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31. Read the texts and find in them the answers to the questions that follow.
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31. Read the texts and find in them the answers to the questions that follow.
a) Windscale Accident
Throughout the years, accidents causing a release of radioactive material to the environment have occurred. Since World War II all over the world large scale nuclear facilities have been built and operated both for civil and defense purposes. Some of the sites on which these facilities were located are heavily contaminated with radioactive substances.
One of the first nuclear reactor accidents of environmental concern was the Windscale accident in October 1957. During the accident the military air-cooled graphite-moderated natural-uranium reactor used for plutonium production caught fire during the liberation of energy in the graphite. Emission from the Windscale lasted for 18 hours. Radioactive material was detectable in many parts of Western Europe but the majority of it was deposited in the United Kingdom.
1. How long did the emission from the Windscale reactor last?
2. What did the emission result in?
b) Chernobyl Accident
The accident, which was of global concern was the accident in Ukraine in the Chernobyl power plant located in Polesye on the River Pripyat.
On 26 April, 1986, Unit 4 of the Chernobyl nuclear plant suffered a major accident. The Chernobyl 4 reactor was a graphite-moderated, light-water-cooled system. The installed electrical generating capacity was 1 GW. The accident followed some engineering tests of a generator.
During the tests, basic operating safety rules were being violated. Most control rods were withdrawn from the core and the safety systems were switched off. Two explosions and a fire that followed them damaged the reactor and the containment building. The graphite started to bum. Explosive energy was released, which resulted in the 1000 ton cover plate of the reactor being lifted up.
A prolonged release of large quantities of radioactive products transported by the cloud from Chernobyl was detected not only in northern and southern Europe but also in Canada, Japan, and the US.
The major part of the release took place over the period of' about ten days. There were two peaks in release rate (26th April and 5th May). Later on, the release continued for many weeks at a lower rate before the destroyed reactor was finally sealed, which took place some five months later.
Initially the cloud of radioactive material was carried over the Baltic Sea into Scandinavia. After a few days the wind direction rotated clockwise and the cloud travelled eastwards across the USSR and southwards to Turkey.
The total mass of the radioactive particles released in the accident was about 6000-8000 Kg. More than half of it was deposited near the plant but the rest travelled thousands of kilometres (see Fig. 26).
There is no doubt that the nuclear plant accidents offer a number of lessons to be learnt.
At present, over 200 nuclear power reactors for commercial electricity production operate in Europe.
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The accident at the Chernobyl nuclear plant has shown that largescale accidents in nuclear power plants can lead to contamination of the entire continent.
1. What was the cause of the Chernobyl accident?
2. What was the path of the radioactive material released in the accident?
3. What can accidents at the nuclear plants lead to?
4. Make a talk on the Chernobyl accidents (use Fig. 26).
Fig. 26. Areas covered by the main body of the cloud on various days during the release.
Assignments in Writing
Письменные задания
Put down the title corresponding thematically to each of the given descriptions.
1) Titles: Two-phase System; Single-phase System, Three-phase System; Poly-phase System.
| ___________________ | 1. An a. c. distributing system employing a single phase at a. c. supplied by the generator; |
| ___________________ | 2. An a. c. distributing system utilizing a number of alternating currents differing in phase; |
| ___________________ | 3. An a. c. system employing three alternating currents of equal strength, differing in phase by one-third of a cycle; |
| ___________________ | 4. An a. c. system employing two alternating currents of equal strength, differing in phase by a quarter cycle, or such that one current has maximum strength when the other is passing through zero. |
2) Titles: Electric Current; Direct Current; Alternating Current; Continuous Current.
| ___________________ | 1. A current which always flows in one and the same direction; |
| ___________________ | 2. A flow of passage of electricity along an electric circuit, usually measured in amperes; |
| ___________________ | 3. A current which periodically alternates or reverses in direction; |
| ___________________ | 4. A current uniform both in strength and in direction. A steady direct current. |
3) Titles: Circuit Breaker; Controller; Control Power Switch; Line Switch.
| ___________________ | 1. A disconnecting or isolating switch in an a. c. or d. c. circuit; |
| ___________________ | 2. A switch used for connecting or disconnecting the source or control power to and from the control bus or equipment; |
| ___________________ | 3. A device for controlling an electric machine or a circuit (a controlling device); |
| ___________________ | 4. A device for opening or closing a circuit, either by hand or automatically, in the case of an overload. |
4) Titles: Voltage Balance Relay; Emergency Direct Current Relay; Current Balance Relay; Impedance Relay.
| ___________________ | 1. A relay which functions when the circuit impedance increases or decreases to predetermined value; |
| ___________________ | 2. A relay which operates on a difference in current output or output of two circuits; |
| ___________________ | 3. A device used to interrupt a direct-current power circuit under emergency conditions; |
| ___________________ | 4. A relay which operates on a difference of voltage between two circuits. |
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5) Titles: Electric Motor; Synchronous Motor; Asynchronous Motor; Induction Motor.
| ___________________ | 1. An a. c. motor in which the rotation takes place in synchronism with the rotating element of the generator supplying the operating current; |
| ___________________ | 2. A machine for transforming electric power into utilizable mechanical power; |
| ___________________ | 3. An a. c. motor in which the rotation is not synchronous with the rotating element of the generator supplying the driving current; |
| ___________________ | 4. An asynchronous a. c. motor in which the current flowing in the winding of the secondary winding is induced electromagnetically by the current flowing in the primary one. |
6) Titles: Control Power T; Air-blast T; Oil-cooled T.
| ___________________ | 1. A T which is cooled, when operating, by a flow of oil through its framework; |
| ___________________ | 2. A T which is cooled, when operating, by a blast of air delivered through its framework; |
| ___________________ | 3. A T which serves as the source for a. c. control power for operating a. c. devices. |
7) Titles: Feeder; Commutator; Converter.
| ___________________ | 1. A machine which operates by means of a rotating commutator to convert a. c. into d. c. for distribution; |
| ___________________ | 2. In an electric distributing system, a supply conductor carrying current from a power-house to main conductors, and not itself connected to motors, lamps, or translating devices; |
| ___________________ | 3. A device for changing the direction of a current. |
8) Titles: Series Generator; Shunt Generator; Turbo-alternator; Compound Motor.
| ___________________ | 1. A machine which generates an electric current (usually a dynamo electric generator, both a shunt winding and a series winding are on its field magnets); |
| ___________________ | 2. A machine consisting of an a. c. generator mounted upon the shaft of a steam turbine; |
| ___________________ | 3. A generator whose field-magnet winding is connected in series with or in succession to its armature; |
| ___________________ | 4. A generator whose field-magnet winding is connected in shunt to, or in parallel with its armature. |
9) Titles: Conduction; Conductor; Conductivity; Sound; Circuit; Copper; Silver; Engine.
| ___________________ | 1. A device for converting one form of energy into another especially for converting other forms of energy into mechanical (i. e. kinetic) energy. |
| ___________________ | 2. The transmission of heat from places of higher to places of lower temperature in a substance. |
| ___________________ | 3. The reciprocal of the resistivity or specific resistance of a conductor. |
| ___________________ | 4. A body capable of carrying an electric current. |
| ___________________ | 5. A red metal. It is unaffected by water or steam. |
| ___________________ | 6. The complete part with an electric current across it. |
| ___________________ | 7. White, rather soft metal. The best-known conductor of electricity. |
| ___________________ | 8. A physiological sensation received by the ear. It is caused by a vibrating source and transmitted as a wave motion through air. |
10) Titles: Electric Field; Direct Current; Alternating Current; Electromagnetic Radiation; Continuous Wave; Electromagnetic Spectrum.
| ___________________ | 1. Radiation consisting of waves of energy associated with electric and magnetic fields. This radiation is emitted by matter in units called photons. |
| ___________________ | 2. The range of frequencies over which electro-magnetic radiations are propagated. The lowest frequencies are radio waves, increases of frequency produce infrared radiation, light, ultra-violet radiation, X-rays, gamma-rays and finally the radiation associated with cosmic rays. |
| ___________________ | 3. Radio or radar transmissions which are generated continuously and not in short pulses. |
| ___________________ | 4. An electric current flowing always in the same direction. |
| ___________________ | 5. A flow of electricity which, after reaching a maximum in one direction, decreases, finally reaching a maximum in the opposite direction, the cycle being repeated continuously. The number of such cycles per second is the frequency. |
| ___________________ | 6. The region near an electric charge, in which a force is acting on a charged particle. |
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11) Titles: Energy; Electrical Energy; Chemical Energy; Radiant Energy; Kinetic Energy; Potential Energy.
| ___________________ | 1. The capacity for doing work. |
| ___________________ | 2. That part of the energy stored within an atom or molecule which can be released by a chemical reaction. |
| ___________________ | 3. The energy which a body possesses by virtue of its position. It is measured by the amount of work the body performs in passing from that position to a standard position in which the energy is considered to be zero. |
| ___________________ | 4. The energy which a body possesses by virtue of its motion. |
| ___________________ | 5. The energy that is transmitted in the form of radiation. |
| ___________________ | 6. The energy associated with electric charges and their movements. It is measured in watt seconds (joules) or kilowatt-hours. |
12) Titles: Accumulator; Cell; Primary Cell; Solar Cell.
| ___________________ | 1. Device for producing an electric current by chemical reaction. |
| ___________________ | 2. A storage battery. A device for «storing» electricity. An electric current is passed between two plates in a liquid; this causes chemical changes in the plates and the liquid. When the changes are complete, the device is charged. |
| ___________________ | 3. Semiconductor devices which are made from thin slices of silicon. Almost all Russian and American satellites have used such cells to supply on-board electrical power. Although the efficiency of these cells is no more than 10%, they provide a reliable electric power source that lasts for years on a satellite. |
| ___________________ | 4. A device for producing an electromotive force and delivering an electric current as the result of a chemical reaction. |
13) Titles: Nuclear Fuel; Nuclear Power; Nuclear Reaction.
| ___________________ | 1. A substance which undergoes nuclear fission or nuclear fusion in a nuclear reactor, a nuclear weapon, or a star. |
| ___________________ | 2. Any reaction which involves a change in the nucleus of an atom, as distinct from a chemical reaction which only involves the orbital electrons. Such reactions occur naturally - on the Earth, in radioactive elements, and in the stars, as thermonuclear reactions. They are also produced in nuclear reactors, and nuclear weapons. |
| ___________________ | 3. Electric or motive power produced from a unit in which the primary energy source is a nuclear reactor. |
14) Titles: Pressured-Water Reactor (PWR); Boiling-Water Reactor (BWR).
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| ___________________ | 1. This is a pressure-vessel reactor fuelled with enriched uranium. The reactor is a thermal one, moderated and cooled with ordinary (light) water. The heat in the reactor is extracted by the boiling water as it passes through the core, and the steam is passed directly to the turbine of the energy conversion cycle. |
| ___________________ | 2. The primary reactor vessel of this reactor is operated at considerable overpressure, which suppresses boiling of the cooling water. |
15) Titles: Nuclear Fusion; Nuclear Fission; Nuclear Charge; Nuclear Energy.
| ___________________ | 1. Energy released during a nuclear reaction as the result of the conversion of mass into energy. Energy of this kind is released in nuclear reactors and nuclear weapons. |
| ___________________ | 2. A reaction between light atomic nuclei as a result of which a heavier nucleus is formed and a large quantity of nuclear energy is released. The temperatures necessary for fusion reactions are extremely high. Reactions of this kind are believed to be the source of the energy of the stars (including the Sun). |
| ___________________ | 3. A nuclear reaction in which a heavy atomic nucleus (e. g. uranium) splits into two approximately equal parts, at the same time emitting neutrons and releasing very large amounts of nuclear energy. |
| ___________________ | 4. The positive electric charge on the nucleus of an atom. Numerically it is equal to the atomic number of the element, to the number of protons in the nucleus, and to the number of electrons surrounding the nucleus in the neutral atom. |
16) Titles: Analog Computer; Computer; Digital Computer; Central Processing Unit.
| ___________________ | 1. The central electronic unit in a computer which processes input information, and information from the store, and produces the output information. This unit and the store form die central part of the computer. |
| ___________________ | 2. A computer in which numerical magnitudes are represented by physical quantities such as electric current, voltage, or resistance. |
| ___________________ | 3. An electronic device which accents data, applies a series of logical processes to it, and supplies the results of these processes as information. The device is used to perform mathematical calculations at a very high speed. This makes them useful for various purposes, such as office calculations, control of industrial processes, and the control of flight paths. |
| ___________________ | 4. A computer which operates on data in the form of digits rather than the physical quantities. |
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