Program - Brookhaven National Laboratory

Development of an Array of Liquid Scintillators to Measure the Prompt Fission Neutron
Spectrum at LANSCE
B.A. Perdue, R.C. Haight, T. Bredeweg, M. Devlin, N. Fotiadis, M. Jandel, A. Laptev, H.Y. Lee, R.O.
Nelson, J.M. O’Donnell, T.N. Taddeucci, J.L. Ullmann, and S.A. Wender
Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 USA
C.Y. Wu, E. Kwan, A. Chyzh, R. Henderson, and J. Gostic
Lawrence Livermore National Laboratory, Livermore, CA 94551 USA
Higher quality measurements of outgoing prompt neutron spectra from neutron-induced fission as a function
of the incoming neutron energy are needed. These data can be used in designing new fast reactors,
predicting criticality for safety analyzes, and developing techniques for global security applications. As part
of the program to measure the prompt fission neutron spectra (PFNS) from the fission of 239 Pu at the Los
Alamos Neutron Science Center, we are developing a new array of liquid-scintillator detectors. This array
will be used to measure the PFNS over a range of outgoing neutron energies from approximately 600 keV
to 12 MeV and incident neutron energies from 0.5 to 30 MeV. The array consists of 54 liquid scintillators
mounted on two separate stands. Each stand consists of 3 arcs, with a single arc holding 9 detectors. The 9
detectors are spaced apart by 15 ◦ in the polar angle starting at θ = 30 ◦ and ending at θ = 150 ◦ . The 3 arcs
on each stand are placed 33 ◦ apart; this spacing can be widened to 45 ◦ if desired. The 17.8 cm diameter
faces of the detectors are located 1 m from the sample center, giving a 10.7 % coverage of 4π for the entire
array. The liquid-scintillator cells contain EJ309 liquid and are coupled to Hamamatsu photomultiplier
tubes. A complete characterization of the detectors and the array as a whole will be carried out, targeted
at understanding the light-output curves, efficiencies, and the neutron multiple-scattering backgrounds.
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).
Session MA Plenary Thursday
Thursday March 7, 2013
Room: Met East at 8:30 AM
MA 1 8:30 AM
Coupled Backward-Forward Monte-Carlo and Total Monte-Carlo for actinides : using High
Performance Computing for better nuclear data.
E. Bauge
CEA DAM DIF, France
D. Rochman, A.J. Koning
NRG Petten, Netherlands
With the advent of modern nuclear reaction codes like TALYS [1] make the process of nuclear data evaluation
much easier and streamlined and allow a high level of automation while resting on solid physical
grounds. The challenge of estimating the uncertainties associated with evaluated nuclear data has
been tackled independently by the Total Monte-Carlo (TMC) [2] and the Backward-Forward Monte-Carlo
(BFMC) [3] approaches, with different focuses. The TMC method has focused on propagating the uncertainties
associated with physical model parameters to differential and then integral observables, while
the focus of the BFMC method has been on obtaining a sampling of the model parameter probability
distribution function which is consistent with the experimental data (differential or integral). The coupling
of these two methods (TMC and BFMC) combines the desirable qualities of both approaches and
is ideally suited for deployment on High Performance Computing platforms. A consistent TMC+BFMC
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