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

Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit:

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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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4.5 Global distribution of coal

Figure 35 shows the global distribution of coal deposits. The major areas are principally in the Northern Hemisphere; with the exception of Australia, the southern continents are relatively deficient in coal deposits.

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4.4 Coal in the European Union

The EU's coal reserves in 2004, after enlargement to 25 member states, stood at 100 × 109 t. Table 3 shows the eight European Union Member States with the most significant reserves ranked in order of greatest tonnage. With a little over 100 × 10 9 t of coal of all ranks, the EU possesses approxima
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4.3 The UK's coal reserves

Production of large quantities of coal in the UK during the 19th and 20th centuries led to the progressive depletion of reserves. In 2005 underground mining was limited to the Carboniferous coalfields of Yorkshire and the East Midlands, with only one underground mine operating in South Wales. However, surface mining sites still work coal in most of the coalfields (Author(s): The Open University

4.2 Coal distribution in the UK and Europe

The UK and Europe were fortunate in having extensive coalfields that powered the Industrial Revolution. Figure 33 shows the distribution of the major Carboniferous mires which became coal-bearing rocks across Europe, either outcropping at the surface or buried beneath younger rocks. The first thing that is evident from t
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3.3.1 Mining subsidence

Subsidence is an inevitable hazard wherever underground mining is carried out.

The major factors affecting the extent of subsidence are seam thickness and its depth beneath the surface.

The amount of subsidence can be calculated roughly by using the formula:

3.3 Underground mining

Underground mining operations have four significant environmental impacts — spoil heaps, methane build-up, subsidence and water pollution. Spoil heaps have always been the principal surface feature of underground mining operations. However, legislation and technical advances have brought improvements in modern mines, and the closure of many of the UK's older mines has often been followed by successful rehabilitation of mine sites and spoil heaps by landscaping and tree planting.

Coal
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3.2 Surface mining

Many environmental issues arise when surface mining is considered, and such mines regularly arouse local opposition. By their very nature, surface mines have a major impact on the landscape, involving the digging of enormous pits with accompanying noise, dust and traffic movements, and destruction of mature landscape. Increasingly, in recent years the environmentally conscious public has used the planning processes to oppose and sometimes prevent mining on sites where the environmental impact
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3.1 Environmental aspects of coal mining

Coal produced by both types of mining is used either to fuel electricity generation or for industrial and domestic heating, both of which result in atmospheric pollution, but here we are concerned with direct environmental impact on the land. Surface and underground mining operations cause significantly different environmental problems. Those that surround surface mining are common to any large quarrying operation: sterilization of the land and restoration of quarry sites; dust; and noise whi
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2.7.1 Recognizing geological problems

The most profitable coal mines are those that possess unbroken, horizontal seams of constant thickness and quality. In mines where this is not so, profit levels will depend on the ability of the mine geologist to predict changes in the seam before they are encountered at the face.

Geological problems fall into two categories — gradual changes and sudden changes. Where a change is gradual, such as a seam thinning or splitting, data from boreholes in advance of the workings, supplemente
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2.7 Geological problems in coal mines

A modern coalface is a very complex operation that represents a large investment in terms of capital, labour and planning. Cutting machines and lengthy conveyors are inflexible and require uniform geological conditions to maximize output. What then are the effects of geological variations on such a mining system?

Geological factors control the selection of working areas. The two principal geological conditions that affect mining operations are, first, the nature of the coal-bearing rock
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