Fission Product Data Measured at Los Alamos for Fission Spectrum and Thermal Neutrons on {sup 239}Pu, {sup 235}U, {sup 238}U

Journal Article · Wed Dec 15 00:00:00 EST 2010 · Nuclear Data Sheets

DOI:https://doi.org/10.1016/j.nds.2010.11.002· OSTI ID:21499797

Mac Innes, M R; Barr, D W; Keksis, A L; Meade, R A; Burns, C J; Chadwick, M B; Wallstrom, T C ^[1]

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1. Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

We describe measurements of fission product data at Los Alamos that are important for determining the number of fissions that have occurred when neutrons are incident on plutonium and uranium isotopes. The fission-spectrum measurements were made using a fission chamber designed by the National Institute for Standards and Technology (NIST) in the BIG TEN critical assembly, as part of the Inter-laboratory Liquid Metal Fast Breeder Reactor (LMFBR) Reaction Rate (ILRR) collaboration. The thermal measurements were made at Los Alamos' Omega West Reactor. A related set of measurements were made of fission-product ratios (so-called R-values) in neutron environments provided by a number of Los Alamos critical assemblies that range from having average energies causing fission of 400-600 keV (BIG TEN and the outer regions of the Flattop-25 assembly) to higher energies (1.4-1.9 MeV) in the Jezebel, and in the central regions of the Flattop-25 and Flattop-Pu, critical assemblies. From these data we determine ratios of fission product yields in different fuel and neutron environments (Q-values) and fission product yields in fission spectrum neutron environments for {sup 99}Mo, {sup 95}Zr, {sup 137}Cs, {sup 140}Ba, {sup 141,143}Ce, and {sup 147}Nd. Modest incident-energy dependence exists for the {sup 147}Nd fission product yield; this is discussed in the context of models for fission that include thermal and dynamical effects. The fission product data agree with measurements by Maeck and other authors using mass-spectrometry methods, and with the ILRR collaboration results that used gamma spectroscopy for quantifying fission products. We note that the measurements also contradict earlier 1950s historical Los Alamos estimates by {approx}5-7%, most likely owing to self-shielding corrections not made in the early thermal measurements. Our experimental results provide a confirmation of the England-Rider ENDF/B-VI evaluated fission-spectrum fission product yields that were carried over to the ENDF/B-VII.0 library, except for {sup 99}Mo where the present results are about 4%-relative higher for neutrons incident on {sup 239}Pu and {sup 235}U. Additionally, our results illustrate the importance of representing the incident energy dependence of fission product yields over the fast neutron energy range for high-accuracy work, for example the {sup 147}Nd from neutron reactions on plutonium. An upgrade to the ENDF library, for ENDF/B-VII.1, based on these and other data, is described in a companion paper to this work.

• OSTI ID: 21499797
• Journal Information: Nuclear Data Sheets, Vol. 111, Issue 12; Other Information: DOI: 10.1016/j.nds.2010.11.002; PII: S0090-3752(10)00101-8; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0090-3752
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BARIUM 140
CERIUM 141
CERIUM 143
CESIUM 137
ENERGY DEPENDENCE
FAST NEUTRONS
FISSION
FISSION CHAMBERS
FISSION PRODUCTS
FISSION SPECTRA
GAMMA SPECTROSCOPY
KEV RANGE 100-1000
LMFBR TYPE REACTORS
MASS SPECTROSCOPY
MEV RANGE 01-10
MOLYBDENUM 99
NEODYMIUM 147
NEUTRON REACTIONS
NUCLEAR DATA COLLECTIONS
OWR REACTOR
PLUTONIUM 239
REACTION KINETICS
SELF-SHIELDING
THERMAL NEUTRONS
URANIUM 235
URANIUM 238
ZERO POWER REACTORS
ZIRCONIUM 95
ACTINIDE NUCLEI
ALKALINE EARTH ISOTOPES
ALPHA DECAY RADIOISOTOPES
BARIUM ISOTOPES
BARYON REACTIONS
BARYONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BREEDER REACTORS
CERIUM ISOTOPES
CESIUM ISOTOPES
DAYS LIVING RADIOISOTOPES
ELEMENTARY PARTICLES
ENERGY RANGE
ENRICHED URANIUM REACTORS
EPITHERMAL REACTORS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXPERIMENTAL REACTORS
FAST REACTORS
FBR TYPE REACTORS
FERMIONS
HADRON REACTIONS
HADRONS
HEAVY NUCLEI
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IONIZATION CHAMBERS
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
KEV RANGE
KINETICS
LIQUID METAL COOLED REACTORS
MATERIALS
MEASURING INSTRUMENTS
MEV RANGE
MINUTES LIVING RADIOISOTOPES
MOLYBDENUM ISOTOPES
NEODYMIUM ISOTOPES
NEUTRON DETECTORS
NEUTRONS
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
NUCLEONS
ODD-EVEN NUCLEI
PLUTONIUM ISOTOPES
RADIATION DETECTORS
RADIOACTIVE MATERIALS
RADIOISOTOPES
RARE EARTH NUCLEI
REACTORS
RESEARCH AND TEST REACTORS
RESEARCH REACTORS
SPECTRA
SPECTROSCOPY
SPONTANEOUS FISSION RADIOISOTOPES
TANK TYPE REACTORS
TEST FACILITIES
TEST REACTORS
THERMAL REACTORS
URANIUM ISOTOPES
WATER COOLED REACTORS
WATER MODERATED REACTORS
YEARS LIVING RADIOISOTOPES
ZIRCONIUM ISOTOPES