Introduction ................................................... XI
Some Background to my Notes on Fermi's Neutron Physics
Lectures (Los Alamos, 1945), by Anthony P. French ............ xxxi
Neutron Physics ................................................. 1
Neutron Physics - A Course of Lectures by E. Fermi .............. 3
1 Sources of Neutrons .......................................... 5
1.1 Natural Sources ......................................... 5
1.1.1 Alpha Particle Sources ........................... 5
1.1.2 Photo-Neutron Sources ............................ 7
1.2 Artificial Sources ...................................... 7
2 The Isotopic Chart: Nuclear Masses and Energies .............. 9
2.1 The Isotopic Chart ...................................... 9
2.2 Energy Balance of Reactions ............................ 10
2.3 The Binding Energies of Nuclei ......................... 12
2.4 The Packing Fraction Curve ............................. 12
3 The Scattering of Neutrons (Part 1) ......................... 17
3.1 General Considerations ................................. 17
3.2 Elementary Theoretical Treatment ....................... 19
3.2.1 Elastic Scattering .............................. 20
3.2.2 Inelastic (n,n) Scattering ...................... 21
3.2.3 Inelastic (n, m) Scattering ..................... 21
3.2.4 Inelastic (n, γ) Scattering ..................... 22
4 Resonance: Models of the Nucleus ............................ 25
4.1 Resonance in Nuclear Reactions ......................... 25
4.2 Two Models of the Nucleus .............................. 27
5 The Scattering of Neutrons (Part 2) ......................... 31
5.1 The Solution of Schrodinger's Equation ................. 31
5.2 The Scattering Cross Section ........................... 34
5.3 Neutron-Proton scattering .............................. 35
5.4 The Breit-Wigner Formula ............................... 36
5.5 The Effect of Chemical Binding on Scattering ........... 38
5.6 Scattering Cross Section for Other Elements ............ 39
6 Slow Neutrons as Waves ...................................... 41
6.1 Introduction ........................................... 41
6.2 Isotopic Effects ....................................... 43
6.3 Penetration by Thermal Neutrons ........................ 44
6.4 The Production of Very Slow Neutrons ................... 46
6.5 Reflection and Refraction .............................. 47
7 The Slowing Down of Neutrons ................................ 49
7.1 Introduction ........................................... 49
7.2 The Energy Loss in One Collision ....................... 50
7.3 Many Collisions ........................................ 52
7.4 The Spatial Distribution of Slowed Neutrons ............ 54
7.5 Theory of the Spatial Distribution ..................... 58
8 The Age Equation ............................................ 65
8.1 Derivation of the Age Equation ......................... 65
8.1.1 Diffusion ....................................... 65
8.1.2 Energy Drift .................................... 66
8.2 The Problem of a Point Source .......................... 68
9 Thermal Neutron Distributions ............................... 71
9.1 The Basic Equation ..................................... 71
9.2 Point Source of Slow Neutrons .......................... 72
9.3 Point Source of Fast Neutrons .......................... 72
9.4 Bounded Media .......................................... 73
9.5 The Measurement of Diffusion Length .................... 76
9.6 Diffusion in Graphite .................................. 77
9.7 Some Useful Quantities and Relationships ............... 80
10 The Reflection of Neutrons .................................. 81
10.1 Introduction ........................................... 81
10.2 Approximate Solution of the Escape Problem ............. 81
10.3 Exact Solution by Integral Equation Method ............. 82
10.4 The Albedo ............................................. 85
10.5 Measurement of the Albedo .............................. 85
11 The Stability of Nuclei ..................................... 87
11.1 The Binding Energy of a Nucleus ........................ 87
11.1.1 The Liquid Drop Model ........................... 87
11.1.2 Nuclear Composition ............................. 88
11.1.3 Coulomb Forces .................................. 89
11.1.4 The Odd-Even Effect ............................. 89
11.2 Determination of Coefficients .......................... 90
11.3 The Binding of Neutrons to Nuclei ...................... 91
12 Nuclear Fission ............................................. 93
12.1 The Possibility of Fission ............................. 93
12.2 Limitations on the Occurrence of Fission ............... 95
12.3 The Liquid Drop Model in Fission ....................... 97
12.4 The Particles of Fission ............................... 99
12.5 Cross Sections for Fission and Other Processes ........ 102
13 The Possibility of a Chain Reaction ........................ 105
13.1 The Properties of Natural Uranium ..................... 105
13.1.1 The High Energy Region ......................... 106
13.1.2 The Thermal Region ............................. 107
13.2 Moderators ............................................ 107
13.3 Homogeneous and Lumped Graphite Piles ................. 108
13.4 The Possibility of a Homogeneous Pile ................. 112
14 The Heterogeneous Pile ..................................... 115
14.1 The Design of a Lumped Pile ........................... 115
14.2 The Determination of Pile Constants ................... 116
14.2.1 The Magnitude of  ............................. 116
14.2.2 (1-ƒR) ......................................... 116
14.2.3 Calculation of ƒT .............................. 117
14.3 Reproduction Factor and Critical Size ................. 119
15 The Time Dependence of a Pile .............................. 123
15.1 The Time-Dependent Equations .......................... 123
15.2 Evaluation of the Period .............................. 125
16 Practical Aspects of Pile Physics .......................... 131
16.1 The Determination of k ................................ 131
16.2 The Study of Pile Materials ........................... 132
16.3 Energy and Radiation Production ....................... 133
16.4 Shielding ............................................. 134
16.5 Other Types of Piles .................................. 136
17 Fast Reactors .............................................. 139
17.1 Elementary Considerations ............................. 139
17.2 The Integral Equation to the Neutron Distribution ..... 141
17.3 The Critical Size for a Fast Reactor .................. 144
17.4 Supercritical Reactors ................................ 151
Problems and Exercises ..................................... 153
Nuclear Reactors .............................................. 159
1 Process for the Production of Radioactive Substances
by E. Fermi, E. Amaldi, B. Pontecorvo, F. Rasetti and
E. Segre ................................................... 161
2 Test Exponential Pile
by E. Fermi ................................................ 181
3 Method of Operating a Neutronic Reactor
by E. Fermi and L. Szilard ................................. 217
3.1 The Chain Fission Reaction ............................ 223
3.1.1 Neutron Loss by Absorption in Uranium .......... 226
3.1.2 Neutron Loss by Absorption in the Moderator .... 228
3.1.3 Neutron Loss by Absorption by Impurities in
the System ..................................... 229
3.1.4 Exterior Neutron Loss in a Neutronic Reactor
of Practical Size .............................. 233
3.2 Measurement of Neutron Losses ......................... 234
3.3 An Illustrative Neutronic Reactor having a Solid
Moderator ............................................. 244
3.4 Graphite in the Reactor ............................... 258
3.5 An Illustrative Neutronic Reactor having a Liquid
Moderator ............................................. 262
3.6 Neutronic Reactors with Other Moderators .............. 269
3.7 Reduction of Losses Due to Resonance Capture .......... 271
3.8 Reduction of Neutron Losses Due to Impurities in the
Material .............................................. 278
3.9 Effect of a Cooling System in a Neutronic Reactor ..... 285
3.10 An Illustrative Gas-Cooled Neutronic Reactor .......... 288
3.11 An Illustrative Liquid-Cooled Neutronic Reactor ....... 298
3.12 Use of Different Lattices in the Same Neutronic
Reactor ............................................... 303
3.13 Critical and Operating Sizes of Neutronic Reactors .... 307
3.14 Control of the Neutronic Reaction by Variation of
Neutron Losses in or from the Neutronic Reactor ....... 315
3.15 Uses of Neutronic Reactors ............................ 323
4 Chain Reacting System
by E. Fermi and M.C. Leverett .............................. 329
5 Neutronic Reactor I
by E. Fermi ................................................ 379
6 Air Cooled Neutronic Reactor
by E. Fermi and L. Szilard ................................. 409
7 Testing Material in a Neutronic Reactor
by E. Fermi and H.L. Anderson .............................. 447
8 Neutron Velocity Selector
by E. Fermi ................................................ 475
9 Neutronic Reactor II
by E. Fermi and L. Szilard ................................. 493
10 Neutronic Reactor III
by E. Fermi, W.H. Zinn and H.L. Anderson ................... 513
11 Neutronic Reactor IV
by E. Fermi and W.H. Zinn .................................. 523
12 Method of Testing Thermal Neutron Fissionable Material
for Purity
by E. Fermi and H.L. Anderson .............................. 535
13 Method of Sustaining a Neutronic Chain Reacting System
by E. Fermi and M.C. Leverett .............................. 549
14 Neutronic Reactor Shield
by E. Fermi and W.H. Zinn .................................. 533
Appendix A: Other Documents not Reported in this Volume ....... 593
Appendix B: The Complete List of Fermi's Papers ............... 621
Bibliography .................................................. 653
Index ......................................................... 657
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