PHYSICS FOR RADIATION PROTECTION

Transcription

1 PHYSICS FOR RADIATION PROTECTION JAMES E. MARTIN School of Public Health The University of Michigan A Wiley-Interscience Publication JOHN WILEY & SONS, INC. New York Chichester Weinheim Brisbane Singapore Toronto

2 CONTENTS Preface 1 Introductory Concepts Structure of Atoms, 2 Two-Proton Atoms, 5 Three-Proton Atoms, 7 Atom Dimensions, 7 Nuclide Chart, 7 Atom Measures: Number, Mass, and Energy, 9 Avogadro's Number, 10 Atomic Mass Unit, 10 Electron Volt, 11 Problems, 14 2 Forces and Energy in Atoms Basic Energy Concepts, 17 Potential and Kinetic Energy in Atoms, 20 Relativistic Energy, 21 Variation of Mass with Velocity, 22 Relativistic Mechanics, 23 Momentum and Energy, 23 Effects of Velocity, 24 Natural Limit, 24 Mass-Energy, 26 Binding Energy of Nuclei, 26 ß-Value, 29 Summary, 29 Problems, 30

3 viii CONTENTS 3 Major Discoveries in Radiation Physics 32 Great Discoveries from Simple Tools, 33 Discovery of X Rays, 34 Discovery of Radioactivity, 35 Discovery of the Electron, 37 Measuring an Electron's Charge, 38 First Concept of the Atom, 39 Theory of Electromagnetic Radiation: The Quantum, 42 Wein's Law, 43 Rayleigh-Jeans Law, 44 Planck's Quantum Theory of Radiation, 45 Quantum Theory and the Photoelectric Effect, 47 Electromagnetic Spectrum, 50 Photon Hypothesis, 51 Compton Effect, 51 Discovery of the Atom's Structure, 55 Rutherford's Alpha-Scattering Experiments, 56 Bohr Model of the Atom, 58 Emission and Absorption Spectra, 59 Wave Mechanics: A Necessary Theory, 63 De Broglie Waves, 64 Confirmation of De Broglie's Hypothesis, 64 De Broglie Waves and the Bohr Model, 67 Wave Mechanics, 68 Exclusion Principle, 70 Uncertainty Principle, 71 Atom Systems, 73 The Neutron, 73 Nuclear Shell Model, 74 Summary, 74 Problems, 77 4 Interactions 79 Production of X Rays, 79 Characteristic X Rays, 81 X Rays and Atomic Structure, 83 Auger Electrons, 84 Nuclear Interactions, 86 Dynamics of Nuclear Interactions, 87 Cross Section, 88 ß-Value, 90 Alpha-Particle Interactions, 92 Alpha-Neutron Reactions, 93 Transmutation by Protons, 94 Proton-Neutron Reactions, 95 Proton-Gamma Reactions, 96 Proton-Deuteron Reactions, 96

4 CONTENTS Transmutation by Deuterons, 96 Deuteron-Proton and Deuteron-Neutron Reactions, 97 Neutron Interactions, 97 Neutron-Alpha Reactions, 98 Neutron-Proton Reactions, 98 Neutron-Neutron Reactions, 98 Radiative Capture Reactions, 99 Photodisintegration Reactions, 99 Medical Isotope Reactions, 100 Transuranium Elements, 101 Fission and Fusion Reactions, 102 Fusion, 103 Thermonuclear Weapons, 106 Summary, 107 Problems, Radioactive Transformation Processes of Radioactive Transformation, 110 Transformation of Neutron-Rich Radioactive Nuclei, 112 Double-Beta Transformation, 115 Transformation of Proton-Rich Nuclei, 116 Positron Emission, 116 Average Energy of Negation and Positron Emitters, 119 Electron Capture, 120 Radioactive Transformation of Heavy Nuclei by Particle Emission, 122 Theory of Alpha-Particle Transformation, 126 Transuranic Radionuclides, 127 Gamma Emission, 127 Internal Transition: Metastable or Isomeric States, 129 Internal Conversion, 129 Multiple Modes of Radioactive Transformation, 135 Transformation by Delayed Neutron Emission, 136 Transformation by Spontaneous Fission, 136 Proton Emission, 138 Decay Schemes, 139 Rate of Radioactive Transformation, 141 Activity of a Radioactive Source, 143 Units of Radioactive Transformation, 143 Mathematics of Radioactive Transformation, 145 Half-Life, 146 Mean Life, 148 Effective Half-Life, 149 Radioactivity Calculations, 150 Half-Life Determination, 153 Activity-Mass Relationships, 154 Specific Activity, 155

5 X CONTENTS Radioactive Series Transformation, 158 Series Decay Calculations, 158 Recursive Kinetics: Bateman Equations, 160 Radioactive Equilibrium, 161 Time of Maximum Activity, 162 Secular Equilibrium, 163 Transient Equilibrium, 164 Radionuclide Generators, 165 Transient Equilibrium: Branching, 166 Total Number of Transformations, 167 Discovery of the Neutrino, 169 Problems, Naturally Occurring Radiation and Radioactivity 174 Discovery and Interpretation of Radioactivity, 175 Background Radiation, 177 Cosmic Radiation, 178 Cosmogenic Radionuclides, 180 Naturally Radioactive Series, 183 Singly Occurring Primordial Radionuclides, 193 Radioactive Ores and By-products, 195 Resource Recovery, 195 Uranium Ores, 196 Water Treatment Sludge, 197 Phosphate Industry Wastes, 197 Elemental Phosphorus, 198 Neptunium Series Radionuclides, 199 Manhattan Project Wastes, 199 Thorium Ores, 201 Radioactivity Dating, 201 Carbon Dating, 201 Dating by Primordial Radionuclides, 202 Potassium-Argon Dating, 203 Ionium ( 230 Th) Method, 204 Lead-210 Dating of Sediments, 204 Radon and its Progeny, 205 Radon Subseries, 206 Working Level for Radon Progeny, 208 Measurement of Radon, 212 Summary, 216 Problems, Interactions of Radiation with Matter 220 Radiation Dose and Units, 220 Radiation Absorbed Dose, 221 Radiation Dose Equivalent, 221 Radiation Exposure, 222

6 Radiation Dose Calculations, 223 Inverse-Square Law, 224 Interaction Processes, 225 Interactions of Alpha Particles and Heavy Nuclei, 226 Recoil Nuclei and Fission Fragments, 228 Range of Alpha Particles, 228 Beta Particle Interactions and Dose, 231 Energy Loss by Ionization, 231 Energy Loss by Bremsstrahlung, 232 Cerenkov Radiation, 233 Attenuation of Beta Particles, 234 Radiation Dose from Beta Particles, 237 Beta Dose from Contaminated Surfaces, 239 Beta Contamination on Skin or Clothing, 240 Beta Dose from Hot Particles, 241 Photon Interactions, 243 Photoelectric Interactions, 243 Compton Interactions, 244 Pair Production, 246 Photodisintegration, 248 Photon Attenuation and Absorption, 248 Attenuation (/x) and Energy Absorption (/i en ) Coefficients, 251 Effect of E and Z on Photon Attenuation and Absorption, 253 Absorption Edges, 253 Energy Transfer and Absorption by Photons, 258 Electronic Equilibrium, 262 Bragg-Gray Theory, 263 Exposure and Dose Calculations, 264 Point Sources, 265 Gamma-Ray Constant, 266 Exposure and Absorbed Dose, 267 Exposure, Kerma, and Absorbed Dose, 268 Summary, 270 Problems, 271 Radiation Shielding Shielding of Alpha-Particle Sources, 273 Shielding of Beta-Particle Sources, 274 Attenuation of Beta Particles, 274 Bremsstrahlung Effects for Beta Shielding, 276 Shielding of Photon Sources, 279 Shielding of Good Geometry Photon Sources, 280 Half- and Tenth-Value Layers, 284 Shielding of Poor Geometry Photon Sources, 286 Use of Buildup Factors, 290 Effect of Buildup on Shield Thickness, 291 Mathematical Formulations of the Buildup Factor, 293

7 xii CONTENTS Gamma Flux for Distributed Sources, 295 Line Sources, 296 Ring Sources, 298 Disc and Planar Sources, 299 Shield Designs for Area Sources, 300 Gamma Exposure from Thick Slabs, 306 Volume Sources, 309 Buildup Factors for Layered Absorbers, 311 Shielding of Protons and Light Ions, 313 Summary, 315 Problems, Production of Activation Products 319 Activation Cross Sections, 319 Neutron Reactions, 319 Activation Products in Nuclear Reactors, 321 Activation Product Calculations, 323 Charged Particle Activation, 329 Activation by Photons, 337 Summary, 339 Problems, Nuclear Fission and its Products 342 Fission Energy, 343 Physics of Sustained Nuclear Fission, 346 Neutron Economy and Reactivity, 350 Nuclear Power Reactors, 352 Reactor Design: Basic Systems, 353 Light Water Reactors, 355 Pressurized Water Reactors, 355 Boiling Water Reactors, 356 Inherent Safety Features of LWRs, 358 Decay Heat in Power Reactors, 359 Uranium Enrichment, 359 Heavy Water Reactors, 361 HWR Safety Systems, 364 Breeder Reactors, 364 Liquid Metal Fast Breeder Reactors, 366 Gas-Cooled Reactors, 368 High-Temperature Gas Reactors, 368 Reactor Radioactivity, 370 Fuel Cladding, 370 Radioactive Products of Fission, 372 Production of Individual Fission Products, 375 Fission Products in Spent Fuel, 377 Fission Product Poisons, 378

8 CONTENTS xiii Radioactive Wastes from Reactors, 381 Low-Level Radioactive Waste, 381 Summary, 384 Problems, Nuclear Criticality 387 Nuclear Reactors and Criticality, 388 "Natural Reactor" Criticality Event, 388 Three Mile Island Accident, 388 Chernobyl Accident, 390 NRX Reactor Accident, 392 SL-1 Accident, 393 K-Reactor Event, 393 Special Reactor Experiments, 394 Nuclear Explosions, 395 Fusion Weapons, 395 Fission Products from Nuclear Explosions, 397 Fission Product Activity and Exposure, 398 Criticality Accidents, 400 Y-12 Plant, Oak Ridge National Laboratory, 400 Los Alamos Scientific Laboratory, 401 Idaho Chemical Processing Plant, 401 Hanford Recuplex Plant, 402 Wood River Junction, 403 UKAEA Windscale Works, 403 Bare and Reflected Metal Assemblies, 404 Radiation Exposures in Criticality Events, 404 Criticality Safety, 405 Criticality Safety Parameters, 406 Fission Product Release in Criticality Events, 411 Fast Fission in Criticality Events, 412 Summary, 414 Problems, Radiation Detection and Measurement 416 Types of Detectors, 416 Gas-Filled Detectors, 416 Crystalline Detectors and Spectrometers, 419 Semiconducting Detectors, 420 Gamma Spectroscopy, 421 Gamma-Ray Spectra: hv < MeV, 421 Gamma-Ray Spectra: hv > MeV, 426 Escape Peaks and Sum Peaks, 427 Gamma Spectroscopy of Positron Emitters, 429 Portable Field Instruments, 430 Geiger Counters, 430 Ion Chambers, 431

9 xiv CONTENTS Microrem Meters, 432 Alpha Radiation Monitors, 432 Survey Instruments for Beta Particles, 433 Removable Radioactive Surface Contamination, 434 Instrument Calibration, 434 Personnel Dosimeters, 435 Laboratory Instruments, 436 Liquid Scintillation Analyzers, 436 Proportional Counters, 440 End-Window GM Counters, 442 Surface Barrier Detectors, 443 Range versus Energy of Beta Particles, 443 Problems, Statistics in Radiation Physics 449 Nature of Counting Distributions, 449 Binomial Distribution, 450 Poisson Distribution, 451 Normal Distribution, 452 Mean and Standard Deviation of a Set of Measurements, 455 Uncertainty in the Activity of a Radioactive Source, 456 Uncertainty in a Single Measurement, 458 Propagation of Error, 458 Statistical Subtraction of a Background Count or Count Rate, 460 Error Propagation of Several Uncertain Parameters, 462 Comparison of Data Sets, 463 Statistics for the Counting Laboratory, 465 Uncertainty of a Radioactivity Measurement, 465 Determining a Count Time, 467 Efficient Distribution of Counting Time, 468 Detection and Uncertainty for Gamma Spectroscopy, 468 Testing the Distribution of a Series of Counts: Chi-Square Statistic, 471 Weighted Sample Mean, 472 Rejection of Data, 473 Levels of Detection, 475 Critical Level, 475 Detection Limit or Lower Level of Detection, 478 Minimum Detectable Concentration or Contamination, 481 Less-Than Level, 484 Interpretations and Restrictions, 484 Uncertainties in Response Time/Dead Time, 485 Problems, Neutrons 488 Neutron Sources, 488 Neutron Parameters, 490

10 CONTENTS XV Neutron Interactions, 491 Neutron Attenuation and Absorption, 493 Neutron Dosimetry, 495 Dosimetry for Fast Neutrons, 495 Dose from Thermal Neutrons, 499 Monte Carlo Calculations of Neutron Dose, 501 Kerma for Neutrons, 503 Dose Equivalent versus Neutron Flux, 503 Boron Neutron Capture Therapy, 504 Neutron Shielding, 505 Neutron Shielding Materials, 506 Neutron Shielding Calculations, 507 Neutron Removal Coefficients, 508 Neutron Attenuation in Concrete, 511 Neutron Detection, 512 Measurement of Thermal Neutrons, 512 Measurement of Intermediate and Fast Neutrons, 513 Neutron Foils, 515 Albedo Dosimeters, 517 Flux Depression of Neutrons, 517 Summary, 518 Problems, XRays 521 Producing and Shaping the X-Ray Beam, 522 X-Ray Yield: Bremsstrahlung Production Fraction, 525 X-Ray Tubes, 527 Focal Spot, 529 Rotating Anodes, 531 Equipment Techniques, 532 Intensity of X-Ray Beams, 533 X-Ray Filters, 536 X-Ray Image Formation, 540 X-Ray Imaging Dosimetry, 542 Capture of the X-Ray Image, 545 Air Gaps and Grids, 545 X-Ray Film and Screen Systems, 549 Image Processing, 551 Optimization of Film Processing, 555 Radiation Protection for X-Rays, 558 Assuring Patient Protection in X-Ray Diagnosis, 558 Radiation Exposure from X Rays, 559 Good Practice, 564 X-Ray Shielding, 566 Shielding Calculations, 566

11 xvi CONTENTS Summary, 572 Problems, 574 Appendix A Contents of Nature and Selected Particle Masses 575 Appendix В Atomic Masses and Binding Energies for Selected Isotopes of the Elements 577 Appendix С Electron Binding Energies 586 Appendix D Radioactive Transformation Data 594 Appendix E Fission Product Chains 678 Appendix F Neutron-Particle Emission Cross-Section Data 699 Answers to Selected Problems 701 Index 707