Understanding Neutron Radiography

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5.2 Half-Value Layers An important concept for radiography is the half value layer (HVL); that is, the thickness of material that will reduce the radiation intensity by a factor of two. A plot of half-value layers for a practical thermal neutron radiographic beam is given in Fig. 10. This information can be used to estimate the transmission and detectability of various materials combined with others. I = I o e –μnt at half value layer I/I o = ½ = e –μnt½ ln 0.5 = –μ n t ½ t ½ = ln 0.5/ -μ n = 0.693/μ n Charlie Chong/ Fion Zhang
5.3 Tenth-Value Layers There will be a thickness of material that is sufficiently thick that little of the neutron beam penetrates. In Fig. 11, thicknesses of material that will transmit only 10% of an incident thermal neutron radiographic beam are plotted. This thickness represents about the limit that should be attempted in normal thermal neutron radiography. Variations in neutron energy should be considered for thicknesses greater than those shown in Fig. 11. Similarly: t 1/10 = Ln 0.1/ - μ n = 2.302/ μ n 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
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Bohr’s Model Charlie Chong/ Fion
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Electron Orbital Charlie Chong/ Fio
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Plasma Sources Radiography with fas
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TABLE 5. Some Radloaalve Sources fo
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TABLE 5. Some Radloaalve Sources fo
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■ (γ,n) Sources The (γ,n) react
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■ Cf-252 On the basis of technica
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Subcritical Flux Boosters By defint
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Neutron Intensity Very few, if any,
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Beam Tailoring A neutron beam extra
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Foil Filters Some materials have sp
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■ Window Filters For some element
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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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Page 185 and 186: PART 4 NEUTRON RADIOGRAPHY STANDARD
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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
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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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Page 221 and 222: http://periodictable.com/Isotopes/0
Page 223 and 224: Neutron Energy & Detectability Slow
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Page 229 and 230: Good Luck Charlie Chong/ Fion Zhang
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Understanding Neutron Radiography

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