Program - Brookhaven National Laboratory

[1] Y. Tall et al., Volatile elements production rates in a proton-irradiated molten lead-bismuth target,
Proceedings of the International Conference on Nuclear Data for Science and Technology, April 22-27,
Nice, France, 2007.
Session GF Neutron Cross Section Measurements
Tuesday March 5, 2013
Room: Central Park East at 1:30 PM
GF 1 1:30 PM
Measurement of Fission Neutron Spectrum and Multiplicity using a Double Time-of-Flight
Setup
E. Blain, Y. Danon
Gaerttner LINAC Center, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
Recent efforts have been made to improve the prompt fission neutron spectrum and nu-bar measurements
for Uranium and Plutonium isotopes particularly in the keV region. A system has been designed at Rensselaer
Polytechnic Institute (RPI) utilizing an array of EJ301 liquid scintillators as well as lithium glass
and plastic scintillators to experimentally determine these values. An array of BaF2 detectors was recently
obtained from Oak Ridge National Laboratory to be used in conjunction with the neutron detectors. The
system uses a novel gamma tagging method for fission which can offer an improvement over conventional
fission chambers due to increased sample mass. A coincidence requirement on the gamma detectors from
prompt fission gammas is used as the fission tag for the system as opposed to fission fragments in a conventional
fission chamber. The system utilizes pulse digitization using Acqiris 8 bit digitizer boards which
allow for gamma/neutron pulse height discrimination on the liquid scintillators during post processing.
Additionally, a 252 Cf fission chamber was designed and constructed at RPI which allowed for optimization
and testing of the system without the need for an external neutron source. The characteristics of
the gamma tagging method such as false detection rate and detection efficiency were determined using
this fission chamber and verified using MCNP Polimi modeling. Prompt fission neutron spectrum data
has been taken using the fission chamber focusing on the minimum detectable neutron energy for each of
the various detectors. Plastic scintillators were found to offer a significant improvement over traditional
liquid scintillators allowing energy measurements down to ∼100 keV. Background was also studied and
characterized for all detectors and will be discussed.
GF 2 2:00 PM
Prompt Fission γ Rays Measured Using Liquid Scintillators
E. Kwan, C.Y. Wu, A. Chyzh, J.M. Gostic, R.A. Henderson
Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94550, USA
R.C. Haight, H.Y. Lee, T.A. Bredeweg, M. Devlin, N. Fotiades, M. Jandel, A. Laptev, R.O. Nelson, J.M.
O’Donnell, B.A. Perdue, T.N. Taddeucci, J.L. Ullmann, S.A. Wender
Los Alamos National Laboratory, Los Alamos, NM 87545 USA
Accurate data on fission products and their distributions as a function of neutron energy are needed for
radiation transport calculations used in a wide range of applied programs. Knowledge on the energy
distribution of the emitted neutrons and γ rays is essential to design proper shielding and cooling systems
used in reactors. Although there have been significant work measuring the neutron-induced fission yields
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