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Evaluation and Application of Delayed Neutron Precursor Data

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Evaluation and Application of Delayed Neutron Precursor Data LA-U534-T Thesis UC-413 Issued: April 1989. LA--U534-T DE89 009586 Evaluation and Application of Delayed Neutron Precursor Data Michaele Clarice Brady* 'Collaborator,Graduate Research Assistant at /.<>> Alamos. Oak Ridge Sulumal laboratory. Oak Ridge. TV ITtiM MASTER DISTRIBUTION OF THIS DOCUMENT IS UNLIMITED v Los Alamos National Laboratory Los Alamos.New Mexico 87545 IV ACKNOWLEDGEMENTS The author wishes to take this opportunity to acknowledge the many peo- ple and organizations who helped to make this work possible. The research presented here was funded in part by Associated Western Universities under a Department of Energy (DOE) contract and also by the DOE Office of Basic Energy Sciences. These organizations are gratefully acknowledged and their assistance in this endeavor is highly appreciated. A special thanks to Dr. T. R. England from whom I have received many benefits based on his expertise, experience, and good nature. I am indebted to him for his guidance and inspiration in performing the work presented here. I would also like to express my appreciation to Dr. T. A. Parish for his encour- agement throughout the course of this work and particularly his assistance in the preparation of this manuscript. Prof. K. -L. Kratz of the University of Mainz; Prof. Gosta Rudstam of the Swedish Research Council's Laboratory at Studsvik; P. Reeder and R. Warner of Pacific Northwest Laboratory; and Prof. G. Couchell of the University of Lowell are gratefully acknowledged for providing their experimental delayed neutron spectral data. A special note of appreciation is expressed to Drs. F. M. Mann and R. E. Schenter of Hanford Engineering Development Laboratory for provid- ing their evaluation of delayed neutron emission probabilities as well as several fruitful discussions. Finally, to the staff of the Applied Nuclear Science Group (T-2) at Los Alamos National Laboratory, I extend my sincere appreciation for their support and encouragement over the three years this work progressed. TABLE OF CONTENTS LIST OF TABLES vii LIST OF FIGURES viii ABSTRACT xiii CHAPTER I. INTRODUCTION 1 CHAPTER II. BACKGROUND AND LITERATURE REVIEW ... 4 HISTORICAL TREATMENT OF DELAYED NEUTRONS FROM FISSION 4 ENDF/B-V CONTENT 11 CHAPTER III. THEORY OF DELAYED NEUTRON EMISSION . 15 DELAYED NEUTRON EMISSION PROBABILITIES 17 FISSION YIELDS 21 SPECTRA 24 CHAPTER IV. THE PRECURSOR DATA BASE 29 PRECURSOR IDENTIFICATION 31 DELAYED NEUTRON EMISSION PROBABILITIES 39 CHAPTER V. EVALUATION OF PRECURSOR SPECTRA .... 42 MEASUREMENT TECHNIQUES 42 THE PRINCIPAL EXPERIMENTAL SPECTRA 46 EVALUATING THE PRINCIPAL EXPERIMENTAL SPECTRA . 53 MODEL SPECTRA 74 UNCERTAINTIES FOR THE MODEL SPECTRA 95 SUMMARY OF PRECURSOR DATA 99 CHAPTER VI. SUMMATION CALCULATIONS 102 TOTAL DELAYED NEUTRON YIELDS 102 AGGREGATE DELAYED NEUTRON SPECTRA Ill VI TABLE OF CONTENTS (Continued) CHAPTER VII. FEW-GROUP APPROXIMATIONS 122 GROUP HALF-LIVES AND FRACTIONS 122 GROUP SPECTRA CALCULATIONS 128 CHAPTER VIII. POINT REACTOR KINETICS CALCULATIONS . 152 REFORMULATION OF THE POINT REACTOR KINETICS EQUATIONS 152 SOLVING THE MODIFIED POINT REACTOR KINET: ; EQUATIONS 154 CHAPTER IX. SUMMARY AND CONCLUSIONS 160 PRECURSOR DATA LIBRARY 160 SUMMATION CALCULATIONS 162 TEMPORAL GROUP REPRESENTATIONS 163 APPLICATIONS OF DATA 163 POINT KINETICS CALCULATIONS 164 SIGNIFICANCE OF COMPLETED WORK 164 CONCLUSIONS 165 REFERENCES 166 APPENDIX A. GENERAL BIBLIOGRAPHY 177 APPENDIX B. BETA CODE 191 B.I. ROUTINES OF THE BETA CODE 192 B.2. INPUT DESCRIPTION 196 B.3. SAMPLE INPUT 201 APPENDIX C. DELAYED NEUTRON EMISSION PROBABILITIES 227 APPENDIX D. DELAYED NEUTRON SPECTRA REFERENCES BY NUCLIDE 245 APPENDIX E. SIX-GROUP PARAMETERS 253 APPENDIX F. EXPLICIT REACTOR KINETICS EQUATIONS . 261 VITA 26S Vll LIST OF TABLES Table Page I Summary of EN'DF/B-V Evaluation for Delayed Neutrons 12 II Evolution of ENDF/B Fission Yield Evaluations 25 III Precursor Emission Probabilities (-/"*„), Sources of Data, and Type of Spectral Modifications 32 IV Summary of Experimental Spectra 48 V Content of Current Data Base 100 VI Comparison of Total Delayed Neutron Yield per 100 Fissions . .103 VII Percent of Total DN Yield From Precursors with Measured Data . 107 VIII Table of Measured Average Energy Comparisons 118 IX Table of Calculated Average Energy Comparisons 120 X Comparison of X2 Values and Group Parameters for Few-Group Fits 125 XI Delayed Neutron Six-group Parameters 130 235 XII Comparison of ,3tff for Godiva ( U(F)] 140 XIII Average Energy Comparisons with Lowell Data 151 XIV Delayed Neutron (DN") Precursor Library 161 C-I Measurements of Delayed Neutron Emission Probability 228 C-II Recommended Pn Values 239 C-III Precursors Having Significant Different Values Than 1984 Evaluation 242 CIV Laboratory Bias Factors 243 C-V Parameters from the Kratz-Herrmann Equation 243 E-I Keepin Recommended Six-Group parameters 254 E-II ENDF/B-V Six-Group Parameters 255 E-III Tuttle Recommended Six-Group parameters 256 E-FV Rudstam Six-Group Parameters 257 E-V England Six-Group Abundances 258 E-VI Normalized Waldo Recommended Six-Group Parameters 259 VJ11 LIST OF FIGURES Figure Page 1 Delayed neutrons from fission 5 2 Delayed-neutron decay following instantaneous irradiations of 235U (fast fission) 7 3 Six-group precursor representation 9 4 ENDF/B-V group one spectra 14 5 Schematic of beta decay plus delayed neutron emission 16 6 Schematic of yield distribution 23 7 Some explicit fission product chains 30 8 Energy resolution for neutron detection methods 44 9 Delayed neutron spectrum for 81Ga (Studsvik) 49 10 Delayed neutron spectrum for 143Cs (Studsvik) 10 11 235U Vi spectra comparisons at 5 s 55 12 Normalized delayed neutron spectra for 79Ga 57 13 Normalized delayed neutron spectra for 80Ga 57 14 Normalized delayed neutron spectra for 81Ga 58 15 Normalized detayed neutron spectra for 85As 58 16 Normalized delayed neutron spectra for 87Br 59 17 Normalized delayed neutron spectra for MBr 59 18 Normalized delayed neutron spectra for 89Br 60 19 Normalized delayed neutron spectra for 90Br 60 20 Normalized delayed neutron spectra for 91Br 61 21 Normalized delayed neutron spectra for 92Br 61 22 Normalized delayed neutron spectra for 92Rb 62 23 Normalized delayed neutron spectra for 93Rb 62 24 Normalized delayed neutron spectra for 94Rb 63 25 Normalized delayed neutron spectra for 95Rb 63 26 Normalized delayed neutron spectra for 96Rb 64 27 Normalized delayed neutron spectra for 97Rb 64 IX LIST OF FIGURES (Continued) Figure Page 28 Normalized delayed neutron spectra for 98Rb 65 29 Normalized delayed neutron spectra for 129In 65 30 Normalized delayed neutron spectra for I30In 66 31 Normalized delayed neutron spectra for 134Sn 66 32 Normalized delayed neutron spectra for 135Sb 67 33 Normalized delayed neutron spectra for I36Te 67 34 Normalized delayed neutron spectra for 137I 6S 35 Normalized delayed neutron spectra for 138I 68 36 Normalized delayed neutron spectra for 139I 69 37 Normalized delayed neutron spectra for 140I 69 38 Normalized delayed neutron spectra for H11 70 39 Normalized delayed neutron spectra for 141Cs 70 40 Normalized delayed neutron spectra for 142Cs 71 41 Normalized delayed neutron spectra for 143Cs 71 42 Normalized delayed neutron spectra for 144Cs 72 43 Normalized delayed neutron spectra for 145Cs 72 44 Normalized delayed neutron spectra for u6Cs 73 45 Normalized delayed neutron spectra for 147Cs 73 46 Spectra as a fraction > E for 92Rb 75 47 Comparison of model spectra for 80Ga 77 48 Comparison of model spectra for 92Rb 78 49 Comparison of model spectra for 97Rb 79 50 Comparison of model spectra for 140I 80 51 Correlation of d/4 [Eq. (21)] with mass number 83 52 Comparison of evaporation spectra with a = 2/ZA for 92Rb .... 84 53 Comparison of evaporation spectra with a = 2/3-4 for 95Rb .... 85 54 Comparison of evaporation spectra with a -- 2/3-4 for 97Rb .... 86 LIST OF FIGURES (Continued) Figure Page 55 Comparison of evaporation spectra with a = 2/3-4 for 134Sn .... 87 56 Comparison of evaporation spectra with a = 2/3.4 for H3Cs .... 88 57 Comparison of spectra for 92Rb 90 58 Comparison of spectra for 94 Rb 91 59 Spectra as a fraction > E for 94Rb 92 60 Comparison of spectra for 96Rb 93 61 Spectra as a fraction > E for 96Rb 94 62 Example of evaporation model uncertainty 97 63 Example of BETA code model uncertainty 98 64(a) Location of delayed neutron precursors (low Z) 109 64(b) Location of delayed neutron precursors (high Z) 110 65 Aggregate spectra for 235U(T) 113 66 Aggregate spectra for 238U(F) 114 67 Aggrecate spectra for 239Pu(F) 115 68 Delayed neutron activity following a fission pulse 123 69 Comparison of DX activity following a 23SU(F) fission pulse .... 126 70 Ratio of few-group results to CINDER-10 for 235U(F) fission pulse . 127 71 Kinetic response to $0.25 reactivity for few-group fits 129 235 72(a) Group 1 normalized ud spectra for U 135 235 72(b) Group 2 normalized ud spectra for U 135 235 72(c) Group 3 normalized ud spectra for U 136 235 72(d) Group 4 normalized vd spectra for U 136 235 72(e) Group 5 normalized ud spectra for U 137 235 72(f) Group 6 normalized ud spectra for U 137 73 Comparisons with Lowell spectra for delay interval 1 (0.17-0.37 s) . 141 74 Comparisons with Lowell spectra for delay interval 2 (0.41-0.85 s) . 142 XI LIST OF FIGURES (Continued) Figure Page 75 Comparisons with Lowell spectra for delay interval 3 (0.79-1.25 s) . 143 76 Comparisons with Lowell spectra for delay interval 4 (1.2-1.9 s) . 144 77 Comparisons with Lowell spectra for delay interval 5 (2.1-3.9 s) . 145 78 Comparisons with Lowell spectra for delay interval 6 (5.7-10.2 s) . 146 79 Comparisons with Lowell spectra for delay interval 7 (12.5-29.0 s) .
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