Understanding Neutron Radiography

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1.1 Development Radiography with thermal neutrons can be traced to the mid-1930s, shortly after the discovery of the neutron. Research work in this field has carried through to the present time, with a significant increase in developmental activity since 1960. Commercial interest in thermal neutron radiography began in the mid-1960s. 1.2 Principles Neutron radiography extends the ability to image the internal structure of a specimen, beyond what can be accomplished with photon (X and gamma) radiation. Similarities, as well as obvious differences, exist when neutron radiography is compared to photon radiographic techniques. Similarities include the ability to produce a visual record of changes in density, thickness and composition of a specimen. Indeed, the neutron radiograph can look very much like a photon radiograph. Charlie Chong/ Fion Zhang
Advantages lt is the differences between the techniques which provide the advantages of neutron radiographyover photon radiography. The major difference is the way in which neutrons are removed from the inspection beam by the specimen. Neutrons interact only with the nuclei of the atoms in the specimen; the neutrons may be scattered or absorbed by the atomic nuclei. Because the neutron interactions involve nuclei rather than the numerous orbital electrons, marked differences between the transmission of neutrons and the transmission of photons through a specimen may take place. Keypoints: Neutrons interact only with the nuclei of the atoms in the specimen Charlie Chong/ Fion Zhang
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Page 3 and 4: Military Applications Charlie Chong
Page 5 and 6: Military Applications Charlie Chong
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Page 9 and 10: 3. Techniques/Calibrations • Bloc
Page 13 and 14: Greek Alphabet Charlie Chong/ Fion
Page 17 and 18: Reading I SECTION 12-Neutron Radiog
Page 19 and 20: The text includes helpful discussio
Page 21: PART 1 PRINCIPLES OF NEUTRON RADIOG
Page 25 and 26: For photons: I = I o e -μx t For N
Page 27 and 28: Figure 1 provides a comparison of t
Page 29 and 30: FIGURE 1. Mass Attenuation Coeffici
Page 33 and 34: Neutron Radiography There is a mark
Page 35 and 36: hydrogen/boron beryllium/ water cad
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
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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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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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Charlie Chong/ Fion Zhang
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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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Charlie Chong/ Fion Zhang
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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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