Understanding Neutron Radiography

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TABLE 4. Average Characteristics of Thermal-Sources Type of Source Typical Resolution** Exposure Characteristics Radiographic Intensity* Time Radioisotope 10 1 to 10 4 Poor to Medium Long Stable operation. medium investment cost. possibly portable. Accelerator 10 3 to 10 6 Medium Average On-off operation. medium cost. possibly mobile. Subcritical 10 4 to 10 6 Good Average Stable operation, Assembly medium to high investment cost, mobility difficult Nuclear reactor 10 5 to 10 8 Excellent Short Stable operation, medium to high investment cost. mobility difficult *<strong>Neutron</strong>s per square centimeter per second. n/cm 2 ∙s **These classifications are relative Charlie Chong/ Fion Zhang
Nuclear Reactor The majority of practical neutron radiography has been done using a nuclear reactor as the source. The main reasons for this are listed below. 1. Reactors are prolific sources of neutrons, even when operating at low to medium power levels. 2. Most reactor beams are rich in thermal neutrons. 3. Most of the early research in, and the applications of, neutron radiography were associated with the reactor community. 4. <strong>Neutron</strong> radiography can be essentially a byproduct of many reactor operations. 5. Organizations that first offered neutron radiography as a commercial service used reactors as their neutron sources. 6. Most present applications have not required portability from the neutron source. 7. Experience with reactors has shown long, relatively trouble-free operation. Question: The reactor described here; as a operating neutron source or as the top of the chain in neutron source production? 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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Page 39 and 40: Radioactive Objects An additional a
Page 41 and 42: lmaging Neutron radiographs usually
Page 43 and 44: PART 2 EQUIPMENT AND PROCEDURES Cha
Page 45 and 46: ■ Fission When a neutron enters a
Page 47 and 48: U-235 and Pu-239. Charlie Chong/ Fi
Page 49 and 50: U-235 and Pu-239. Charlie Chong/ Fi
Page 51 and 52: Alpha Particles Charlie Chong/ Fion
Page 53 and 54: Alpha Particles Charlie Chong/ Fion
Page 55 and 56: Photoneutrons The necessary energy
Page 57 and 58: Radioactive Decay Charlie Chong/ Fi
Page 59 and 60: 2.2 Neutron Energies As with all pe
Page 61 and 62: Thermal Neutrons “Produced by slo
Page 63 and 64: There are applications in which the
Page 65 and 66: FIGURE 2. Neutron Radiographs of Hi
Page 67 and 68: Fast Neutrons “Fast neutrons prov
Page 69 and 70: Moderators A complete description o
Page 71 and 72: TABLE 2. Slowing Down Properties of
Page 73 and 74: TABLE 3. Some Thermallzatlon Factor
Page 75 and 76: 2.4 Neutron Collimation Beam extrac
Page 77 and 78: FIGURE 4. Neutron Collimators: (a)
Page 79 and 80: Divergent Collimators The primary a
Page 81 and 82: As in X- radiography, the geometric
Page 83 and 84: Geometric Unsharpness (neutron radi
Page 85 and 86: I ≈ Ф 16(L/D) 2 for my ASNT exam
Page 87 and 88: Backscatter It is good practice to
Page 89: TABLE 4. Average Characteristics of
Page 93 and 94: Accelerators Numerous nuclear react
Page 95 and 96: (d.T) Source A reaction that has re
Page 97 and 98: Nuclear physicist at the Idaho Nati
Page 99 and 100: The gas pressure in the ion source
Page 101 and 102: (X.n) Sources Electron accelerators
Page 103 and 104: The threshold energy for photoneutr
Page 105 and 106: Bremsstrahlung , from bremsen "to b
Page 107 and 108: Characteristic x-rays are emitted f
Page 109 and 110: The frequencies of the characterist
Page 111 and 112: "Bremsstrahlung" means "braking rad
Page 113 and 114: 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
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■ Time of Flight It is possible t
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2.7 Neutron Image Detectors All the
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FIGURE 5. Diagrams for Neutron Radi
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TABLE 6. Properties of Some Thermal
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■ Transfer Method In the transfer
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Transfer Method Examples Transfer r
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■ Exposures, Contrast, Resolution
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■ Reciprocity-Law Failure Scintil
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■ Neutron-Gamma Response One impo
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■ Real-Time Neutron Image Detecti
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■ Other Detectors for Thermal Neu
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■ Track-Etch Results The track-et
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1) Epithermal Neutrons Work with ne
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3) Fast Neutrons The other energy r
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As an example, copper screens are o
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■ Detector Discussion Image detec
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3.1 General General applications fo
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FIGURE 6. Radiographs of Explosive
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FIGURE 7. Thermal Neutron Radiograp
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3.8 Nuclear Industry Nuclear applic
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PART 4 NEUTRON RADIOGRAPHY STANDARD
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4.2 System Performance Standards St
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Those sources of radiation subject
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■ Personnel Protection All NRC li
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5.1 Neutron cross sections Neutron
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TABLE 9. Thermal Neutron Linear Att
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As an example, consider the calcula
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FIGURE 10. Half-Value Layers of Sel
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FIGURE 11. Tenth-Value Layers of Se
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5.3 Tenth-Value Layers There will b
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End Of Reading Charlie Chong/ Fion
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Source of Neutrons Charlie Chong/ F
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Radioactive Decay Interactive http:
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Source of Neutrons-Beta Decay Decay
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Source of Neutrons 236 U 92 ? Charl
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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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