Active Interrogation in Nuclear Security (eBook)

Igor Jovanovic is a Professor of Nuclear Engineering and Radiological Sciences at the University of Michigan and has previously also taught at Penn State University and Purdue University. He received his Ph.D. from University of California, Berkeley and worked as physicist at Lawrence Livermore National Laboratory. Dr. Jovanovic has made numerous contributions to the science and technology of radiation detection, as well as the radiation sources for use in active interrogation in nuclear security. He has taught numerous undergraduate and graduate courses in areas that include radiation detection, nuclear physics, and nuclear security. At University of Michigan Dr. Jovanovic is the director of Neutron Science Laboratory and is also associated with the Center for Ultrafast Optical Science.   Anna Erickson is an Assistant Professor in the Nuclear and Radiological Engineering Program of the G.W. Woodruff School of Mechanical Engineering at Georgia Institute of Technology. Previously, she was a postdoctoral researcher in the Advanced Detectors Group at Lawrence Livermore National Laboratory. Dr. Erickson received her PhD from Massachusetts Institute of Technology with a focus on radiation detection for active interrogation applications. Her research interests focus on nuclear non-proliferation including antineutrino analysis and non-traditional detector design and characterization. She teaches courses in advanced experimental detection for reactor and nuclear nonproliferation applications, radiation dosimetry and fast reactor analysis.

Preface 7
Contents 9
Contributors 11
1 Introduction 12
1.1 Historical Perspective on Nuclear Security 12
1.2 The Problem of Nuclear Terrorism 15
1.3 The Role of Policy in Nuclear Security and Arms Control 19
1.4 Institutionalized Efforts to Curb Nuclear Terrorism 21
1.5 Overview of the Active Interrogation Method 24
1.6 Synopsis of the Book 26
References 27
2 Overview of Signatures and Measurement Needs 29
2.1 Overview of Signatures of SNM 29
2.2 Prompt Signatures 31
2.2.1 Prompt Gamma Rays 32
2.2.2 Prompt Neutrons 33
2.3 Delayed Signatures 34
2.3.1 Delayed Neutrons 34
2.3.2 Delayed Gamma Rays 36
2.4 Considerations of Background Radiation 36
References 39
3 Features and Limitations of Passive Measurements 40
3.1 Magnitude of Passive Signatures and Backgrounds 40
3.1.1 Characteristic Emissions from SNM 41
3.1.2 Naturally Occurring Radionuclide Background 42
3.1.3 Cosmic Background 44
3.1.4 Radionuclide Background Related to Human Activities 46
3.2 Principles of Passive Measurements 49
3.2.1 Gross Radiation Counting 51
3.2.2 Gamma-Ray and Neutron Spectroscopy 52
3.2.3 Fusion of Multiple Measurement Modalities 54
3.3 Technology for Passive Measurements 56
3.3.1 Gamma-Ray and Fast Neutron Imaging 56
3.3.2 Radiation Portal Monitors 60
3.4 Limitations of Passive Measurements 61
3.4.1 Example of Passive Detection by Gross Radiation Counting 61
3.4.2 Signal to Noise Ratio Scaling 62
3.4.3 Relative Importance of Detector Efficiency, Resolution, and Background 63
References 65
4 Foundations of Active Interrogation 67
4.1 Introduction to the Active Interrogation Technique 67
4.2 Impact of Active Measurements on Detectability 69
4.2.1 Passive Techniques and Their Limits 69
4.2.2 Improved Detectability by Active Interrogation 71
4.3 Technology for Active Measurements 72
4.3.1 Induced Fission 72
4.3.1.1 Fission Signatures 72
4.3.1.2 Interrogation Sources 74
4.3.1.3 Techniques Involving Detection of Delayed Radiation 76
4.3.1.4 Techniques Involving Detection of Prompt Radiation 77
4.3.2 Nuclear Resonance Fluorescence 78
4.3.2.1 NRF Cross Section 81
4.3.2.2 Sources in Nuclear Resonance Fluorescence Experiments 87
4.3.2.3 Detection Schemes 90
4.3.3 Background in Active Interrogation 92
4.3.3.1 Ambient Background 93
4.4 Modeling and Simulation for Active Measurements 95
4.4.1 Simulation of the Induced Fission Process and Its Signatures 95
4.4.2 Simulation of Nuclear Resonance Fluorescence 96
4.5 Limitations of Active Measurements 97
4.5.1 Interrogation Sources 97
4.5.2 Shielding and Attenuation of Signatures 98
4.5.3 Radiation Detection Techniques for Active Interrogation 99
References 100
5 Active Interrogation Probe Technologies 104
5.1 General Characteristics of AI Probe Technologies 104
5.1.1 Maturity of Applicable Accelerator Technology 106
5.1.2 Emerging Accelerator Technologies 107
5.1.2.1 Direct Laser Acceleration 107
5.1.2.2 Inverse Compton Scattering X-ray Sources 108
5.2 Linear Accelerators and Bremsstrahlung Sources 109
5.2.1 Components of a Linear Accelerator 109
5.2.2 Electron and Ion Sources 110
5.2.3 Low-Energy Injectors 112
5.2.4 Electron Linac Technology 113
5.2.5 Radiofrequency Systems 116
5.2.5.1 The Magnetron 116
5.2.5.2 The Klystron 117
5.2.6 Special Relativity, Particle Dynamics, and Accelerating Beams 118
5.2.7 Accelerating Structures 122
5.2.7.1 Traveling Wave vs Standing Wave Operation 125
5.2.7.2 Phase Space and Beam Emittance 126
5.2.7.3 Quality Factor and Shunt Impedance 127
5.2.8 Beam Focusing 128
5.2.8.1 Space Charge Forces 128
5.2.8.2 Radiofrequency Defocusing Forces 129
5.2.8.3 Solenoidal Magnet Focusing 129
5.2.8.4 Quadrupole Focusing in a Linac 130
5.2.9 Induction Accelerators 131
5.2.10 KLYNAC 133
5.2.11 Frontier Accelerators 134
5.2.12 Generating Bremsstrahlung X Rays 134
5.2.13 Bremsstrahlung Based Photoneutron Production 135
5.3 Ion Accelerators and Low-Energy Nuclear Reactions 136
5.3.1 Neutron Generators 136
5.3.2 Compact Cyclotrons 137
5.3.3 The Radiofrequency Quadrupole (RFQ) Accelerator 140
5.3.4 Measuring Low-Energy Nuclear Reaction Signatures 142
5.3.5 High-Energy Systems and Large Standoff AI 144
5.4 Laser-Based Radiation Sources 145
5.4.1 Introduction: Laser Driven Sources for AI 145
5.4.2 Monoenergetic, Narrow-Divergence Photon Beams Using Laser Scattering 147
5.4.3 Laser-Plasma Acceleration for Compact Monoenergetic Photon Sources 151
5.4.4 Laser-Driven Neutron Sources 156
5.4.5 Conclusion 157
References 158
6 Detectors in Active Interrogation 164
6.1 General Characteristics of the Detectors for AI 164
6.2 Gaseous Detectors 166
6.2.1 Interaction Mechanisms in Gaseous Detectors 166
6.2.2 3He Gaseous Tubes 167
6.2.3 10B-Based Gaseous Detectors 168
6.2.4 Applications of Gaseous Detectors to Fission Signatures 169
6.2.4.1 Prompt and Delayed Neutron Counting (with Moderation) 170
6.2.4.2 Multiplicity 171
6.2.4.3 Differential Die-Away Self-Interrogation (DDSI) 171
6.3 Scintillation Detectors 171
6.3.1 Scintillation Mechanism in Organic and Inorganic Scintillators 172
6.3.1.1 Inorganic Scintillators 173
6.3.1.2 Organic Scintillators 174
6.3.2 Gamma Detection with Scintillators 175
6.3.3 Fast Neutron Detection with Organic Scintillators 175
6.4 Hybrid and Other Detector Types 177
6.4.1 4He Detectors 177
6.4.2 Threshold Activated Detectors 178
6.4.3 Superheated Emulsions and Bubble Detectors 178
6.4.3.1 Neutron Interaction Mechanisms 179
6.4.3.2 Application of Superheated Emulsions for the Detection of Special Nuclear Materials in AI 180
6.4.4 Interaction Mechanisms in Hybrid Detectors 180
6.4.5 Cs2LiYCl6 (CLYC) 180
6.4.6 Capture-Gated Organic Scintillators 181
6.4.7 Heterogeneous Composite Scintillators 183
6.4.8 Cherenkov Detectors 184
6.4.9 Imaging with Arrays of Cherenkov Detectors 187
6.5 Applications to Fission Signatures 188
6.5.1 Photofission Time of Flight 188
6.5.2 Detection of Delayed Neutron Emission Profile 190
6.5.3 Neutron Interrogation with Imaging 192
6.5.4 Neutron Multiplicity Counting 195
References 196
7 Data Acquisition and Processing Systems 203
7.1 Introduction 203
7.1.1 Gamma-Ray and Neutron Detection 204
7.1.2 Overview of Data Acquisition 204
7.2 Analog Data Acquisition 205
7.2.1 Detection Mode 206
7.2.2 The Data Acquisition Chain 207
7.2.3 Charge Integration and Pulse Shaping 207
7.2.4 Peak Sensing Analog-to-Digital Conversion 208
7.2.5 Charge-to-Digital Conversion 209
7.2.6 Counter-Timer/Scaler 210
7.2.7 Multichannel Analyzer 211
7.2.8 Multichannel Scaler (MCS) 212
7.2.9 Triggering 213
7.2.10 Dead Time 215
7.2.11 Analog Pulse Shape Discrimination 216
7.3 Digital Data Acquisition 222
7.3.1 Advantages of Digital DAQ 222
7.3.2 Digital Sampling 223
7.3.3 The Digitizer 224
7.3.4 Triggering 226
7.3.5 Pulse Height Analysis 227
7.3.6 Charge Integration 228
7.3.7 Digital Pulse Shape Discrimination 229
7.3.8 Time Stamp List Mode 230
7.3.9 Multichannel DAQ Systems 232
7.3.9.1 Channel-to-Channel Synchronization 232
7.3.9.2 Synchronization of Two or More Digitizer Boards 233
7.4 Data Processing and Storage 235
7.4.1 Analog Systems 235
7.4.2 Digital Systems 237
7.4.3 Data Formats and Data Storage 240
7.4.4 Real-Time Versus Offline Processing 240
7.4.5 Data Reduction 242
7.5 AI Data Acquisition Challenges 246
7.5.1 Event Rate 246
7.5.2 Pulse Pile-Up 247
7.5.2.1 Pile-Up in Analog DAQ Systems 247
7.5.2.2 Pile-Up in Digital DAQ Systems 248
7.5.3 Baseline Estimation 249
7.5.4 Time Development of Active Signatures 250
7.5.5 Pulsed Interrogation 251
References 252
8 Data Interpretation and Algorithms 255
8.1 Introduction 255
8.2 Planar and Tomographic Imaging Systems 257
8.2.1 X-ray Radiography/Computed Tomography 258
8.2.2 Gamma-Ray Radiography 260
8.2.3 Neutron Radiography 260
8.2.4 Muon Tomography 261
8.2.4.1 Muon Scattering 261
8.2.4.2 Point of Closest Approach (POCA) Reconstruction 263
8.3 Principal Component Analysis and Related Methods 264
8.3.1 Principal Component Analysis 265
8.3.2 Data Smoothing 267
8.3.3 Least Squares Curve Fitting 269
8.3.4 Maximum Likelihood 270
8.3.5 Artificial Neural Networks 272
8.4 Signature Unfolding Techniques 274
8.4.1 Elements of Signature Unfolding 274
8.4.2 Least Squares Full Spectrum Unfolding 275
8.4.3 Chi-Square Full Spectrum Unfolding 277
8.4.4 Peak Driven Spectrum Unfolding 277
8.5 Advanced Algorithms for Distributed Detection Systems 278
8.5.1 Elements of Sensor Networks 278
8.5.2 Bayesian Methods in Distributed Detection 279
8.5.3 Hierarchical Source Model Detection 280
8.5.4 Other Distributed Detection Methods 281
8.6 Conclusion 282
References 282
9 Examples of Active Interrogation Systems 285
9.1 Introduction and Range of Application 285
9.2 Nuclear Carwash 286
9.2.1 Neutron Source Design 288
9.2.1.1 T(d,n) Neutron Source at En=14MeV 289
9.2.1.2 D(d,n) Neutron Source at En=7MeV 289
9.2.1.3 Interrogation Source Pulse Structure 291
9.2.2 Detector Design 293
9.2.2.1 Liquid Scintillators 293
9.2.2.2 Solid Plastic Scintillators 294
9.2.3 Threat Configurations of Interest 295
9.2.3.1 Fissionable Target Characteristics 295
9.2.3.2 Cargo Characteristics 296
9.2.4 Predicted Fission Rates 296
9.2.5 Interferences 297
9.2.6 Test Results 299
9.2.6.1 Detection Probability for Small SNM Targets 299
9.2.6.2 Extrapolation to Performance with Goal Quantities of SNM 301
9.2.6.3 Concept of Operations for Field Implementation 302
9.2.6.4 Isotopic Identification 303
9.2.7 Efficacy and Limitations 304
9.3 Rapiscan's Pulsed Fast Neutron Analysis 304
9.4 EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) 305
9.5 Photon Interrogation Prototype by Passport Systems 306
9.6 Inverse Compton Scattering Prototype Systems 307
References 310
10 Radiation Dose in Active Interrogation 313
10.1 Introduction 313
10.2 Radiation of Concern in Active Interrogation 314
10.3 Regulations of Dose Exposure 315
10.3.1 ICRU/ICRP/NCRP Recommendations 316
10.3.1.1 NCRP Recommendations 317
10.3.1.2 ICRP Recommendations 317
10.3.2 Code of Federal Regulations 318
10.3.3 Standards 320
10.4 External Dose Assessment 322
10.4.1 Fundamental Dose Quantities 322
10.4.2 Relating Physical, Operation, and Protection Quantities Using Dose Coefficients 323
10.4.3 Protection Quantities 324
10.4.3.1 Equivalent and Effective Dose 324
10.4.3.2 Radiation-Weighting Factors 325
10.4.3.3 Tissue-Weighting Factor 327
10.4.4 Operational Quantities 327
10.4.4.1 Area Monitoring 328
10.4.4.2 Personnel Monitoring 328
10.4.5 Fluence-to-Dose Coefficients 329
10.5 Methods of Dose Reduction in Active Interrogation 331
References 335
11 Active Interrogation Testing Standards 337
11.1 Introduction 338
11.2 Specific AI Systems 339
11.2.1 Targets 340
11.3 Testing of AI Systems 341
11.4 Existing Related Standards 342
11.4.1 ANSI N42.41 342
11.4.2 ANSI N42.46 343
11.4.3 IEC 62523 344
11.5 Development of an AI Technical Capability Standard 344
11.6 Modeling of AI Modalities 346
11.6.1 Differential Die-Away Models 346
11.6.2 Photofission Models 348
11.6.3 Conclusion 350
References 350
12 Conclusion 352
Glossary 356
Index 362