Program - Brookhaven National Laboratory

multi-foil Parallel Plate Avalanche Counter contains the 239 Pu and gives much better timing and much less
neutron scattering than fission chambers used by us in the past. We are developing two arrays of neutron
detectors, one based on liquid organic scintillators and the other on 6 Li-glass detectors. The range of fission
neutrons detected by organic liquid scintillators extends from about 600 keV to well over 1 MeV, with the
lower limit being defined by the limit of pulse-shape discrimination. The 6 Li-glass detectors have a range
from very low energies to about 1 MeV, where their efficiency then becomes small. Waveform digitizers are
used for data acquisition. The status of this program including results of initial experimental measurements
will be presented. This work benefits from the LANSCE accelerator facility and is supported by the U.S.
Department of Energy under contracts DE-AC52-06NA25396 (LANL) and DE-AC52-07NA27344 (LLNL).
[1] P. Talou et al., Nucl. Sci. Eng. 166, 254 (2010). [2] D. G. Madland and J. R. Nix, Nucl. Sci. Eng. 81,
213 (1982).
BA 2 11:00 AM
Neutron-Induced Gamma-Ray Reference Cross Section Measurements with GEANIE at
LANSCE
R. O. Nelson, N. Fotiades, M. Devlin
LANSCE-NS, Los Alamos Neutron Science Center, Los Alamos, NM 87545
Accurate reference cross sections simplify accurate measurements by allowing relative measurements to be
performed. Many of the experiment-related variables cancel in such relative measurements simplifying the
analysis. Work on neutron-induced gamma-ray measurements at LANSCE convinced us that most gammaray
reference cross sections were not accurate beyond the 5% level and often the uncertainties were much
larger. In the past few years we have worked to improve the accuracy of some long-used gamma-ray cross
sections, and to develop more reliable and more accurate reference cross sections. Through this work, we
have improved the uncertainties on some cross sections and are now working to refine data for new reference
cross sections that we expect will improve the accuracy obtained and ease of use. The Li(n,n’γ=478keV) and
Ti(n,n’γ=984keV) partial gamma-ray cross sections together may provide reliable cross sections covering
the neutron energy range, 1 MeV < En < 14 MeV. Several other candidates were examined in this search
and found unacceptable for a variety of reasons. The rationale behind these choices will be discussed and
the present status of the data will be described. This work benefits from the LANSCE accelerator facility
and is supported by the U.S. Department of Energy under contract DE-AC52-06NA25396.
BA 3 11:20 AM
Measurements of the 237 U Neutron-Induced Fission Cross Section at LSDS Facility
M. Jandel, T. A. Bredeweg, E. M. Bond, M. Devlin, A. Gavron, R. C. Haight, W. A. Moody, J. M.
O’Donnell, D. J. Vieira, S. A. Wender and J. B. Wilhelmy
Los Alamos National Laboratory, Los Alamos, NM 87545 USA
C. W. Alexander
Oak Ridge National Laboratory, Oak Ridge, TN USA
G. Bélier and T. Granier
CEA, DAM, DIF, F-91297 Arpajon, France
New or improved data on neutron-induced fission cross section of actinides are needed for many nuclear
technology applications and for better understanding of the fission process. Measurements with the radioactive
targets, such as 237 U (T 1/2=6.75 days), are complicated especially if the half-lives of the target
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