Nuclear Fission and Neutron-Induced Fission Cross-Sections

List of Abbreviations

Chapter I Introduction

Chapter II Basic Physics of the Fission Process

II.A Introduction

II.B Various Phases of the Fission Process

II.B.1 Formation of the Initial State

II.B.2 From the Initial State to Scission

II.B.3 From Scission to the Formation of Fission Products (Fast Processes)

II.B.4 Deexcitation of the Fission Products (Delayed Processes)

II.C Some Properties of the Low-energy Fission of Actinide Nuclei

II.C.1 Mass Distribution of the Fission Products

II.C.2 Prompt-Fission Neutron Emission

II.C.3 Kinetic Energy of the Fission Fragments

II.C.4 Energy Balance in Fission

II.D Neutron-induced Fission

II.D.1 Introduction

II.D.2 Fissile and Non-Fissile Nuclei

II.D.3 Fast-Neutron Fission Cross-Sections

II.D.4 Fission Cross-Sections in the Resonance Region

II.D.5 Thermal-Neutron Fission Cross-Sections

II.D.6 A. Bohr's Theory of Fission Exit Channels

II.D.7 Some Effects Associated with a Double-Hump Shape of the Fission Barrier

Chapter III Fission Cross-section Requirements for the Nuclear Energy Program

III.A Introduction

III.B Fuel Cycles and the Qualitative Role of Nuclear Data

III.B.1 Fuel Cycles and Important Fission Cross-Sections

III.B.2 Importance of the Energy Dependence of Cross-Sections

III.C Reactor Calculations and the Quantitative Role of Nuclear Data

III.C.1 Group Averaged Cross-Sections

III.C.2 Reactor Calculations for which Nuclear Data are Required

III.C.3 Sensitivity of Calculations to Nuclear Data Uncertainties

III.C.4 Examples of Sensitivity Calculations

III.D Integral Measurements

III.D.1 Methods for Taking into Account the Results of Integral Measurements

III.D.2 The Accuracy Requirements for Cross-Section Measurements When Integral Measurements are Taken into Account

III.D.3 Examples of the Changes in Cross-Section Measurement Requirements when Integral Measurements are Taken into Account

III.E Summary of Fission Cross-section Requirements for the Nuclear Energy Program

III.E.1 Primary Actinides

III.E.2 Secondary Actinides

Chapter IV Measurements of Fission Cross-sections

IV.A Introduction

IV.B Essentials of Cross-section Measurements

IV.C Measurement Techniques

IV.D Fission Detection

IV.D.1 Fission Fragment Detection

IV.D.2 Fission-Neutron and Fission-Gamma-Ray Detection

IV.E Selected Examples of Fission Cross-section Measurements

IV.E.1 Precise Measurement of the 2200 m/s Fission Cross-Section of 235U

IV.E.2 High Resolution Fission Cross-Section Measurements in the Resonance Region for the Main Fissile Isotopes

IV.E.3 Measurement of the 235U Fission Cross-Section from 1 to 6 MeV

IV.E.4 Measurement of the 235U Fission Cross-Section in the Energy Range 1 keV to 1 MeV

IV.E.5 Measurement of the 235 U Fission Cross-Section in the Fast-Neutron Energy Range (35 keV to 3.5 MeV)

IV.E.6 Measurement of the 238U to 235U Fission Cross-Section Ratio Over the Energy Range 1 keV to 30 MeV

IV.E.7 Fission Cross-Section Measurement for a Short-Lived Isotope

IV.F Data Reduction and Storage

IV.F.1 Data Reduction

IV.F.2 Data Storage

IV.G Data Analysis

IV.G.1 Introduction

IV.G.2 Resonance Formalisms

IV.G.3 Doppler and Resolution Broadenings

IV.G.4 Resonance Analysis

IV.G.5 Resolved and Unresolved Resonance Regions

IV.H Data Evaluation

IV.H.1 Introduction

IV.H.2 Need for Evaluated Cross-Sections

IV.H.3 Uncertainties in Measured and Evaluated Fission Cross-Sections

IV.H.4 Cross-Sections of Fissile Nuclei Below 1 eV

IV.H.5 The 235U Fission Cross-Section from 1 eV to 100 keV

IV.H.6 The 235U Fission Cross-Section from 0.1 to 20 MeV

IV.H.7 Conclusions

IV.I Comparison of Experimental Results with Needs

IV.I.1 Fissile Isotopes; 233U, 235U, 239Pu, and 241Pu

IV.I.2 Fertile Isotopes: 232Th, 238U, and 240Pu

IV.I.3 Secondary Actinides

IV.J Future Measurements

Chapter V Theoretical Methods for Calculating the Cross-sections of Fissionable Nuclei

V.A Introduction

V.B The Compound Nucleus and Hauser-feshbach Theory

V.B.1 The Compound Nucleus^ Independence of Formation and Decay

V.B.2 The Compound Nucleus Formation Cross-Section: Relation to the Transmission Coefficient

V.B.3 Formulations and Models for the Transmission Coefficient

V.C Calculation of Neutron Transmission Coefficients

V.C.1 Statistical Concepts for High Neutron Energies

V.C.2 Nuclear Structure Effects in Neutron Transmission Coefficients

V.D Radiative Transmission Coefficients

V.D.1. Statistical Concepts

V.D.2 Nuclear Structure Effects

V.E Level Densities

V.E.1 Independent Quasi-Particle States

V.E.2 The Blocking Effect; The Independent Particle Model

V.E.3 Rotational States

V.E.4 Experimental Data on Level Densities

V.F Fission Transmission Coefficients

V.F.1 Statistical Concepts

V.F.2 Structure Effects in Fission Transmission Coefficients

V.F.3 Assessment of Barrier Parameters

V.G Computational Methods for Calculating Cross-sections of Fissionable Nuclides

V.G.l Introduction

V.G.2 The Program EVAPF

V.G.3 The Program AVXS

V.G.4 Examples of Calculated Cross-Sections

V.H Conclusions

Chapter VI Conclusion

References

Glossary

Subject Index