Nuclear Fission: Theories, Experiments and Applications

Preface
	References
Contents
Contributors
About the Editors
1 Fission Cross Sections
	1.1 General Observations
		1.1.1 Historical Notes
		1.1.2 Some Terminology: Fissile, Fissionable, and Fertile
		1.1.3 Low-Energy Fission Cross Sections
			1.1.3.1 Resolved Neutron Resonances
			1.1.3.2 The (n,γf) Reaction
			1.1.3.3 The Unresolved Resonance Region
			1.1.3.4 Resonance Features on a Grosser Scale
		1.1.4 Multi-Chance Fission at Higher Excitation Energies
		1.1.5 Other Entrance Channels
		1.1.6 Fission Product Angular Distributions
		1.1.7 Shape Isomers
	1.2 Experimental Setups and Data
		1.2.1 How to Measure Fission Cross Sections
		1.2.2 Detectors for Cross Section Measurements
			1.2.2.1 Ionization Chambers
			1.2.2.2 Time Projection Chambers
			1.2.2.3 Normalization Techniques
		1.2.3 Fission Cross Section Data
		1.2.4 Fission Fragment Angular Distribution Data
		1.2.5 Direct vs. Transfer (Surrogate) Fission Reactions
	1.3 Theoretical Interpretation
		1.3.1 Compound Nucleus Reaction Cross Section Theory
			1.3.1.1 The Compound Nucleus and Related Models
			1.3.1.2 Neutron Transmission Coefficients
			1.3.1.3 Level Density
			1.3.1.4 Radiative Capture
		1.3.2 The Fission Decay Mode and Transmission Coefficient
		1.3.3 R-Matrix Theory Incorporating Fission
		1.3.4 Shell Effects in the Fission Process
			1.3.4.1 Phenomena Not Explained by the Simple Liquid Drop Model
			1.3.4.2 Shell Correction Theory
			1.3.4.3 Class-I and Class-II Compound States and their Coupling
			1.3.4.4 Observations and Analysis of Narrow Intermediate Resonances
			1.3.4.5 Effect of Statistical Properties of Resonances on Average Cross Sections
			1.3.4.6 Properties of Transition States in the Double-humped Fission Barrier
			1.3.4.7 Barrier Penetrability
			1.3.4.8 Model Calculations of Fission Cross Sections
			1.3.4.9 The (n,γf) Reaction
		1.3.5 Angular Distributions of Fission Products
		1.3.6 More Complex Fission Barriers
		1.3.7 Summary of Barrier Properties
	1.4 Evaluations
		1.4.1 Fission Paths and Fission Barriers
		1.4.2 Transition States
		1.4.3 Transmission Coefficients
		1.4.4 Multi-Chance Fission
		1.4.5 Evaluated Fission Cross Sections
	References
2 Fission Fragments and Fission Products
	2.1 General Observations
		2.1.1 Basic Definitions
		2.1.2 Experimental Data
			2.1.2.1 Kinetic Properties of Fission Fragments
			2.1.2.2 Fission Fragment Mass Yields
			2.1.2.3 Charge Distribution of Fission Fragments
	2.2 Experiments
		2.2.1 The Double Kinetic Energy (2E) Method
		2.2.2 Mass Identification Based on Time-of-Flight
		2.2.3 Mass Separators
		2.2.4 Gamma Spectroscopy Techniques
		2.2.5 Inverse Kinematics
		2.2.6 Gamma-Ray Spectroscopy of Fission Fragments
	2.3 Fission Yield Theories
		2.3.1 Fission Shape Dynamics
			2.3.1.1 Shape Families
			2.3.1.2 Potential Energy
			2.3.1.3 Inertial Mass
			2.3.1.4 Dissipation
			2.3.1.5 Transport Treatment of Nuclear Shape Dynamics
			2.3.1.6 Strong Dissipation
			2.3.1.7 Brownian Shape Motion
			2.3.1.8 Shape-Dependent Level Density
		2.3.2 Microscopic Approaches to Fission
			2.3.2.1 Methods and Approximations
			2.3.2.2 Nuclear Energy Density Functional Theory
			2.3.2.3 Static Description of Fission
			2.3.2.4 Fission Dynamics
			2.3.2.5 Initial Conditions of the Fission Fragments
		2.3.3 Summary
	2.4 Evaluation of Fission Product Yields
		2.4.1 Evaluation Method
		2.4.2 Evaluation of Experimental Data
		2.4.3 β Decays of Fission Products
		2.4.4 FPY Models
			2.4.4.1 Primary Fission Fragment Mass Distribution
			2.4.4.2 Primary Fission Fragment Charge Distribution
			2.4.4.3 Prompt Neutron Multiplicities
			2.4.4.4 Statistical Hauser-Feshbach Approach
		2.4.5 Isomeric Ratios
		2.4.6 Energy Dependence of FPYs
			2.4.6.1 Fission Dynamics
			2.4.6.2 Multi-Chance Fission
		2.4.7 Energy Dependence of the Delayed Neutron Yield
	References
3 Prompt and Delayed Emission
	3.1 General Observations
		3.1.1 Time Scales in Fission
		3.1.2 Neutron Emission
			3.1.2.1 Multiplicity
			3.1.2.2 Energy Spectrum
			3.1.2.3 Single Neutron Angular Distributions
			3.1.2.4 Neutron Emission Anisotropy Due to Fragment Spin
			3.1.2.5 Pre-scission Neutron Emission
			3.1.2.6 Multi-Chance Fission and Pre-equilibrium Neutron Emission
			3.1.2.7 Delayed Neutrons
		3.1.3 Gamma Emission
			3.1.3.1 Time Scales for Prompt Gamma Emission
			3.1.3.2 Multiplicity Distributions
			3.1.3.3 Energy Spectrum
			3.1.3.4 Energy Dependence of Prompt Gamma Emission
			3.1.3.5 Dependence of Gamma Emission on Fragment Characteristics
			3.1.3.6 Gamma Emission Anisotropy as a Function of Fragment Spin
			3.1.3.7 X-Ray Emission
		3.1.4 Correlations
			3.1.4.1 Neutron-Neutron
			3.1.4.2 Neutron-Light Fragment
			3.1.4.3 Neutron-Gamma
			3.1.4.4 Gamma-Gamma
	3.2 Experimental Measurements
		3.2.1 Prompt Neutron Measurements
			3.2.1.1 Energy Spectra by Time of Flight
			3.2.1.2 Multiplicity, Including Dependence on Fragment Mass and Energy
			3.2.1.3 Modern Neutron Experiments
		3.2.2 Prompt γ-Ray Measurements
			3.2.2.1 General Considerations for γ-Ray Detectors
			3.2.2.2 Neutron-Gamma Discrimination
			3.2.2.3 Unfolding the Detector Response
			3.2.2.4 γ-Ray Multiplicity as a Function of Fragment Mass
			3.2.2.5 Prompt Fission Gamma Spectra Measurements
		3.2.3 Correlated Neutron-Neutron, Neutron-Light Fragment and Neutron-Gamma Measurements
	3.3 Theory and Modeling of Prompt Emission
		3.3.1 Mechanisms of Prompt Neutron Emission
			3.3.1.1 Emission During the Acceleration Phase
			3.3.1.2 Emission from Ternary Fission
			3.3.1.3 Scission Neutrons
			3.3.1.4 Multi-Chance Fission
			3.3.1.5 Pre-fission Neutron Emission Mechanisms
		3.3.2 Mechanisms of Prompt Gamma Emission
			3.3.2.1 Energy Available for Gamma Emission
			3.3.2.2 Statistical and Discrete Transitions
		3.3.3 Models of Prompt Neutron and Photon Emission
			3.3.3.1 Deterministic Models
			3.3.3.2 Monte Carlo Codes
		3.3.4 Prompt Neutron Observables
			3.3.4.1 Multiplicity
			3.3.4.2 Spectrum
			3.3.4.3 Correlations
		3.3.5 Prompt Gamma Observables
			3.3.5.1 Multiplicity
			3.3.5.2 Spectrum
			3.3.5.3 Time Evolution of Gamma Emission
			3.3.5.4 Prompt Gamma Emission and Fragment Spin
		3.3.6 Neutron-Gamma Correlations
	3.4 Delayed Neutron and Gamma Emission
		3.4.1 Origin of Delayed Neutron and Gamma Emission
		3.4.2 Main Precursors
		3.4.3 Examples of Delayed Neutron and Gamma Spectra
			3.4.3.1 DANCE/NEUANCE
		3.4.4 Influence of Incident Neutron Energy on Delayed Multiplicity
	References
4 Impact on Science and Technology
	4.1 Reactor Physics
		4.1.1 Introduction
			4.1.1.1 Historical Context
			4.1.1.2 Basics of Reactor Physics
			4.1.1.3 Nuclear Reactor Designs
		4.1.2 Fission Phenomena at Play in Reactor Physics
			4.1.2.1 Fission Cross Sections
			4.1.2.2 Prompt Fission Neutrons
			4.1.2.3 ps: [/EMC pdfmark [/Subtype /Span /ActualText (beta) /StPNE pdfmark [/StBMC pdfmarkβps: [/EMC pdfmark [/StPop pdfmark [/StBMC pdfmark-Delayed Neutrons
			4.1.2.4 Prompt and Delayed Fission Gammas
			4.1.2.5 Fission Products
	4.2 Global Security and Defense Applications
		4.2.1 Critical Assemblies
			4.2.1.1 Fission Data for Criticality Simulations
			4.2.1.2 Neutron-Diagnosed Subcritical Experiment (NDSE)
		4.2.2 Fission Signatures of Special Nuclear Materials
			4.2.2.1 Coincidence and Neutron Multiplicity Counting
			4.2.2.2 Anisotropy of Prompt Fission Neutron Emission
			4.2.2.3 Prompt and Delayed Gamma-Ray Spectroscopy
		4.2.3 Radiochemistry and Postdetonation Nuclear Forensics
			4.2.3.1 K-Factors, Q-Factors and R-Values
			4.2.3.2 Radiochemistry of Extinct Species
		4.2.4 Nuclear Explosions as a Source of Neutrons
	4.3 Nuclear Fission in Astrophysics
		4.3.1 Evidence of Actinide Production in Nature
		4.3.2 Fission in the r Process
			4.3.2.1 Fission Barriers
			4.3.2.2 Fission Processes
			4.3.2.3 Timescales for Fission in the r Process
			4.3.2.4 Fission Yields in the r Process
		4.3.3 Prospects for Future Observations of Fissionin the r Process
	References
Index