Text 13. Nuclear power plant

The heart of the nuclear power plant is the reactor which contains the nuclear fuel. The fuel usually consists of hundreds of uranium pellets placed in long thin cartridges of stainless steel. The whole fuel cell consists of hundreds of these cartridges. The fuel is situated in a reactor vessel filled with a fluid. The fuel heats the fluid and the super-hot fluid goes to a heat exchanger, i.e. steam generator, where the hot fluid converts water to steam in the heat exchanger. The fluid is highly radioactive, but it should never come into contact with the water that is converted into steam. Then this steam operates steam turbines in exactly the same way as in the coal or oil fired power-plant.

A nuclear reactor has several advantages over power-plants that use coal or natural gas. The latter produce considerable air pollution, releasing combusted gases into atmosphere, whereas a nuclear power plant gives off almost no air pollutants. As to nuclear fuel, it is far cleaner than any other fuel for operating a heat engine. Furthermore our reserves of coal, oil and gas are decreasing so nuclear fuel is to replace them. It means that coal and oil can be used for some other purposes. The amount of nuclear fuel which the nuclear power-plant consumes is negligible while the world's uranium and thorium resources will last for hundreds of years.

The construction of the world's first nuclear power-plant in Obninsk near Moscow was a great historical event and the beginning of atomic energetics. Since then our country has achieved a great progress in this field. It should be noted that while the unit capacity of the Obninsk nuclear power-plant was five thousand kW, that of the first unit of the Leningradskaya nuclear power-plant was one million kW.

Our industry produces two main types of reactors namely vessel-type reactors and channel-type reactors. The former are installed at the Novovoronezhskaya and the Armenian nuclear power-plants, the latter operating at the Leningradskaya and Kurskaya power-plants.

It is necessary to mention here that channel-type reactors have been operating since 1954 at the world's first nuclear power-plant and in the far North-East of our country where they produce both electricity and heat.

The nuclear power-stations are mostly designed for generation of electricity. If a station generates only electric energy, it is equipped with condensing turbines and the station is known as a condensing one. At present the nuclear power-stations mainly operate as condensing plants. The nuclear power-stations designed to produce not only electrical energy but also heat are called nuclear heat-and-power plants.

A fast-neutron reactor which supplies both electricity and heat for desalting sea water was put into operation in Shevchenko on the Caspian Sea. Its capacity is partly used for generating electricity, the rest is going as heat to obtain desalted water. It should be also mentioned that the area has no natural fresh water and was a lifeless desert before the nuclear power plant began operating there.

According to the program of nuclear power development, the nuclear power plants were mainly built in the European part of the USSR. This increased the power supply reliability in the most industrially developed areas of our country. Besides it reduces the transportation of fuel from the East and saves million tons of coal and oil. In 1979, there were 226 nuclear power-plants all over the world. Of all the methods of energy production nuclear power engineering presents the least danger to nature.

Text 14. GENERATORS

The dynamo invented by Faraday in 1831 is certainly a primitive apparatus compared with the powerful, highly efficient generators and alternators that are in use today. Nevertheless, these machines operate on the same principle as the one invented by the great English scientist. When asked what use his new invention had, Faraday asked in his turn: “What is the use of a new-born child?” As a matter of fact, “the new-born child” soon became an irreplaceable device we cannot do without.

Although used to operate certain devices requiring small currents for their operation, batteries and cells are unlikely to supply light, heat and power on a large scale. Indeed, we need electricity to light up millions of lamps, to run trains, to lift things, and to drive the machines. Batteries could not supply electricity enough to do all this work.

That dynamo-electric machines are used for this purpose is a well-known fact. These are the machines by means of which mechanical energy is turned directly into electrical energy with a loss of only a few per cent. It is calculated that they produce more than 99.99 per cent of all the world’s electric power.

There are two types of dynamos, namely, the generator and the alternator. The former supplies d.c. which is similar to the current from a battery and the latter, as its name implies, provides a.c.

To generate electricity both of them must be continuously provided with energy from some outside source of mechanical energy such as steam engines, steam turbines or water turbines, for example.

Both generators and alternators consist of the following principal parts: an armature and an electromagnet. The electromagnet of a d.c. generator is usually called a stator for it is in a static condition while the armature (the rotor) is rotating. Alternators may be divided into two types: 1. Alternators that have a stationary armature and a rotating electromagnet; 2. Alternators which armature serves as a rotor but this is seldom done. In order to get strong electromotive force (e.m.f.- that very force that moves the electrons from one point in an electric circuit towards another), the rotors in large machines rotate at a speed of thousands of revolutions per minute (r.p.m.). The faster they rotate, the greater the output voltage the machine will produce.

In order to produce electricity under the most economical conditions, the generators must be as large as possible. In addition to it, they should be kept as fully loaded as possible. In addition to it, they should be kept as fully loaded as possible all the time. It is interesting to note here that the biggest generators ever installed at any hydroelectric station in the world are those installed in the former USSR. The Bratskaya hydroelectric station is equipped with 225,000 kilowatt (kW) generators.

Alternator – генератор переменного тока

armature [ˈɑːmətʃə] – якорь