Table Of ContentNCRP Report No. 144
Radiation Protection for
Particle Accelerator Facilities
Recommendations of the
NATIONAL COUNCIL ON RADIATION
PROTECTION AND MEASUREMENTS
Issued December 31, 2003
Revised March 4, 2005
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NationalCouncilonRadiationProtectionandMeasurements.
Radiationprotectionforparticleacceleratorfacilities:recommendationsofthe
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p.cm.--(NCRPreport;no.144)
‘‘IssuedDecember2003.’’
Rev.ed.of:Radiationprotectiondesignguidelinesfor0.1-100MeVparticle
acceleratorfacilities.1977.
Includesbibliographicalreferencesandindex.
ISBN0-929600-77-0
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(Radiation)3.Radiation--Safetymeasures.I.NationalCouncilonRadiation
ProtectionandMeasurements.Radiationprotectiondesignguidelinesfor0.1-
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Preface
TheNationalCouncilonRadiationProtectionandMeasurements
(NCRP) Report No. 51, Radiation Protection Design Guidelines for
0.1–100 MeV Particle Accelerator Facilities, was published in 1977.
Sincethen,NCRPhasissuedtworeportsthatdiscussspecificradio-
logical protection issues at particle accelerators: NCRP Report
No.72, Radiation Protection and Measurements for Low-Voltage
NeutronGeneratorsandNCRPReportNo.79,NeutronContamina-
tionfromMedicalElectronAccelerators.NCRPReportNo.88,Radia-
tionAlarmsandAccessControlSystemsisalsoofinterestforthose
who operate accelerators, but until now, there has been no recent
attempttoreaddresstheentireissueofacceleratorradiologicalpro-
tection in a single report.
Inlightofthesignificantexperiencewiththeoperationanddesign
ofacceleratorfacilitiesandtheincreasedunderstandingofaccelera-
torradiationenvironmentsobtainedoverthepast25y,itwasconsid-
ered appropriate to revise NCRP Report No. 51 while maintaining
its extremely valuable practical utility.
Accordingly,ScientificCommittee46-8wasestablishedandgiven
the general charge to ‘‘review and update Report No. 51 to include:
new shielding data, extension of the energy range up to the giga-
electron volt region, skyshine radiation, transmission of radiation
through ducts and labyrinths, induced radioactivity, and envi-
ronmental considerations such as radioactive airborne and liquid
effluents.’’
Some of the material in this Report is historical and refers to
studiesperformedmany decadesago.Insuch cases,thequantities,
unitsandreferencesasformattedareretainedintheiroriginalform.
This publication was made possible, in part, by Grant Number
R24 CA74296-05 from the National Cancer Institute (NCI) and its
contentsarethesoleresponsibilityoftheNCRPanddonotnecessar-
ily represent the official views of the NCI, National Institutes of
Health. Additionally, publication of this Report was supported in
part by the Idaho Accelerator Center, a research center of Idaho
State University, Pocatello, Idaho.
Those who served on Scientific Committee 46-8 were:
iii
iv / PREFACE
Ralph H. Thomas, Chairman
University of California
Members
W. Robert Casey Lester A. Slaback, Jr.
Brookhaven National Laboratory National Institute of
Upton, New York Standards and Technology
Gaithersburg, Maryland
J. Donald Cossairt
Fermi National Accelerator Geoffrey B. Stapleton
Laboratory Thomas Jefferson National
Batavia, Illinois Accelerator Facility
Newport News, Virginia
Keran O’Brien
Northern Arizona State William P. Swanson*
University Lawrence Berkeley National
Flagstaff, Arizona Laboratory
Berkeley, California
Norman Rohrig
National Engineering and
Environmental Laboratory
Idaho Falls, Idaho
Consultants
Lutz E. Moritz Vaclav Vylet
TRIUMF, National Laboratory Duke University Medical
forParticle and Nuclear Center
Physics Durham, North Carolina
Vancouver, Canada
Advisor
David R. Perry
Rutherford Appleton Laboratory
Chilton, Oxon, United Kingdom
NCRP Secretariat
Constantine J. Maletskos, Consultant (1998–2003)
Thomas M. Koval, Senior Staff Scientist (1993–1998)
James A. Spahn, Senior Staff Scientist (1986–1993)
Cindy L. O’Brien, Managing Editor
The Council wishes to express its appreciation to the Committee
members for the time and effort devoted to the preparation of this
Report.
Thomas S. Tenforde
President
*deceased
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 (cid:1) 200 MeV) ......................................... 74
3.4.3.2 Neutron Production at Intermediate
Energies (200 MeV (cid:1) E (cid:1)1 GeV) ......... 80
3.4.3.3 Neutron Production at High Energies
(E (cid:2) 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 (cid:2) 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 ProducedDirectlyinAir .... 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
