Contents Preface ........................................................................................ iii Executive Summary ................................................................ 1 1. Introduction ......................................................................... 5 1.1 Purpose ............................................................................. 6 1.2 Scope ................................................................................. 6 1.3 Particle Accelerator Safety ............................................. 7 1.4 Regulatory and Advisory Agencies ................................ 7 1.4.1 Federal Regulation ............................................... 8 1.4.2 State Regulation ................................................... 8 1.4.3 Local (County, City) Regulation .......................... 9 1.4.4 Advisory Organizations ........................................ 9 1.4.4.1 International Agencies ............................ 9 1.4.4.2 National Organizations ........................... 10 1.5 Radiological Protection Standards ................................. 10 2. Particle Accelerators and Accelerator Facilities ........ 12 2.1 Particle Accelerators—Definitions ............................... 12 2.2 Classification of Particle Accelerators .......................... 12 2.3 Brief Historical Review ................................................. 13 2.4 Accelerator Radiation .................................................... 17 2.5 Ion and Electron Sources .............................................. 18 2.6 Particle Accelerating Schemes ...................................... 19 2.7 Beam Delivery Systems ................................................ 23 2.8 Beam Stops .................................................................... 24 2.9 Auxiliary Systems .......................................................... 25 2.9.1 High-Voltage and Microwave Power Supplies .. 25 2.9.2 Cooling Systems .................................................. 27 2.9.3 Vacuum Systems ................................................. 27 2.10 Summary of the General Specifications and Parameters of Accelerators ........................................... 28 2.11 Applications of Accelerators ......................................... 28 2.12 Future Developments in Accelerators ......................... 29 2.13 Siting and Layout .......................................................... 29 v vi / CONTENTS 3. Sources of Ionizing Radiation from Accelerators ...... 33 3.1 Introduction ..................................................................... 33 3.2 General Considerations ................................................... 35 3.3 Radiation Production at Electron Accelerators ............. 39 3.3.1 General .................................................................. 39 3.3.2 Electron Beams ..................................................... 40 3.3.3 Photon Fields ........................................................ 41 3.3.3.1 External Bremsstrahlung ....................... 41 3.3.3.2 High Energies .......................................... 49 3.3.4 Neutron Production .............................................. 59 3.3.5 Muon Production ................................................... 62 3.3.6 Electromagnetic Cascade ..................................... 65 3.4 Radiation Protection at Proton Accelerators ................. 70 3.4.1 General .................................................................. 70 3.4.2 Proton Beams ........................................................ 73 3.4.3 Neutron Yields ...................................................... 73 3.4.3.1 Neutron Production at Low Energies (E Ͻ 200 MeV) ......................................... 74 3.4.3.2 Neutron Production at Intermediate Energies (200 MeV Յ E Յ 1 GeV) ......... 80 3.4.3.3 Neutron Production at High Energies (E Ն 1 GeV) ............................................. 80 3.4.4 Muon Production ................................................... 98 3.4.5 Hadronic (Nuclear) Cascade ................................ 101 3.4.5.1 General ..................................................... 101 3.4.5.2 Qualitative Description of the Hadronic Cascade .................................................... 102 3.4.6 Radiation Environment ........................................ 103 3.4.6.1 Neutron Energy Spectra ......................... 105 3.4.6.2 Spectra Outside Accelerator Shielding .. 108 3.5 Radiation Production at Accelerators of Positive Ions . 112 3.5.1 General .................................................................. 112 3.5.2 Light Ions .............................................................. 113 3.5.3 Heavy Ions ............................................................. 118 3.6 Radioactivation at Accelerators ...................................... 132 3.6.1 General .................................................................. 132 3.6.2 Activation by Low-Energy Particles .................... 133 3.6.3 Activation by High-Energy Particles ................... 136 4. Radiation Shielding at Accelerators .............................. 146 4.1 Introduction ..................................................................... 146 4.2 Theory of Radiation Transport ....................................... 148 4.2.1 Introduction ........................................................... 148 4.2.1.1 Construct of the Boltzmann Equation ... 150 CONTENTS / vii 4.2.1.2 Approximate Solutions of the Boltzmann Equation ............................... 152 4.2.2 Computer Codes for Shielding Calculations ....... 154 4.2.2.1 The Monte-Carlo Method ...................... 154 4.2.2.2 MARS ..................................................... 156 4.2.2.3 EGS4 Code System ................................ 156 4.2.2.4 FLUKA ................................................... 157 4.2.2.5 NMTC/HETC ......................................... 157 4.2.2.6 MCNP ..................................................... 158 4.2.2.7 Integrated Tiger Series ......................... 158 4.2.2.8 MORSE-CGA ......................................... 158 4.2.2.9 TOMCAT ................................................ 159 4.2.2.10 MUSTOP ................................................ 159 4.2.2.11 MUCARLO ............................................. 159 4.2.2.12 MUON89 ................................................ 160 4.2.2.13 SHIELD11 ............................................. 160 4.2.2.14 PHOTON ................................................ 160 4.2.2.15 STAC8 .................................................... 160 4.2.2.16 SKYSHINE-KSU ................................... 161 4.2.2.17 SKYSHINE III ....................................... 161 4.2.2.18 TRIPOLI ................................................ 161 4.3 Practical Shield Design ................................................... 161 4.3.1 General .................................................................. 161 4.3.2 Photon Transmission ............................................ 163 4.3.3 Neutron Transmission .......................................... 167 4.3.4 Scattering—Albedo ............................................... 178 4.3.5 Scatter Paths ......................................................... 179 4.4 Radiation Goals and Area Occupancy and Use Factors .............................................................................. 183 4.5 Determination and Specification of the Beam-Loss Terms ............................................................................... 185 4.6 Shielding of Electron Accelerators in the Energy Range from 1 to 100 MeV ............................................... 188 4.6.1 Source Term for Simple Accelerators .................. 189 4.6.1.1 Workload .................................................. 190 4.6.1.2 Primary and Secondary Barriers and the Orientation (Use) Factor .................. 191 4.6.1.3 Occupancy Factor .................................... 191 4.6.2 Primary Barriers for Photons .............................. 191 4.6.3 Secondary Barriers for Photons ........................... 194 4.6.3.1 Leakage Radiation .................................. 194 4.6.3.2 Scattered Photons ................................... 194 4.6.4 Shielding Against Neutrons ................................. 195 viii / CONTENTS 4.7 Shielding of Large Electron Accelerator Facilities at Higher Energies (E Ͼ 100 MeV) .................................... 197 4.7.1 Review of Source Terms ....................................... 197 4.7.1.1 Electromagnetic Cascade ........................ 197 4.7.1.2 Neutron Source Terms and Attenuation .............................................. 198 4.7.2 Design of High-Intensity Beam Stops and Walls ...................................................................... 202 4.7.3 Distributed Loss Issues ........................................ 204 4.7.3.1 Synchrotron-Radiation Facilities ........... 205 4.7.3.2 Photon Shielding Experiments ............... 208 4.7.3.3 Generalized Loss Model .......................... 212 4.8 Proton Accelerators—Transverse Shielding .................. 213 4.8.1 Particle Yields from the Proton-Nucleus Interaction ............................................................. 214 4.8.2 Proton Energies Below 3 GeV .............................. 216 4.8.3 Proton Energies Above 3 GeV—The Moyer Model ..................................................................... 218 4.8.3.1 Introduction ............................................. 218 4.8.3.2 Generalized Formulation