Materials in Nuclear Energy Applications

Volume II

C.K. Gupta

• Publisher: CRC Press
• Year: 2018
• Print ISBN: 9781315895758
• eBook ISBN: 9781351091756
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

The text combines an account of scientific and engineering principles with a description of materials and processes of importance in nuclear research and industry. The coverage includes fuel materials, control and shileding materials, and so on - in fact, for most of the important pasts of a reactor.

CHAPTER 1

ELEMENTS OF NUCLEAR ENERGY

I. INTRODUCTION^{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}

Energy is one of the primary necessities of man as evidenced by its use for light, heat, food production, manufacturing, transportation, and indeed for almost every human activity. The more developed and organized a human society becomes, the more energy it uses up. In talking about energy, reference naturally is directed towards the resources. These generally fall into three broad groupings: fossil fuels, and renewable and nuclear resources.

The fossil fuels are coal, oil, and natural gas. They are derived from organic decay over millions of years and, therefore, are not renewable. There has, in fact, been an overwhelming dependence upon nonrenewable fossil fuels. Fossil fuels have played the major part in our industrial development. It is, however, a matter of great concern that, even allowing for new discoveries, fossil fuels are rapidly becoming depleted. In recent years, about half the world energy has come from oil, yet oil will become scarce and expensive in the long term. Coal is plentiful in some parts of the world. There is a growing need to conserve the fossil fuels for applications other than energy generation, since they constitute essential raw materials in numerous chemical and metallurgical industries. Coal, for example, is destined to be needed increasingly for uses other than producing electricity — as a feed stock for chemicals and fertilizers, and a source of liquid fuel and gas.

Renewable resources is the name assigned to natural resources such as the sun, wind, waves, and so on, which by and large, will continue to be present whether or not we extract energy from them. Geothermal energy is usually classified as renewable, but in fact, extracting the earth’s heat does exhaust the local reservoir of it. It is, however, a vast source, and on this score is regarded as practically inexhaustible.

The sun has been regarded as the ultimate answer to the world’s need for energy. The sun is not a rapidly depleting resource, and the use of solar energy may cause few environmental problems. There are huge areas of the world where the sun streams down most of the day, and in these sunny lands of the earth, there is appreciable use of solar energy for domestic water heating, but not for generation of electricity. Solar cells can be used for conversion of sunlight into electricity and are used in space missions. All designs available today are very expensive indeed in relation to the electrical power they generate. Electricity can be produced by using a system of mirrors to concentrate sunlight onto a boiler and to produce steam in a conventional way. The problem is again simply one of capital cost — the cost of mirrors and machinery for directing sunlight on the boiler as the sun moves across the sky. There are, however, two disadvantages that are associated with utilization of solar energy: one is that the sun’s energy is diffuse (i.e., it is spread out very thinly), and the other is that it is intermittent — the sun shines only during the day and is often obscured by clouds. Efficient means are yet to be developed for collecting this energy, and also for storing it. What remains uncertain and controversial is whether or not economical ways can be developed in these areas. It is unlikely that the sun’s energy would contribute very much on a relevant time scale. The hydroelectric resources of the world have all been, more or less, explored and the most suitable sites have been harnessed. The rate of growth of this energy is limited.

Tidal power is confined to particular places. There are only a few parts of the world where tides are large enough to enable appreciable quantities of electricity to be produced from them. Probably some of the world’s highest tides exist on the coasts of France and Great Britain. The waves of the sea, although very powerful, are very unpredictable, diffuse, and variable. Only very small scale research work has been done in this field up til now. The potential of wave power must be considerable. It, however, requires massive structures out at sea, with significant control and transmission problems and unknown economies. A demonstration plant is yet to be engineered.

Wind power appears in the given list of renewable energy resources and has started to be taken more seriously as a potential method of supplying a substantial proportion of the future energy needs of many countries. The power in the wind is proportional to the cube of the wind speed and, in general, the wind speed also increases with height within the boundary layer of the earth, varying with the type of terrain. Recent attempts to harness wind energy, both for small-scale private use and in megawatt-size producers of electricity for utilities, started just after the oil crisis in 1974. Wind mills, at one time, constituted a major source of energy for grinding grain or for pumping water. However, wind power is greedy in land space, unsightly, and perhaps noisy. A large program implies massive construction on remote sites; mechanical and electrical engineering also need development. For example, a windmill designed to operate at low wind speeds is blown over by high winds. If it has smaller drive surfaces to be stable under hurricane conditions, it is quite inoperative for other times of the year. Wind power has reached an interesting stage of development. It is one of the few renewable technologies which shows signs of emerging as a commercial technology.

Aside from hydroelectric power, geothermal energy is, perhaps, the only one with some promise. In most parts of the world there is a steady rise in temperature as one descends into the depth of the earth (on an average, the temperature rise is l°C/30 m). In certain areas, one meets hot magma flows, which can be at a temperature of up to 1000°C. Iceland, Italy, New Zealand, parts of Japan, and California are all areas where, because of volcanic activity not far below the surface, geothermal energy is used for electric power generation. At Lardariello, Italy there are 500 drillings over an area of 250 km² down to a depth of about 1000 m, and about 200 of these deliver steam at a temperature of 240°C. The power station that uses this steam has a capacity of 400 MW(e). The biggest geothermal power station in the world, which has an output of 1000 MW, is located at Geysers, California. The present total world capacity of geothermal power stations is about 3000 MW. It seems unlikely that there would be much more expansion than this. Geothermal fluids contain a high percentage of sulfur compounds, and cause a good deal of corrosion and lead to a very short working life for turbines and other equipment. They also cause a lot of atmospheric pollution.

Recorded history bears out the fact that only a few single events have crucially altered the course of civilization. The completion and successful operation of the first nuclear reactor is one such epochal event. It is an accomplished feat that has been compared to the invention of steam engines, or the manufacture of the first automobile or of the first airplane in its impact on the future and its significance for phenomenal social changes. The first emergence of nuclear power came about in the awesome form of the atomic bomb. It is, however, nuclear power from the controlled nuclear reactor system that provides the answer to the continuous supply of energy for human needs. Nuclear power shows a marked cost advantage against competing forms of energy. The reason nuclear power is so much cheaper than electricity produced from fossil fuel sources is related to the cheapness of the fuel, since uranium has a much higher energy content per unit mass than fossil fuels. Fuel resources for nuclear power are abundant. Fossil-fuel power stations can only be built in areas where there is sufficient ease of transportation to permit thousa...

Table of contents

• Cover
• Title Page
• Copyright Page
• Table of Contents
• Chapter 1 Elements of Nuclear Energy
• Chapter 2 Nuclear Fission Reactor
• Chapter 3 Fast Reactors
• Chapter 4 Nuclear Fuel Materials
• Index