Understanding Neutron Radiography

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2) Resonance Neutrons Another approach for neutrons in this energy range involves the use of a neutron pulse and a timeof- flight scheme to permit detection of neutrons at a particular energy. Neutron pulses have been provided by reactors and accelerators and detected by a variety of methods. Time-gated detectors such as position sensitive proportional counters, scintillators with time-gated image intensifiers, and photomultiplier tubes have been used. Charlie Chong/ Fion Zhang
3) Fast Neutrons The other energy range of interest for neutron radiography is fast neutrons, energies above 10 keV. Neutron cross sections at these energies tend to be low so that detectors generally require greater neutron exposures than do thermal neutron radiographs. The detection approaches are similar to those used for thermal neutrons, but different conversion materials are normally used. Direct exposure has been obtained with fluorescent screens made for X-radiography; the screens are combined with light-sensitive X-ray films. The X-ray phosphor screens work primarily because neutron interactions with hydrogen, in the plastic binder or in the plastic or paper backing, yield protons that stimulate light from the phosphor. Fast X-ray phosphor screens and film provide neutron radiographs of Me V energy neutrons with total exposures on the order of 10 7 to 10 8 n/cm 2 . X-ray film without screens also responds to fast neutrons but requires exposures of 4 X 10 8 n/cm 2 to more than 10 9 n/cm 2 . Charlie Chong/ Fion Zhang
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Understanding Neutron Radiography R
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Military Applications Charlie Chong
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Military Applications Charlie Chong
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Charlie Chong/ Fion Zhang
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3. Techniques/Calibrations • Bloc
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Greek Alphabet Charlie Chong/ Fion
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Reading I SECTION 12-Neutron Radiog
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The text includes helpful discussio
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PART 1 PRINCIPLES OF NEUTRON RADIOG
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Advantages lt is the differences be
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For photons: I = I o e -μx t For N
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Figure 1 provides a comparison of t
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FIGURE 1. Mass Attenuation Coeffici
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Neutron Radiography There is a mark
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hydrogen/boron beryllium/ water cad
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Radioactive Objects An additional a
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lmaging Neutron radiographs usually
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PART 2 EQUIPMENT AND PROCEDURES Cha
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■ Fission When a neutron enters a
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U-235 and Pu-239. Charlie Chong/ Fi
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U-235 and Pu-239. Charlie Chong/ Fi
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Alpha Particles Charlie Chong/ Fion
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Alpha Particles Charlie Chong/ Fion
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Photoneutrons The necessary energy
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Radioactive Decay Charlie Chong/ Fi
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2.2 Neutron Energies As with all pe
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Thermal Neutrons “Produced by slo
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There are applications in which the
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FIGURE 2. Neutron Radiographs of Hi
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Fast Neutrons “Fast neutrons prov
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Moderators A complete description o
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TABLE 2. Slowing Down Properties of
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TABLE 3. Some Thermallzatlon Factor
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2.4 Neutron Collimation Beam extrac
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FIGURE 4. Neutron Collimators: (a)
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Divergent Collimators The primary a
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As in X- radiography, the geometric
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Geometric Unsharpness (neutron radi
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I ≈ Ф 16(L/D) 2 for my ASNT exam
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Backscatter It is good practice to
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TABLE 4. Average Characteristics of
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Nuclear Reactor The majority of pra
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Accelerators Numerous nuclear react
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(d.T) Source A reaction that has re
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Nuclear physicist at the Idaho Nati
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The gas pressure in the ion source
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(X.n) Sources Electron accelerators
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The threshold energy for photoneutr
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Bremsstrahlung , from bremsen "to b
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Characteristic x-rays are emitted f
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The frequencies of the characterist
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"Bremsstrahlung" means "braking rad
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Bohr’s Model Charlie Chong/ Fion
Page 115 and 116: Bohr’s Model Charlie Chong/ Fion
Page 117 and 118: Electron Orbital Charlie Chong/ Fio
Page 119 and 120: Plasma Sources Radiography with fas
Page 121 and 122: TABLE 5. Some Radloaalve Sources fo
Page 123 and 124: TABLE 5. Some Radloaalve Sources fo
Page 125 and 126: ■ (γ,n) Sources The (γ,n) react
Page 127 and 128: ■ Cf-252 On the basis of technica
Page 129 and 130: Subcritical Flux Boosters By defint
Page 131 and 132: Neutron Intensity Very few, if any,
Page 133 and 134: Beam Tailoring A neutron beam extra
Page 135 and 136: Foil Filters Some materials have sp
Page 137 and 138: ■ Window Filters For some element
Page 139 and 140: Fig.14-5 The neutron yield strongly
Page 141 and 142: ■ Time of Flight It is possible t
Page 143 and 144: 2.7 Neutron Image Detectors All the
Page 145 and 146: FIGURE 5. Diagrams for Neutron Radi
Page 147 and 148: TABLE 6. Properties of Some Thermal
Page 149 and 150: ■ Transfer Method In the transfer
Page 151 and 152: Transfer Method Examples Transfer r
Page 153 and 154: ■ Exposures, Contrast, Resolution
Page 155 and 156: ■ Reciprocity-Law Failure Scintil
Page 157 and 158: ■ Neutron-Gamma Response One impo
Page 159 and 160: ■ Real-Time Neutron Image Detecti
Page 161 and 162: ■ Other Detectors for Thermal Neu
Page 163 and 164: ■ Track-Etch Results The track-et
Page 165: 1) Epithermal Neutrons Work with ne
Page 169 and 170: As an example, copper screens are o
Page 171 and 172: ■ Detector Discussion Image detec
Page 173 and 174: 3.1 General General applications fo
Page 175 and 176: FIGURE 6. Radiographs of Explosive
Page 177 and 178: FIGURE 7. Thermal Neutron Radiograp
Page 183 and 184: 3.8 Nuclear Industry Nuclear applic
Page 185 and 186: PART 4 NEUTRON RADIOGRAPHY STANDARD
Page 187 and 188: 4.2 System Performance Standards St
Page 189 and 190: Those sources of radiation subject
Page 191 and 192: ■ Personnel Protection All NRC li
Page 193 and 194: 5.1 Neutron cross sections Neutron
Page 195 and 196: TABLE 9. Thermal Neutron Linear Att
Page 197 and 198: As an example, consider the calcula
Page 199 and 200: FIGURE 10. Half-Value Layers of Sel
Page 201 and 202: FIGURE 11. Tenth-Value Layers of Se
Page 203 and 204: 5.3 Tenth-Value Layers There will b
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Page 207 and 208: Source of Neutrons Charlie Chong/ F
Page 209 and 210: Radioactive Decay Interactive http:
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Page 213 and 214: Source of Neutrons-Beta Decay Decay
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Radioactive Decay Charlie Chong/ Fi
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http://periodictable.com/Isotopes/0
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Neutron Energy & Detectability Slow
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Neutron Energy & Detectability Slow
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■ωσμ∙Ωπ∆º≠δ≤>ηθ
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Good Luck Charlie Chong/ Fion Zhang
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Understanding Neutron Radiography

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