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Title: Fission Product Yields from {sup 232}Th, {sup 238}U, and {sup 235}U Using 14 MeV Neutrons

Abstract

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 {sup 89}Kr, −90, and −92 and {sup 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 {sup 84}As to {sup 146}La are presented.

Authors:
 [1];  [2];  [3];  [4];  [1]
  1. Department of Nuclear Engineering Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd., Ann Arbor, MI 48109 (United States)
  2. (United States)
  3. Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States)
  4. Department of Mechanical and Nuclear Engineering, Pennsylvania State University, 227 Reber Bldg., University Park, PA 16802 (United States)
Publication Date:
OSTI Identifier:
22645632
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nuclear Data Sheets; Journal Volume: 139; Other Information: Copyright (c) 2017 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ARSENIC 84; DEPLETED URANIUM; DEUTERIUM; FISSION; FISSION PRODUCTS; FISSION YIELD; HIGHLY ENRICHED URANIUM; KRYPTON 89; KRYPTON 90; KRYPTON 92; LANTHANUM 146; MEV RANGE 10-100; NEUTRON ACTIVATION ANALYSIS; NEUTRON GENERATORS; NEUTRONS; NUCLEAR DATA COLLECTIONS; THORIUM; THORIUM 232; THORIUM OXIDES; TRITIUM; URANIUM 235; URANIUM 238; XENON 138; XENON 139; XENON 140

Citation Formats

Pierson, B.D., E-mail: bpnuke@umich.edu, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, Greenwood, L.R., Flaska, M., and Pozzi, S.A. Fission Product Yields from {sup 232}Th, {sup 238}U, and {sup 235}U Using 14 MeV Neutrons. United States: N. p., 2017. Web. doi:10.1016/J.NDS.2017.01.004.
Pierson, B.D., E-mail: bpnuke@umich.edu, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, Greenwood, L.R., Flaska, M., & Pozzi, S.A. Fission Product Yields from {sup 232}Th, {sup 238}U, and {sup 235}U Using 14 MeV Neutrons. United States. doi:10.1016/J.NDS.2017.01.004.
Pierson, B.D., E-mail: bpnuke@umich.edu, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, Greenwood, L.R., Flaska, M., and Pozzi, S.A. Sun . "Fission Product Yields from {sup 232}Th, {sup 238}U, and {sup 235}U Using 14 MeV Neutrons". United States. doi:10.1016/J.NDS.2017.01.004.
@article{osti_22645632,
title = {Fission Product Yields from {sup 232}Th, {sup 238}U, and {sup 235}U Using 14 MeV Neutrons},
author = {Pierson, B.D., E-mail: bpnuke@umich.edu and Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 and Greenwood, L.R. and Flaska, M. and Pozzi, S.A.},
abstractNote = {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 {sup 89}Kr, −90, and −92 and {sup 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 {sup 84}As to {sup 146}La are presented.},
doi = {10.1016/J.NDS.2017.01.004},
journal = {Nuclear Data Sheets},
number = ,
volume = 139,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2017},
month = {Sun Jan 15 00:00:00 EST 2017}
}
  • A study of the isotope shifts in the atomic spectra of the medium-weight elements was undertaken. Experimental data were obtained on the isotope shifts in the spectra of strontium, molybdenum, and ruthenium. A correlation between the binding energy of the last pair of neutrons, obtained from mass spectroscopic data, and isotope shifts was determined. The correlation is explained qualitatively in terms of shell energies and the potential energy of nuclear deformation. (auth)
  • The time-of-flight analysis and D(d,n)He/sup 3/ neutron source were utilized in determination of the neutron fission cross sections of Th/sup 232/, U/ sup 235/, Np/sup 237/, and U/sup 2 / 3>s/sup 8/ at 10 to 22 Mev. The time-of- flight method was used for separating the monoenergy neutron effects in the reaction. The deuteron energy was varied from 6.5 to 19.5 Mev (neutron energy 9.7 to 21.7 Mev, respectively) by means of interchangeable foils placed in front of the target. The energy straggling determined by the thickness of the deuterium gas target was 250 kev at E/sub d/ = 19.5more » Mev and 700 kev at E/sub d/ = 6.5 Mev. All measuremerts were taken at O deg angle to the deuteron beam. The statistical error of measurements does not exceed 3%. The distribution of U/sup 235/ fission cross sections is sharply nonmonotonic due to the (n,3n) reaction threshold of about 1.5 Mev which exceeds the tertiary fission. The fission cross section of U/sup 235/ at 10 to 22 Mev is smaller than anticipated. (R.V.J.)« less
  • The neutron and gamma-ray leakage spectra from pulsed spheres having a radius equal to 1.0 mean-free path (mfp) for 14-MeV neutrons in /sup 232/Th, /sup 235/U (with radii of 0.7 and 1.5 mfp), /sup 238/U (with radii of 0.8 and 2.8 mfp), and /sup 239/Pu (with radii of 0.7 and 1.25 mfp) were measured by using time-of-flight techniques. The neutron spectra were measured between 0.9 and 15 MeV with stilbene and NE-213 scintillators. For the gamma rays, the electron recoil spectra were measured between 0.35 and 8 MeV with the NE-213 detector only. Pulse-shape discrimination and flight paths of approx.more » 10 m were used in these measurements. The measured spectra are compared with calculations carried out with TARTNP, a coupled neutron-photon Monte Carlo transport code. The Lawrence Livermore Laboratory ENDL (neutron and photon cross sections) and ENDF/B-IV libraries were used in these calculations. In the region between 10 and 15 MeV, the calculated neutron spectra are in good agreement with the measurements (+-5%). The maximum discrepancy observed for the neutrons between 0.9 and 10 MeV is 30%. The notable exception is /sup 232/Th, where calculations carried out with the ENDF/B-IV underestimate by a factor of 2 the neutron emission between 5 and 10 MeV. The gamma-ray emission calculations were carried out only with ENDL, because of its overall better representation of the neutron measurements; ENDL overestimates the gamma-ray production, with discrepancies ranging between 5 and 20%. However, use of the measured detector efficiency would reduce the maximum discrepancy to < 13%. To facilitate the use of the neutron data for calculational purposes by other laboratories, an experimental one-dimensional neutron energy spectrum is given for each measurement. 10 figures, 7 tables.« less