Atoms, Radiation, and Radiation Protection
Description
As a result, the text offers advanced students and professionals comprehensive coverage of the major concepts behind the origins and transport of ionizing radiation in matter. It covers the detection and measurement of radiation and the statistical interpretation of the data, thoroughly describing the procedures that are used to protect humans and the environment from the potential harmful effects. Throughout, the basic principles are elucidated using numerous worked examples that exemplify practical applications and each chapter includes problem sets (with partial answers) and extensive tables and graphs for continued use as a reference work.
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Persons
Darryl J. Downing is Vice President, Statistical and Quantitative Sciences, at GlaxoSmithKline Pharmaceutical company. He was previously a member of the research staff at Oak Ridge National Laboratory and led the Statistics Group for 10 of his 20 years at ORNL. Dr. Downing graduated from the University of Florida in 1974 with a Ph.D. in Statistics. He has authored over 50 publications and has been a Fellow of the American Statistical Association since 2002. He is also a member of the International Statistics Institute since 1997 and serves on the editorial board for Pharmaceutical Statistics.
Robert L. Coleman is a Senior Scientist at Oak Ridge National Laboratory and Technical Lead for in-vivo radio bioassay measurements. He manages the technical and day-to-day aspects of whole body, lung and organ measurements for gamma and x-ray emitting radionuclides in support of the ORNL radiation dosimetry program.
Keith F. Eckerman is Staff Scientist at Oak Ridge National Laboratory in the Energy and Environmental Sciences Divison. He obtained his Ph.D in Radiological Physics from Northwestern University and joined the Oak Ridge National Laboratory as leader of the Dosimetry Research Group after working at Argonne National Laboratory and with the U.S. Nuclear Regulatory Commission. He is a member of Committee 2 of the International Commission on Radiological Protection (ICRP) and Chairman of its Task Group on Dose Calculations. In 1999 he received the Distinguished Scientific Achievement Award from the Health Physics Society and in 2001 the Loevinger-Berman Award from the Society of Nuclear Medicine.
James E. Turner (1930-2008) was a retired Corporate Fellow from Oak Ridge National Laboratory and an Adjunct Professor of Nuclear Engineering at the University of Tennessee. In addition to extensive research and teaching both in the U. S. and abroad, Dr. Turner served on the editorial staffs of several professional journals, including Health Physics and Radiation Research, and was active in a number of scientific organizations.
Content
Classical Physics
Discovery of X-Rays
Some Important Dates in Atomic and Radiation Physics
Important Dates in Radiation Protection
Sources and Levels of Radiation Exposure
Suggested Reading
ATOMIC STRUCTURE AND ATOMIC RADIATION
The Atomic Nature of Matter (ca. 1900)
The Rutherford Nuclear Atom
Bohr's Theory of the Hydrogen Atom
Semiclassical Mechanics, 1913-1925
Quantum Mechanics
The Pauli Exclusion Principle
Atomic Theory of the Periodic System
Molecules
Solids and Energy Bands
Continuous and Characteristic X Rays
Auger Electrons
Suggested Reading
Problems
Answers
THE NUCLEUS AND NUCLEAR RADIATION
Nuclear Structure
Nuclear Binding Energies
Alpha Decay
Beta Decay (beta-)
Gamma-Ray Emission
Internal Conversion
Orbital Electron Capture
Positron Decay (beta+)
Suggested Reading
Problems
Answers
RADIOACTIVE DECAY
Activity
Exponential Decay
Specific Activity
Serial Radioactive Decay
Natural Radioactivity
Radon and Radon Daughters
Suggested Reading
Problems
Answers
INTERACTION OF HEAVY CHARGED PARTICLES WITH MATTER
Energy-Loss Mechanisms
Maximum Energy Transfer in a Single Collision
Single-Collision Energy-Loss Spectra
Stopping Power
Semiclassical Calculation of Stopping Power
The Bethe Formula for Stopping Power
Mean Excitation Energies
Table for Computation of Stopping Powers
Stopping Power of Water for Protons
Range
Slowing-Down Time
Limitations of Bethe's Stopping-Power Formula
Suggested Reading
Problems
Answers
INTERACTION OF ELECTRONS WITH MATTER
Energy-Loss Mechanisms
Collisional Stopping Power
Radiative Stopping Power
Radiation Yield
Range
Slowing-Down Time
Examples of Electron Tracks in Water
Suggested Reading
Problems
Answers
PHENOMENA ASSOCIATED WITH CHARGED-PARTICLE TRACKS
Delta Rays
Restricted Stopping Power
Linear Energy Transfer (LET)
Specific Ionization
Energy Straggling
Range Straggling
Multiple Coulomb Scattering
Suggested Reading
Problems
Answers
INTERACTION OF PHOTONS WITH MATTER
Interaction Mechanisms
Photoelectric Effect
Energy-Momentum Requirements for Photon Absorption by an Electron
Compton Effect
Pair Production
Photonuclear Reactions
Attenuation Coefficients
Energy-Transfer and Energy-Absorption Coefficients
Calculation of Energy Absorption and Energy Transfer
Suggested Reading
Problems
Answers
NEUTRONS, FISSION, AND CRITICALITY
Introduction
Neutron Sources
Classification of Neutrons
Interactions with Matter
Elastic Scattering
Neutron-Proton Scattering Energy-Loss Spectrum
Reactions
Energetics of Threshold Reactions
Neutron Activation
Fission
Criticality
Suggested Reading
Problems
Answers
METHODS OF RADIATION DETECTION
Ionization in Gases
Ionization in Semiconductors
Scintillation
Photographic Film
Thermoluminescence
Other Methods
Neutron Detection
Suggested Reading
Problems
Answers
STATISTICS
The Statistical World of Atoms and Radiation
Radioactive Disintegration-Exponential Decay
Radioactive Disintegration-a Bernoulli Process
The Binomial Distribution
The Poisson Distribution
The Normal Distribution
Error and Error Propagation
Counting Radioactive Samples
Minimum Significant Measured Activity-Type-I Errors
Minimum Detectable True Activity-Type-II Errors
Criteria for Radiobioassay, HPS Nl3.30-1996
Instrument Response
Monte Carlo Simulation of Radiation Transport
Suggested Reading
Problems
Answers
RADIATION DOSIMETRY
Introduction
Quantities and Units
Measurement of Exposure
Measurement of Absorbed Dose
Measurement of X- and Gamma-Ray Dose
Neutron Dosimetry
Dose Measurements for Charged-Particle Beams
Determination of LET
Dose Calculations
Other Dosimetric Concepts and Quantities
Suggested Reading
Problems
Answers
CHEMICAL AND BIOLOGICAL EFFECTS OF RADIATION
Time Frame for Radiation Effects
Physical and Prechemical Chances in Irradiated Water
Chemical Stage
Examples of Calculated Charged-Particle Tracks in Water
Chemical Yields in Water
Biological Effects
Sources of Human Data
The Acute Radiation Syndrome
Delayed Somatic Effects
Irradiation of Mammalian Embryo a
1
About Atomic Physics and Radiation
1.1 Classical Physics
As the nineteenth century drew to a close, man's physical understanding of the world appeared to rest on firm foundations. Newton's three laws accounted for the motion of objects as they exerted forces on one another, exchanging energy and momentum. The movements of the moon, planets, and other celestial bodies were explained by Newton's gravitation law. Classical mechanics was then over 200 years old, and experience showed that it worked well.
Early in the century Dalton's ideas revealed the atomic nature of matter, and in the 1860s Mendeleev proposed the periodic system of the chemical elements. The seemingly endless variety of matter in the world was reduced conceptually to the existence of a finite number of chemical elements, each consisting of identical smallest units, called atoms. Each element emitted and absorbed its own characteristic light, which could be analyzed in a spectrometer as a precise signature of the element.
Maxwell proposed a set of differential equations that explained known electric and magnetic phenomena and also predicted that an accelerated electric charge would radiate energy. In 1888 such radiated electromagnetic waves were generated and detected by Hertz, beautifully confirming Maxwell's theory.
In short, near the end of the nineteenth century man's insight into the nature of space, time, matter, and energy seemed to be fundamentally correct. While much exciting research in physics continued, the basic laws of the universe were generally considered to be known. Not many voices forecasted the complete upheaval in physics that would transform our perception of the universe into something undreamed of as the twentieth century began to unfold.
1.2 Discovery of X Rays
The totally unexpected discovery of X rays by Roentgen on November 8, 1895 in Wuerzburg, Germany, is a convenient point to regard as marking the beginning of the story of ionizing radiation in modern physics. Roentgen was conducting experiments with a Crooke's tube-an evacuated glass enclosure, similar to a television picture tube, in which an electric current can be passed from one electrode to another through a high vacuum (Fig. 1.1). The current, which emanated from the cathode and was given the name cathode rays, was regarded by Crooke as a fourth state of matter. When the Crooke's tube was operated, fluorescence was excited in the residual gas inside and in the glass walls of the tube itself.
Figure 1.1 Schematic diagram of an early Crooke's, or cathode-ray, tube. A Maltese cross of mica placed in the path of the rays casts a shadow on the phosphorescent end of the tube.
It was this fluorescence that Roentgen was studying when he made his discovery. By chance, he noticed in a darkened room that a small screen he was using fluoresced when the tube was turned on, even though it was some distance away. He soon recognized that he had discovered some previously unknown agent, to which he gave the name X rays.1 Within a few days of intense work, Roentgen had observed the basic properties of X rays-their penetrating power in light materials such as paper and wood, their stronger absorption by aluminum and tin foil, and their differential absorption in equal thicknesses of glass that contained different amounts of lead. Figure 1.2 shows a picture that Roentgen made of a hand on December 22, 1895, contrasting the different degrees of absorption in soft tissue and bone. Roentgen demonstrated that, unlike cathode rays, X rays are not deflected by a magnetic field. He also found that the rays affect photographic plates and cause a charged electroscope to lose its charge. Unexplained by Roentgen, the latter phenomenon is due to the ability of X rays to ionize air molecules, leading to the neutralization of the electroscope's charge. He had discovered the first example of ionizing radiation.
1.3 Some Important Dates in Atomic and Radiation Physics
Events moved rapidly following Roentgen's communication of his discovery and subsequent findings to the Physical-Medical Society at Wuerzburg in December 1895. In France, Becquerel studied a number of fluorescent and phosphorescent materials to see whether they might give rise to Roentgen's radiation, but to no avail. Using photographic plates and examining salts of uranium among other substances, he found that a strong penetrating radiation was given off, independently of whether the salt phosphoresced. The source of the radiation was the uranium metal itself. The radiation was emitted spontaneously in apparently undiminishing intensity and, like X rays, could also discharge an electroscope. Becquerel announced the discovery of radioactivity to the Academy of Sciences at Paris in February 1896.
Figure 1.2 X-ray picture of the hand of Frau Roentgen made by Roentgen on December 22, 1895, and now on display at the Deutsches Museum. (Figure courtesy of Deutsches Museum, Munich, Germany.)
The following tabulation highlights some of the important historical markers in the development of modern atomic and radiation physics.
1810 Dalton's atomic theory. 1859 Bunsen and Kirchhoff originate spectroscopy. 1869 Mendeleev's periodic system of the elements. 1873 Maxwell's theory of electromagnetic radiation. 1888 Hertz generates and detects electromagnetic waves. 1895 Lorentz theory of the electron. 1895 Roentgen discovers X rays. 1896 Becquerel discovers radioactivity. 1897 Thomson measures charge-to-mass ratio of cathode rays (electrons). 1898 Curies isolate polonium and radium. 1899 Rutherford finds two kinds of radiation, which he names "alpha" and "beta," emitted from uranium. 1900 Villard discovers gamma rays, emitted from radium. 1900 Thomson's "plum pudding" model of the atom. 1900 Planck's constant, h = 6.63 × 10-34 J s. 1901 First Nobel prize in physics awarded to Roentgen. 1902 Curies obtain 0.1 g pure RaCl2 from several tons of pitchblend. 1905 Einstein's special theory of relativity (E = mc2). 1905 Einstein's explanation of photoelectric effect, introducing light quanta (photons of energy E = hv). 1909 Millikan's oil drop experiment, yielding precise value of electronic charge, e = 1.60 × 10-19 C. 1910 Soddy establishes existence of isotopes. 1911 Rutherford discovers atomic nucleus. 1911 Wilson cloud chamber. 1912 von Laue demonstrates interference (wave nature) of X rays. 1912 Hess discovers cosmic rays. 1913 Bohr's theory of the H atom. 1913 Coolidge X-ray tube. 1914 Franck-Hertz experiment demonstrates discrete atomic energy levels in collisions with electrons. 1917 Rutherford produces first artificial nuclear transformation. 1922 Compton effect. 1924 de Broglie particle wavelength, ? = h/momentum. 1925 Uhlenbeck and Goudsmit ascribe electron with intrinsic spin ?/2. 1925 Pauli exclusion principle. 1925 Heisenberg's first paper on quantum mechanics. 1926 Schroedinger's wave mechanics. 1927 Heisenberg uncertainty principle. 1927 Mueller discovers that ionizing radiation produces genetic mutations. 1927 Birth of quantum electrodynamics, Dirac's paper on "The Quantum Theory of the Emission and Absorption of Radiation." 1928 Dirac's relativistic wave equation of the electron. 1930 Bethe quantum-mechanical stopping-power theory. 1930 Lawrence invents cyclotron. 1932 Anderson discovers positron. 1932 Chadwick discovers neutron. 1934 Joliot-Curie and Joliot produce artificial radioisotopes. 1935 Yukawa predicts the existence of mesons, responsible...