Fission Product Yields from 232 Th, 238 U, and 235 U Using 14 MeV Neutrons B. D. Pierson, 1, 2, ∗ L. R. Greenwood, 2 M. Flaska, 3 and S. A. Pozzi 1 1 Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd., Ann Arbor, MI 48109, USA 2 Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA 3 Department of Mechanical and Nuclear Engineering, Pennsylvania State University, 227 Reber Bldg., University Park, PA 16802, USA (Received 7 June 2016; revised received 12 July 2016; accepted 6 August 2016) Neutron-induced fission yield studies using deuterium-tritium fusion-produced 14 MeV neutrons have not yet directly measured fission yields from fission products with half-lives on the order of seconds (far from the line of nuclear stability). Fundamental data of this nature are important for improving and validating the current models of the nuclear fission process. Cyclic neutron activation analysis (CNAA) was performed on three actinide targets—thorium-oxide, depleted uranium metal, and highly enriched uranium metal—at the University of Michigan’s Neutron Science Laboratory (UM-NSL) using a pneumatic system and Thermo-Scientific D711 accelerator-based fusion neutron generator. This was done to measure the fission yields of short-lived fission products and to examine the differences between the delayed fission product signatures of the three actinides. The measured data were compared against previously published results for 89 Kr, -90, and -92 and 138 Xe, -139, and -140. The average percent deviation of the measured values from the Evaluated Nuclear Data Files VII.1 (ENDF/B-VII.1) for thorium, depleted-uranium, and highly-enriched uranium were -10.2%, 4.5%, and -12.9%, respectively. In addition to the measurements of the six known fission products, 23 new fission yield measurements from 84 As to 146 La are presented. CONTENTS I. INTRODUCTION 171 II. BACKGROUND 172 III. EXPERIMENT 173 IV. DATA AND ANALYSIS 174 A. Peak Area Corrections 175 1. Gamma Self-shielding 175 2. Dead-time 176 B. Isotope Identification 177 V. RESULTS 181 A. Arsenic and Selenium 181 B. Bromine and Krypton 182 C. Rubidium and Strontium 183 D. Yttrium and Zirconium 184 E. Tellurium and Iodine 185 F. Xenon and Cesium 186 G. Barium and Lanthanum 186 VI. CONCLUSIONS 187 * Corresponding author: bpnuke@umich.edu Acknowledgments 187 References 187 I. INTRODUCTION Fission yields and the fission process have been under investigation since fission’s discovery by Lise Meitner and Otto Frisch in 1935 [1]. From the original fission yield curves measured using radiochemical assay to the high- est precision measurements performed using ISOLDE at CERN, SPIDER at Los Alamos National Laboratory (LANL), LOHENGRIN at the Institute Laue-Langevin, OSIRIS at Studsvik, Miss Piggy at the University of Berne, and TITAN at TRIUMF-ISAC [2–11], nuclear fis- sion has continued to provide new insights into the shell structure of the nucleus, prolate and oblate nuclei, the interstellar r-process, and the nuclear structure of multi- fermion systems [12, 14–17, 52]. However, even with over 84 years of study, a comprehensive model of fission ca- pable of accurately predicting the independent yields of all fission products, including isomers, has yet to be de- veloped. The most widely used model is the Bohr liq- uid drop model, expanded to include effects from charge distribution, random neck rupture, multi-modal fission (symmetric and asymmetric break-up), shell structure, Available online at www.sciencedirect.com Nuclear Data Sheets 139 (2017) 171–189 0090-3752/© 2017 Elsevier Inc. All rights reserved. www.elsevier.com/locate/nds http://dx.doi.org/10.1016/j.nds.2017.01.004