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Title: Energy dependence of fission product yields from 235U, 238U and 239Pu for incident neutron energies between 0.5 and 14.8 MeV

In this study, Fission Product Yields (FPY) have historically been one of the most observable features of the fission process. They are known to have strong variations that are dependent on the fissioning species, the excitation energy, and the angular momentum of the compound system. However, consistent and systematic studies of the variation of these FPY with energy have proved challenging. This is caused primarily by the nature of the experiments that have traditionally relied on radiochemical procedures to isolate specific fission products. Although radiochemical procedures exist that can isolate all products, each element presents specific challenges and introduces varying degrees of systematic errors that can make inter-comparison of FPY uncertain. Although of high importance in fields such as nuclear forensics and Stockpile Stewardship, accurate information about the energy dependence of neutron induced FPY are sparse, due primarily to the lack of suitable monoenergetic neutron sources. There is a clear need for improved data, and to address this issue, a collaboration was formed between Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL) and the Triangle Universities Nuclear Laboratory (TUNL) to measure the energy dependence of FPY for 235U, 238U and 239Pu. The measurements have been performed at TUNL,more » using a 10 MV Tandem Van de Graaff accelerator to produce monoenergetic neutrons at energies between 0.6 MeV to 14.8 MeV through a variety of reactions. The measurements have utilized a dual-fission chamber, with thin (10-100 μg/cm2) reference foils of similar material to a thick (100-400 mg) activation target held in the center between the chambers. This method allows for the accurate determination of the number of fissions that occurred in the thick target without requiring knowledge of the fission cross section or neutron fluence on target. Following activation, the thick target was removed from the dual-fission chamber and gamma-ray counted using shielded HPGe detectors for a period of 1-2 months to determine the yield of various fission products. To the extent possible all irradiation and counting procedures were kept the same to minimize sources of systematic errors. FPY have been determined at incident neutron energies of 0.6, 1.4, 2.4, 3.5, 4.6, 5.5, 8.9 and 14.8 MeV.« less
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  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. McMaster Univ., Ontario (Canada)
  4. Duke Univ., Durham, NC (United States); Triangle Univ. Nuclear Lab., Durham, NC (United States)
  5. Triangle Univ. Nuclear Lab., Durham, NC (United States); North Carolina State Univ., Raleigh, NC (United States)
Publication Date:
Report Number(s):
LA-UR-15-26521; LLNL-JRNL-696175
Journal ID: ISSN 0090-3752; PII: S009037521500071X
Grant/Contract Number:
AC52-06NA25396; NA0001839; AC52-07NA27344
Accepted Manuscript
Journal Name:
Nuclear Data Sheets
Additional Journal Information:
Journal Volume: 131; Journal Issue: C; Journal ID: ISSN 0090-3752
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Duke Univ., Durham, NC (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Security (NA-70)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1339640; OSTI ID: 1378545