Design and Construction of Nuclear Power Plants

Rüdiger Meiswinkel, Julian Meyer, Jürgen Schnell

• Publisher: Ernst & Sohn
• Year: 2013
• ISBN:
  9783433602751
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Construction & Architectural Engineering
• Index: Technology & Engineering

Despite all the efforts being put into expanding renewable energy sources, large-scale power stations will be essential as part of a reliable energy supply strategy for a longer period. Given that they are low on CO2 emissions, many countries are moving into or expanding nuclear energy to cover their baseload supply.
Building structures required for nuclear plants whose protective function means they are classified as safety-related, have to meet particular construction requirements more stringent than those involved in conventional construction. This book gives a comprehensive overview from approval aspects given by nuclear and construction law, with special attention to the interface between plant and construction engineering, to a building structure classification. All life cycle phases are considered, with the primary focus on execution. Accidental actions on structures, the safety concept and design and fastening systems are exposed to a particular treatment. Selected chapters from the German concrete yearbook are now being published in the new English "Beton-Kalender Series" for the benefit of an international audience.
Since it was founded in 1906, the Ernst & Sohn "Beton-Kalender" has been supporting developments in reinforced and prestressed concrete. The aim was to publish a yearbook to reflect progress in "ferro-concrete" structures until - as the book's first editor, Fritz von Emperger (1862-1942), expressed it - the "tempestuous development" in this form of construction came to an end. However, the "Beton-Kalender" quickly became the chosen work of reference for civil and structural engineers, and apart from the years 1945-1950 has been published annually ever since.

1

Introduction

1.1 The Demand for Energy

As the world's population grows, the demand for primary energy, and hence electrical energy, is growing massively with it. At the same time, the demand for individual electrical power is increasing, especially as the so-called emerging nations are seeing their energy demand soar as they strive to become industrialised. The International Energy Agency (IEA) estimates that businesses and private households will need around 60% more energy by 2030 than they do today. With their massive populations, China and India will account for two-thirds of the increasing demand forecast.

The result, ‘More and more people needing more and more energy’, is shown in Figure 1.1. Between 2000 and 2020, world population is set to increase from six to eight billion (33%), but the demand for energy is forecast to rise at nearly twice the rate, by around 62%. This increase will mean major challenges in terms of a sustainable energy supply, based on the three-pillar concept of balancing economics, ecology and society, as set at the world summit in Rio de Janeiro in 1992.

Fig. 1.1 Growth in global energy demand

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1.2 Electricity Generation

A number of options are available to cover this energy demand: they can basically be divided into two groups, thermal power plants and power plants running on renewable energy sources. Thermal power plants break down into oil-fired, gas-fired, lignite-fired, hard-coal-fired and nuclear power plants. Apart from hydroelectric power, the main renewable energy sources are wind power, solar energy, biomass and geothermal energy.

Different electricity production options are rated differently in environmental and economic terms, but the difference in generating power (a 1000 MW coal-fired power plant is equivalent to 200 offshore or 400 onshore wind farms, for example) makes it clear that, essentially, the only way that rising world energy demand will be met is by using powerful cogeneration plants.

As Figure 1.2 shows, even though renewable energies are set to expand enormously in the coming decades, the capacity they actually generate will only grow slightly, so that their percentage share of total electricity generated will actually fall. The forecasts by World Energy Council (WEC) and IEA also say that even after 2020, more than 70% of energy will be obtained from coal, oil and gas, and the share of nuclear power will increase considerably. As well as output, having a reliable electricity supply is also extremely important, which also shows that thermal power plants are essential. If we look at a typical day load curve as in Figure 1.3 – broken down into baseload, average load and peak load – it is clear that thermal power plants are needed for baseload particularly.

Fig. 1.2 World energy demand and coverage (WEC reference scenario)

Fig. 1.3 Energy supply load curve

1.3 Importance of Nuclear Energy

In contributing towards covering world energy demand over a forecast period up to 2050 (Figure 1.2), nuclear energy plays a key role in generating electricity, which will mean a large number of newbuild projects worldwide. As the overview in Figure 1.4 shows, as at autumn 2009, as well as the 437 nuclear power plants already in operation, another 53 new nuclear power blocks were under construction, and another 76 new blocks were planned. The new blocks currently being built or planned mostly have (electricity) outputs from 1000 to 1600 MW. (Please note: the figures given in MW below indicate electrical energy, as opposed to thermal energy, which is stated in MW_th.)

Fig. 1.4 Generating energy from nuclear power [1]

Nuclear energy now provides around 15% of the electricity generated worldwide. It avoids around 2.5 bn tonnes of CO₂ emissions, so it makes a major contribution towards a sustainable electricity supply which achieves the goals in terms of economics, capability and the environment to a large extent.

For Germany, which uses wind energy relatively intensively, direct comparison shows that theoretically more wind energy was installed than nuclear in 2008 (23,300 MW as against 21,497 MW), but nuclear generated much more energy than wind, at 148.8 TWh as against 40.2 TWh. In other words, nuclear energy generates nearly 50% of baseload electricity in Germany.

Just how important nuclear energy is can also be seen from how economical it is in generating electricity. Building new nuclear power plants is relatively expensive in terms of capital costs, but the fuel costs involved (uranium), including disposal, are so low that the total cost (including disposal and end stage planning) of generating electricity is around 3–4 Euro cents per kWh [2]. This means that nuclear power is not affected by volatile fuel prices and guarantees a reliable supply, as the uranium deposits that are worth extracting at today's prices will be enough for more than 200 years, are spread across the world and the countries they originate in are politically stable.

The world, and Europe in particular, has recognised how important nuclear energy is when it comes to generating electricity, as the many newbuild projects show. A number of European countries, including Finland, France and Britain, have actually been building new nuclear power plants or planning them since 2005. These newbuild projects impose different requirements on structural engineering, not just in building them, but in interim and final storage and restoration work. We will look at these tasks, with their specific safety requirements, below.

2

Nuclear Energy

2.1 Generating Electricity by Nuclear Power Plants

Basically, nuclear power plants work in the same way as coal- and gas-fired plants, converting heat to electricity. Whereas fossil-fuel-fired power plants run on energy media such as oil, lignite or hard coal, nuclear power plants use the heat given off when atomic nuclei split.

Figure 2.1 shows how a nuclear power plant works (in this case, a pressurised water reactor, cf. Section 2.4.2) and shows the whole energy conversion process. Nuclear fission inside the reactor pressure vessel generates heat, which heats water until it vaporises, turning thermal energy into latent energy in steam. This steam, which is under high pressure, then drives the turbines (converting to mechanical energy), which turn the generators connected to them, generating electrical energy, like a bicycle dynamo. Condensing the steam required to drive the turbines is done either by direct flow or seawater cooling or via a cooling system using a cooling tower.

Fig. 2.1 How a nuclear power plant works (pressurised water reactor model)

2.2 Nuclear Fission

Most elements on Earth are stable, and the structure of their atomic nuclei is constant. A few of them decompose radioactively, however: that is to say, their atomic nuclei turn into those of other elements by emitting radiation or particles.

In a nuclear reactor, or a reactor at a nuclear power plant, nuclear fission is induced deliberately and the resulting radioactive decay used. Atomic nuclei are split by bombarding them with neutrons.

The process of nuclear fission is shown in Figure 2.2. In the reactor, uranium U-235 nuclei are bombarded with neutrons, causing them to fission and emit radiation, known as ‘nuclear radiation’ (cf. Section 3). The products of decay are usually two fission products, such as krypton or barium, and two or three neutrons. The neutrons that are emitted can in turn split other atomic nuclei, setting off a chain reaction in which energy is released.

Fig. 2.2 The nuclear fission process

The fission products that arise when atomic nuclei split are unstable: they give off radioactive radiation, turning into stable end products, releasing more energy in the process. This post-decay heat keeps on being generated even after a nuclear reactor has been shut down, and requires special post-cooling systems (Figure 2.3).

Fig. 2.3 Thermal output from a reactor once it is shut down

A constant steady chain reaction needs a certain minimum mass of fissionable material, also kno...

Table of contents

• Cover
• Series Page
• Title Page
• Copyright
• Editorial
• Preface
• Chapter 1: Introduction
• Chapter 2: Nuclear Energy
• Chapter 3: Approval Aspects
• Chapter 4: Building Structures for Nuclear Plants
• Chapter 5: Extraordinary Actions Involved When Designing Nuclear Installations
• Chapter 6: Safety Concept and Design
• Chapter 7: Fastening Systems
• Chapter 8: Waterproofing of Structures
• Chapter 9: Ageing and Life Cycle Management
• References
• Index