Protection Against Environmental Pollution

Any operating nuclear power plant releases fission products into the environment, which causes environmental pollution.

For the harmful effects of nuclear power release to be prevented, the nuclear power plants are supplied with protective installations that serve as carriers to the pollution.

First, the nuclear fuel and the fission products are confined within sealed tubes made of stainless steel or zirconium. Then the assembly of tubes is placed in a steel reactor vessel. And finally the steel reactor vessel is placed in a large steel and concrete housing.

As to the hot radioactive waste products they are disposed in heavily shielded cylinders. The cylinders are buried 305 to 610 metres underground.

For several reasons, the relative importance of the various types of power plants has been shifting. Good sites for new hydroelectric plants have become scarce in many countries. Distribution networks have been extended so that less expensive power from large steam-electric stations has been replacing power from smaller diesel-generator units. Nuclear-electric power plants have been built instead of fossil-fuel steam-electric plants because the cost of coal and oil has been increasing.

In the United States in 1970, fossil-fuel steam-electric plants accounted for 76% of the power generated, hydroelectric plants for 16%, and nuclear plants for 2%.

In 2000 45% of the electric power in the United States is generated from fossil-fuel steam-electric plants, 45% from nuclear plants, and10% from hydroelectric plants.

What Is Heat?

When heat, a form of energy, is supplied to a substance, we expect it to produce a rise of temperature. In other words, heat usually causes an increase in the average kinetic energy of the random motion of the molecules of which the substance is made up. However, heat may also produce a change of state without any temperature change.

Today heat is known to be a form of energy. But about a century ago heat was considered to be a kind of a weightless substance, which was neither created, nor destroyed. This substance called "caloric" was believed to pass from a hotter body to a colder one. eventually both of them coming to the same temperature. To explain that phenomenon was easy: a hot body, it was supposed, contains more of the heat fluid, i. e. caloric, than a cold one; and this fluid flows from hot to cold. Again, people knew that it takes more caloric to raise the temperature of a pound of water 10° than a pound of iron. They naturally supposed water to have higher caloric content than the iron. In fact, the caloric theory of heat, as it was called, accounted for almost everything that was known about heat at that time, except one important phenomenon, namely: the production of heat due to friction. However, numerous laboratory experiments demonstrated that each time, when mechanical energy was expended as a result of friction, a corresponding amount of heat was produced.

In spite of that inability to explain the production of heat by friction, the caloric theory of heat seemed to be the only acceptable theory.

Our great scientist and poet Lomonosov was among the first to find and state that heat phenomena were due to the motion of molecules. That statement of his resulted from many carefully performed laboratory experiments, from study and observation.

Lomonosov's theory laid the foundation for the present-day molecular-kinetic theory of heat. As was often the case; he left his contemporaries far behind and his statement was finally proved long after his death. The caloric theory of heat is known to have existed almost up to the middle of the 19th century.

The unit of heat is called a therm or a caloric; the latter term appears to come from the Latin word "calor" which means heat.

A calorie is defined as the amount of heat required, at a pressure of one atmosphere, to raise the temperature of one gram of water one degree Centigrade. (We know the gram to be a metric weight equal to 15.432 grains of the English system of weights).

One should not think that the very amount of heat which will raise the temperature of one gram of water from 0 to 1° C will also raise the temperature of the same mass of water from, say, 60 to 61° C Experiments have shown that the quantities of heat to be required in these two cases are slightly different. Hence, the true calorie is defined as that quantity of heat, which will raise the temperature of 1 gr of water from 19.5 to 20.5° C.