Program - Brookhaven National Laboratory

nuclei are short. We will describe a series of new measurements that were performed at the Lead Slowing-
Down Spectrometer (LSDS) facility at Los Alamos National Laboratory (LANL), directed to measure the
neutron-induced fission cross section of 237 U. The target was prepared by irradiation of an isotopically enriched
sample of 236 U in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL),
followed by a chemical separation and electro-deposition of the 237 U sample. A dedicated compensated
ionization chamber was designed at the Nuclear and Radiochemistry Group (C-NR), LANL, consisting of
two identical chambers for the simultaneous measurements of 235 U(n,f) and 237 U(n,f) rates. The samples
of 235 U and 237 U were electroplated on opposite sides of the same Ti plate, at C-NR, LANL, and HFIR,
ORNL, respectively. The four-day long measurement was carried out at the LSDS facility where a cube of
high purity lead, 1.2 m on the side was driven by a high intensity pulsed neutron source in its center produced
by 800 MeV protons on a tungsten target. The neutrons were moderated by scattering interactions
with the lead resulting in a time-neutron energy correlation. The compensated ionization chamber was
installed in one of the channels of LSDS and neutron-induced reaction rates were measured as a function
of the neutron slowing-down time in the LSDS. Signals from the ionization chamber were recorded using
waveform digitizers and saved for off-line analysis. Progress on the cross section data analysis will be presented.
This work benefited from the LANSCE accelerator facility and was performed under the auspices
of the U.S. Department of Energy under contract DE-AC52-06NA25396.
BA 4 11:40 AM
Cross Section Measurement of 237 Np(n, γ) at J-PARC/MLF/ANNRI
K. Hirose, K. Furutaka, K.Y. Hara, H. Harada, A. Kimura, T. Kin, F. Kitatani, M. Koizumi, S.
Nakamura, M. Ohshima, Y. Toh
Japan Atomic Energ Agency
M. Igashira, T. Katabuchi, M. Mizumoto
Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Japan
T. Kamiyama, K. Kino, Y. Kiyanagi
Graduate School of Engineering, Hokkaido University, Japan
J. Hori
Research Reactor Institute, Kyoto University, Japan
The cross section of the 237 Np(n, γ) reaction has been measured in an energy range from 10 meV to 1 keV
at the Japan Proton Accelerator Research Complex (J-PARC). The NaI(Tl) spectrometer installed in the
accurate neutron-nucleus reaction measurement instrument (ANNRI) was used for the measurement. The
relative cross section was obtained using the neutron spectrum measured by the 10 B(n, α1) reaction. The
absolute value of the cross section was deduced by normalizing the relative cross section to the evaluated
value in JENDL-4.0 at the first resonance. In this presentation, the obtained results for the cross section,
the Westcott factor and the resonance analysis are reported. This work was supported by JSPS KAKENHI
Grant Number 22226016.
Session BC Nuclear Reaction Models
Monday March 4, 2013
Room: Empire East at 10:30 AM
BC 1 10:30 AM
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