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1992 | Book

Introduction Read chapter Read first chapter

Nuclear Engineering

An Introduction

Authors: K. Almenas, R. Lee

Publisher: Springer Berlin Heidelberg

Included in: Professional Book Archive

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About this book

***VERKAUFSKATEGORIE*** 1 e This textbook covers the core subjects of nuclear engineering. Developed to meet the needs of today's students and nuclear power plant operators, the text establishes a framework for the various areas of knowledge that comprise the field and explains rather than just defines the relevant physical phenomena. For today's engineer the principal analytical design tool is the personal computer. The text takes advantage of this recent development. PC programs are provided which either expand the computational range accessible to the student, or serve to illustrate the relevant physical phenomena. Some of the included programs are simplified versions of computational procedures used in the field and can be used as training tool for design calculations. The text devotes special attention to subjects which have an impact on the safe operation of nuclear power reactors. This includes the design of safety optimized core configurations, the physical mechanisms underlying the various reactivity coefficients, and the calibration procedures for control rods. A final chapter is devoted to the licensing and safety evaluation of power reactors.

Table of Contents

Frontmatter
1. Introduction
Abstract
The knowledge which has to be acquired in every engineering field can be divided roughly into two categories:
(a)
“General” knowledge which is common to all engineers.
 
(b)
“Unique” knowledge which distinguishes one engineering field from another.
 
K. Almenas, R. Lee
2. Neutron/Nuclei Balance — The Fission Source
Abstract
The distribution of the neutron population in a reactor must be known in order to determine the rate at which various neutron-nuclei interactions occur. For example, fission events are produced by neutron-fissile interaction and these events in turn produce more neutrons. The fission reactions also yield a large amount of energy (approximately 200 MeV for a neutron and U-235 fission reaction). Therefore, the fission events play an essential role both in propagating the chain reaction and also in producing the energy. Knowledge of the spatial and energy distribution of the neutron population is consequently needed to determine the spatial distribution of the energy production rate.
K. Almenas, R. Lee
3. Neutron Interaction with Matter
Abstract
The design and operation of a nuclear reactor requires the ability to determine how neutrons are distributed within a reactor core. This can be achieved by deriving and solving “neutron balance” equations which include all the relevant neutron loss and gain rates. The first step in such a derivation must be the development of a method by which the rates of neutron interaction with matter can be calculated. That is the subject of this chapter. It is a broad and quite complicated subject. One of the main complications is that it is not realy appropriate to speak of the neutrons that will be present in a reactor as if they were a single entity. As shown in Chap. 2 during the discussion of fission events, the neutrons generated by fission events have a wide distribution of energies. The neutron energies will become even more varied as the neutrons interact with reactor materials. The kinetic energy that a neutron posesses has a very large influence upon the rate at which it interacts with other nuclei. Thus the calculation of a single interaction rate which represents all neutrons in a core requires carefull averaging procedures and even then has limited usefulness. As you will see, it turns out to be more appropriate to evaluate several reaction rates which apply to neutrons of various energies. Such “multi-energy” group cross sections will be considered in Chap. 5. In this chapter the basic definitions and concepts which are required to evaluate neutron-neuclei interaction rates are presented.
K. Almenas, R. Lee
4. Neutron Diffusion — Basic Concepts
Abstract
The previous chapters presented two of the most widely used parameters in reactor theory, the neutron flux and the neutron current. It was shown that both are products of the neutron number density and a characteristic speed. Consequently both have the same units (that is, [n/cm3] * [cm/s] = n/cm2/s), but nevertheless both parameters are also fundamentally different. The flux is proportional to the gross number of neutrons that move across a unit area and is used to calculate neutron-nuclei interaction rates. The neutron current is proportional to the net number of neutrons and is required in order to evaluate the movement of neutrons in or out of a specific volume. The distinction can also be summarized using mathematical terminology: one (the flux) is a scalar quantity which describes all of the path length’s that neutrons traverse per unit volume per second. The other (the current) is a vector quantity, which describes the direction and magnitude of neutron transfer.
K. Almenas, R. Lee
5. Neutron Balance — Energy
Abstract
The basic framework of the neutron balance equation has been derived and presented in the previous chapters. However, before we can proceed to realistic neutronic calculations, the various neutron-nuclei interaction rates must be considered in more detail. Of the various interactions that occur (e.g. capture, fission, scattering) the scattering interactions are by far the most prelevant. For example, in all types of reactors neutrons are produced as ‘fast’ neutrons which have an average energy of ~ 2.0 MeV. However, in ‘thermal’ reactors most of these neutrons are absorbed only after they have reached quite low, ‘thermal’ kinetic energy levels (well below 1 eV). They approach these low levels by loosing energy in repeated scattering interactions. A neutron is absorbed only once, but before it does so, it can experience up to a hundred or even more scattering events (this depends upon the type of the reactor). Thus looking at neutron interactions from the total interaction rate point of view, the scattering interaction is indeed the dominant interaction type.
K. Almenas, R. Lee
6. Criticality
Abstract
One of the central concepts of nuclear reactor theory is the self reproducing, or ‘critical’ neutron population. The basic definition of criticality was introduced in Chap. 3. At that time a simple method for estimating the critical condition called the ‘six factor’ formula was presented. The six factor formula can provide a useful overview, but for most practical reactor calculations a more precise method for evaluating criticality parameters is required. In this chapter the criticality concept will be reviewed in terms of the basic tool of nuclear engineering — the multigroup neutron balance equation.
K. Almenas, R. Lee
7. Neutron Balance — Time
Abstract
A nuclear power reactor which is operating at a steady power (and thus has a neutron population which is constant with time) could be likened to a car which is driven down a straight stretch of highway at a constant speed. That is an important, but only one of the possible operational modes for both the car and the reactor. Just as it must be possible to accelerate and stop the car, it must be possible to start up, to shutdown and to adjust the power (and to do so precisely!) of a nuclear reactor. The power of a nuclear reactor can be changed by changing the neutron population within its core, thus in a fundamental sense the understaning how a reactor can be controlled requires an understanding how the neutron population in the core can be altered. The basic mathematical tool for this is the same set of neutron balance equations derived previously, except that now the term including the time derivative of the neutron population must be retained.
K. Almenas, R. Lee
8. Gamma and Neutron Radiation Effects
Abstract
Most of the attention in this book has been devoted to neutrons. It is neutrons that determine the fission rate and core criticality, so this emphasis is entirely proper. However, when shielding or decay heat problems are to be solved then another neutral entity, the gamma rays, have to be considered. An operating (and also a shutdown) nuclear reactor core produces large numbers of gamma rays. They can be divided into three general categories: the ‘prompt’, the ‘delayed’ and the ‘activation’ gamma rays.
K. Almenas, R. Lee
9. Shielding
Abstract
A characteristic feature of every reactor is the shielding which surrounds its core and some of the plant components. Indeed, in some cases in terms of the bulk and visibility, it can be the dominant feature. An extensive design effort is required to assure that the shielding is properly optimized to meet protection, bulk and cost criteria. Furthermore, this effort is not terminated after the plant has been built. Radiation sources and access requirements change during operation, so that shielding type calculations are required at various times.
K. Almenas, R. Lee
10. Core Heat Removal
Abstract
The main purpose of a nuclear power plant is the conversion of a very inaccessible form of energy (the binding energy of the nucleus), into an energy form that is accessible and useful (preferably electrical energy). The ideal conversion process would be a direct one, and maybe in the future power plants will be developed which can achieve this. Presently this is not the case. In the nuclear power plants of today the binding energy of the fissioning nucleus is first changed into the kinetic energy of fission fragments, then into the average kinetic energy of the surrounding fuel molecules (that is, thermal energy). From that point on the details of the transformation steps depend somewhat on the type of the plant in which the fission has occurred, but in all cases the energy is transported by conduction to some fluid (usually water) and from the fluid (maybe after another step) to the rotational kinetic energy of a turbine shaft. Then finally about 30 to 33% of the original thermal energy is converted into electrical energy in the generator.
K. Almenas, R. Lee
11. Reactor Licensing
Abstract
Government regulations permeate all aspects of our lives. What began as an effort to protect citizens against obvious and flagrant violations in the areas of safety, ecology and resource management, has evolved into an all encompassing envelope of regulations. Although this development can be analyzed on a societal, political or even philosophical ground, none of these are appropriate here. For nuclear engineers, the regulations dealing with the nuclear industry are first and foremost a matter of law. It is a set of laws that is administered thoroughly and rigorously, and it is taken very seriously by the industry. It is a set of laws that has not only guided, but actually shaped the industry. That is not an exaggeration. The design of a nuclear power plant, its operational procedures, even the type of analyses we, as nuclear engineers will perform are to a large degree defined by the government and enforced by a set of regulations. A single chapter devoted to the subject in this text does not match the importance that it has. As you progress in your career and acquire the valuable commodity called ‘professional experience’ to a significant degree, this experience will include the interpretation of nuclear regulations.
K. Almenas, R. Lee
Backmatter
Metadata
Title
Nuclear Engineering
Authors
K. Almenas
R. Lee
Copyright Year
1992
Publisher
Springer Berlin Heidelberg
Electronic ISBN
978-3-642-48876-4
Print ISBN
978-3-642-48878-8
DOI
https://doi.org/10.1007/978-3-642-48876-4