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6 Summary

Nuclear power generation results from fission of uranium isotopes when bombarded by neutrons. Conventional burner reactors require relatively scarce uranium-235, whereas fast breeder reactors (which have not yet been developed on any significant scale) would exploit more abundant uranium-238.

In the early 21st century over 400 nuclear — mainly burner — reactors produced 16% of global electricity demand.

The UK played a leading role in nuclear power developments during the 1950
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4.5 Geological criteria for safe radioactive waste disposal

Even in the best of circumstances, containers such as the one shown in Figure 19 will survive for only 100–1000 years, although the glass itself may inhibit the migration of radioactive isotopes for a further 1000 years. So, in view of the long decay times (Author(s): The Open University

4.4 Radioactive waste disposal

Most fission products from nuclear reactors are solid at ordinary temperatures. They cluster around atomic mass numbers 90 and 140 (see, for example, Equation 2). From the point of view of waste disposal, the problem is that most of them are highly radioactive. The common radioactive isotopes produced in nuclea
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4.1 Introduction

Nuclear power generation involves concentrated fissionable fuels which, after fission, leave significant quantities of fission-product isotopes, some of which are highly radioactive. Much of the criticism levelled against the industry falls under four main headings to which we have alluded in preceding sections:

  1. the operational safety of nuclear reactors;

  2. the biological effects of abnormal radiation levels arising from fuel transport,
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3.3 Uranium production and economics

Table 3 lists the major uranium-producing countries. Currently, Canada (with 29% of global supply in 2003) is the world's largest producer of uranium, followed by Australia (21%), both having increased production since about 1980, whereas production from the USA, France, and South Africa has declined (
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3.2 Uranium occurrence and ore deposits

In igneous rocks, uranium is more abundant in granites (~3.5 ppm) than in basalts (~1 ppm). The large size of the uranium atom prevents it from easily entering the structures of common rock-forming minerals, so it is an incompatible element that tends to remain in magmas until a late stage of crystallisation, when it enters minor minerals, or even the uranium oxide, uraninite (UO2). In suitable circumstances, following fractional crystallisation of uranium-rich granitic magm
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3.1 Introduction

Just how readily available are uranium resources, and do their distribution and cost impose restrictions on nuclear power generation? Compared to a coal-fired power station a nuclear power station requires far less fuel in terms of mass. You have seen that a 1 GW burner reactor requires 5000 t of natural uranium over 30 years, whereas a comparable modern coal-fired power station needs 10 000 t of coal every day. However, uranium does not occur naturally in metallic form, nor in the concentrat
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2.5 The growth, decline and future of nuclear power

The Calder Hall Magnox reactor near Sellafield fired the UK's first commercial nuclear power station in 1956, and launched an early UK lead in global nuclear developments. By 1960 six commercial reactors were operating, and Magnox technology had been exported to Italy and Japan. The UK Magnox building programme was complete in 1971 with eleven stations, each producing between 245 MW and 840 MW. Author(s): The Open University

2.3.2 Fast breeder reactors

If fast neutrons produced in the chain reactions are not moderated or absorbed, the rate of conversion of uranium-238 into plutonium-239 (Equation 3) can exceed the fission rate of plutonium-239. Reactors that use fast neutrons in this way are called fast breeder reactors.

Their main fuel is
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2.3 Nuclear reactors

A critical mass of uranium is necessary for nuclear chain reactions (Equations 1 to 3) to occur. A smaller concentration of ura
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2.2 Nuclear fission

Every atom has a nucleus consisting of positively charged protons and electrically neutral neutrons. Protons and neutrons have virtually identical mass and the total number of protons and neutrons defines the mass number of a particular atom. The number of protons in the nucleus is the atomic number and this quantity is always the same for each particular chemical element. However, some elements have several isotopes, each with different numbers of ne
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1 Nuclear energy

The transformation of radioactive uranium and, in some instances, thorium isotopes provides vastly more energy per unit mass of fuel than any other energy source, except nuclear fusion, and therein lies its greatest attraction. The key to that remarkable fact is the conversion of matter (with mass, m) into energy (E), according to Einstein's famous equation E = mc2, where c is the speed of light (3×108 m s−1 ).

The p
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Learning outcomes

By the end of this unit you should be able to:

  • distinguish between energy produced by nuclear fission and radioactive decay;

  • describe the principles behind nuclear 'burner' and nuclear 'breeder' reactors;

  • understand the geoscientific principles underlying the enrichment of uranium in ore deposits;

  • summarise and explain the hazards associated with nuclear wastes and their safe disposal;

  • summarise the fluctuating fortunes
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Introduction

The transformation of radioactive uranium and, in some instances, thorium isotopes provides vastly more energy per unit mass of fuel than any other energy source, except nuclear fusion, and therein lies its greatest attraction.

The potential of nuclear fuels for energy production became a reality when the first experimental atomic pile, built by Enrico Fermi and Léo Szilárd at the University of Chicago, began functioning in December 1942. That led to the manufacture of fissionable mat
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Acknowledgements

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6 Summary

  1. Waterlogged organic matter accumulates in deltaic, coastal barrier or raised mires to form peat. Coal forms by the compaction and decomposition of peat. Chemical changes imposed by increasing temperature and pressure over time determine the coal rank.

  2. Coalfields can be classified as either exposed or concealed, depending on whether or not the coal-bearing rocks are hidden by younger strata. In most coalfields, mining commenced in the shallower
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5 Coal production in the UK early in the 21st century

This section examines the UK's coal industry in a little more detail, to see how the complex interplay of location, economics and politics has led to the rapid demise of an industry that was once at the heart of the UK's economy.

Figure 38 shows production and consumption figures for coal mined in the UK since 1945 a
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4.6 Global coal reserves and their life expectancy

In 2003, global proven coal reserves were estimated at 984.5 × 109 t, of which slightly over half (52.7%) was anthracite and bituminous coal and the rest (47.3%) was sub-bituminous coal and lignite.

Figure 37 shows the breakdown of global reserves by continental regions. North America has 26% of total g
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