. Private utility companies own most of the nuclear power plants in the United States. The rest are publicly owned. Private companies also manufacture reactors, mine uranium, and handle most other aspects of U.S. nuclear power production.

Canada's nuclear power plants are all publicly owned. Atomic Energy of Canada Limited (AECL), a government corporation, has overall responsibility for the country's nuclear research and development program. AECL also designs the CANDU (CANada Deuterium oxide-Uranium) heavy water reactors used by all Canadian nuclear plants. Private companies make the various reactor parts and mine and process the country's uranium. Canada has no uranium enrichment plants because CANDU reactors operate with unenriched uranium fuel.

The industry and the economy. The main economic advantage of nuclear power plants is that this fuel is less expensive than fossil fuels. But nuclear plants cost somewhat more to build than do fossil-fuel plants.

Under normal economic conditions, a nuclear plant's savings in fuel eventually make up for its higher construction expenses. At first, these expenses add to the cost of producing electricity. But after some years, a plant will have paid off its construction costs. It can then produce electricity more cheaply than a fossil-fuel plant can. But two main problems--sharply higher costs and equipment failures--have somewhat lessened this long-run economic advantage of nuclear power plants. Many nuclear plants in the United States have had to shut down for months at a time because of equipment failures. Such losses of operating time further add to the cost of producing electricity.

The industry and the environment. Unlike fossil-fuel plants, nuclear plants do not release solid or chemical pollutants into the atmosphere. A nuclear plant releases small amounts of radioactive gas into the air. In addition, the cooling water used in pressurized water plants picks up a small amount of radioactive tritium in the steam condenser. The tritium remains in this water when it is returned to a river or lake. But these small amounts of radiation released into the environment are not believed to be harmful. Thermal pollution remains a problem at some nuclear plants. But cooling towers help correct this problem.

In a small number of nuclear accidents, hazardous amounts of radiation have been released into the atmosphere. Accidental releases of radioactive substances have occurred in Russia, the United States, and the United Kingdom; and an especially serious accident occurred in 1986 at the Chernobyl nuclear power plant in Ukraine (then part of the Soviet Union). The subsection Hazards and safeguards that appears earlier in this article discusses the main methods of guarding against accidents.

Critics of nuclear power also fear another danger to the environment. As power production increases, the creation of high-level radioactive wastes also increases. The United States has no permanent storage place for such wastes. The problem of storing radioactive wastes is discussed in the subsection Wastes and waste disposal.

Government regulation. The Nuclear Regulatory Commission (NRC), an agency of the federal government, regulates nonmilitary nuclear power production in the United States. One of the NRC's main duties is to ensure that nuclear power plants operate safely, and it makes and enforces a variety of safety standards. Every nuclear reactor and power plant must be inspected and licensed by the NRC before it may begin operations. The NRC also supervises the manufacture and distribution of nuclear fuels, and controls the disposal of radioactive wastes from commercial production.

The Atomic Energy Control Board, a Canadian government agency, regulates Canada's nuclear energy industry. The board's duties resemble those of the Nuclear Regulatory Commission.

Careers in nuclear energy cover a wide range of occupations and require widely varying amounts of training. A high percentage of the jobs require a college degree or extensive technical education. Many of these jobs are in large research laboratories, which work to improve nuclear processes and to lessen their hazards. Other careers requiring advanced training are in such areas as uranium mining and processing, reactor manufacturing and inspection, power plant operation, and government regulation.

Many colleges and universities offer undergraduate and graduate degrees in such highly specialized fields as nuclear engineering, nuclear physics, and nuclear technology. The industry also employs many workers with college degrees in various branches of engineering and in such fields as biology, chemistry, geology, and medicine. Many vocational and technical schools and some high schools prepare students for specialized jobs in the industry.

The Nuclear Fuel Cycle

Uranium, as it is mined from the earth's crust, is not directly useable for power generation. Much processing must be carried out to concentrate the fissile isotope U-235 before uranium can be used efficiently to generate electricity.

More so than other energy resources such as coal, oil and natural gas, uranium has its own distinctive and very complicated fuel cycle. This is called the 'Nuclear Fuel Cycle'. There are several steps in the nuclear fuel cycle - mining and milling, conversion, enrichment, and fuel fabrication. These steps are known as the 'front end' of the cycle.

Once uranium becomes 'spent fuel' (after being used to produce electricity), the 'back end' of the cycle follows. This may include: temporary storage, reprocessing, recycling, and waste disposal.

The Nuclear Fuel Cycle

nfc1-1 http://www.uic.com.au/nfc.htm

http://www.uic.com.au/nfc.htm

Like coal, oil and natural gas, uranium is an energy resource which must be processed through a series of steps to produce an efficient fuel for use in generating electricity. Each fuel has its own distinctive fuel cycle: however the uranium or 'nuclear fuel cycle' is more complex than the others.

nfcycle http://www.uic.com.au/nfc.htm

1) Mining and milling

Uranium is usually mined by either surface or underground mining techniques, depending on the depth at which the ore body is found. In Australia the Ranger mine in the Northern Territory is open cut, while Olympic Dam in South Australia is an underground mine (which also produces copper, with some gold and silver). The newest Canadian mines are underground.

From these, the mined uranium ore is sent to a mill which is usually located close to the mine. At the mill the ore is crushed and ground to a fine slurry which is leached in sulfuric acid to allow the separation of uranium from the waste rock. It is then recovered from solution and precipitated as uranium oxide (U₃0₈) concentrate.

Sometimes this is known as "yellowcake", though it is finally khaki in colour.

Some mines in Australia, USA and Kazakhstan use in situ leaching (ISL) to extract the uranium from the ore body underground and bring it to the surface in solution. It is recovered in much the same fashion.

U₃0₈ is the uranium product which is sold. About 200 tonnes is required to keep a large (1000 MWe) nuclear power reactor generating electricity for one year.

2) Conversion

Because uranium needs to be in the form of a gas before it can be enriched, the U₃0₈ is converted into the gas uranium hexafluoride (UF₆) at a conversion plant in Europe, Russia or North America.

3) Enrichment

The vast majority of all nuclear power reactors in operation and under construction require 'enriched' uranium fuel in which the proportion of the U-235 isotope has been raised from the natural level of 0.7% to about 3.5% or slightly more. The enrichment process removes about 85% of the U-238 by separating gaseous uranium hexafluoride into two streams: One stream is enriched to the required level and then passes to the next stage of the fuel cycle. The other stream is depleted in U-235 and is called 'tails'. It is mostly U-238.

Figures in the diagram assume enrichment to 3.5% U-235 and a tails assay of 0.25%. The 220t figure should be 172t (146 tU)

So little U-235 remains in the tails (usually less than 0.25%) that it is of no further use for energy, though such 'depleted uranium' is used in metal form in yacht keels, as counterweights, and as radiation shielding, since it is 1.7 times denser than lead.

http://www.uic.com.au/nfc.htm

The large Tricastin enrichment plant in France (beyond cooling towers)
The four nuclear reactors in the foreground provide over 3000 MWe power for it.

The first enrichment plants were built in the USA and used the gaseous diffusion process, but more modern plants in Europe and Russia use the centrifuge process. This has the advantage of using much less power per unit of enrichment and can be built in smaller, more economic units. Research is being conducted into laser enrichment, which appears to be a promising new technology.

A small number of reactors, notably the Canadian CANDU and early British gas-cooled reactors, do not require uranium to be enriched.

4) Fuel fabrication

Enriched UF₆ is transported to a fuel fabrication plant where it is converted to uranium dioxide (UO₂) powder and pressed into small pellets. These pellets are inserted into thin tubes, usually of a zirconium alloy (zircalloy) or stainless steel, to form fuel rods. The rods are then sealed and assembled in clusters to form fuel assemblies for use in the core of the nuclear reactor.

http://www.uic.com.au/nfc.htm

A PWR fuel assembly

Some 25 tonnes of fresh fuel is required each year by a 1000 MWe reactor.

5) The nuclear reactor

Several hundred fuel assemblies make up the core of a reactor. For a reactor with an output of 1000 megawatts (MWe), the core would contain about 75 tonnes of low-enriched uranium. In the reactor core the U-235 isotope fissions or splits, producing heat in a continuous process called a chain reaction. The process depends on the presence of a moderator such as water or graphite, and is fully controlled.

http://www.uic.com.au/nfc.htm

Diablo Canyon nuclear power plant, USA

Some of the U-238 in the reactor core is turned into plutonium and about half of this is also fissioned, providing about one third of the reactor's energy output.

As in fossil-fuel burning electricity generating plants, the heat is used to produce steam to drive a turbine and an electric generator, in this case producing about 7 billion kilowatt hours of electricity in one year.

To maintain efficient reactor performance, about one-third of the spent fuel is removed every year or 18 months, to be replaced with fresh fuel.

6) Spent fuel storage

Spent fuel assemblies taken from the reactor core are highly radioactive and give off a lot of heat. They are therefore stored in special ponds which are usually located at the reactor site, to allow both their heat and radioactivity to decrease. The water in the ponds serves the dual purpose of acting as a barrier against radiation and dispersing the heat from the spent fuel.

http://www.uic.com.au/nfc.htm

Storage pond for spent fuel at UK reprocessing plant

Spent fuel can be stored safely in these ponds for long periods. It can also be dry stored in engineered facilities, cooled by air. However, both kinds of storage are intended only as an interim step before the spent fuel is either reprocessed or sent to final disposal. The longer it is stored, the easier it is to handle, due to decay of radioactivity.

There are two alternatives for spent fuel:

reprocessing to recover the usable portion of it
long-term storage and final disposal without reprocessing.

7) Reprocessing

Spent fuel still contains approximately 96% of its original uranium, of which the fissionable U-235 content has been reduced to less than 1%. About 3% of spent fuel comprises waste products and the remaining 1% is plutonium (Pu) produced while the fuel was in the reactor and not "burned" then.

Reprocessing separates uranium and plutonium from waste products (and from the fuel assembly cladding) by chopping up the fuel rods and dissolving them in acid to separate the various materials. Recovered uranium can be returned to the conversion plant for conversion to uranium hexafluoride and subsequent re-enrichment. The reactor-grade plutonium can be blended with enriched uranium to produce a mixed oxide (MOX) fuel, in a fuel fabrication plant.

MOX fuel fabrication occurs at facilities in Belgium, France, Germany, UK, Russia and Japan, with more under construction. There have been 25 years of experience in this, and the first large-scale plant, Melox, commenced operation in France in 1995. Across Europe about 30 reactors are licensed to load 20-50% of their cores with MOX fuel and Japan plans to have one third of its 54 reactors using MOX by 2010.

The remaining 3% of high-level radioactive wastes (some 750 kg per year from a 1000 MWe reactor) can be stored in liquid form and subsequently solidified.

Reprocessing of spent fuel occurs at facilities in Europe and Russia with capacity over 5000 tonnes per year and cumulative civilian experience of 90,000 tonnes over almost 40 years.

8) Vitrification

After reprocessing the liquid high-level waste can be calcined (heated strongly) to produce a dry powder which is incorporated into borosilicate (Pyrex) glass to immobilise the waste. The glass is then poured into stainless steel canisters, each holding 400 kg of glass. A year's waste from a 1000 MWe reactor is contained in 5 tonnes of such glass, or about 12 canisters 1.3 metres high and 0.4 metres in diameter. These can be readily transported and stored, with appropriate shielding.

http://www.uic.com.au/nfc.htm

Loading silos with canisters containing vitrified high-level waste in UK,
each disc on the floor covers a silo holding ten canisters

This is as far as the nuclear fuel cycle goes at present. The final disposal of vitrified high-level wastes, or the final disposal of spent fuel which has not been reprocessed spent fuel, has not yet taken place.

9) Final disposal

The waste forms envisaged for disposal are vitrified high-level wastes sealed into stainless steel canisters, or spent fuel rods encapsulated in corrosion-resistant metals such as copper or stainless steel. The most widely accepted plans are for these to be buried in stable rock structures deep underground. Many geological formations such as granite, volcanic tuff, salt or shale will be suitable. The first permanent disposal is expected to occur about 2010.

Most countries intend to introduce final disposal sometime after about 2010, when the quantities to be disposed of will be sufficient to make it economically justifiable.

Professions

There are many professions at a nuclear plant. They are necessary for different important purposes.

The microbiologist The programmer

The electrician The engineer The laboratory assistant

Civilian and military uses of nuclear energy

It is the technical, continuously working system intended for peaceful use to satisfy needs of people in electric and thermal energy.

It is technical system intended for conducting wars and destructing during war operations.

Nuclear reactors can be used in the military purposes (an operating time of plutonium for nuclear charges and for starting of the fighting surface and underwater ships)

Conclusion

The world's chief sources of energy are, in order of importance, fossil fuels, water power, and nuclear energy. Wood, solar, wind, tidal, chemical, and geothermal sources also provide energy. Future energy sources may include fuel cells, solid and liquid wastes, hydrogen, and magnetohydrodynamic (MHD) generators.

Fossil fuels include, in order of the amount used worldwide, petroleum, coal, and natural gas. Bituminous sands and oil shale form important energy resources for the future.

Petroleum furnishes 40 percent of the commercial energy used both in the world and in the United States. Most of the heat energy in petroleum is used to produce transportation fuels, such as gasoline and diesel fuel, and heating fuels.

Most petroleum is removed from deep within the earth as a liquid called crude oil. Workers pump crude oil out of the earth through wells drilled into oil-bearing formations called reservoirs. Because it is a liquid, crude oil can be economically transported over long distances by pipeline to refineries. Refineries process crude oil into gasoline and other useful petroleum products. Refining removes many impurities that could cause pollution from crude oil.

Coal provides 26 percent of all the commercial energy used in the world. It furnishes 23 percent of the energy used in the United States. Much of the heat energy in coal is used to produce steam in boilers. The steam, in turn, generates electricity or operates steam engines. Coal also is used in the manufacture of steel. In many countries of Asia and Europe, people use coal to heat homes and other buildings.

The mining and burning of coal involve certain problems. Accidents in coal mines and diseases that result from breathing coal dust make coal mining a dangerous occupation. When burned, coal releases sulfur and other impurities that pollute the air. To reduce pollution, many large factories that burn coal have installed filters and other cleaning devices.

Chemists have developed various methods of turning coal into a gas or a liquid. Gasification and liquefaction convert coal into a clean fuel that has a low sulfur content. However, such conversion is expensive and requires huge quantities of coal.

Natural gas accounts for about 21 percent of the commercial energy used in the world and about 25 percent of that used in the United States. Most of the heat energy contained in natural gas is used to generate steam for electricity or steam engines, to heat buildings, and for cooking and other household needs.

Like petroleum, natural gas comes from deposits in the earth. Natural gas is a clean source of energy because it is refined naturally during its formation within the earth and does not require further refining. In addition, natural gas can be compressed into a liquid and transported long distances through pipelines.

Bituminous sands and oil shale may become energy sources in the future. Bituminous sands, also called tar sands, are deposits of sand covered with an oil-producing substance. Oil shale is a type of rock that can be processed to yield crude oil and natural gas. The cost of obtaining oil from tar sands and oil shale is higher than that of obtaining petroleum, coal, or natural gas directly from the earth. But as reserves of these fuels run out, it will become necessary to recover the more costly energy from tar sands and oil shale.

Water power, or hydropower, furnishes about 7 percent of the world's commercial energy and 4 percent of the energy used in the United States. Where water flows from a high place to a lower one, the gravitational energy of the falling water can be captured and used to produce other forms of energy. Most water power is used to generate electricity. Water power supplies energy without pollution and without using up the water in the process. But costly dams and other structures are required to harness water power.

Nuclear energy provides about 6 percent of the commercial energy used in the world and 8 percent of the energy used in the United States. Today, nuclear energy comes from fission--that is, the splitting of atomic nuclei of certain elements, especially uranium. But scientists hope eventually to produce nuclear energy from fusion, the combining of atomic nuclei.

Nuclear fission creates huge amounts of energy from small amounts of fuel. The heat energy produced during controlled fission reactions can be used to power submarines and other ships and to generate electricity.

But fission has several disadvantages as a source of energy. Fission plants produce hot waste water that may damage the environment. To reduce this thermal pollution, most new nuclear power plants have large, expensive cooling devices. Nuclear power plants also generate radioactive wastes that remain dangerous for long periods. These wastes must be isolated to protect the environment from radioactivity. In addition, a serious accident at a nuclear power plant can release harmful radioactivity into the air.

Scientists and engineers have developed experimental breeder reactors. But no breeder yet produces enough energy for commercial use.

Nuclear fusion produces the heat and light of the sun and other stars, and the explosive force of the hydrogen bomb. Scientists and engineers are working on ways to control nuclear fusion reactions. Experimental fusion devices use forms of hydrogen known as deuterium and tritium for fuel. Because hydrogen is found in large quantities in the world's oceans, fusion could provide an unlimited source of fuel. In addition, fusion devices are safer than fission devices. Fusion would not create a waste disposal problem because most products of fusion reactions are not radioactive. However, fusion devices have yet to produce usable amounts of energy.

Wood once served as the world's chief fuel. In many developing countries, wood is still the main source of heat energy. But in the United States and many other developed countries, the use of wood for heating is limited mainly to fireplaces.

Solar energy is used throughout the world to perform various small jobs. People capture this type of energy with various devices that change the sun's energy into heat or electrical energy. Flat-plate collectors convert solar energy into heat energy to heat water and the air inside buildings. Solar cells, also called photovoltaic cells, convert solar energy into electrical energy.

Solar power can provide a clean and almost unlimited source of energy. But it is thinly distributed over a wide area and must be collected and concentrated to produce energy. In addition, darkness and bad weather interrupt the supply of sunlight.

Wind power turns windmills and propels sailboats. Private uses of the clean energy that is provided by wind occur all over the world. But wind power is commercially practical only in areas that have strong, steady winds.

Tidal energy comes from the gravitational energy of water as it flows from high tide to low tide. This energy can be captured by closing a bay with a dam. As the tide rises, the bay fills with water. At high tide, the dam is closed to hold the water in the bay. At low tide, the stored water is released through a turbine in order to generate electricity. The chief disadvantage of tidal power plants is that they can produce energy only during falling tides. In addition, the plants can be built in few places.

Chemical energy is released during chemical reactions. The most common use of such energy is to generate electrical power in batteries. Some chemical reactions are reversible. As a result, storage batteries such as those found in automobiles can be recharged.

Geothermal power is generated wherever water comes in contact with hot rocks below the earth's surface. The rocks give off heat that makes the water hot enough to turn into steam. Power companies can drill wells and pump the hot water or steam to the surface, where it can be used to generate energy. In areas where no underground water or steam exists naturally, engineers can pump water into the ground to be heated by hot rocks. The production of geothermal energy can occur only in areas where hot rocks lie near the earth's surface. Iceland, Italy, Japan, the Philippines, New Zealand, and the United States have developed geothermal power plants.

Fuel cells are battery like devices in which gas or liquid fuels combine chemically to generate electricity. For example, fuel cells in spacecraft combine hydrogen and oxygen to produce electrical energy. Fuel cells convert chemical energy directly into electricity without burning fuel or producing much waste heat. As a result, they can produce twice as much electricity as can ordinary generators from a given amount of fuel. But fuel cells are expensive to make, and so their use is limited.

Solid and liquid wastes also can provide energy. Burning trash can produce heat energy and electricity. Some paper and lumber mills use waste wood to fuel boilers, which generate steam for the plant.

Many cities throughout the world produce usable energy by burning trash. Burning wastes also reduces the amount of trash that must be placed in landfills. Cities also can process liquid organic wastes, such as sewage, to produce methane gas that can be used for fuel. Another process, called bioconversion, converts organic plant and animal wastes into useful liquid fuels, such as methanol, natural gas, and oil.

Hydrogen could someday replace both gas and oil as a fuel. It burns easily, giving off huge amounts of heat and one harmless by-product, water. Chilled to liquid form, hydrogen can be transported in pipelines and stored in tanks. Aircraft and automobiles may someday use this nonpolluting, lightweight, and efficient fuel. Hydrogen is removed from water by a process called hydrolysis, which involves running an electric current through the water. But the process requires enormous amounts of electricity, making hydrogen a costly energy source.

Magnetohydrodynamic (MHD) generators convert fuel directly into electricity. An MHD generator burns coal or some other fuel at high temperatures to produce hot, ionized (electrified) gases. These gases are forced through a duct in a magnetic field, where they produce an electric current that is drawn off by electrodes. After this gas has passed through the generator, it can be used to drive a turbine and generate more electricity. MHD generators convert fossil fuels into electricity more efficiently than do conventional boilers and steamdriven turbines. But many technical problems must be solved before MHD generators become common.

The world society doesn’t have enough energy for its development. The reserves of gas, oil and coal are constantly decreasing as a result of it the political situation in the world is aggravating. The scientists- power engineers should concentrate on effective usage of non-renewable sources of energy and on creating new technologies of using alternative sources of energy. The society should use all the possibilities of getting energy from different sources. Many European countries are interested in this problem. For example, Germany has been getting energy from the solar and wind sources, German scientists have established many institutes and laboratories to learn alternative sources of energy. One day we will have reached the limit of all the reserves of gas, oil and coal and will use the possibilities of nuclear and natural sources of energy.

Bibliography

1). http://images.google.com/images?q=Nuclear+fuel+cycle&hl=en&um=1&ie=UTF-8&sa=X&oi=images&ct=title

2). http://www.uic.com.au/nfc.htm

3). http://www.images.yandex.ru/

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5) .Macsacovskiy V. P. Geographical card of the world. The first part. - М.: 1996

6) .Macsakovskiy V. P. Geographical card of the world. The third part. - М.: 1996 Power resources of the world. Under Neporozhnego P.S., Popkova V. I. 's edition - М.: Energoatomizdat. 1995

7). Кононов JU. D. Power and economy. Problems of transition to new energy sources. - М.: the Science, 1981.