Radiation Protection for Particle Accelerator Facilities

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 of the Moyer Model ...... 219 4.8.3.3 Determination of the Moyer Model Parameters ...... 222 4.8.3.3.1 Attenuation Parameter ...... 222 4.8.3.3.2 Angular-Relaxation Parameter ...... 223 4.8.3.3.3 Source-Strength Parameter .... 224 4.8.3.4 Practical Examples ...... 226 4.8.3.4.1 Point Source ...... 226 4.8.3.4.2 Inﬁnite Uniform Line Source . 227 4.8.3.4.3 Finite Uniform Line Source .... 228 4.8.3.5 Conclusions and Limitations of the Moyer Model ...... 229 4.9 Proton Accelerators—Forward Shielding ...... 232 4.9.1 Proton Energies Below 3 GeV ...... 232 4.9.2 Hadronic Cascade Above 3 GeV ...... 232 4.9.3 Muon Shielding ...... 239 4.10 Shielding Materials ...... 242 4.10.1 Earth ...... 243 4.10.2 Concrete ...... 244 4.10.3 Other Hydrogenous Materials ...... 246 4.10.4 Steel ...... 249 4.10.5 Special Materials ...... 252 4.10.5.1 Materials of High Atomic Number .... 252 4.10.5.2 Materials of Low Atomic Number ..... 254 CONTENTS /ix

4.10.6 Special Considerations ...... 254 4.11 Tunnels, Labyrinths and Ducts ...... 255 4.11.1 Introduction ...... 255 4.11.2 Design Example for Photons Using Albedos ... 257 4.11.3 Straight Penetrations—Neutrons and Photons ...... 258 4.11.4 Transmission of Neutrons Through Labyrinths ...... 259 4.11.5 Transmission of Neutrons Through Curved Tunnels ...... 266 4.11.6 Door Design ...... 267

5. Techniques of Radiation Measurement at Particle Accelerators ...... 269 5.1 Introduction to Radiation Dosimetry at Particle Accelerators ...... 269 5.2 Special Consideration of the Techniques of Radiation Dosimetry in Accelerator Environments ...... 272 5.3 Application of ‘‘Conventional Techniques’’ to Measurements in Accelerator-Radiation Environments .. 273 5.3.1 Introduction ...... 273 5.3.2 Ionization Chambers ...... 273 5.3.3 Geiger-Mueller Counters ...... 275 5.3.4 Thermoluminescence Dosimeters ...... 276 5.4 Neutron Dosimetry at Particle Accelerators ...... 276 5.4.1 Introduction ...... 276 5.4.2 Passive Detectors Used for Neutron Dosimetry . 277 5.4.2.1 Thermoluminescence Dosimeters ...... 277 5.4.2.2 Nuclear Emulsions ...... 279 5.4.2.3 Activation Detectors ...... 280 5.4.2.4 Threshold Detectors ...... 281 5.4.2.5 Moderated Detectors ...... 285 5.4.2.6 Track-Etch Detectors ...... 287 5.4.2.7 Bubble Detectors ...... 289 5.4.3 Active Detectors Used for Neutron Dosimetry ... 291 5.4.3.1 Moderated Detectors ...... 291 5.4.3.2 Fission Counters ...... 297 5.4.4 Neutron Spectrometry ...... 299 5.4.4.1 Bonner Spheres ...... 299 5.4.4.2 Spectrum-Unfolding Methods ...... 301 5.4.4.3 Proton-Recoil Counters ...... 303 5.5 Mixed-Field Dosimetry ...... 304 5.5.1 Introduction ...... 304 5.5.2 Recombination Chambers ...... 305 x/CONTENTS

5.5.3 Tissue-Equivalent Proportional Counters and Linear Energy Transfer Spectrometry ...... 307 5.5.4 Other Techniques for Direct Assessment of Quality Factor and Dose Equivalent ...... 310 5.5.5 Universal Dose-Equivalent Instruments ...... 310 5.6 Environmental Monitoring ...... 311 5.6.1 Introduction ...... 311 5.6.2 Neutrons ...... 312 5.6.2.1 Active Moderated Counters ...... 312 5.6.2.2 Thermoluminescence Dosimeters ...... 312 5.6.3 Photons ...... 313 5.6.3.1 Introduction ...... 313 5.6.3.2 Ionization Chambers ...... 313 5.6.3.3 Geiger-Mueller Counters ...... 314 5.6.3.4 Thermoluminescence Dosimeters ...... 315 5.6.4 Muons ...... 315 5.6.4.1 Introduction ...... 315 5.6.4.2 Ionization Chambers ...... 315 5.6.4.3 Counter Telescopes ...... 316 5.6.4.4 Other Techniques ...... 316 5.6.5 Monitoring of Radioactive Emissions in Air ...... 317 5.6.5.1 Radioactive Gas Monitors ...... 317 5.6.5.2 Radioactive Aerosols ...... 319 5.7 Epilogue ...... 319

6. Environmental Radiological Aspects of Particle Accelerators ...... 320 6.1 Introduction ...... 320 6.2 Skyshine ...... 321 6.2.1 General Considerations ...... 321 6.2.2 Neutron Skyshine ...... 323 6.2.3 Photon Skyshine ...... 331 6.2.4 Comparisons of Skyshine Calculations ...... 334 6.2.4.1 Neutron Skyshine ...... 334 6.2.4.2 Photon Skyshine ...... 336 6.2.5 Collective Exposure to the Population ...... 336 6.3 Induced Radioactivity of Environmental Concern Produced by Accelerators ...... 337 6.3.1 Radionuclides Produced in Air ...... 338 6.3.1.1 Radionuclides Produced Directly in Air .... 338 6.3.1.2 Photoactivation ...... 340 6.3.1.3 Thermal-Neutron Capture ...... 341 6.3.1.4 Activation by High-Energy Neutrons .... 343 6.3.1.5 Radionuclides Produced in Dust ...... 346 CONTENTS /xi

6.3.1.6 Gaseous Radionuclides Released from Irradiated Water ...... 347 6.3.1.7 Environmental Impact of Airborne Radionuclides ...... 347 6.3.1.8 Collective Exposure to the Population from Radioactivity in the Air ...... 347 6.3.2 Radioactivity Produced in Earth Shielding and Groundwater ...... 348 6.3.2.1 Radionuclides Identiﬁed in Earth and Water ...... 349 6.3.2.2 Magnitude of Radionuclide Concentrations ...... 349 6.3.2.3 Environmental Impact and Exposure to Members of the Public ...... 352 6.3.2.3.1 Ingestion ...... 353 6.3.2.3.2 Drinking Contaminated Water ...... 353 6.3.2.3.3 Inhalation ...... 355 6.3.3 Transfer of Radioactivity at Accelerators ...... 355 6.4 Radiolysis in Water and Air ...... 357

7. Operational Radiation Safety Program for Accelerators ...... 360 7.1 Introduction ...... 360 7.2 Program Elements ...... 360 7.2.1 Organization ...... 360 7.2.2 Facility Design ...... 362 7.2.2.1 Access and Egress ...... 362 7.2.2.2 Radioactivation ...... 363 7.2.2.3 Ventilation ...... 364 7.2.2.4 Facility and Equipment Complexity ...... 365 7.2.3 Warning and Personnel Security ...... 365 7.2.4 Monitoring and Control ...... 366 7.2.4.1 Control of Radioactive Material ...... 366 7.2.4.2 Radioactive Waste Management ...... 367 7.2.4.3 Contamination Control ...... 369 7.2.4.4 Surface Contamination Standards ...... 369 7.2.4.5 Guidance for Clearance ...... 371 7.2.5 Training ...... 371

Appendix A. Importance Functions for Neutrons and Photons ...... 373 Appendix B. Kinematic Relations ...... 390 xii / CONTENTS

Glossary ...... 405 References ...... 417 The NCRP ...... 470 NCRP Publications ...... 479 Index ...... 489