Program - Brookhaven National Laboratory

C. Arnold, E. Bond, T. Bredeweg, M. Fowler, W. Moody, R. Rundberg, G. Rusev, D. Vieira, J. Wilhelmy
Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
J. Becker, R. Macri, C. Ryan, S. Sheets, M. Stoyer, A. Tonchev
Lawrence Livermore National Laboratory, Livermore, California 94550, USA
In order to resolve long-standing differences between LANL and LLNL regarding the correct fission basis
for analysis of nuclear test data [1,2], a collaboration between TUNL/LANL/LLNL has been formed to
perform high-precision measurements of neutron induced fission product yields. The main goal is to make
a definitive statement about the energy dependence of the fission product yields to an accuracy of better
than 2-3% between 1 and 15 MeV, where experimental data are very scarce. At TUNL, we have completed
the design, fabrication and testing of three dual fission chambers dedicated for 235 U, 238 U, and 239 Pu. The
dual-fission chambers were used to make measurements of the fission product activity relative to the total
fission activity, as well as for high-precision absolute fission yield measurements. The activation method
was employed, utilizing the mono-energetic neutron beams available at TUNL. Neutrons of 4.6, 9.0, and
14.5 MeV were produced via the 2 H(d, n) 3 He reaction, and for neutrons at 14.8 MeV, the 3 H(d, n) 4 He
reaction was used. After activation, the induced γ-ray activity of the fission product yields was measured
for three months using high-resolution HPGe detectors in a low-background environment. Results for the
yield of sixteen fission fragments for 235 U, 238 U, and 239 Pu and a comparison to available data at other
energies are reported. For the first time results are now available for neutron energies between 1.5 and 14
MeV.
Corresponding author: A. Tonchev
[1] M.B. Chadwick and others, Nucl. Data Sheets 111, 2923 (2010) [2] H.D. Selby and others, Nucl. Data
Sheets 111, 2891 (2010)
CF 3 2:20 PM
Mo-99, Nd-147, Zr-95 and Ba-140 Yields from Fission of U-235 Induced by 0.57, 1.0 and
1.5 MeV Neutrons
J. Feng, Y. Yang, S. Liu, Y. Liu
China Institute of Atomic Energy
The chain yields of fission products, 99 Mo, 95 Zr, 147 Nd and 140 Ba were determined for the fission of 235 U
induced by 0.57 MeV, 1.0 MeV and 1.5 MeV neutrons. Absolute fission rates were monitored with a
double-fission chamber. Fission product activities were measured by HPGe γ-ray spectrometry. MCNP
IVB was applied to simulate neutron spectrum in the Uranium samples, and the effects of all kinds of
secondary neutrons on fission yield data were discussed. The yields data were compared with those of
other labs. Our results are in agreement with those of ANL within the scope of experimental uncertainties
after necessary corrections.
CF 4 2:40 PM
Energy Dependence of Plutonium Fission-Product Yields and Average Fragment Total
Kinetic Energies
J. P. Lestone, T. T. Strother
Los Alamos National Laboratory
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